Article Development of a Dynamic Hands-Free Door Opener to Prevent COVID-19 Pandemic Spreading

Vítor Maranha 1,2, Pedro Maia 3,4, Luís Margalho 1 , Nicolle Lourenço 5 , Diogo Oliveira 5, Diogo Maurício 6, João F. Caseiro 6 and Luis Roseiro 1,2,*

1 Coimbra Polythecnic-ISEC, 3030-199 Coimbra, Portugal; [email protected] (V.M.); [email protected] (L.M.) 2 Center for Mechanical Engineering, Department of Mechanical Engineering, Materials and Processes (CEMMPRE), University of Coimbra, 3030-788 Coimbra, Portugal 3 Polytechnic of Coimbra, ESEC, Rua Dom João III—Solum, 3030-329 Coimbra, Portugal; [email protected] 4 Department of Communication, Campus Universitário de Santiago, [ID+] Research Institute for Design, Media and Culture, Art University of Aveiro, 3810-193 Aveiro, Portugal 5 Shapetek, R. António Champalimaud 10-A, 3100-514 Pombal, Portugal; [email protected] (N.L.); [email protected] (D.O.) 6 Centimfe, Z.I. Casal da Lebre, Rua da Espanha, Lt8, 2430-028 Marinha Grande, Portugal; [email protected] (D.M.); [email protected] (J.F.C.) * Correspondence: [email protected]; Tel.: +351-967845829

Abstract: The situation caused by COVID-19 has shown several vulnerabilities in the attitudes and habits of modern society, inducing the need to adopt new behaviors that will directly impact daily activities. The quickly spreading virus contaminates the surfaces of handles and objects, and



subsequent contact with the eyes, nose, or mouth is one of the main contagion factors. There is an
 urgent need to rethink how we interact with the most-touched surfaces, such as door handles in

Citation: Maranha, V.; Maia, P.; public places with a high flux of people. A revision was performed of the most-used door handles to Margalho, L.; Lourenço, N.; Oliveira, develop a proposal that could be applied to already existing models, thus avoiding the need for their D.; Maurício, D.; Caseiro, J.F.; Roseiro, total replacement. Through interaction between engineering, design, and ergonomics, an auxiliary L. Development of a Dynamic hands-free door opener device was developed, following iteration improvement from an initial static Hands-Free Door Opener to Prevent geometry and culminating in a dynamic system aiming to provide greater ergonomic comfort in its COVID-19 Pandemic Spreading. use. The development followed a methodology using 3D modelling supported by 3D printing of Designs 2021, 5, 56. https://doi.org/ the various components to accurately understand their functioning. In addition, the finite element 10.3390/designs5030056 method supported the prediction of the structural behavior of the developed systems. The final models were produced through CNC machining and submitted to functional validation tests with Academic Editor: Ernesto Benini volunteers. The developed HFDO demonstrated relevant differentiation from the existing models

Received: 14 July 2021 on the market: for its geometry and material, but mainly for its strong emphasis on the interaction Accepted: 24 August 2021 between the object and the user, resulting from the dynamic component in its use/manipulation. Published: 3 September 2021 Keywords: COVID-19; handle; industrial design; ergonomics; doors openers

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Considering the current pandemic and the future challenges to global health, the need to develop and implement solutions that mitigate or eliminate the various means of contamination with viruses and bacteria, especially COVID-19, in daily activities becomes Copyright: © 2021 by the authors. evident. In this sense, door handles, being among the most varied architectural elements, Licensee MDPI, Basel, Switzerland. characterized by high human interaction, have been identified as one of the main contagion This article is an open access article points. According to the Portuguese Standard EN 1906, from 2017, door handles are defined distributed under the terms and either lever or round handles with a mirror or rosette intended to activate locks. According conditions of the Creative Commons to the Human Factors Design Handbook by Woodson et al., the most common door handles Attribution (CC BY) license (https:// are L-shaped or lever systems, knob handles, and fixed D-shaped pieces, with closed or creativecommons.org/licenses/by/ open ends [1]. 4.0/).

Designs 2021, 5, 56. https://doi.org/10.3390/designs5030056 https://www.mdpi.com/journal/designs Designs 2021, 5, 56 2 of 21

1.1. Handles in the Spread of Viruses and Bacteria Handles in public places are significant factors in contagion, since they are potential agents in the spread of viruses and bacteria. In this sense, their role in contamination, especially in the hospital context, has been a target of analysis for a long time. However, this problem has gained even more significance in the current pandemic situation. Woj- gani et al. [2] developed a study in two intensive care units and a long-term care unit to determine whether the microbial contamination of door handles was related to their design, location, or/and use. They found a significant correlation between the frequency of move- ments through a door and the degree of contamination. The handles, when compared the push plates, revealed, on average, a level of contamination that was five times higher. The study by Wojgani et al. [2] also showed that door handles applied in clinical environments, in their daily use, were contaminated with bacteria, and the design, location, mode, and frequency of operation had a direct impact on the number of bacteria found. An identical analysis was described in the study by Odigie et al. [3], where the microbiological examina- tion of samples from several hospital units revealed that handles in different sections of a hospital environment are contaminated by a variety of pathogenic and non-pathogenic microorganisms. It was also shown that the location of the doors had a significant role in the distribution of the microorganisms. These authors also found that the samples from the bathroom door handle registered the highest bacterial load, which can be attributed to the increased exposure rates to the bacteria disseminated by users who enter and leave without proper hand hygiene. Additionally, the surfaces of the internal handles could act as potential transmitters in the spread of diseases. These two studies reported situations in the hospital context. However, identical conditions can be found in schools, universities, and public buildings with a substantial inflow of people. Thus, it is imperative to find strategies that prevent users from becoming infected via their hands.

1.2. Door Opening Systems The various door opening systems, handrails, and switches are, perhaps, the most used interfaces in the experience of people in different types of buildings. This relationship, decisive in humans’ interactions with architecture, dates back to its appearance in ancient Egypt. Throughout the history of mankind, doors and their opening systems also assumed a decorative role. A door is akin to an extension of the wall that moves to allow the isolation and the penetration of spaces, as quoted in Carvalho, 2012 [4], calling it an “operable wall”. Chang and Drury, as cited in Carvalho, 2012 [4], classified doors according to their interaction with humans, dividing them into three types, as shown in Figure1: (1) normal force on the door—includes doors with a rotation axis, “pull/push” or swivel, reciprocating and through-throttle suspensions (e.g., ribbons, beads); (2) horizontal force Designs 2021, 5, x FOR PEER REVIEW 3 of 22 parallel to the door plane—sliding or folding doors; and (3) vertical force parallel to the door plane—garage doors and similar.

FigureFigure 1. 1.Types Types of of door door and and their their interaction interaction with with the the user: user: normal normal force force (left (left);); horizontal horizontal force force (middle(middle);); vertical vertical force force (right (right). ).

TheThe current current door door opening opening mechanisms mechanisms are are configured configured so so that that the the user’s user’s hand hand carries carries outout the the different different operations: operations: apprehending, apprehending, pulling, pulling, and and pushing. pushing. Various Various situations situations are are evident, whether for hygiene reasons or for fear of contamination, where the user strives to find strategies to interact with the door without holding its handle. One of the most vulnerable places where such situations happen is hospitals, in which cross-transmission of various pathogens occurs despite the demanding hygienic and aseptic standards. Carvalho, 2012 [4], compared the norms for this type of device defined in Australia, the United Kingdom, the United States, and Portugal. It was verified that the general characteristics for the operation of doors, such as handles and locks, are similar and can be identified as: being easy to grip; being easy to operate with a single closed hand; not requiring a firm grip or wrist rotation; offering minimal resistance to performance; having non-slip properties; and having chromatic contrast identification concerning the door surface for easy visual detection. The author also mentioned that fixed D-shaped handles are identified in the four norms as being suitable for people with strength and manual dexterity difficulties. Knob handles, however, are contraindicated in all studied standards. Additionally, it is important to mention that the English norm advises lever movements (e.g., lever puller) for solutions regarding devices with mobile characteristics. Although most users can manage all types of systems correctly, children and people with reduced mobility have difficulties with most types of openings. In this sense, L- shaped (with a lever) can be considered the best handles, since they do not have to be tightened, and their appearance offers the quick perception of their use [1].

1.3. Auxiliary Devices for Door Opening Systems Several projects for auxiliary door opening devices have been developed to reduce direct contact between users’ hands and different types of handles. These include arm/forearm opening systems for direct fixation to the door, systems for fitting or fixing to the handle, and opening systems with the foot. With regard to of opening systems activated by the arm with direct fixation to the door, three systems can be referred to: (1) Sanitgrasp [5], manufactured in stainless steel and developed according to the standards of the Americans with Disabilities Act (ADA); (2) Toepener [6], also compatible with ADA and made of stainless steel, with easy and safe assembly through four screws; (3) Sanitary Door Opener Device [7], in aluminum, with rounded curves and anodized coating, in a shape that seeks to avoid the risk of trapping the user’s arm in the handle, even when the door is pushed abruptly and forcefully by a person on the other side. From the systems that are being fixed to already existing handles, the functional solution that this project seeks to follow can be highlighted [8], which seeks to eliminate direct contact with devices such as handles, elevator buttons, telephones, computer mice and keyboards. The proposed system is produced in acrylonitrile-butadiene-styrene (ABS). The Intulon System [9] is a circular handle adapter with a diameter of less than 18 mm. The Materialize company [10] offers free models for fastening with screws, whose

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evident, whether for hygiene reasons or for fear of contamination, where the user strives to find strategies to interact with the door without holding its handle. One of the most vulnerable places where such situations happen is hospitals, in which cross-transmission of various pathogens occurs despite the demanding hygienic and aseptic standards. Carvalho, 2012 [4], compared the norms for this type of device defined in Australia, the United Kingdom, the United States, and Portugal. It was verified that the general characteristics for the operation of doors, such as handles and locks, are similar and can be identified as: being easy to grip; being easy to operate with a single closed hand; not requiring a firm grip or wrist rotation; offering minimal resistance to performance; having non-slip properties; and having chromatic contrast identification concerning the door surface for easy visual detection. The author also mentioned that fixed D-shaped handles are identified in the four norms as being suitable for people with strength and manual dexterity difficulties. Knob handles, however, are contraindicated in all studied standards. Additionally, it is important to mention that the English norm advises lever movements (e.g., lever puller) for solutions regarding devices with mobile characteristics. Although most users can manage all types of systems correctly, children and people with reduced mobility have difficulties with most types of openings. In this sense, L-shaped (with a lever) can be considered the best handles, since they do not have to be tightened, and their appearance offers the quick perception of their use [1].

1.3. Auxiliary Devices for Door Opening Systems Several projects for auxiliary door opening devices have been developed to reduce di- rect contact between users’ hands and different types of handles. These include arm/forearm opening systems for direct fixation to the door, systems for fitting or fixing to the handle, and opening systems with the foot. With regard to of opening systems activated by the arm with direct fixation to the door, three systems can be referred to: (1) Sanitgrasp [5], manufactured in stainless steel and developed according to the standards of the Americans with Disabilities Act (ADA); (2) Toepener [6], also compatible with ADA and made of stainless steel, with easy and safe assembly through four screws; (3) Sanitary Door Opener Device [7], in aluminum, with rounded curves and anodized coating, in a shape that seeks to avoid the risk of trapping the user’s arm in the handle, even when the door is pushed abruptly and forcefully by a person on the other side. From the systems that are being fixed to already existing handles, the functional solution that this project seeks to follow can be highlighted [8], which seeks to eliminate direct contact with devices such as handles, elevator buttons, telephones, computer mice and keyboards. The proposed system is produced in acrylonitrile-butadiene-styrene (ABS). The Intulon System [9] is a circular handle adapter with a diameter of less than 18 mm. The Materialize company [10] offers free models for fastening with screws, whose geometry and assembly instructions can be downloaded online in order for each user to produce the model autonomously through additive manufacturing. Still, within the scope of devices to be fixed to the handle, the Shaftmodule system is composed of a shell-type metallic piece and is fixed with the use of screws [11]. A particular system for round handles, to be printed in 3D, was proposed by Adapta [12]. There are also systems that involve activation with the foot. These systems work by means of mechanical parts fixed at the door’s bottom, connected to the handle by a cable, such as the Planet NoHandler [13]. In this context, we highlight the StepNpull® system [14], an anodized aluminum device, which allows for opening a door hands-free by using a foot, a cane, or a crutch. This system consists of a metal plate with a serrated edge that is screwed to the bottom of the door, allowing the user to step on it and, in this manner, open the door. With features similar to StepNpull [14], there are the HandsFreeDoorPull [15], with rounded geometry, and the Metiba System [16], which is also fixed to the bottom of the door but is retractable. Designs 2021, 5, 56 4 of 21

1.4. Proposed Dynamic Hands-Free Door Opener This work presents an innovative door opening system to be implemented and used without the hands, designed as a hands-free door opener (HFDO), focusing on its potential application in hospitals, health units, and other public areas with a high inflow of people. For this purpose, design and engineering disciplines created synergies, developing the opening system as a solution to help mitigate the problems mentioned. A consortium of two companies and two non-business entities from the Portuguese national R&D system was created, supported by the Research Incentive System and Technological Development promoted by the National Innovation Agency. The objective was to design and develop a simple product from scratch with high aesthetic and functional value, characterized by great usability, versatility, affordable cost, easy installation, and low maintenance. In this sense, the developed product has a strong incorporation of design and mechanical design methodologies, emphasizing the ergonomic aspects in its cognitive, physical, and anthropometric dimensions, with respect for the current rules in terms of safety and procedures. The solution presented and described in this work enables its adaptation to different handle geometries. The description is based on the L-shaped geometry and the ‘’bar” category systems, with both a horizontal and a vertical assembly. This proposal provides the option of opening the door using an arm, or even a foot, by incorporating different mechanisms and/or handles while guaranteeing the fundamental biomechanical charac- teristics, emphasizing their strength and mechanical rigidity, associated with a geometry that can be easily decontaminated.

2. Materials and Methods In this project, an attempt was made to develop an opening system that works without the use of the hands, adaptable to doors with a “pull/push” axis of rotation, which is the most common in the majority of buildings. These systems, commonly referred to as handles, are usually pieces of wood, metal, or porcelain pulled to open drawers and doors.

2.1. Ergonomics, Interaction Concepts and Design Ergonomics can be considered a decisive factor in each product design project, and can be involved in three complementary approaches [17]: (1) developing new techniques and strategies that can allow an unaided person to perform better on the spot at work, at home or in the community; (2) developing specialized tools or assisted technologies that can maximize the use of residual skills and compensate for missing skills; (3) changing the design of the world to make it more usable and to offer a broader range of skills and abilities. The domain of interaction, where ergonomics is central, influences the symbiotic relationship between humans and the product, allowing the user to understand what to do and then evaluate the results to determine the following action [18]. In this way, we identified 4 of the 6 Norman principles, affordance, signifiers, constraints, and feedback, as important concepts in the development of this project: • “Affordance” is probably the principle that could have the most significant impact on this project and can be defined as the relationship between a physical object and a person (or any agent: animal, human, or even machine and robot). The quality of an object allows the user to identify its functionality without previous explanation, which can happen intuitively (e.g., doorknob) or based on previous experiences (e.g., white colour can mean peace). The greater the “affordance”, the better the identification of its use. It is important to note that “affordances” of physical objects are based on their size, format, and weight, while those of virtual object (web, app, etc.) happen through graphic representations and metaphors; • “Signifiers” refer to any mark, sound, or any perceptible indicator that communicates the appropriate behavior to a person. These signs can be deliberate and intentional, but also accidental and unintentional; Designs 2021, 5, 56 5 of 21

• “Constraints” are powerful clues limiting the set of possible actions, which can be of physical, cultural, semantic, and logical order. The deliberate use of design restric- tions allows people to readily determine the appropriate course of action, even in a new situation; • “Feedback” concerns the communication of the results of an action and contributes decisively to reducing the user’s frustration and stress. Another characteristic intrinsic to the objectives of this project is attractiveness, which, as highlighted by Norman [19], is a consequence of aesthetic quality that can function as a valuable attribute. HFDOs’ basic operative concepts show that for a correct interaction between the user and a hands-free opening device, the device needs to allow the user to easily place the forearm in a vertical position behind the front part of the handle and pull (1). This way, the hands never touch the handle and remain clean and hygienic (2). The user rotates and moves away when the door opens, naturally releasing the arm (3). The ends of the handle must be rounded to prevent injures (4). For the correct performance of these actions, the Americans with Disabilities Act (ADA) standards guide [20] states that the operable parts must be usable with one hand, must not require gripping, pinching, or twisting of the wrist, and must require no more than 22.3 N of force to operate. The guiding principles of this project follow the premises of universal design that can be defined as strategies to create environments suitable for use by anyone, regardless of age, size, or capacity [21]. Universal design can be considered the practice of designing products or environments that can be used effectively and efficiently, both by people without limitations and by those who operate with functional limitations, for example, due to physical-motor handicaps [17]. In this sense, the design of the proposed system was developed to be attractive, easy to learn, and effective in being easily operated by the user. The project’s technical specifications involved two complementary domains, namely the scientific aspects presented in the previous point and the definition of technical requirements and performance variables. To identify technical specifications, visits were made to a number of Portuguese hospitals, duly accompanied by technicians from the maintenance sector, and it was concluded that the vast majority of doors were equipped with handles of the lever type with a circular profile or a blade profile. Complimentary visits were made to other locations with a high flow of people, such as shopping centers and public service institutions, emphasizing schools and banking entities, showing that the most commonly used handles were those with circular and square tubular sections. Based on these visits, oral discussions, questions, and answers from stakeholders and through the observation of existing equipment, the technical requirements and design were produced for a device with modular characteristics, which is easy to assemble, with a base for a lever handle with a circular profile (identified as being the predominant type) and with simple adaptation to other types of handles by changing the device’s accessories. The creation of this system device resulted from a continuous iterative process, reaching the following objectives: • Creating a system appropriate for various handle geometries, ensuring its versatility; • Manufacturing using an easy-to-clean material and geometry,enabling its decontamination; • Guaranteeing fundamental characteristics/properties for intensive use, considering mechanical resistance, stiffness, and resistance to fatigue; • Designing for intuitive use. The research previously presented in the introductory section showed the existence of solutions on the market that, despite being partially effective, were not efficient. As static devices, without any dynamic component, they do not allow a continuous movement between the rotation of the door around its axis of connection to the wall and the passage of the user in front of it, who is obliged to remain behind it. Because of that, users often need to resort to the foot to immobilize the door and thus overcome it. This difficulty is mostly evident in doors with an automatic closing spring, present in most educational and health institutions. Designs 2021, 5, 56 6 of 21

Thus, the addition of dynamism to the device was considered, assuming that it would result in greater functional efficiency, aiming to help the user to understand the existence of the original handle, promoting the notion that this device is an auxiliary to the existing handle, helping in the perception of its correct use.

2.2. Geometrical Models—Description of the Project Evolution The three-dimensional geometry of the models was created using modelling software (Solidworks® 2019, Dassault Systèmes SOLIDWORKS Corp., Waltham, MA, USA). Table1 presents a summary of the Auxiliary Door Opening Device’s (ADOD) evolution. The description of the project’s evolution is described.

Table 1. The predisposition of the participants to the use of devices.

Model Procedures and Implementation The first approach to adapt to different geometries. ADOD-V1 Identification of improvements to be implemented in the leaf. Relevance to the implementation of the dynamism. Development of a leaf with ergonomic language. ADOD-V2 Identification of improvements in the clamp system and dimensions. Definition of the L and D shapes as a priority to match the system. The first approach to a dynamic component. Inclusion of a planar spring. ADOD-V3 Identification of the improvements in the leaf’s dimensions, the clamp system and the type of spring. Implementation of a simple torsional spring. ADOD-V4 Addition of a simple clamp, allowing four positions of the leaf. Addition of a second torsional spring to allow the rotation of the leaf in ADOD-V5 both directions. Implementation of improvements in the clamp system with two components to ADOD-V6 allow its implementation in closed handles: tested with a planar spring (V6) and ADOD-V7 two torsional springs (V7). Implementation of an angular discrete coupled system to allow different initial ADOD-V8 positions of the leaf (based on V7). Implementation of a torsional spring with a double effect, allowing better Final Model performance and more compact geometry. Evolution of the geometry transition Dynamic between the leaf and flat hinge components. Adjustments in the final dimensions of the components. Based on the same language of the dynamic model, but without the rotation Final Model component. A simplified version with the possibility of leaf Static position adjustments.

Based on the models mentioned above, the first geometric model resulted from an attempt to adapt to different handle geometries, namely cylindrical and “L” type shapes. Ergonomics was also considered, mainly in the contact region between the forearm and the device, to make the door opening experience as pleasant as possible. This prototype also tried to guide the user towards correct use, demonstrating that its geometry is intuitive to manipulate. Figure2 illustrates the result of this first approach, purely technical and functional, designed as Auxiliary Door Opening Device, version 1 (ADOD-V1). Designs 2021, 5, x FOR PEER REVIEW 7 of 22

Implementation of a torsional spring with a double effect, allowing better Final Model performance and more compact geometry. Evolution of the geometry Dynamic transition between the leaf and flat hinge components. Adjustments in the final dimensions of the components. Based on the same language of the dynamic model, but without the Final Model rotation component. A simplified version with the possibility of leaf Static position adjustments.

Based on the models mentioned above, the first geometric model resulted from an attempt to adapt to different handle geometries, namely cylindrical and “L” type shapes. Ergonomics was also considered, mainly in the contact region between the forearm and the device, to make the door opening experience as pleasant as possible. This prototype also tried to guide the user towards correct use, demonstrating that its geometry is Designs 2021, 5, 56 intuitive to manipulate. Figure 2 illustrates the result of this first approach, purely 7 of 21 technical and functional, designed as Auxiliary Door Opening Device, version 1 (ADOD- V1).

Figure 2.Figure Auxiliary 2. Auxiliary Door Opening Door OpeningDevice—ADOD-V1: Device—ADOD-V1: (a) 3D model; (a) 3D (b model;) representation (b) representation of system of system coupled tocoupled a cylindrical to a cylindrical handle; ( handle;c) representation (c) representation of the system of the coupled system coupledto a D type to ahandle. D type handle.

The researchThe research previously previously presented presented in the in introduction the introduction showed showed the theexistence existence of of solu- solutionstions on the on themarket market that, that, despite despite being being partially partially effective, effective, were were not not efficient, efficient, being being static static devices.devices. Based Based on on the the identified identified difficul difficultiesties associated associated with with the the static static systems, systems, the the addi- additiontion of ofdynamism dynamism to to the devicedevice waswas considered considered as aas project a project reference reference for development. for development.Assuming Assuming that the that dynamic the dynamic component comp wouldonent would result inresult greater in greater functional functional efficiency, the efficiency,next the focus next was focus to transmit was to to transmit the prototype to the a language prototype that a wouldlanguage simultaneously that would translate simultaneouslythe mentioned translate dynamism the mentioned associated dynamism with ergonomics associated and with integration ergonomics in the door.and In this integrationcontext, in the it door. was hoped In this that context, the formal it was languagehoped that would the formal result inlanguage a simple would and attractive result piece in a simplewithout and attractive sharp edges, piece which without would sharp induce edges, its which correct would form ofinduce use. its correct form of use. This piece, in its initial version, was a compact block of material. Still, for aesthetic, Thishygiene, piece, in and its weightinitial version, reasons (visuallywas a compact and physically), block of material. an opening Still, in thefor verticalaesthetic, piece was hygiene,designed, and weight thus reasons reducing (visually the surface and phys availableically), for an contamination. opening in the This vertical opening piece was also intended to help the user understand the original handle’s existence, promoting the notion that this device is an auxiliary to the existing handle, helping in the perception of its correct use. Figure3 show this new language (ADOD-V2). Although the device’s compatibility with different door handles is a critical component, the identification of doors for which the product is intended mainly includes two types of handle: “L” and “D” shaped. This assumption, identified by the consortium, as described above, led to the development of a requirement to prioritize this type of handle. Thus, this project considers these two types of handles, resulting in a simpler geometry. At this stage, an approach to a mechanism for fixing the prototype to the handle has already been developed. The part was divided into two components, the fixation to the handle and the vertical element. This will allow greater versatility in future situations, since it will permit keeping the vertical component while only producing new fixing parts, according to the different existing handles’ geometry. Designs 2021, 5, x FOR PEER REVIEW 8 of 22

was designed, thus reducing the surface available for contamination. This opening was also intended to help the user understand the original handle’s existence, promoting the notion that this device is an auxiliary to the existing handle, helping in the perception of its correct use. Figure 3 show this new language (ADOD-V2). Although the device’s compatibility with different door handles is a critical component, the identification of doors for which the product is intended mainly includes two types of handle: “L” and “D” shaped. This assumption, identified by the consortium, as described above, led to the development of a requirement to prioritize this type of handle. Thus, this project considers these two types of handles, resulting in a simpler geometry. At this stage, an approach to a mechanism for fixing the prototype to the handle has already been developed. The part was divided into two components, the fixation to Designs 2021, 5, 56 the handle and the vertical element. This will allow greater versatility in future situations, 8 of 21 since it will permit keeping the vertical component while only producing new fixing parts, according to the different existing handles’ geometry.

(a) (b)

Figure 3. Three-dimensionalFigure 3. Three-dimensional visualization of visualization the ADOD-V2 of the system ADOD-V2 with a system vertical with leaf: a ( verticala) without leaf: (a) without opening; (b) withopening; opening. (b) with opening.

In addition, Ina spring addition, was a springincluded was in includedthis model in that this modelwould thatallow would the dynamic allow the dynamic component tocomponent be put into to effect. be put Initially, into effect. we considered Initially, we using considered a spring usingsince it a does spring not since it does affect the product’snot affect geometry the product’s in an geometry evident inway. an evidentAdditionally, way. Additionally, some dimensional some dimensional adjustments adjustmentswere made to were the madeheight to of the the height vertical of theelement vertical (leaf) element so that (leaf) the dynamic so that the dynamic movement canmovement be accompanied can be accompanied by a comfortable by a comfortablecontact surface, contact with surface, the arm with or forearm, the arm or forearm, that effectivelythat adapts effectively to the adapts dynamism to the of dynamism the opening of themovement. opening movement.Figure 4a shows Figure the4a shows the first developmentsfirst developments of the model of ADOD-V3, the model ADOD-V3,including the including dynamic the component dynamic componentwith a with a spring. The highspring. number The high of components number of componentsin the system in for the fixing system the for device fixing to the the device handle to the handle is evident, inis addition evident, to in the addition presence to the of holes presence and of geometric holes and details geometric that could details promote that could promote the accumulationthe accumulation of pathogens, of so pathogens, the next iteration so the next considered iteration the considered elimination the eliminationof these of these Designs 2021, 5, x FOR PEER REVIEW critical areas.critical Thus, areas.a further Thus, evolution a further of evolutionthe model of (Figure the model 4b) reveals (Figure a4 b)smaller reveals 9number of a smaller22 number of componentsof components and a geometry and a geometry that faci thatlitates facilitates cleaning cleaning and anddecontamination decontamination and and transmits transmits a languagea language of continuity of continuity between between the thevertical vertical leaf leaf and and the theconnection connection to the to han- the handle. This dle. This languagelanguage was was achieved achieved by byrepl replacingacing the the spring spring with with a torsion a torsion spring. spring.

(a) (b)

Figure 4. ADOD-V3Figure system: 4. ADOD-V3 (a) simple system: version; (a) ( simpleb) refined version; version. (b) refined version.

To guarantee theTo guaranteecoupling to the different coupling type tos different of handle types geometry, of handle an evolution geometry, of an the evolution of the system, with asystem, simple withclamp a simpleand a clampsimple and spring a simple (ADOD-V4), spring (ADOD-V4), was defined was (Figure defined 5a). (Figure 5a). The The previous previousmodel fulfils model its fulfils function, its function, but only but if onlythe rotation if the rotation is carried is carried out in out one in one direction, direction, as onlyas only a single a single torsion torsion spring spring was was applied, applied, which which only only allows allows this this type type of of movement. movement. In this way, a second torsion spring was added to increase the versatility of the device and make it possible to be mounted on any door, whatever the direction of its opening. This characteristic required geometric modifications that resulted in the ADOD- V5 model (Figure 5b). With a quadrangular connection, both systems provide four different positions, allowing them to be implemented on different handles. This project is a typical example of how the creation of a product develops. Initial assumptions are considered that change or consolidate throughout the various iterations. Sometimes it is questioned whether all of the decisions and paths taken were the correct ones, and, in most cases, the solution to this type of challenge lies in simplicity. In this sense, the team decided to develop a model based on simplicity while maintaining the main requirements. In previous models, the possibility of mounting on the “L” and “D” handles was an objective that was only partially fulfilled, since the geometry of the connection between the handle and the device only allowed for fixing on open handles, as is the case of the “L” handles. The “D” handles, being closed, do not allow the device to be anchored. Thus, the connection geometry was changed and now consists of two components that make it possible to mount the device on both “L” and “D” handles (Figure 6a,b). These changes led to the realization that, although its functionality was not compromised, ergonomics and language coherence, considered as being important requirements in this project, were included. In this sense, there was a need to rethink the type of spring used, since the formal and dynamic component that characterizes the device is dependent on mechanical components that allow dynamism. The mechanical components that particularly allow the type of movement desired—that is, rotation after load application and subsequent return to the initial position—are the springs. For this reason, different geometric approaches were carried out, considering the diversity of so- lutions that the said mechanical component offers.

Designs 2021, 5, 56 9 of 21

In this way, a second torsion spring was added to increase the versatility of the device and make it possible to be mounted on any door, whatever the direction of its opening. This characteristic required geometric modifications that resulted in the ADOD-V5 model (Figure5b). With a quadrangular connection, both systems provide four different positions, allowing them to be implemented on different handles. This project is a typical example of how the creation of a product develops. Initial assumptions are considered that change or consolidate throughout the various iterations. Sometimes it is questioned whether all of the decisions and paths taken were the correct ones, and, in most cases, the solution to this type of challenge lies in simplicity. In this sense, the team decided to develop a model based on simplicity while maintaining the main requirements. In previous models, the possibility of mounting on the “L” and “D” handles was an objective that was only partially fulfilled, since the geometry of the connection between the handle and the device only allowed for fixing on open handles, as is the case of the “L” handles. The “D” handles, being closed, do not allow the device to be anchored. Thus, the connection geometry was changed and now consists of two components that make it possible to mount the device on both “L” and “D” handles (Figure6a,b). These changes led to the realization that, although its functionality was not compro- mised, ergonomics and language coherence, considered as being important requirements in this project, were included. In this sense, there was a need to rethink the type of spring used, since the formal and dynamic component that characterizes the device is depen- dent on mechanical components that allow dynamism. The mechanical components that particularly allow the type of movement desired—that is, rotation after load application and subsequent return to the initial position—are the springs. For this reason, different Designs 2021, 5, x FOR PEER REVIEW 10 of 22 geometric approaches were carried out, considering the diversity of solutions that the said mechanical component offers.

(a) (b)

FigureFigure 5. Three-dimensional 5. Three-dimensional visualization: visualization: (a) ADOD-V4 (a) ADOD-V4 system system with with a simple a simple clamp clamp and and spring; spring; (b) ADOD-V5 system with a double clamp and a double spring. (b) ADOD-V5 system with a double clamp and a double spring.

(a) (b) Figure 6. Three-dimensional visualization: (a) ADOD-V6 system; (b) ADOD-V7 system.

At this stage, it was also considered essential to study the influence that two parameters could have on the functioning and performance of the device under development: the distance from the vertical component to the center of rotation of the prototype and the vertical dimensions of the forearm’s contact zone with the device. All of the evolutionary prototypes developed were also produced through additive manufacturing, using 3D printers, to observe preliminary functional tests, and these dimensions were adjusted based on experimental tests. Through this functional analysis based on produced components, combined with the 3D modelling implemented, it was found that during the opening movement, the axis of rotation of the device was gradually tilting. This fact led us to implement a solution based on coupling with angular discretization (30°), as represented in Figure 7. The image on the left (Figure 7b) shows a vertical starting position of the leaf, with a final inclination.

Designs 2021, 5, x FOR PEER REVIEW 10 of 22

Designs 2021, 5, 56 (a) (b) 10 of 21 Figure 5. Three-dimensional visualization: (a) ADOD-V4 system with a simple clamp and spring; (b) ADOD-V5 system with a double clamp and a double spring.

(a) (b) Figure 6. Three-dimensional visualization: (a) ADOD-V6 system; (b) ADOD-V7 system. Figure 6. Three-dimensional visualization: (a) ADOD-V6 system; (b) ADOD-V7 system. At this stage, it was also considered essential to study the influence that two At this stage, it was also considered essential to study the influence that two param- parameters could have on the functioning and performance of the device under eters could havedevelopment: on the functioning the distance and from performance the vertical of component the device to under the center development: of rotation of the the distance fromprototype the vertical and componentthe vertical dimensions to the center of the of rotationforearm’s ofcontact the prototype zone with andthe device. the All vertical dimensionsof the of theevolutionary forearm’s prototypes contact zone develop withed the were device. also All produced of the evolutionary through additive prototypes developedmanufacturing, were also using produced 3D printers, through to additive observe manufacturing,preliminary functional using 3Dtests, print- and these ers, to observe preliminarydimensions were functional adjusted tests, based and on theseexperimental dimensions tests. were adjusted based on experimental tests. Through this functional analysis based on produced components, combined with the Through this3D functional modelling analysisimplemented, based it was on produced found that components,during the opening combined movement, with the axis of 3D modelling implemented,rotation of the itdevice was was found gradually that during tilting. theThis opening fact led us movement, to implement the a solution axis of based on coupling with angular discretization (30°), as represented in Figure 7. The image on Designs 2021, 5, x FOR PEER REVIEWrotation of the device was gradually tilting. This fact led us to implement a solution11 based of 22 the left (Figure 7b) shows a vertical starting position of the leaf, with a final inclination. on coupling with angular discretization (30◦), as represented in Figure7. The image on the left (Figure7b) shows a vertical starting position of the leaf, with a final inclination. TheThe imageimage onon thethe rightright (Figure(Figure7 7c)c) shows shows an an initial initial inclination inclination position, position, leading leading to to the the final final verticalvertical positionposition ofof thethe leaf.leaf.

(a)

(b) (c)

FigureFigure 7.7. LeafLeaf positioningpositioning system:system: ((aa)) angularangular discretediscrete coupledcoupled system;system; ((bb)) initialinitial verticalvertical positionposition ofof thethe leafleaf withwith aa finalfinal inclination;inclination; ((cc)) inclinationinclination initialinitial positionposition ofof thethe leafleaf with with a a final final vertical vertical position. position.

As the different models were being developed, prototypes were produced to test several aspects of their functionality, such as ergonomics and design. Figure 8a shows an example of 3D prototyping, with a Prusa mk3s+ equipment, producing the mechanical components in polyethylene glycol terephthalate with carbon fiber (PETG-CF), a material with good mechanical properties. Figure 8b shows an example of a brass prototype produced with a CNC machine.

(a) (b) Figure 8. (a) Visualization of 3D printing in PETG-CF material; (b) brass prototype produced with CNC machining.

Adjusting 3D printing parameters is an essential procedure to obtain components with the desired precision and mechanical characteristics. After a process of adjustment and optimization, the parameters considered are presented in Table 2.

Table 2. Three-dimensional printing parameters used for printing with the PETG-CF.

Parameter Units Temperature 260 °C

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The image on the right (Figure 7c) shows an initial inclination position, leading to the final vertical position of the leaf.

(a)

(b) (c) Designs 2021, 5, 56 11 of 21 Figure 7. Leaf positioning system: (a) angular discrete coupled system; (b) initial vertical position of the leaf with a final inclination; (c) inclination initial position of the leaf with a final vertical position.

AsAs the the different different models models were were being being developed, developed, prototypes prototypes were were produced produced to to test test severalseveral aspects aspects of of their their functionality, functionality, such such as as ergonomics ergonomics and and design. design. Figure Figure 8a8a shows an exampleexample of of 3D 3D prototyping, prototyping, with with a a Prusa Prusa mk3s+ mk3s+ equipment, equipment, producing producing the the mechanical mechanical componentscomponents in in polyethylene polyethylene glycol glycol terephthal terephthalateate with with carbon carbon fiber fiber (PETG-CF), (PETG-CF), a a material material withwith good good mechanical mechanical properties. properties. Figure Figure 8b8b shows shows an example of a brass prototypeprototype producedproduced with with a a CNC CNC machine. machine.

(a) (b)

FigureFigure 8. 8. (a()a )Visualization Visualization of of 3D 3D printing printing in in PETG-CF PETG-CF material; material; (b (b) )brass brass prototype prototype produced produced with with CNC CNC machining. machining.

AdjustingAdjusting 3D 3D printing printing parameters parameters is is an an essential essential procedure procedure to to obtain obtain components components withwith the the desired desired precision precision and and mechanical mechanical char characteristics.acteristics. After After a a process process of of adjustment adjustment andand optimization, optimization, the the parameters parameters co considerednsidered are are presented presented in in Table Table 22..

TableTable 2. 2. Three-dimensionalThree-dimensional printing printing parameters parameters used used for for printing printing with with the the PETG-CF. PETG-CF.

ParameterParameter Units Units TemperatureTemperature 260 260 °C◦C Heated bed Temperature 90 ◦C Layer Height 0.1 mm Extrusion Width 0.5 mm Number of Perimeters 4 Type of Filling Gyroid Filling Density 25% Part Cooling 0% Speed 45 mm/s

2.3. Final Models For experimental validation and proof of concept, two final devices were defined, based on all sequential developments—one short-fixed (without dynamism) and the other dynamic (with dynamism). Figure9 presents a 3D visualization of the short-fixed device (Figure9a), and the dynamic system represented with an exploded view (Figure9b). The short-fixed system has two main components, a leaf (1) and a clamped system (2) with two components for leaf positioning. The main dimensions of this device are: L = 68 mm; W = 58 mm; H = 114 mm. The representation of the figure corresponds to a circular-type handle, but, as explained, this geometry can be prepared to fit other types of handle section. The dynamic system has four main structural components: the leaf with a geometric transition (3), the flat hinge component (4), the clamp system to match the handle (5, 6), and a torsional spring to allow the rotation of the leaf during the use. The main dimensions of the mounted device are: L = 92 mm; W = 58 mm; H = 114 mm. Figure 10 shows, as an example, the visualization of both systems clamped in a D-type handle. Designs 2021, 5, x FOR PEER REVIEW 12 of 22

Heated bed Temperature 90 °C Layer Height 0.1 mm Extrusion Width 0.5 mm Number of Perimeters 4 Type of Filling Gyroid Filling Density 25% Part Cooling 0% Speed 45 mm/s

2.3. Final Models For experimental validation and proof of concept, two final devices were defined, based on all sequential developments—one short-fixed (without dynamism) and the other dynamic (with dynamism). Figure 9 presents a 3D visualization of the short-fixed device (Figure 9a), and the dynamic system represented with an exploded view (Figure 9b). The short-fixed system has two main components, a leaf (1) and a clamped system (2) with two components for leaf positioning. The main dimensions of this device are: L = 68 mm; W = 58 mm; H = 114 mm. The representation of the figure corresponds to a circular-type handle, but, as explained, this geometry can be prepared to fit other types of handle section. The dynamic system has four main structural components: the leaf with a geometric transition (3), the flat hinge component (4), the clamp system to match the handle (5, 6), and a torsional Designs 2021, 5, 56 spring to allow the rotation of the leaf during the use. The main dimensions12 of of 21the mounted device are: L = 92 mm; W = 58 mm; H = 114 mm. Figure 10 shows, as an example, the visualization of both systems clamped in a D-type handle.

(a) (b) Designs 2021, 5, x FOR PEER REVIEW 13 of 22

FigureFigure 9. Three-dimensional9. Three-dimensional model model visualization: visualization: (a) short-fixed (a) short-fixed system system with a leafwith (1) a andleaf a (1) clamped and a systemclamped (2); system (b) dynamic (2); (b) systemdynamic with system a leaf (3), with a flat a leaf hinge (3), component a flat hinge (4), component a handle clamp (4), a system handle with clamp two system components with two (5,6) components and a torsional (5,6) spring and (7).a tor- sional spring (7).

(a) (b)

Figure 10.Figure Visualization 10. Visualization of the systems of the clamped systems to clamped a D-type to handle: a D-type (a handle:) short-fixed; (a) short-fixed; (b) dynamic. (b) dynamic.

2.4. Material2.4. Material The productionThe production of the final of prototypes the final prototypes was performed was performedusing aluminum using alloy aluminum 7075 T6 alloy 7075 through T6CNC through machining. CNC machining.This material This was material chosen was for chosenthe devices for the due devices to its due excellent to its excellent mechanicalmechanical properties, properties, good ductility, good ductility,high strength, high strength,toughness, toughness, good fatigue good resistance, fatigue resistance, and the easinessand the of easiness its machining. of its machining. The mechanic Theal mechanical properties propertiesof the alloy of are the presented alloy are in presented Table 3. Within Table this3. material, With this the material, short-fixed the short-fixed prototype prototype weighed weighed190 g and 190 the g anddynamic the dynamic prototypeprototype weighed weighed255 g. 255 g.

Table 3. MechanicalTable 3. Mechanical properties properties of the aluminum of the aluminum alloy 7075 alloy T6. 7075 T6.

Property Property Young’s ModulusYoung’s Modulus 71.70 GPa 71.70 GPa Poisson’s Poisson’sRatio Ratio 0.33 0.33 Yield StrengthYield Strength 503 MPa 503 MPa Tensile Strength 572 MPa Tensile StrengthElongation at break 572 MPa 11% Elongation at break 11%

2.5. Numerical Models The models were numerically studied using Ansys® Mechanical, Release 2020 R2 for finite element analysis. The defined models for the studies assumed isotropic properties with a bilinear elastoplastic hardening for all of the components. The force condition was based on the standard EN 1906: 2012 for the handles, considering 200 N of force applied onto surface E, as represented in Figure 11, considering extreme use situations. Only the finite element model for the dynamic system is presented, which corresponds to the worst case. The finite element model was defined with tetrahedral parabolic solid elements (Solid187 element from Ansys library), with 3 degrees of freedom per node, representing the translations in the three orthogonal directions. The model was considered when clamped onto a tubular L-type handle, and the boundary conditions assumed the restraint of all the nodes in the internal face of the handle. Considering the symmetry of the system and for computational purposes, only half of the model was considered, as shown in Figure 4. The contacts between components were modelled using a frictionless-type formulation. The bolt connections for clamping the components of the system and the system to the handle were virtually modelled considering the Bolt Pretension tool of the software, with 1000 N of force. A mesh convergence study was performed, leading to 1,275,990 elements with a size of 0.2 mm.

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2.5. Numerical Models The models were numerically studied using Ansys® Mechanical, Release 2020 R2 for finite element analysis. The defined models for the studies assumed isotropic properties with a bilinear elastoplastic hardening for all of the components. The force condition was based on the standard EN 1906: 2012 for the handles, considering 200 N of force applied onto surface E, as represented in Figure 11, considering extreme use situations. Only the finite element model for the dynamic system is presented, which corresponds to the worst case. The finite element model was defined with tetrahedral parabolic solid elements (Solid187 element from Ansys library), with 3 degrees of freedom per node, representing the translations in the three orthogonal directions. The model was considered when clamped onto a tubular L-type handle, and the boundary conditions assumed the restraint of all the nodes in the internal face of the handle. Considering the symmetry of the system and for computational purposes, only half of the model was considered, as shown in Figure4. The contacts between components were modelled using a frictionless-type formulation. The bolt connections for clamping the components of the system and the system to the handle were virtually modelled considering the Bolt Pretension tool of the Designs 2021, 5, x FOR PEER REVIEW 14 of 22 software, with 1000 N of force. A mesh convergence study was performed, leading to 1,275,990 elements with a size of 0.2 mm.

(a) (b)

FigureFigure 11. Representation 11. Representation of the of the finite finite element element model model for for the the dynamicdynamic system: (a (a) )E—surface E—surface for for applied applied force; force; F—bound- F—boundary ary surface; A—bolt connection between the components for; B—bolt connection for clamping the system to the handle; surface;C—rotational A—bolt connectionpin; (b) visualization between of the the componentsmesh. for; B—bolt connection for clamping the system to the handle; C—rotational pin; (b) visualization of the mesh. 2.6. Manufacturing 2.6. ManufacturingThe manufacturing of the components was performed by means of MAS CNC ma- chiningThe manufacturing(MAS MCV 800), ofand the all components the preparations was were performed made with by Mastercam means of MASsoftware, CNC ma- chining2019 version. (MAS MCV 800), and all the preparations were made with Mastercam software, 2019 version.

2.7. Usability Testing Protocol A protocol with a set of usability tests was prepared to identify the results obtained with the developed system. Usability testing is a technique used in user-centered interaction design to evaluate a product by testing it on users. It provides direct input on how real

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users use the system [22]. As a result of usability testing, a measure of a human-made product’s capacity to meet its intended purpose will become available. There are several scale usability scores (SUS) available. A SUS allows for evaluating a wide variety of products, becoming a reference in the industry [23]. These scale use a list of questions, and for each of them, a Likert scale is used to provide an answer. Some of the questions have a positive emphasis, while the others have a negative one. To analyze the results, a score must be created. An average score of 68 points, on a 0–100 scale, means there are no usability problems with the product. The usability tests were performed within a university campus context (Polytechnic of Coimbra, School of Engineering) in a building with several equal doors and handles. Three doors were prepared with one of the different kinds of devices on each: • Short-fixed, referred to as “A”. The simplest device, without dynamic rotation and with a short distance to the handle; • Long-fixed, referred to as “B”. The same as dynamic, but with dynamic rotation blocked; • Dynamic, referred to as “C”. The developed device, with dynamic rotation to follow the arm. The tests were performed for several days, and a total of 52 volunteers participated in the usability study. Before participation in the usability test, the volunteers were informed about the objectives and methodology and gave informed consent. As a criterion for inclusion in the sample, being a member of the university was the only criterion considered. As an exclusion criterion, the inability to perceive informed consent was considered. The protocol for usability tests with the volunteers was prepared to follow the Declaration of Helsinki and was approved by the Polytechnic of Coimbra Ethical Committee (Reference No. 110_CEPC2/2020). The protocol involved opening 4 doors, and the volunteer had to open and transpose the door without using their hands, in a random order, following the intuition to use the system. One of the doors did not have any device clamped to the handle, and the other three doors each had one of the devices clamped onto it. All the doors opened to the same side. Figure 12 shows a volunteer opening the door “C”, prepared with the dynamic system clamped onto the handle.

2.8. Experimental Tests To identify the experimental behavior of the two models, dynamic and static, two sets of test equipment were developed and built, based on the NP EN 19106:2017 standard, also taking into account the numerical model. This standard is applicable to lever- and round- type handles, which activate locks and other devices, thus representing an experimental test solution for extreme conditions, given that these devices were designed to adapt to these types of handles. Although this new device does not completely fit into the scope of this standard, it was understood that these tests should be based on what is described therein. Uniaxial traction (Figure 12a) and durability tests (Figure 12b, indicated by the standard) were chosen for implementation. This equipment can be visualized in Figure 12—(a) uniaxial traction and (b) durability. For the uniaxial traction, 1000 N was applied and maintained for a few seconds. For durability, forces P = 50 N and R = 10 N were used. The motor, which generated the knob’s rotational movement, was made to rotate at a frequency of one cycle every 2 s. The equipment was kept in continuous rotation for 111 h—that is, 4.5 days—to complete 200,000 processes. Five devices of each type were tested. Figure 13 shows an example of the two models after the tests. On the left, in Figure 13a, the area where a very slight gap due to wear was identified can be observed. On the right, the static device can be seen without any identification of problems. Designs 2021, 5, x FOR PEER REVIEW 16 of 22

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(a) (b) Figure 12. Equipment developed for experimental tests: (a) uniaxial traction; (b) durability.

Figure 13 shows an example(a) of the two models after the tests. On the(b )left, in Figure 13a, the area whereFigure a12. very Equipment slight developed gap due for experimentalto wear was tests: identified (a) uniaxial traction; can be (b )observed. durability. On the right, the staticFigure device 12. Equipment can be developedseen without for experimental any identification tests: (a) uniaxial of problems. traction; (b ) durability. Figure 13 shows an example of the two models after the tests. On the left, in Figure 13a, the area where a very slight gap due to wear was identified can be observed. On the right, the static device can be seen without any identification of problems.

(a) (b) (a) (b) Figure 13. Examples of the models after experimental tests: (a) dynamic Model; (b) static Model. Figure 13. ExamplesFigure 13. Examples of the models of the modelsafter experimental after experimental tests: tests: (a) (dynamica) dynamic Model; Model; ( (bb)) static Model. Model.

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3. Results 3. Results 3.1.3. Numerical Results Results 3.1. Numerical Results 3.1.The Numerical stress field Results obtained is presented in Figure6. All the regions of the component show stressThe stress values field lower obtained than the is yieldpresented strength in Fi ofgure the 6. material, All the regions demonstrating of the component an adequate The stress field obtained is presented in Figure 6. All the regions of the component strength.show stress Figure values 14b showslower thethan details the yield of the stre bolts’ngth connection,of the material, where demonstrating peak stress is an obtained ade- quateshow strength. stress values Figure lower 14b showsthan the the yield details stre ofngth the ofbolts’ the connection,material, demonstrating where peak stress an ade- is correspondingquate strength. to stressFigure hotspots 14b shows that the arise details due of to the geometric bolts’ connection, discontinuities. where peak It should stress also is beobtained mentioned corresponding that the 200 to N loadstress applied hotspots corresponds that arise due to a to limited geometric case discontinuities. (for instance, in It the shouldobtained also corresponding be mentioned to that stress the hotspots200 N load that applied arise due corresponds to geometric to a discontinuities.limited case (for It case of an emergency), and that this load is significantly higher than the normal operating instance,should also in the be casementioned of an emergency), that the 200 andN load that applied this load corresponds is significantly to a higherlimited than case the(for conditions of the door opening. Considering the rigidity of the system, a maximum value normalinstance, operating in the case conditions of an emergency), of the door andopen thating. this Considering load is significantly the rigidity higher of the system,than the of 34.692 mm for the equivalent displacement was obtained (Figure 14a), which can be anormal maximum operating value conditionsof 34.692 mm of the for door the equivaopening.lent Considering displacement the wasrigidity obtained of the (Figuresystem, considered adequate for the force conditions of the model. A fatigue study (Figure 15b) was 14a),a maximum which can value be consideredof 34.692 mm adequate for the for equiva the forcelent displacementconditions of thewas model. obtained A fatigue(Figure also performed, taking into account the results obtained with the static analysis and the study14a), which(Figure can 15b) be was considered also performed, adequate taking for the into force account conditions the results of the obtained model. Awith fatigue the S–N curve of the material [24]. This analysis shows that at least 105 cycles can be achieved staticstudy analysis (Figure and 15b) the was S–N also curve performed, of the material taking into [24]. account This analysis the results shows obtained that at leastwith 10 the5 5 forcyclesstatic the considered cananalysis be achieved and conditions. the forS–N the curve considered of the material conditions. [24]. This analysis shows that at least 10 cycles can be achieved for the considered conditions.

(a) (b) (a) (b) Figure 14. Representation of the results obtained with the finite element model: (a) Von Mises equivalent stress distribu- Figure 14. Representation of the results obtained with the finite element model: (a) Von Mises equivalent stress distribution; tion;Figure (b) 14.Von Representation Mises stress distribution of the results with obtained hotspot with deta theils due finite to elementgeometric model: discontinuities (a) Von Mises of the equivalent model. stress distribu- (b) Vontion; Mises (b) Von stress Mises distribution stress distribution with hotspot with detailshotspot due deta toils geometricdue to geometric discontinuities discontinuities of the of model. the model.

(a) (b) (a) (b) Figure 15. Representation of the results obtained with the finite element model: (a) visualization of the distribution of the Figure 15. Representation of the results obtained with the finite element model: (a) visualization5 of the distribution of the Figuretotal 15. displacement;Representation (b) visualization of the results of obtained the distribution with the offinite the fatigue element safety model: factor (a for) visualization 10 cycles. of the distribution of the total displacement; (b) visualization of the distribution of the fatigue safety factor for 105 cycles. total displacement; (b) visualization of the distribution of the fatigue safety factor for 105 cycles.

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3.2. Usability Results 3.2. Usability Results 3.2.1. Participants 3.2.1. Participants A total of 52 volunteers were included in the study. Participants were randomly selectedA total to participate,of 52 volunteers including were included 12 females in andthe study. 40 males. Participants As this test were was randomly performed se- lectedat a university to participate, campus, including 38 participants 12 females were and students, 40 males. 9 As were this teachers, test was and performed 5 were staff.at a universityParticipants’ campus, ages ranged38 participants from 18 were to 58 students, years old, 9 withwere ateachers, mean age and of 5 26.4 were years staff. and Par- a ticipants’standard ages deviation ranged of from 9.8 years. 18 to 58 years old, with a mean age of 26.4 years and a standard deviationParticipants of 9.8 years. opened and transposed the four doors designated for the study, with the firstParticipants one having noopened handle and to transposed serve as a referencethe four doors (Figure designated 16). After for performing the study, thiswith task, the firstparticipants one having received no handle the private to serve link as to a access reference and (Figure answer the16). questionnaire,After performing in which this task, they participantsexpressed their received agreement the private with the link sentences to access in it.and Answers answer werethe questionnaire, recorded for each in which of the theythree expressed devices, enabling their agreement the calculation with the of sentences the usability in it. score Answers concerning were recorded each device. for each of the three devices, enabling the calculation of the usability score concerning each device.

(a) (b)

Figure 16. Dynamic system: ( (aa)) visualization visualization of of the the system system clamped clamped in in the the handle handle and and the the hand hand po positionsition for for opening; opening; ( (bb)) sequence of opening pe performedrformed by a volunteer.

3.2.2.3.2.2. Habits/Easiness Habits/Easiness of of door Door opening Opening WhenWhen participants participants were were asked asked about about their their habits habits regarding regarding door door opening opening during during the currentthe current SARS-COV-2 SARS-COV-2 pandemic, pandemic, 26 of 26 them of them mentioned mentioned using using their their elbow/forearm, elbow/forearm, 21 mentioned21 mentioned using using their their hand, hand, and and four four mentioned mentioned using using their their wrist. wrist. TableTable 44 presents presents the the answers answers about about how how often often each each participant participant would would use use each each device. de- vice.We observed We observed that most that participantsmost participants are willing are willing to use these to use devices, these devices, although although the dynamic the dynamicoption (Device option C) (Device demonstrates C) demonstrates more preferences more preferences in the Always in the option. Always option.

TableTable 4. 4. TheThe participants’ participants’ predisposition predisposition towards towards the theuse useof the of devices the devices (each (each cell indicates cell indicates the num- the bernumber of participants of participants choosing choosing each eachlevel levelof the of answer). the answer).

DeviceDevice Always Always Frequently Frequently Neutral Neutral Rarely Rarely Never Never Short-Fixed (A) 21 23 4 2 2 Short-Fixed (A) 21 23 4 2 2 Long-Fixed (B) (B) 24 24 21 21 3 3 2 2 2 2 Dynamic (C) (C) 25 25 21 21 2 2 2 2 2 2

TheThe analysis analysis of of the questionnaire answer concerning the the easiness of door opening showsshows that that most most participants participants found found it it more more complex to open the door with no device. In contrast,contrast, most most participants participants chose chose Device Device C C as as the the device device giving more support to opening thethe door door without without hand hand use. use. Fi Figuregure 1717 showsshows the the results results concerning the ease of use.

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Figure 17. Distribution of the number of answers to each level in the Likert scale for the question Figureabout the17. easinessDistribution of door of the opening number with of noanswers device to or each with level devices in the A, BLikert or C. scale for the question about the easiness of door opening with no device or with devices A, B or C. 3.3. Statistical Results 3.3. StatisticalStatistical Results analysis of the data was performed using the open-source software R version 4.0.3,Statistical together withanalysis R-Studio of the versiondata was 1.3.1093. performed using the open-source software R ver- sion 4.0.3,A usability together comparison with R-Studio was performed, version 1.3.1093. and the usability means index was determined for eachA usability of the three comparison devices. Thewas questionnaireperformed, and used the to usability run the usabilitymeans index test consistedwas deter- of mined12 questions, for each each of the of whichthree devices. allowing The answers questionnaire in a Likert used scale to withrun the seven usability levels, test ranging con- sistedfrom stronglyof 12 questions, disagree each (1) to of strongly which allowing agree (7). answers Eight of thesein a Likert questions scale exhibited with seven a positive levels, rangingemphasis, from and strongly the remaining disagree four (1) to exhibited strongly a agree negative (7). emphasis.Eight of these questions exhibited a positiveFor each emphasis, question and with the aremaining positive emphasis, four exhibited the contribution a negative toemphasis. the final score was the valueFor chosen each inquestion the Likert with scale a positive minus 1, emphasis, while for the questionscontribution with to a the negative final score emphasis, was thethe value contribution chosen in to the Likert final score scale was minus seven 1, while minus for the the value questions chosen with in thea negative Likert scale. em- phasis,To obtain the a contribution score ranging to from the final 0 to 100,score the wa finals seven score minus in the the usability value chosen test was in multipliedthe Likert scale.by 1.388. To obtain a score ranging from 0 to 100, the final score in the usability test was mul- tipliedOverall, by 1.388. answers regarding device C collected the majority of preferences for questions withOverall, a positive answers emphasis regarding compared device with C answers collected for the devices majority A and of preferences B. for ques- tions Thewith usability a positive means emphasis index compared was determined with answers for each for ofdevices the three A and devices. B. Device A presentedThe usability a mean means value ofindex 80.16, was while determined this value for was each 81.20 of the for three device devices. B and Device 81.33 forA presenteddevice C. Thea mean standard value deviations of 80.16, werewhile 12.00, this 12.06value andwas 11.22, 81.20 respectively, for device B for and devices 81.33 A, for B, deviceand C (TableC. The2 standardand Figure deviations 18). Each were participant 12.00, 12.06 graded and each 11.22, device respectively, with a score for larger devices than A, B,the and reference C (Table value 2 and of 68Figure for the 18). usability Each participant score, reflecting graded the each absence device of withusability a score problems. larger than Thethe reference Shapiro–Wilk value test of for68 for the the normality usabilit ofy score, index reflecting distributions the returnedabsence ofp-values usability of problems.0.0288, 0.02216 and 0.04482, respectively, for devices A, B, and C, allowing us to not reject the assumption of normality for a significance level of α = 0.01. The Shapiro–Wilk test for the normality of index distributions returned p-values of Bartlett’s test for homogeneity of variances presented a value of 0.8503. With the same 0.0288, 0.02216 and 0.04482, respectively, for devices A, B, and C, allowing us to not reject level of significance, distributions were assumed to have equal variances. the assumption of normality for a significance level of α = 0.01. Although no statistically significant differences in means we observed (ANOVA test Bartlett’s test for homogeneity of variances presented a value of 0.8503. With the to compare means presented a p-value of 0.856 (Table5)), it was device C, the dynamic one, same level of significance, distributions were assumed to have equal variances. that exhibited the largest mean index. Although no statistically significant differences in means we observed (ANOVA test to compare means presented a p-value of 0.856 (Table 5)), it was device C, the dynamic Table 5. One-way ANOVA table for comparison of mean indexes. one, that exhibited the largest mean index. Source Degrees of Freedom Sum Sq. Mean Sq. F Value p-Value Table 5. One-way ANOVA table for comparison of mean indexes. Device 2 43 21.5 Source Degrees of Freedom Sum Sq. Mean Sq. F Value0.155 p-Value 0.856 Residuals 153 21.171 138.4 Device 2 43 21.5 0.155 0.856

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Designs 2021, 5, 56 19 of 21 Residuals 153 21.171 138.4

FigureFigure 18. 18. HistogramsHistograms ( (toptop row row)) and and boxplots boxplots (bottom rowrow)) ofof usabilityusability indexes—devices indexes—devices A, A, B, B, and and C. C. 3.4. Experimental Results 3.4. ExperimentalThe results Results of the uniaxial traction show that none of the tested models feature any deformation and abnormality. The results of the uniaxial traction show that none of the tested models feature any Regarding the durability tests, after the stipulated load cycles, the devices were deformation and abnormality. removed and observed. In the case of the static model, no anomalies or deformation were Regarding the durability tests, after the stipulated load cycles, the devices were re- observed. In the dynamic model, a slight slack was observed without compromising the moved and observed. In the case of the static model, no anomalies or deformation were system’s proper functioning. observed. In the dynamic model, a slight slack was observed without compromising the system’s4. Discussion proper functioning. The impact of COVID-19 in day-to-day life has raised the sensation of insecurity in the 4. Discussion population, but simultaneously has made people much more open to trying and adopting solutionsThe impact that can of mitigateCOVID-19 the in spread day-to-day of the virus.life has raised the sensation of insecurity in the population,Through this but study, simultaneously it was possible has to made realize people that even much without more HFDO open devicesto trying applied and adoptingto normal solutions doors, many that can people mitigate already the spread try to develop of the virus. strategies by using the forearm or elbowThrough so as not this to study, touch theit was handle possible with to their realize hand. that even without HFDO devices ap- plied toThe normal results doors, show many that thepeople static already devices, try withoutto develop any strategies dynamic by component, using the forearm are less orappreciated elbow so as by not users, to touch precisely the handle because with the ergonomictheir hand. comfort of the movement to operate the doorThe results is not fluid show and that requires the static elaborate devices, body without movements. any dynamic In the questionnairecomponent, are used less to appreciatedfind the usability by users, score, precisely the Cronbach’s because alpha the ergonomic concerning comfort the questions of the relatedmovement to the to devices oper- atewas the 0.743, door revealing is not fluid an acceptableand requires internal elaborate consistency. body movements. Additionally, In thethe meanquestionnaire usability usedscore to for find each the device usability was score, larger the than Cronbach 68, meaning’s alpha that concerning participants the found questions no problem related with to theusability devices with was the 0.743, proposed revealing devices. an acceptable The results internal also suggest consistency. that universal Additionally, dimensions, the meanproper usability contact score surface, for aesthetics, each device ergonomics, was larger and than affordances, 68, meaning defined that participants as the quality found of an noobject problem that allowswith usability the user with to identify the proposed its functionality devices. withoutThe results previous also suggest explanation that uni- [18], versalwere thedimensions, main characteristics proper contact that contributedsurface, aesthetics, to the success ergonomics, of this product.and affordances, de- fined Inas thisthe quality sense, this of an study object aimed that toallows find newthe user strategies to identify that help its functionality in the interaction without and previousergonomics explanation between users[18], were and HFDO.the main The characteristics developed dynamic that contributed HFDO adopts to the ergonomics, success of thisconsidered product. a major aspect of product design, mainly through the dynamic approach and suitableIn this shape sense, for this adequate study aimed interaction to find with new the strategies human body,that help making in the the interaction door opening and ergonomicsexperience asbetween pleasant users as possible. and HFDO. The developed dynamic HFDO adopts ergonom- ics, consideredIn this context, a major the aspect formal of language product ofdesign, HFDO mainly results through in a simple the anddynamic attractive approach piece without sharp edges. An opening in the vertical piece was designed to reduce weight, the

Designs 2021, 5, 56 20 of 21

surface available for contamination by the virus, and adding aesthetic value, hygiene, and visual and physical lightness. This hole was also intended to help the user to understand the existence of the original handle, promoting the notion that this device is auxiliary and, at the same time, allowing the perception of its correct use. The experimental results obtained from the tests carried out show that the devices have a high structural strength and performance level, even with the introduction of a double-effect spring. From the perspective of scale economy, the system presented was divided into two components—the fixation to the handle and the vertical element. This solution will allow greater versatility in future situations, since it will permit keeping the vertical component while only producing new fixing parts, according to the different geometries of existing handles. This is one of the differences from existing products manufactured as a single piece or, at least, without the possibility of adapting one of the parts to different diameters and geometries without manufacturing a new HFDO. Another differentiating factor is the incorporation of dynamics in a piece that, instead of fixing directly to the door, fixes to the existing handle, generating potential economic gains, since it will be possible to mitigate the transmission of the virus without having to replace the original handles on existing doors. From the beginning of this study, the working premise was to develop a product that could be CNC machined. This constraint, which determined the development of the project and its final result, namely the prototypes, is directly related to the technical capabilities of one of the partners promoting the project. This option influenced the production cost of the final system, as one of its present limitations, with all the mechanical components produced with CNC machining. However, other economic manufacturing processes can be considered for the implementation of the product on the market, for example, through casting moulds with subsequent finishing. This will be a work to be taken into account shortly, in the implementation phase of the device on the market.

5. Conclusions In the present work, an innovative device that allows for opening doors without using one’s hands was proposed. The system allows dynamic movement that provides higher comfort to the user when opening doors. This device was designed for various handle geometries, using an easy-to-clean material that enables its correct decontamination. The geometric aspects do not affect its hygiene and guarantee the design for intuitive use. They also ensure intensive use, mechanical resistance, stiffness, and fatigue resistance. This solution will also contribute to improving the accessibility of handles to individu- als with limited joint mobility of the hands (neurological patients, trauma sequelae, etc.) or those with occupied upper limbs who have various difficulties in opening doors. In the future, the team intends to develop a system connected to the handle, which would enable opening the door with a pedal. Designed in harmony with the characteristics of the already developed handle, it should form a homogeneous set. In addition, it is envisaged to create fasteners for different handle geometries, thereby extending the scope of application of this project.

Author Contributions: Conceptualization, V.M., P.M. and L.R.; methodology, P.M., L.R.; software, V.M., D.O., D.M. and J.F.C.; validation, V.M, L.M. and N.L.; writing—original draft preparation, P.M., V.M. and L.R.; writing—review and editing, V.M., L.M., N.L. and J.F.C. All authors have read and agreed to the published version of the manuscript. Funding: This work is co-financed by the European Regional Development Fund (ERDF), through the partnership agreement Portugal2020 - Regional Operation Program CENTRO2020, under the project Centro-01-02B7-FEDER-059035: COVID-Doors Openers. Designs 2021, 5, 56 21 of 21

Institutional Review Board Statement: The usability test study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of POLYTECHNIC OF COIMBRA (Reference No. 110_CEPC2/2020, 11 December 2020). Informed Consent Statement: Informed consent was obtained from all subjects involved in the study of usability. Data Availability Statement: Not applicable. Acknowledgments: This research is sponsored by national funds through FCT—Fundação para a Ciência e a Tecnologia, under the project UIDB/00285/2020. Conflicts of Interest: The authors declare no conflict of interest.

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