Applied Ergonomics 97 (2021) 103528

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Applied Ergonomics

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Review article The application of additive manufacturing / 3D printing in ergonomic aspects of product design: A systematic review

Tjaˇsa Kermavnar a, Alice Shannon b, Leonard W. O’Sullivan a,* a School of Design, Confirm Smart Manufacturing Centre and Health Research Institute, University of Limerick, Limerick, Ireland b School of Design, University of Limerick, Limerick, Ireland

ARTICLE INFO ABSTRACT

Keywords: Additive Manufacturing (AM) facilitates product personalization and iterative design, which makes it an ideal 3D printing technology for ergonomic product development. In this study, a systematic review was conducted of the liter­ Additive manufacturing ature regarding the use of AM in ergonomic-product design, and methodological aspects of the studies were Ergonomics analyzed. A literature search was performed using the keywords “3D print*,” “additive manufacturing,” “ergo­ Human factors nomic*” and “human factors”. Included were studies reporting the use of AM specificallyin ergonomic design of products/prototypes including the detailing of an ergonomic testing methodology used for evaluation. Forty studies were identified pertaining to the fields of medicine, assistive technology, wearable technology, hand tools, testing devices and others. The most commonly used technology was fused deposition modeling with polylactic acid, but the overall preferred material was acrylonitrile butadiene styrene. Various combinations of objective/subjective and qualitative/quantitative product evaluation methods were used. Based on the findings, recommendations were developed to facilitate the choice of most suitable AM technologies and materials for specific applications in ergonomics.

1. Introduction modifications based on user evaluations of prototypes. As user evalua­ tions should be performed on full-size physical prototypes of products Additive Manufacturing (AM), also known as three-dimensional and realized in near-final materials (McDonald et al., 2016), AM is an printing (3DP) technology, is used to build physical objects from digi­ ideal technology for product/prototype manufacture for ergonomic tal 3D-model data, i.e., Computer-Aided Design (CAD) files, by succes­ testing, in particular in relation to applications requiring bespoke fit to sive addition of material (ISO/ASTM 52900:2015). Initially AM was humans, and also in relation to iterative testing and redesign. mainly limited to manufacturing prototypes and was synonymous with CAD models for AM can be created using 3D-modeling software, but Rapid Prototyping (RP) (Carlstrom¨ and Wargsjo,¨ 2017), but it is being also through Reverse Engineering (RE) approaches using different progressively used for direct fabrication of end products and compo­ scanning techniques, e.g., 3D scanning, Computer Tomography (CT) nents, and as such also now known as Rapid Manufacturing (RM) scanning and Magnetic Resonance Imaging (MRI). RE is especially (Hopkinson et al., 2006). useful for the reproduction of organic shapes and objects based on in­ For ergonomic purposes, AM has been increasingly utilized across dividual anatomy (Carlstrom¨ and Wargsjo,¨ 2017), allowing for the diverse fields related to product/prototype design, including in medi­ design of highly personalized, custom-made ergonomic products. cine, development of assistive technologies (AT), wearable technologies Recently, advanced computer techniques such as automatic measure­ (WT), and physical human-machine interfaces (pHMI). The aim of er­ ment of anthropometric dimensions, skin deformation, posture change, gonomics is to inform the design of safe, comfortable and efficient virtual fittesting, prediction of contact pressure, or estimation of muscle products and tasks, based on the study of human characteristics and force have also been applied to 3D-scan data (Ballester et al.; Dai et al., human-machine/environment interactions (HFES, 2020). Thus, the 2011; Lee et al., 2018; Lei et al., 2012; Reed et al.). ergonomics-based development of products is typically an iterative By enabling users’ involvement in the design process, AM can facil­ “design-evaluation-redesign” process comprising several design itate enhanced User-Centered Design (UCD). Moreover, AM methods are

* Corresponding author. E-mail address: [email protected] (L.W. O’Sullivan). https://doi.org/10.1016/j.apergo.2021.103528 Received 9 June 2020; Received in revised form 24 May 2021; Accepted 1 July 2021 Available online 10 July 2021 0003-6870/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). T. Kermavnar et al. Applied Ergonomics 97 (2021) 103528 becoming increasingly available at affordable prices due to expiring 2. Method patents and increasing competition, open-source sites and cloud-based CAD software, which, together with user-friendly interfaces, enables 2.1. Literature search and study selection non-AM experts to create products easily (Jafri and Ali, 2015). Thus, the use of AM for custom, on-site production of individualized products is A systematic literature search was performed on May 6, 2020 using likely to extend to several areas in the future, assisting the progress of Scopus and EBSCOhost databases. To identify articles of interest, the ergonomic product design. following keywords were used: “3D print*” OR “additive The International Standard ISO/ASTM 52900:2015 classifies AM manufacturing,” AND “ergonomic*” OR “human factors” in the title OR technologies into seven categories: (1) Binder Jetting (BJ); (2) Directed the abstract. The search was limited to papers in the English language, Energy Deposition (DED); (3) Material Extrusion (ME); (4) Material and articles from trade publications and magazines were excluded. An Jetting (MJ); (5) Powder Bed Fusion (PBF); (6) Sheet Lamination (SL); additional search was performed on May 14, 2021 using the same da­ and (7) Vat Photopolymerization (VP). These processes are either tabases and keywords to update the review with studies published in liquid-, solid- or powder-based (Wong and Hernandez, 2012). The cat­ 2020 and 2021. Based on the abstract and full-text review, results not egories and sub-categories of AM processes are presented in Fig. 1. reporting on the use of AM specificallyin ergonomic design of products Factors affecting the choice of AM technology for specific applica­ or prototypes were excluded. In addition, it was required that the studies tions include cost, choice of material, post-processing requirements, specifically include the description of the ergonomics-testing method­ requirements of surface finish and dimensional accuracy, possibility of ology. Relevant studies referenced in the selected papers were also sterilization, fabrication speed (layer thickness per unit time), and res­ included. The search results and study selection criteria are presented in olution (minimum feature area and minimum layer thickness) Fig. 2. Two of the authors (T.K. and A.S.) conducted the study search and (Imˇsirovi´c and Kumnova, 2017; Lee et al., 2017). The most common AM selection based on the pre-agreed criteria outlined above. Both re­ processes and their applications are described in Table 1 according to viewers identified the same articles for inclusion. the currently available data. However, it is of note that specifications like maximum build volume, fabrication speed, and machine cost, as well as the materials available for use with the individual technologies 2.2. Data extraction and synthesis are changing with the development of AM. Recent developments have introduced 4D printing, an AM technol­ Data and details were extracted from the selected studies under the ogy that integrates smart materials that change their shape or physical following criteria: (1) field of application, product description, stage of properties in a useful manner under the influence of external stimuli. product development, and ergonomic problem addressed; (2) AM pro­ Examples include enhanced smart nanocomposites, shape memory al­ cedure description, from CAD-model acquisition to 3D printing and post- loys, shape memory polymers, actuators for soft robotics, self-evolving processing of the prototypes; (3) digital model analyses and/or testing of structures, anti-counterfeiting system, active origami, and controlled physical prototypes for ergonomics evaluation; and (4) findings and sequential folding (Khoo et al., 2015). commentary regarding AM technology use and the outcomes from an The aim of this work was to perform a systematic review of the ergonomics perspective. literature regarding the use of AM technologies in ergonomics studies related to product/prototype design and to develop recommendations 3. Results regarding the use of this technology and their materials in the context of ergonomic product design. 3.1. Product fields of application and problems addressed

Forty relevant papers were identified and analyzed. Regarding the fields of application, 11 products were in the field of medicine, more specifically, 7 in surgery (2 patient-specific surgical guides, 3 surgical instruments, 1 surgical robot, and 1 external fixator),1 in anesthesiology

Fig. 1. Classification of additive manufacturing technologies with bonding principles and typical materials used, based on standard ISO/ASTM 52900:2015, Imˇsirovi´c and Kumnova (2017), and Lee et al. (2017). BJ – Binder Jetting, CDLP – Continuous Digital Light Processing, DED – Direct Energy Deposition, DLP – Digital Light Processing, DMLS - Direct Metal Laser Sintering, DOD – Drop On Demand, EBAM – Electron Beam Additive Manufacturing, EBM – Electron Beam Melting, FFF – Fused Filament Fabrication, LENS – Laser Engineered Net Shaping, LOM – Laminated Object Manufacturing, ME – Material Extrusion, MJ – Material Jetting, MJF – Multi Jet Fusion, NPJ – Nanoparticle Jetting, PBF – Powder Bed Fusion, SL – Sheet Lamination, SLA – Stereolithography, SLM – Selective Laser Melting, SLS – Selective Laser Sintering, VP – Vat Photopolymerization.

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Table 1 Characteristics of most common AM processes (ordered alphabetically). Based on Imˇsirovi´c and Kumnova (2017), Lee et al. (2017), Low et al. (2017), Wong and Hernandez (2012), and the information provided on websites by 3Dnatives, 3DSourced, All3DP, AMFG, CompositesWorld, Dassault Syst`emes, Formlabs, Hubs, Sculpteo, and Thomas Publishing Company.

AM Process description Maximum Layer Resolution Fabrication Machine Machine Material examples Example technology build thickness (elements/ speed examples cost applications volume (μm) mm3) (mm/h) (Manufacturer) ($) (mm)

BJ Particles joined together by 4000 × 50–400 1900 12–36 Viridis3D 30,000 to Ceramic, metal, Industrial selective deposition of 2000 × (Voxeljet) >450,000 glass, sand, applications, liquid bonding agent on 1000 VX series polymer, silica sand, architectural thin layers of powdered (EnvisionTEC) stainless steel, models, material S-Print, M- ceramic beads, packaging, toys, Print, M-Flex chromite, zircon, figurines (ExOne) soda lime glass PartPro350 xBC (XYZprinting) DLP Photosensitive liquid 192 × 5–150 N/A 20–36 FabPro 1000 400 to Photopolymers: Highly-detailed polymer exposed to 120 × 230 (3D Systems) >250,000 ABS-like, prototypes, projections of light (mainly Typical B9 Core Series rigid PC-like, semi- jewelry, UV) emitted by a digital desktop: (B9Creations) flexible PE-like, sculptures, projector (image of the 58 × 32 × D4K Pro, durable PP-like dentistry, entire layer at once) 127 Perfactory P4K medical devices solidifies through series photopolymerization (EnvisionTEC) ProMaker L series (Prodways Tech) EBM Melting of powder particles 350 × 50–90 211 25 Q10Plus, >250,000 Steel, Al, Ti, Ni- Aircraft, using high-voltage electron 350 × 380 Q20Plus, alloys aerospace and laser beam, followed by Spectra H, A2X automotive recoater adding and (Arcam) industry, smoothing another powder military, motor layer sports, prosthetics FFF Thermoplastic material 2000 × 50–400 46 50–150 Extreme 1000 100 to ABS, ASA, PA, PC, Simple extrusion through a 2000 × PRO (Builder) >250,000 PC-ABS, prototypes, preheated nozzle, and 1500 DF2, DF3, DI1- PC-ISO, PEI, PLA, automotive, deposition in thin layers Typical 335 (DediBot) PMMA, PPSF, TPU, aerospace, that bind and fully solidify desktop: F120, F123 wood, carbon, medical and by cooling on the substrate 200 × Series, Fortus bronze other industries 200 × 200 family (Stratasys) PartPro300 xT (XYZprinting) MJ Droplets of photopolymer 1000 × 16–32 15,200 4–15 ProJet family 10,000 to Photopolymers: Realistic, deposited on working 800 × 500 (3D Systems) >250,000 ABS-like, functional platform are exposed to UV- Objet family rigid PC-like, semi- prototypes/end light and solidify through (Stratasys) flexible PE-like, products photopolymerization Polaris, Magnet- durable PP-like o-Jet, Ares (Vader) SLA Photosensitive liquid 2100 × 25–200 3152 7–36 ProX family (3D 400 to Photopolymers: Highly-detailed polymer exposed to laser 700 × 800 Systems) 500,000 ABS-like, prototypes, (mainly UV) or free radicals Typical Aria rigid PC-like, semi- jewelry, solidifies through desktop: (EnvisionTEC) flexible PE-like, sculptures, photopolymerization 145 × FORM family durable PP-like dentistry, 145 × 175 (Formlabs) medical devices ProMaker P1000 series (Prodways Tech) SLM Melting of powder particles 500 × 20–50 211 20–105 Formiga P110 >250,000 Steel, Al, Ti, Ni- Aircraft, using highly energized CO2- 280 × 360 Velocis, EOS P- alloys, PEEK aerospace and laser beam, followed by family (EOS) automotive recoater adding and DMP Dental industry, smoothing another powder family (3D jewelry, layer Systems) dentistry, SLM family medical devices (SLM Solutions) EP- family (Shining 3D) SLS Sintering of powder 700 × 60–150 211 7–68 Formiga P100, 10,000 to PA, PS, PEKK, Industrial 3D particles using highly 380 × 380 EOS M100 >250,000 acrylic styrene, printing of energized CO2-laser beam, (EOS) thermoplastic functional followed by recoater adding ProX SLS 6100 elastomers, prototypes and and smoothing another (3D Systems) reinforced polymers certain end powder layer Lisa (Sinterit) (continued on next page)

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Table 1 (continued )

AM Process description Maximum Layer Resolution Fabrication Machine Machine Material examples Example technology build thickness (elements/ speed examples cost applications volume (μm) mm3) (mm/h) (Manufacturer) ($) (mm)

EP-C5050 products, (Shining 3D) dentistry

ABS – Acrylonitrile Butadiene Styrene, Al – Aluminum, ASA – Acrylic Styrene Acrylonitrile, BJ – Binder Jetting, DLP – Digital Light Processing, EBM – Electron Beam Melting, FFF – Fused Filament Fabrication, MJ – Material Jetting, Ni-alloy – Nickel-based alloys, PA – Polyamide (Nylon), PC – Polycarbonate, PC-ABS – Polycarbonate- Acrylonitrile butadiene styrene blend, PC-ISO – Medical-grade Polycarbonate, PE – Polyethylene, PEI – Polyethylenimine, PEKK – Polyetherketoneketone, PLA – Polylactic acid, PMMA – Polymethyl Methacrylate, PPSF – Polyphenylsulfone, PS – Polystyrene, SLA – Stereolithography, SLM – Selective Laser Melting, SLS – Selective Laser Sintering, Ti – Titanium, TPU – Thermoplastic Polyurethane.

Fig. 2. Literature search results and study selection.

(a laryngoscope handle), 1 in oncology (an oral light applicator), 1 in causes discomfort and potential tissue damage; and 2. musculoskeletal neonatology (oxygen-therapy prong support), and 1 was a digital- disorders due to non-neutral joint positions or excessive muscle force stethoscope encapsulation. Eleven products were applied to the field resulting in discomfort, pain and early fatigue, especially of the upper of AT (2 prostheses, 1 orthosis, 5 exoskeleton components, 2 tactile limbs and neck. Other field-specificuses addressed: 3. cumbersome use displays for the visually impaired and 1 hearing aid), 3 to WT (head of tools due to their shape or dimensions that limit the view or freedom mount, earphones, and insoles), 6 to hand tools (1 electronic drawing of manipulation; 4. exposure of tissues to excessive pressure, vibration pen, 1 explosive ordnance disposal tool, 2 vibration tool handles, 1 saw or radiation; 5. highly skill-dependent accuracy and success rate of handle, and 1 vacuum tool), 4 to ergonomics-testing devices (foot shells medical procedures; and 6. high weight, difficultydonning and doffing, for pressure-sensitivity evaluation, a thermal manikin head, a trajectory- and poor aesthetics of wearable devices. tracing platform for augmented reality, physical components of virtual workspace for mixed reality), 1 arm support, 1 translational/rotatory control element, 1 device for mounting tissue sections, 1 bottle lid, and 1 3.2. Additive manufacturing procedures personalized parametric chair. In general, two main ergonomic problems were addressed: 1. poor 3.2.1. Digital models dimensional fitor kinematic incompatibility of wearable devices due to Digital models were generated directly with CAD software in 24 inter-individual body size, shape or biomechanical variability, that studies. The most commonly used software was SolidWorks (8), fol­ lowed by Rhinoceros (4) and Catia V5 (3). Eighteen studies did not

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Fig. 3. Types of AM processes used in studies reviewed. BJ – Binder Jetting, DED – Direct Energy Deposition, DMLS - Direct Metal Laser Sintering, EBM – Electron Beam Melting, FFF – Fused Filament Fabrication, LENS – Laser Engineered Net Shaping, LOM – Laminated Object Manufacturing, ME – Material Extrusion, MJ – Material Jetting, PBF – Powder Bed Fusion, SL – Sheet Lamination, SLA – Stereolithography, SLM – Selective Laser Melting, SLS – Selective Laser Sintering, VP – Vat Photopolymerization. specify the software used. 3.2.2. 3D printing and post-processing In 13 studies, digital models were acquired using scanning tech­ The most common AM technology in the reviewed studies was Fused niques. For 3 applications in the medical field, anatomical information Filament Fabrication – FFF (21), followed by Selective Laser Sintering – was obtained using CT scans, and for 10 applications, commercial 3D SLS (6), Material Jetting – MJ (3), Stereolithography – SLA (3), Binder scanners were used. With commercial surface scanners, body parts and Jetting – BJ (1) and Direct Metal Laser Sintering – DMLS (1) (Fig. 3). objects were scanned directly in 3 studies, and in the remaining 7, Twelve papers did not report on the technology used, while nine studies molds, casts and body-part impressions were scanned. In two instances, used more than one, combining different FFF machines; FFF with BJ, MRI/CT scans were obtained from existing databases, and five studies MJ, SLA and SLS; MJ with SLS; or SLS with SLA. In one study, prototypes did not specify the type of image-acquisition equipment. were printed using FFF, SLA and SLS separately for comparison. Most commonly used AM machines were the EOS Formiga P100 (4, SLS), Stratasys Objet family (3, MJ), Stratasys Dimension family (3, FFF),

Fig. 4. Materials used in the studies reviewed. ABS – Acrylonitrile Butadiene Styrene, BJ – Binder Jetting, DMLS - Direct Metal Laser Sintering, FFF – Fused Filament Fabrication, MJ – Material Jetting, N/A – information not provided, PA – Polyamide (Nylon), PLA – Polylactic acid, PPSF – Polyphenylsulfone, SLA – Stereolithography, SLS – Selective Laser Sintering, TPU – Thermoplastic Polyurethane.

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Table 2 Selected studies, the product details, AM procedure used and ergonomics aspects studied.

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

Medicine 1 CT Mimics 14.1 FFF Mentally-demanding and 1 Surgeon (surgical Evaluation of tumor Surgical jig for femur Magics RP Fortus 400mc potentially hazardous procedure on 1 resection accuracy, osteosarcoma version 14 (Stratasys) conventional navigation- cadaveric femur operative time resection PPSF guided osteotomy and 1 patient) measurement. (End product) BJ approach that requires Zprinter 310 simultaneous monitoring (Zcorporation) of virtual images on the Ceramics navigation display and manipulation of the oscillating saw in the operative field. Surgical jig with anatomically shaped cutting blocks matching bone surface at the defined resection level. Custom ceramic bone models for trial positioning of the jig prior to surgery. 2 CT N/A N/A Experience-dependent 10 experienced Simulated bone cutting Surgical guide for N/A conventional procedure surgeons + with pneumatic pelvic bone tumor (N/A) accuracy, mentally- 14 in-training oscillating saw on resection PA demanding continuous residents synthetic bone models: (Prototype for tracking and registration measurement of bone- ergonomic steps that cause errors and cutting accuracy and evaluation) are time-consuming. operative time. Patient-specific instrument for desired resection strategy. Bone-specific guide surface for easy positioning. 3 None Catia V5 R21 SLS Uncomfortable arm 6 novice clinicians Stapedotomy on a Disposable Cartesian Formiga P100 position, tremor, limited surgical phantom: Robot (EOS) view and manipulation evaluation of for stapedotomy PA2200 degrees of freedom. positioning accuracy (Prototype for Medical robot for and forces applied. ergonomic telemanipulation of evaluation) tissues. 4 COMET LED- Unigraphics DMLS Technology-related 15 neurosurgeons Fine microsuturing of Microforceps replica 2M NX 6 Eosint M270 differences in surface and sciatic nerve (Prototype for (Steinbichler) (EOS) mechanical properties anastomosis on white ergonomic Stainless Steel influencinguse between albino rat with original evaluation) PH1 original microsurgical instrument and 3D- instruments and their printed replica. additively-manufactured Subjective evaluation replicas. (3-point Likert-like Replica of microforceps scale) of texture, force for neurosurgery. applied, needle holding, specific use. Measurement of applied force for tip matching. Surface roughness analysis. Medicine 5 None SolidWorks SLS Reduced usability/ N/A Simulated inguinal (Cont.) Army-Navy retractor, HiQ performance of polymer 4 iterations hernia repair on human scalpel handle, (Sinterstation) replicas of metal cadavers: forceps, hemostats, DuraForm EX instruments that requires iterative improvement needle driver design modifications. of shape, dimensions, (Prototype for Surgeon-specific basic and strength of surgical ergonomic set of instruments. instruments according evaluation) to surgeon’s feedback. 6 None Autodesk FFF Skill-dependent success 40 medical Endotracheal Laryngoscope 123D Cubicon Single rate of endotracheal students intubation of airway support grip (HighVision) intubation; limited glottic manikin with (Prototype for TPU view. Macintosh (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

ergonomic Add-on ergonomic laryngoscope (blade evaluation) support grip. size 3) with/without the grip. Measurements: intubation time, number of intubation attempts, first- intubation attempt success rate, overall success rate, airway CL grade, peak force at tip of blade. 7 None Autodesk MJ Light delivery using 10 healthy subjects Applicators positioned Oral light applicator Fusion 360 Objet30 Pro inconvenient posts, + for 10 min: for photodynamic (Stratasys) holders, reflectors or light 5 patients Discomfort rating on 5- therapy VeroBlue pipes; need for patient point scale (physical (End product) VeroBlack sedation. discomfort, fatigue/ Anterior/posterior, numbness, possibility buccal and retromolar of immediately light applicators in repeating procedure). child, middle and adult 35 min of light delivery size for improved with breaks every 10 comfort, precision and min: stability of uniform light Treatment success delivery in conscious evaluation. subjects. 8 CT SolidWorks SLA Experience-dependent, 3 patients 20–25 weeks of Fracture external SPS600B complex manipulation of external fixator use: fixator (Shaanxi conventional external - fracture healing (End product) Hengtong fixators, patients’ and success monitoring. Intelligent surgeons’ excessive - clinician and patient Machine Co.) exposure to radiation, feedback at usability Resin patient dissatisfaction workshops: task with usability and analysis, observation, esthetics, leading to non- interviews. compliance. Patient-specific external fixator geometry based on computer simulation of fracture reduction for fixation-pin positioning. Personalized form and aesthetics. 9 None SolidWorks FFF Uncomfortable body and 80 surgeons CAD-model stress Laparoscopic forceps Objet Studio Dimension hand position, looking 2 iterations analysis. handle Catalyst EX uPrint into a monitor; discomfort Subjective evaluation (Prototype for (Stratasys) and pain in hand, wrist, (5-point scale): grip, ergonomic ABS Plus-P430 arm, neck, shoulder. functionality, comfort, evaluation) MJ Function-based wrist posture. Objet260 Connex modification of add-on (Stratasys) handle: pistol-type grip, ABS Plus-P430 increased hand-handle VeroWhite contact area, neutral TangoPlus wrist position. Handle size based on hand anthropometrics and grip strength measurements of 282 South Indian males: adjustment to minimum, maximum and mean hand size made possible by rubber inserts. 10 None N/A FFF Use error due to device 1 physician Usability testing: 10- Digital-stethoscope Prusa i3 features and use 6 iterations item system usability encapsulation with (BQ) environment. scale (6-point scale; 0 ECG-sensing PLA 4 models of device = totally disagree, 5 = capabilities TPU housing. totally agree) (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

(Early prototypes for Conductive, proof of concept and carbon based ergonomic composite evaluation) filament (diaphragm) Medicine 11 None SolidWorks FFF Pressure-induced necrosis 5 neonates Clinical observation of (Cont.) Patient-specificprong Ultimaker 2+ of nasal interior wall and 6 iterations necrosis occurrence. support to prevent (Ultimaker) perinasal tissues caused nasal necrosis caused coupled with by prongs/masks. by prongs/masks for Discov3ry Patient-specific prong oxygen therapy of paste extruder support to relieve premature infants Medical grade interface pressure. (Early prototypes for room- proof of concept, end temperature- product) vulcanizing silicone rubber Assistive 12 NDI Polaris Matlab SLS Micro-misalignments in 2 participants 8-kg weight placed on Technologies Exoskeleton forearm Vicra Formiga P100 wearable technology shell for 30 s: shell (Northern (EOS) caused by inter-subject Interface pressure (Early prototype for Digital N/A variability. measurement with proof of concept) Instruments) Individualized forearm Prescale LLLW film, shell based on limb Fujifilm geometry for enhanced fittingaccuracy and increased contact area to lower peak pressure. 13 None N/A Polychrome 3D Guiding efficacyof tactile 46 blind, 5 tasks simulating Tactile map printing maps with flat-relief blindfolded low reading tactile map at (Prototype for N/A symbols. vision and home to learn about a ergonomic (N/A) Tactile map with blindfolded new place. evaluation) N/A volumetric (3D) tactile sighted; Measurement of symbols. different levels of duration and experience with discrimination errors tangible graphics of tactile symbol locating. 14 None N/A FFF Manufacturing- 3 subjects with Measurement of Braille display Dimension Elite technology-dependent total vision loss, geometrical (Prototype for (Stratasys) readability of Braille able to read Braille dimensions and ergonomic ABS characters and comfort in printing defects. evaluation) FFF reading. Subjective evaluation Custom low-cost 4 versions of printed (5-point Likert scale) of 3D printer word “laboratory” in printed-word PLA Braille: readability, effort for - embossed paper; reading, tactile comfort - layered FFF with during reading. professional-level printer; - layered FFF with low- cost printer; - continuous-flow FFF with low-cost 3D printer. 15 None Matlab SLS Kinematic incompatibility 1 participant Motion capture of Exoskeleton elbow Catia Formiga P100 between the upper limb forearm movement joint (EOS) and exoskeleton; high relative to the upper (Early prototype for PA interaction forces, arm during elbow proof of concept) MJ pressure sores, inability to flexion-extension using Objet30 achieve long wearing an electromagnetic (Stratasys) times. tracking system; Endur Individualized Calculation of required exoskeleton elbow joint joint geometry; considering carrying Comparison of custom angle and soft tissue exoskeleton joint with movement. natural elbow motion and revolute joint. 16 None SolidWorks N/A Upper-limb function 1 healthy human Motion-capture: Upper limb soft N/A impairment in patients 4 patients post comparison of exoskeleton (N/A) with dyskinesia, and stroke exoskeleton and (Prototype for N/A limited ability to perform human movement (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

ergonomic activities of daily living. trajectories. evaluation) Soft bionic exoskeleton EMG: comparison of robot with 7 degrees of muscle force during freedom for assistance water-drinking motion with shoulder, elbow, with and without forearm and wrist device assistance. movement. Motion-assisted experiments on patients: - wrist and forearm rotation range; - lifting hand to mouth. Assistive 17 Plaster cast of Skanect FFF Spastic hand: progression 1 child/Cerebral Evaluation of orthosis Technologies Low-cost wrist-hand- upper limb 3ds Max 3DCloner of deformities, decreased Palsy (7-point scale): user, (Cont.) fingers orthosis – (EtechBrasil) functionality; extreme 2 therapists family, occupational (End product) 3D scan of cast PLA cases of size and therapists’ perception. Kinect 360 deformity; difficulty (Microsoft) donning, high weight, poor aesthetics of splints; user discomfort and number of visits to obtain orthosis. Personalized, lightweight orthosis based on limb geometry data. 18 Stump mold Customizer FFF Inability to perform daily 1 child amputee Anthropometric Transradial – Rhinoceros CubeX Duo activities, write, close 1 iteration measurements: mechanical 3D scan of mold Meshmixer (3D Systems) zippers/buttons. biceps circumference, prosthesis ATOS I 2M PLA User-specific forearm length, hand (End product) (GOM) FFF lightweight prosthesis; length. Sethi3D AiP easy attachment/ Picking up simple (Sethi3D) placement and objects, writing, TPU activation; comfortable closing zippers/ fit at the left limb; buttons using an simple hygiene; larger adapter. contact surface and increased friction at palm and fingers;thumb rotation; personalized aesthetics. 19 Cast of impaired N/A FFF Impaired functional range 5 children with Southampton Hand Adaptive device for hand Prusa MK2 of the hand, negative mild Assessment Procedure improving impaired – (Prusa Research) psychological effects due symbrachydactily test, adapted for hand function in mild 3D scan of cast N/A to adaptive-device-related children: comparing symbrachydactily N/A social rejection/stigma. the functional range of (End product) (Artec 3D) Assistive device for the impaired hand with impaired hand function the healthy, based on improvement, printed in time recordings. child’s favorite color. - Testing of impaired hand with and without the device. - 2–3 weeks of training program: 4 activities (rolling a dice to throw six, throwing a ball in a cup, placing dominos in a shape, eating with a fork) or playing any type of board game. - Testing of dominant hand and retesting of impaired hand with and without the device. 20 Ear canal and N/A FFF Size and shape-related fit 1 test subject 1-min wearing of each Anatomical hearing concha mold N/A and comfort of hearing prototype. aid with impression (N/A) aids. Subjective evaluation (Prototypes for silicone (®ABR) PLA 48 prototypes: (7-point Likert scale) of – SLA - full-shell/half-shell fit and comfort. (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

ergonomic 3D scan of mold N/A - with/without ear- evaluation) N/A (N/A) canal extension (RangeVision) ABS - 12 scaled sizes: SLS 70–125% N/A (N/A) PA 21 Motion capture N/A N/A Rigid back-support N/A Perceived discomfort Scissor-hinge with Vicon Vero N/A structures limit the range during lifting (3 mechanism for active 2.2 (N/A) of motion and only assist repetitions) wearing back-support N/A with very specific the device: rating of exoskeleton movements. discomfort at the neck, (Early prototype for Scissor-hinge upper back, lower proof of concept and mechanism for an active back, buttock (11-point ergonomic back-support scale; 0 = no evaluation) exoskeleton that adapts discomfort at all, 10 = to the user to assist with extreme discomfort) the complete set of postures assumed during back-loading tasks. Assistive 22 3D scan of right N/A N/A Fatigue, muscular effort, 4 healthy young Transmission stiffness Technologies Reinforced hand N/A localized interface males test; (Cont.) glove of a soft wrist (N/A) pressure peaks, and Transmission exosuit for flexion ABS comfort during static displacement test; assistance holding and lifting of Static holding 1.5-kg (Prototype for loads ≤ 3 kg. weight for 3 min, with ergonomic Highly-compliant forearm and hand evaluation) plastic glove aligned horizontally, reinforcement for with and without optimal actuator-to- exosuit assistance; ◦ wrist force transfer. 15 repetitions of 60 ◦ wrist flexion at 35 /s ◦ and 70 /s, holding 1.5- kg weight, with and without exosuit assistance. Measurement: EMG (m. flexor carpi radialis, m. flexorcarpi ulnaris, m. extensor carpi ulnaris, m. extensor digitorum) Wearable 23 None N/A FFF Arm fatigue and 15 participants 100 trials of testing of Technologies Head-mounted DaVinci 1.0 shoulder/neck discomfort accuracy and speed of display frame (XYZprinting) due to extended periods of task performance. (Prototype for N/A arm elevation and Subjective evaluation ergonomic downwards gaze. of interaction evaluation) Frame to angle head- experience. mounted display in 4 different angles downwards toward user’s hands. 24 Left ear Shinning FFF Improper fit of standard 6 test subjects Design verification by Earphones impression Version MostFun earphones. (usability testing) wearing printed (Prototypes for (ABR ear 1.7.1. (Chengdu Anthropometric earphone for 1 h with ergonomic impression Rhinoceros MostFun SandT measurements and no discomfort/pain, evaluation) silicone) 4.0 Co.) characteristic and while running/ – Matlab TPU anthropometric point skipping. 3D scan of ear coordinate impression identification on 310 Einscan-S young Chinese people. (Shining3D) Classification of shapes of auricular conchae into 24 groups and use as reference for earphone design. 25 None SolidWorks FFF Pain and discomfort at 23 production Preliminary testing: Insoles Fortus the feet during work. workers - Questionnaire of pain (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

(Prototype for (Stratasys) User-specific insoles for experienced at the foot: ergonomic ABS maximized insole-foot 5-point scale; figure: evaluation) contact area to reduce sole of the foot, divided and redistribute into five areas. pressure under the foot. - Measurement of pressure distribution and peak pressure at the foot during 10 m walk Testing with 3D- printed insole: - EMG of low-back and leg muscles during 5 h of working activity - Measurement of pressure distribution and peak pressure at the foot Hand Tools 26 None N/A N/A Personal preferences and 117 grade 3 and 4 Video-recording of Children’s electronic N/A usability of electronic elementary school students’ pen-holding drawing pen (N/A) drawing pens for children, students position and pen use. (Prototypes for N/A depending on pen shape Time recording of ergonomic and style. image-tracing test on evaluation) 3 prototypes of drawing paper. pens with circular, Subjective evaluation: quadrangular, and - Preliminary intuitive triangular cross-section. ranking of prototypes’ suitability for drawing with explanation. - Pen suitability re- evaluation after image- tracing test. 27 None N/A N/A Learnability, efficiency, 13 professional Post-use evaluation (7- Civil engineering N/A memorability, errors, and users point scale) of: explosive ordnance (N/A) satisfaction of tools/jigs 10 iterations effectiveness, disposal tools and jigs N/A for Air Force operations. (EODB), N/A efficiency, safety, (Prototype for An Explosive Ordnance iterations (ARB) utility, learnability and ergonomic Disposal Bracket and memorability of evaluation) Autonomous Robot devices. Brackets. Hand Tools 28 6 alginate SolidWorks N/A Musculoskeletal disorders 1 participant’s Subjects gripped the (Cont.) Vibration tool handle models of hand- N/A due to hand-arm hand impressions handle attached to an (Prototype for grip (N/A) vibration. 12 healthy males exciter (frequency ergonomic impressions ABS 6 anatomically-shaped tested range: 0–1000 Hz) with evaluation) – handles to reduce constant force: 3D scanning of vibration transmitted to - measurement of hand-grip the wrist. vibration transmitted impressions from handle to wrist; N/A - subjective evaluation of ease of holding the tool and vibration perception (Borg’s CR- 10 scale). 29 6 alginate SolidWorks N/A Musculoskeletal disorders 15 right-handed Preliminary Low-frequency models of hand- N/A due to hand-arm male anthropometric vibration tool handle grip (N/A) vibration. measurement: (Prototype for impressions ABS Anatomically shaped middle finger length, ergonomic – handle to minimize thumb length, grip evaluation) 3D scanning of gripping force and diameter. hand-grip increase contact area. Hand-arm vibration impressions measurement. N/A Subjective rating (7- point scale) of shape, fit, grip, performance, pressure on hand, numbness in fingers, cramped muscle. 30 None N/A FFF Comfort, efficiency and 5 participants Subjective evaluation Vacuum tool for N/A safety of a vacuum tool (3-point scale) after 10 (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

picking plastic bottles (FusedForm) for manual handling of bottles handled of: in recycling center N/A bottles. handle length, handle (Prototype for Tool for pick-place tasks diameter, tool weight, ergonomic that can be manipulated suction cup position, evaluation) by robot and/or activation button operator. position. Human-robot collaboration test. 31 None N/A FFF Material-related comfort 10 healthy young Subjective comfort Foxtail saw handle CR-10 S4 and performance of tool participants rating during a sawing (Prototype for (Creality) handles, uneven contact task (pushing and ergonomic TPU pressure distribution for pulling with relatively evaluation) (experimental) common handles. high grasping forces): PLA (control) 4 optimal-size handles: comfort-rating - 3 relative densities of questionnaire (8-point cellular TPU scale; 1 = totally metamaterial (6%, 10%, uncomfortable, 7 = 14%) totally comfortable). - 1 rigid PLA Ergonomics- 32 N/A Rhinoceros FFF Foot pressure sensitivity 7 scanned Pressure-induced Testing Foot shells for Ultimaker 2+ testing. 21 healthy tested discomfort threshold Devices pressure-sensitivity (Ultimaker) 6 experimental foot measurement at 20 evaluation PLA shells for pressure- points of the foot in 2 (End product) sensitivity testing: positions, using - 3 sizes: 37–39, 40–43, advanced force gauge 44-47 meter with cylindrical - 2 positions: foot flat, PLA indenter (10-mm toe-off (heel lifted 65 diameter, 3-mm fillet mm) radius). - 20 holes (diameter 11 mm) for indenter 33 100 MRI scans N/A N/A Headgear heat transfer / 60 min exposure of 3 Anthropometric from ICBM N/A testing. commercial helmet thermal manikin database (N/A) 3D model of 50th types to air flow in head for heat transfer N/A percentile biophydelic open-loop wind tunnel quantification of western head with with controlled air headgear heating elements, velocity, temperature, (End product) temperature sensors and relative humidity; surface openings for external heat source sweating simulation. simulation. Convective and radiative heat exchange measurement. 34 CT scans from N/A FFF Augmented-reality 10 subjects with Simulation of cutting Trajectory-tracing skull and Dimension Elite display testing. normal visual flat parts in an platform for acetabulum (Stratasys) Rectangular plate, and acuity industrial augmented reality datasets ABS replicas of a portion of manufacturing process, head-mounted skull and acetabulum and complex surgical display testing with 3 spherical incision tasks: (End product) markers; templates for - trajectory-tracing trajectory-accuracy accuracy and duration. testing. - user experience evaluation (5-point Likert scale). Ergonomics- 35 None N/A FFF Mixed-reality assessment N/A Simulation of assembly Testing Physical components N/A of industrial workstations. task (assembly of two Devices of virtual workplace (N/A) Real-size and weight components) and (Cont.) for mixed-reality N/A physical replicas of a mounting of assembled ergonomic groove and support, part at the welding assessment of manipulated by the station. industrial operator during In-silico ergonomic workstations simulation. analysis: lumbar (End product) loading, RULA. Miscellaneous 36 None Catia FFF Incorrect body posture 29 dentists (21 with 1 week of support use. Arm support for N/A leading to MSDs in high risk of MSDs) Subjective evaluation dentists (N/A) dentists. questionnaire. (Prototype for PLA Height-adjustable arm RULA (continued on next page)

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Table 2 (continued )

Field of Study # AM Procedure Ergonomics application Product Model Technology Study objective Ergonomics Testing (Development stage) Template/ Software AM process Ergonomic problem Participants/ Method/approach Scanning Printer addressed # Iterations (if method (Manufacturer) Product/prototype detailed) Material

ergonomic support attached to evaluation) dental unit. 37 None N/A FFF Interface shape 20 healthy students Preliminary test of 2 Adaptive N/A requirements for 3 iterations control-element shapes translational/ (N/A) precision/high-force using 3-finger and full- rotatory control ABS manual operation hand power grip: element SLS controls. - positioning accuracy (Prototypes for Formiga P100 N/A and speed ergonomic (EOS) measurement; evaluation, ABS - force/torque end product) transmission measurement. Grip force measurement during prototype use. Subjective comfort evaluation. 38 None Fusion 360 SLA Suboptimal efficiency of 2 professionals Comparison of tissue- Device for mounting Form 2 SLA conventional methods for N/A iterations section mounting time tissue sections (Formlabs) mounting tissue sections using the traditional (End product) white, onto slides. and new method. transparent resin Mechanized device for FFF mounting tissue sections I3 MK2S onto slides in buffer (Prusa Research) solution PLA 39 None N/A N/A Comfort and perceived 18 healthy females Opening a bottle with Bottle lid N/A exertion related to the the lid twisted with the (Prototypes for (N/A) shape of bottle lids.. maximum force of a ergonomic PLA 3 lid designs: healthy 20-year old evaluation) - 2 shapes (square, male. hexagonal) Subjective evaluation: - serrate texture - perceived exertion - concave areas for (Borg’s CR-10 scale) ; finger grip - User satisfaction (5- point scale, custom questionnaire); - Comfort (custom questionnaire); Grip-type analysis. Miscellaneous 40 Motion capture Grasshopper N/A Interpersonal differences 5 females, 5 males Interface-pressure (Cont.) Personalized using Kinect v2 Rhinoceros Robotic arm 3D in preferred sitting distribution (behavior-based) camera printer posture. measurement parametric chair Interface- (N/A) Chair design, based on Comfort evaluation: (Early prototype for pressure N/A participant’s posture interview proof of concept) measurement and interface pressure using pressure- distribution during sensing comfortable sitting. wearables and Stratasys Fortus (2, FFF). sterilization, component binding and addition of fixation and comfort Overall, the preferred AM material was Acrylonitrile Butadiene material. Styrene – ABS and variations of it (11). For FFF, Polylactic acid – PLA was most commonly used (9), followed by ABS (6), Thermoplastic 3.2.3. Advantages and disadvantages of AM technologies Polyurethane – TPU (5), and Polyphenylsulfone – PPSF (1). With SLS, Certain advantages and disadvantages of individual AM technologies Polyamide – PA was most common (3), but ABS and DuraForm EX were and materials were reported across the reviewed studies. Petropolis also employed. With MJ, versions of Vero material were favored (3), but et al. (2015) found that the most common combination of PLA and FFF also ABS Plus-P430 and Endur were used. ABS and an unspecified allows for printing of finer details when compared to ABS or Poly­ photosensitive resin were used in SLA, stainless steel in DMLS, and ce­ ethylene Terephthalate – PET. However, for products like bottle lids, the ramics in BJ. In twelve cases, the material was not specified. Materials hardness of PLA was found to negatively influence user experience used in the reviewed studies are summarized in Fig. 4. (Manzano-Hernandez et al., 2019). For FFF, Fu and Luximon (2020) Five studies reported on the prototype build time, which ranged from highlighted the roughness of the prototype surface and the influenceof 5 min for a Braille display (Loconsole et al., 2016), to 12 h for a pair of printing layer thickness on product size. Weiss et al. (2017) also reported insoles (Khadijah et al., 2018). The requirement for post-processing of difficultremoval of support structures. Loconsole et al. (2016) compared the printed objects was reported in six papers and consisted of physical layered and continuous-flow FFF when producing Braille writings and removal of support material and residue, surface finishing,cleaning and found that the former can only be used with 3D printers capable of finer

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Table 3 Advantages and disadvantages of common AM processes based on the reviewed studies and the previous guidance by Lee et al. (2017), Imˇsirovi´c and Kumnova (2017), Wong and Hernandez (2012), Carlstrom¨ and Wargsjo¨ (2017) and Guerin and Da Costa (2016). BJ – Binder Jetting, DMLS - Direct Metal Laser Sintering, EBM – Electron Beam Melting, FFF – Fused Filament Fabrication, LENS – Laser Engineered Net Shaping, LOM – Laminated Object Manufacturing, MJ – Material Jetting, SLA – Stereolithography, SLS – Selective Laser Sintering.

ADVANTAGES DISADVANTAGES

Short High Large Good Complex Good Wide range Printing of Printing Printing of Multi- Low Long Poor build resolution build dimensional geometry surface of materials polymers of metals composites material cost build resolution time volume accuracy finish printing time

BJ £ £ £ £ £ £ EBM £ £ £ £ £ FFF £ £ £ £ £ £ £ LENS £ £ £ £ LOM £ £ £ £ £ £ £ MJ £ £ £ £ £ £ £ SLA £ £ £ £ £ £ £ DLP £ £ £ £ £ £ DMLS £ £ £ £ £ SLS £ £ £ £ £ £ £

details, whereas the latter is necessary when using low-cost 3D printers. consisted of user feedback acquired through observation, interviews and SLS was found to offer production time short enough to allow for questionnaires. next-day prototype improvements, but requires additional curing of Objective ergonomics methods were used mainly for prototype- printed objects to avoid fluid absorption and staining due to porous functionality assessment and user-performance evaluation with and surfaces (George et al., 2017). Fu and Luximon (2020) noted the without the ergonomic intervention in simulated or actual settings. roughness of the SLS-printed object’s surface and PA powder falling off Analyzed were success rate, accuracy and speed of task performance; the surface. Hein et al. (2018) noted that PA prototypes were incapable overall posture and the position and functional range of body parts; of sustaining high forces at the joints of their exoskeleton design, and kinematic compatibility with natural body movement; applied force, George et al. (2017) found insufficient strength of DuraForm EX for force/torque transmission to body parts, pressure distribution and its direct adaptation to fully functional medical instruments. Other re­ effect on tissue viability; muscle activity; hand-arm vibration; and heat ported disadvantages of SLS include the anisotropic effects of build exchange. In one study where a thermal manikin was developed for orientation (Entsfellner et al., 2014; George et al., 2017), and insuffi­ ergonomics testing of headgear (Mukunthan et al., 2019), live partici­ cient resolution to ensure good form and fit of hinges (George et al., pants were not included. 2017). In eight studies, 1–10 iterations were made throughout product With DMLS, the texture of a stainless steel microforceps replica was development; in two instances, the number of iterations was not speci­ also rougher and the applied force requirement higher compared to the fied. Nine studies used 3–48 different prototype configurations original instrument, produced by subtractive manufacturing (Singh simultaneously. et al., 2016). Whereas SLA provided a smooth surface finish and was The reviewed studies are summarized and organized chronologically therefore found to be more suitable than FFF and SLS for hearing-aid according to fields of application in Table 2. prototypes (Fu and Luximon, 2020). MEDICINE: 1 – Wong et al. (2012), 2 – Cartiaux et al. (2014), 3 – Several advantages of AM-compatible digital 3D models were iden­ Entsfellner et al. (2014), 4 – Singh et al. (2016), 5 – George et al. (2017), tifiedin the reviewed studies as well. Firstly, CAD models can be easily 6 – Kim et al. (2018), 7 – Mallidi et al. (2019), 8 – Li et al. (2020), 9 – adapted to different users’ anthropometrics (Li et al., 2020) and Sreekanth et al. (2020), 10 – Baptista et al. (2020), 11 – Mirnia et al. different AM techniques/materials without additional costs (Entsfellner (2021); ASSISTIVE TECHNOLOGY: 12 – Reimer et al. (2014), 13 – Gual et al., 2014). Furthermore, the possibility of archiving and reusing in­ et al. (2015), 14 – Loconsole et al. (2016); 15 – Rosenmann et al. (2018), dividuals’ anatomical models and personalized devices can lower the 16 – Hein et al. (2018), 17 – Li et al. (2018), 18 – da Silva et al. (2019), cost and time involved in custom-device development (Rosenmann 19 – Haring et al. (2019), 20 – Fu and Luximon (2020), 21 – Roveda et al. et al., 2018). Finally, the shareability of digital models enhances the (2020), 22 – Chiaradia et al. (2020); WEARABLE TECHNOLOGY: 23 – reproducibility of scientific studies (Kim et al., 2018). Devine et al. (2017), 24 – Ji et al. (2018), 25 – Khadijah et al. (2018); HAND TOOLS: 26 – Chen and Cheng (2016), 27 – Shields et al. (2016), 28 – Tony et al. (2019), 29 – Tony and Alphin (2019), 30 – Hernandez 3.3. Ergonomic evaluation of the AM-generated products et al. (2020), 31 – Cupar et al. (2021); ERGONOMICS-TESTING DE­ VICES: 32 – Buso and Shitoot (2019), 33 – Mukunthan et al. (2019), 34 – Products and prototypes were evaluated using different combina­ Condino et al. (2020), 35 – Bruno et al. (2020); MISCELLANEOUS: 36 – tions of objective/subjective and qualitative/quantitative ergonomics Hallaj and Razi (2016), 37 – Weiss et al. (2017), 38 – Habbal et al. methods. Objective methods were used in 29 studies, of which 23 were (2019), 39 – Manzano-Hernandez et al. (2019), 40 – Zeng and Qiu quantitative and 6 qualitative; subjective methods were used in 26 (2021). ABS – Acrylonitrile Butadiene Styrene, BJ – Binder Jetting, DMLS - studies, 17 being quantitative and 10qualitative, one study used both. Direct Metal Laser Sintering, FFF – Fused Filament Fabrication, MJ – Ma­ Both objective and subjective methods were used in 15 studies. terial Jetting, N/A – information not provided, PA – Polyamide (Nylon), PLA Subjective ergonomics methods were based primarily on usability – Polylactic Acid, PPSF – Polyphenylsulfone, SLA – Stereolithography, SLS – testing of shape, fit,functionality, ease of use, physical dis-/comfort and Selective Laser Sintering, TPU – Thermoplastic Polyurethane. aesthetics evaluation, and overall user satisfaction assessment. For quantitative assessment, rating scales were employed in 17 studies: Likert or Likert-similar scales consisting of either 3, 5, 6, 7, 8 or 11 points (15), and Borg’s CR-10 scale (2). Subjective qualitative assessment

14 T. Kermavnar et al. Applied Ergonomics 97 (2021) 103528

DISADVANTAGES

Limited Limited part Poor Poor Anisotropic Residual Specific Support Post- Products Limited Health High build complexity surface strength of nature of internal atmosphere structures processing sensitive to range of hazard cost volume finish product product stresses required required required UV and materials during moisture printing £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £ £

4. Discussion For low-cost prototypes in the later stages of product development that need to more closely resemble the surface quality of the end Forty studies reporting the use of AM in ergonomic design of prod­ product, SLA or DLP can be used. However, these technologies typically ucts and prototypes were included in this systematic review. Most only allow for printing of single materials at a time, thus, post-print studies applied AM to the design of medical and assistive devices, with assembly is required for objects consisting of materials with different the remainder relating to the design of wearable non-assistive devices, properties (e.g., flexibleand rigid, or materials of different colors). This hand tools, ergonomics-testing devices, and other applications. The can be avoided with the use of MJ which enables multi-material print­ oldest study in the selected papers was published in 2012 and described ing, but at the price of increasing the prototype production cost. a patient-specificsurgical guide for bone tumor resection, printed using PPSF with FFF (Wong et al., 2012). In fact, in 2009, the patent for FFF 4.1.2. End products expired, followed by the patents for SLS in 2014 and SLA in 2014–2016, which led to a substantial increase in the accessibility and affordability 4.1.2.1. Medical devices. Medical devices for invasive procedures of AM, and a consequent rise in the number of applications and manu­ generally need to be biocompatible, sterilizable, and must maintain their factured parts (3ders.org; Popescu and Laptoiu, 2016). dimensional and mechanical properties after sterilization (Popescu and Recommended AM technologies and materials for the individual Laptoiu, 2016). It is important that they are impact-resistant and resis­ applications were identified based on the systematic review and are tant to breakage under mechanical stress. Surgical guides must be discussed below. The role of AM in product personalization and mass dimensionally accurate and rigid enough not to deform during use customization is also addressed, as well as the importance of usability (Popescu and Laptoiu, 2016; Ramakrishna et al., 2001), whereas sur­ testing and iterative design for the development of ergonomic products. gical instruments must also be fatigue-resistant, have good strength-to-weight ratio and good surface finish( Singh et al., 2016). In 4.1. Fields of application and corresponding AM technology and material many cases, medical devices must be biologically inert, and the possi­ choice bility of having complex geometric shapes is also desirable. The choice of material for surgical instruments depends on their In ergonomics, AM can either be used A) to produce mock-ups that function. Where material flexibility is required (e.g., forceps), printing aid in the initial ideation phase of product development, B) for iterative in medical-grade PA with SLS, or titanium-base alloys with SLM/DMLS/ prototyping to facilitate ergonomic assessment of various designs, or C) EBM produces detailed, fatigue-resistant instruments with a good for the production of end products, especially when highly-complex or strength-to-weight ratio. When high stiffness is required (e.g., needle user-specific objects are required. Each of these applications has its driver, retractor, scalpel handle), instruments can be printed using distinct requirements that influence the choice of AM process and ma­ medical-grade glass-filled PA with SLS, or stainless steel with SLM, terial. Some of the typical uses of AM, also identified among the DMLS or EBM. To produce plastic instruments with highly detailed reviewed studies are discussed below, and important considerations hinges, SLA is most appropriate. regarding the individual AM technologies and materials are detailed at Surgical guides are mainly constructed during preoperative plan­ the end of Discussion. ning; thus, long build time is not necessarily a limitation. Being based on gross anatomy, high resolution is not a strict requirement. Fatigue- 4.1.1. Early prototypes and iterative product development resistance of surgical guides is not of critical importance for many ap­ Low cost and short build time that allow for several quick iterations plications, as they are single-use. Therefore, high-quality but costly are often important requirements for early prototypes intended for surgical guides can be produced using medical-grade PA with SLS design conceptualization and ergonomics testing. Where there are no (Popescu and Laptoiu, 2016). Slightly more economical, highly detailed requirements for specific durability, strength or hardness, high resolu­ guides can be produced using medical-grade acrylate resins with SLA tion or heat-resistance of early models, FFF using ABS or PLA, or LOM (Popescu and Laptoiu, 2016); ABS- or PC-like resin can potentially also using paper or polymer film can be the technologies of choice. Addi­ be used. Guides printed using medical-grade ABS or PPSF with FFF have tionally, the option of a range of materials with various properties, the poorer mechanical properties and surface finish,but are produced faster possibility of multi-material printing, and large build volume of FFF can and at lower cost (Popescu and Laptoiu, 2016; Shi et al., 2007). be advantageous in creating low-fidelity models to simulate the inten­ ded mechanical properties of the designed product. 4.1.2.2. Assistive technologies. The primary requirements of prostheses,

15 T. Kermavnar et al. Applied Ergonomics 97 (2021) 103528 orthoses and exoskeletons are their ability to withstand high forces and preferences and operative techniques (George et al., 2017). Such cus­ repeated use, biocompatibility of parts in contact with skin, and good tomization and enhanced functionality of instruments could, in turn, strength-to-weight ratio. Resistance to disinfectant fluids can be make medical procedures easier, reduce operating time and improve the important as well, and in many cases the possibility of large build vol­ clinician’s comfort, as well as minimize procedure invasiveness, thereby umes, complex geometry, good surface finish,and accessible price of the optimizing clinical outcomes (Choi and Kim, 2015; Javaid and Haleem, end-product are also required. These conditions are best met by PA and 2018; Kumar et al., 2016). TPU printed with SLS, or titanium with SLM/DMLS/EBM where very With RE and AM, patients’ anatomy can be physically reproduced to high forces are present. Due to the anisotropic nature of printed objects, better understand the pathology and facilitate preoperative planning, FFF is only appropriate for non-load-bearing parts that are not exposed implant and bioartificial-tissue design, and medical education and to repetitive mechanical loading. training (Hoang et al., 2016; Javaid and Haleem, 2018; Popescu and Laptoiu, 2016; Rengier et al., 2010). The possibility of 4.1.2.3. Wearable technologies. The requirements of WT are similar to surgical-instrument development based on preoperative virtual resec­ those of AT, although not as high regarding product strength and tion planning allows for direct transfer of the planned procedure to the fatigue-resistance. Thus, various polymer materials can be printed using physical surgical field (Cartiaux et al., 2014; Wong et al., 2012). It can SLA or DLP for small objects that require high resolution and good also enable development of simple all-in-one solutions for bone resec­ surface finish, or the less expensive FFF for larger objects where poor tion and custom prosthesis reconstruction (Wong et al., 2012). resolution and surface finish do not represent a drawback. The more In general, the use of highly personalized objects based on in­ expensive MJ also offers high resolution and good surface finish. How­ dividuals’ anatomy can increase comfort (e.g., in tool handles, pros­ ever, products built by MJ, SLA, and DLP are susceptible to UV and theses and orthoses) and efficiency (e.g., positioning of patient-specific thermal degradation over time. Both, FFF and MJ support simultaneous surgical guide), but only for the person they are designed for. This can printing of different materials which is an advantage. Some SLA printers present a drawback especially in the case of handles, based on a single also allow for multi-material printing, but that is not typical for this individual’s anatomy, such as those described by Tony et al. (2019) and technology. Tony and Alphin (2019). In addition, when using RE, inaccuracies of digital models arising from scanning processes and the transfer to 4.1.2.4. Hand tools. Tool handles and pHMI need to be relatively strong Standard Tessellation Language (STL) need to be considered (Popescu and fatigue-resistant, and possibly resistant to disinfectant fluids, espe­ and Laptoiu, 2016). Moreover, lighting conditions and temperature cially when they are intended for public use. For pHMI, high-resolution, change may also result in changes in the scan data (Singh et al., 2016). complex-geometry printing can be required, whereas tool handles Geometrical data of the user’s body can be of limited value if obtained require good strength-to-weight ratio. For both, the possibility of multi- incorrectly, e.g., when product shapes based on scanned geometry do material printing and good surface finish can be advantageous. Thus, not consider tissue deformation that occurs at the contact of the body SLA and MJ of ABS-, PA-, PC- or PP-like materials meet the requirements with other objects (Reimer et al., 2014). Where the movement of the for highly detailed pHMI, and SLS of PA those of tool handles and scanner or the subject is present, medium resolution of scanning pro­ simpler, more robust pHMI. vides higher fitting accuracy than high resolution, due to high noise common with the latter (Reimer et al., 2014). 4.1.2.5. Devices for ergonomics testing. Ergonomics-testing devices often need to be highly durable to withstand repetitive use, but short pro­ 4.3. Usability testing and iterative design duction time and high resolution are usually not required. Thus, PA, and the more expensive PEEK, PEI, and TPU printed with SLS are a suitable Usability and measures for quality in use are described in ISO stan­ – choice for such products. When anisotropicity of the printed part is not a dards (ISO 9241 11:2018; ISO/IEC 25022:2016). According to ISO/IEC drawback, ABS, PC, or TPU can also be used with the more affordable 25022:2016, quality in use of a product can be measured by the effec­ FFF. When surface smoothness at the interface with the human body is tiveness (i.e., tasks completed, objectives achieved, errors in a task, tasks essential, postprocessing (e.g., sanding and polishing) should be with errors, and task error intensity), efficiency (i.e., task time, time considered, rather than the use of photopolymer-based technologies. efficiency, cost-effectiveness, productive time ratio, unnecessary ac­ The latter are appropriate mainly when mechanical loading of the tions, and fatigue) and satisfaction (i.e., overall satisfaction, satisfaction printed object is expected to be low, but high fidelity and/or material with features, discretionary usage, feature utilization, proportion of transparency are of key importance. users complaining, proportion of user complaints about a particular feature, user trust, user pleasure, and physical comfort) of intended users at achieving their goals. Of the 40 reviewed studies, two used 4.2. Product personalization subjective qualitative evaluation methods only, and nine only objective quantitative methods. In the former case, no quantifiable evaluation The possibility of quick, cost-effective fabrication and modification criteria were used that would enable comparison of competing designs of geometrically complex prototypes facilitates the integration of user in terms of effectiveness, efficiency or user satisfaction; whereas in the requirements and user testing in product development (Walker and latter case, user satisfaction with the product was not directly addressed. Maracaja, 2020). Thus, AM technology can advance ergonomics-based Due to the ease of CAD-model sharing that allows for good reproduc­ UCD of products by enabling users to participate in the development ibility of studies, measurable objective and subjective results would of highly personalized tools and devices, so that they are safe, allow for comparison among similar studies, which could, in turn, comfortable, efficient to use and aesthetically pleasing. This can help facilitate the development of effective ergonomic solutions. solve important problems, particularly in the AT and medical fields,e.g., Among the reviewed studies, only six employed iterative design non-use or abandonment of purchased assistive device (Phillips and modifications.In UCD and HF, iterative design based on usability testing Zhao, 1993), or the mismatch between personal preferences of surgical is essential, as it leads to measurable improvements between the first approaches and the possibilities offered by standard surgical in­ and last iterations (Bailey, 1993). Future studies employing AM in er­ struments. An example of the beneficial impact of user participation in gonomics could easily introduce multiple iterations in their design formal and aesthetic development of products is increased engagement process by choosing the appropriate AM process for early prototyping. of AT users in device use and therapeutic process (Rosenmann et al., 2018). Clinician involvement in medical instrument design could enable mass customization of surgical instruments according to personal

16 T. Kermavnar et al. Applied Ergonomics 97 (2021) 103528 ­

4.4. Important considerations regarding the choice of AM technology and al. Poly et £ £ £ £ £ £ £ materials SLS – Filament VeroWhite PEI £ £ £ £ Presently, several different AM technologies and materials are DMLS available, each with their own advantages and disadvantages which Fused – Honigmann £ £ £ £ SLA Ketone,

make them appropriate for some applications but not for others. Thus, Stratasys FFF – and £ £ £ £ £ the choice of technology should be made on a case-by-case basis to MJ ), S4 Ether adequately address the most critical requirements of the printed object , £ £ LOM 720 2018 (Redwood et al., 2017). It can be guided by cost and accessibility, ma­ Melting, terial choice, geometric accuracy, mechanical properties, durability, or RGD Polyether £ £ £ LENS Beam

surface-finish quality of parts, or by other factors. – Across the reviewed studies, FFF was by far the most commonly used £ £ £ £ £ £ £ £ £ £ FFF Fullcure AM technology, with PLA and ABS as the favored materials. ABS is PEEK Electron – £ £ £ commonly chosen due to its high strength, toughness and impact EBM PROCESS Jammalamadaka, -resistance, flexibility, durability (Al-Dulimi et al., 2021; Tan et al., resin, £ £ £ £ £ £ AM BJ Stratasys EBM and

2020), and temperature-resistance, whereas PLA is favored for its – PC-like biodegradability, accessibility, and price (Pham et al., 2018). It is, S3 £ £ £ £ High cost Tappa

however, important to acknowledge the poor surface finishquality with ( and Sintering, a distinct staircase effect typical for this technology, particularly when Sintering.

low-cost machines are used (Madden and Deshpande, 2015). Moreover, Material, Laser (2016), the printed objects tend to have low tensile and flexural strengths, and Laser resistant

their mechanical properties are largely influencedby build orientation, Dental Metal Costa Polycarbonate £ £ £ £ £ £ £ £ £ £ £ Heat (autoclavable)

infill and raster orientation (Madden and Deshpande, 2015; Shih et al., – Selective Da –

2017; Vlasceanu et al., 2018). Support structures are also required that Direct PC Stratasys and - –

can be difficultto remove in some cases. Thus, taking into consideration SLS

its favorable cost, build time, and CAD-to-prototype ease (Madden and S2 £ £ £ £ £ £ £ £ Good chemical resistance DMLS Guerin Deshpande, 2015), the most appropriate use of FFF in ergonomics is for (Nylon), early-prototype production. ), Material, Jetting, SLS was the second most used technology, and PA the favored ma­ 2017 £ £ Good surface finish Polyamide terial. PA is recognized particularly for its robustness (Tan et al., 2020) al., Stereolithography, – et – and flexibility.It is important to note that SLS is characterized by grainy Binder – surface finishwhich can be undesirable when the printed objects are in PA SLA BJ

contact with sensitive tissues, especially for longer periods of time (e.g., Bio-Compatible Bourell ( resin,

hearing aid), or when a certain amount of movement relative to the body , £ £ High dimensional accuracy surface is expected during use (e.g., prosthetic socket). The surface Jetting, Titanium; (2017) Stratasys

quality and resolution of SLS can also impair the movement of highly – ABS-like ratio – al. detailed parts relative to each other (e.g., in hinges). However, it can be Ti S1 Material and et

advantageous when friction at the interface with the body needs to be – £ £ £ £ Good strength-to- weight Lee Steel, resin, high to prevent displacement of the device (e.g., colorectal stent). MJ

Moreover, because powder-based technologies do not require additional Styrene £ £ £ £ Flexible

support structures, very complex parts can be produced using PP-like studies, Stainless

non-assembly printing. – and Butadiene

Apart from the smooth surface finish characteristic for SLA, its ac­ SSt Manufacturing,

curacy was also found to be slightly better than that of SLS in previous reviewed £ £ £ £ £ £ £ £ £ £ Impact resistant studies (Madden and Deshpande, 2015). However, SLS is more alloys, the to cost-effective and requires no support structures that would have to be Object on Polypropylene Acrylonitrile

removed after printing (Madden and Deshpande, 2015). Both, SLA and – – PP based £ £ £ £ SLS do not provide sufficientstrength of very small, thin parts (Madden Resistant scratching ABS and Deshpande, 2015), therefore, metal-based AM technologies (e.g., Laminated to – SLM, DMLS, EBM) should be considered for such applications. LOM Finally, a common drawback of the technologies based on photo­ materials Cobalt-Chrome-base £ £ £ £ £ £ £ £ £ £ £ £ £ Resistant breakage polymerization (i.e., DLP, MJ, SLA) is that they tend to produce brittle – AM objects that lose their mechanical strength with exposure to moisture Acrylonitrile, Polyphenylsulfone, Shaping, Co-Cr and sunlight (Redwood et al., 2017). Thus, when smooth surface is – Net Styrene £ £ £ £ £ £ £ £ £ £ £ Fatigue- resistant

required, as well as good mechanical properties, these technologies can common be used to produce molds for casting of the desired materials. This PPSF

approach is especially useful for the production of silicone objects (e.g., most Acid, Acrylic of – earbuds, epitheses), also because very few 3D-printable materials with Polyurethane, Engineered properties similar to silicone are currently approved for human use. ASA £ £ £ £ £ £ £ £ £ £ £ £ £ £ Biocompatible PROPERTIES Laser ).

To provide a quick reference, Tables 3 and 4 have been developed Polylactic – comparing important properties of the most commonly used AM tech­ – applications ASA ABS PA PC PEEK PEI PET PLA PPSF PP TPU Vero Co- Cr SSt Ti

nologies and materials respectively. Quantitative data for AM technol­ PLA Thermoplastic LENS and ogies is provided in the Introduction (Table 1). It is of note that material – Simplify3D ( properties vary depending on the AM technology (Wong and Hernandez, 4 TPU 2012). POLYMERS METALS Plus, Fabrication, Table Properties (2018) ethylenimine,

17 T. Kermavnar et al. Applied Ergonomics 97 (2021) 103528

4.5. Limitations electrocardiography signals: the SmartHeart case study. J. Med. Eng. Technol. 44, 153–161. Bourell, D., Kruth, J.P., Leu, M., Levy, G., Rosen, D., Beese, A.M., Clare, A., 2017. There may be other studies that fall outside the search and inclusion Materials for additive manufacturing. CIRP Ann. 66, 659–681. criteria of this systematic review. However, we would expect the key Bruno, F., Barbieri, L., Muzzupappa, M., 2020. A Mixed Reality system for the ergonomic – findings above to represent the current state regarding AM- technology assessment of industrial workstations. Int. J. Interact. Des. Manuf. 14, 805 812. Buso, A., Shitoot, N., 2019. Sensitivity of the foot in the flat and toe off positions. Appl. use in ergonomic product design. Ergon. 76, 57–63. Carlstrom,¨ M., Wargsjo,¨ H., 2017. Printing Prosthetics: designing an additive manufactured arm for developing countries. Dissertation. Retrieved from. http:// 5. Conclusions urn.kb.se. Cartiaux, O., Paul, L., Francq, B.G., Banse, X., Docquier, P.-L., 2014. Improved accuracy Our systematic search identified40 studies that reported on the use with 3D planning and patient-specific instruments during simulated pelvic bone of AM in ergonomic design of products and prototypes, the majority tumor surgery. Ann. Biomed. Eng. 42, 205. Chen, T.H., Cheng, P.J., 2016. Children’s intuitive and post use assessment of electronic from the fields of medical and assistive devices but also wearable de­ drawing pens made for children. In: Applied System Innovation - Proceedings of the vices, hand tools, ergonomics-testing devices and others. The most International Conference on Applied System Innovation, ICASI 2015, pp. 687–690. commonly used AM technologies and materials were FFF with PLA and Chiaradia, D., Tiseni, L., Xiloyannis, M., Solazzi, M., Masia, L., Frisoli, A., 2020. An assistive soft wrist exosuit for flexion movements with an ergonomic reinforced ABS, and SLS with PA. glove. Front. Robot. AI 7, 595862-595862. AM technology in combination with reverse engineering enables Choi, J.W., Kim, N., 2015. Clinical application of three-dimensional printing technology cost-effective manufacture of user-specific products regarding their in craniofacial plastic surgery. Arch. Plast. Surg. 42, 267. CompositesWorld, 2018. HP enters metal additive manufacturing with production- shape, size and aesthetics, among other attributes. The possibility of focused Binder Jetting machine. Retrieved 16 May 2021, from. https://www.compo quick fabrication and modificationof prototypes was found to facilitate sitesworld.com/articles/hp-enters-metal-additive-manufacturing-with-prod iterative design based on user feedback, although very few studies uction-focused-binder-jetting-machine. Condino, S., Fida, B., Carbone, M., Cercenelli, L., Badiali, G., Ferrari, V., Cutolo, F., 2020. exploited this approach. Usability testing employed various combina­ Wearable augmented reality platform for aiding complex 3D trajectory tracing. tions of objective/subjective and qualitative/quantitative evaluation Sensors 20, 1612. methods. Most commonly used were objective quantitative methods, Cupar, A., Kaljun, J., Dolˇsak, B., Harih, G., 2021. 3D printed deformable product handle material for improved ergonomics. Int. J. Ind. Ergon. 82, 103080. followed by subjective quantitative methods. The majority of studies da Silva, L.A., Medola, F.O., Rodrigues, O.V., Rodrigues, A.C.T., Sandnes, F.E., 2019. employed more than one type of evaluation method. Interdisciplinary-based Development of User-Friendly Customized 3D Printed Upper Some advantages and disadvantages of 3D-scanning techniques, in­ Limb Prosthesis. 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