Year 34 | Edition 1 | February 2016 Main article 3d printingoffunctionalstructures Lustrum edition To infinity Celebrating thepast,into thefuture, tabletable ofof contentscontents table of contents

Most people consider 3d printing as a crea- Tings have changed with the Vonk you are tive hobby. the TST group however see it as reading right now. To give an impression of Masthead a key technology for technological progress how we came to this new format, we made a Editorial in the medical world, robotics and even ae- trip to the press for you! Here we got infor- De Vonk ronatuics and astronautics! In this article a mation about the old fashioned and the di- Periodical of E.T.S.V. Scintilla. Publis- nice presentations of the almost endless po- gital version of printing and the new way of A new hed four a year in the amount Main Article 10 sibilities of 3d printing will be given. printing which made this Vonk the way it is. 33 On Location of 700 copies. 2016, the year afer the Scintilla Lus- trum, working on a Vonk with a perfect year 34, edition 1 new design: smaller and better. Whilst October 2015 writing this article, I sit next to one of Tis year is a lustrum year for Scintilla, and In this junction Mark Bentum, director my lovely committee members who is Editorial team not just any lustrum, but the 50th lustrum! of the study electrical engineering, talks swearing on the articles which refuse to Tim Broenink, Guus Frijters, Lynn In this Vonk we take a look at some acti- about his experience as a student, a tea- adjust to the new lay-out. Bruins, Mark van Holland, Jippe vities organized so far to celebrate this an- cher, and a director. He also talks about Rossen, Céline Steenge, Maarthen niversary, like the gala diner and the actual his home life and other interesting and But more about last year, and the plans Toonen, Nahuel Manterola. Dies. fun things to know. for this year. Last year a lot went on: I Lustrum 30 10 Junction studied, broke my ankle and studied Cover Artist less. I tried to give the frst a terri- Robert Fennis fc camp during the Kick-In, created my own type of Puck in the theatre show Print Midsummer Night’s Dream of - Gildeprint, Enschede Presidential Note Lustrum speare, and of course did a lot more. As Celebrating out past, into the future, you all know, the Scintilla-lustrum was Editorial office 3 30 to infnity also in 2015, which meant a lot of ac- E.T.S.V. Scintilla, University of Twente, tivities, with a lot of fun, laughter, and Postbus 217, 7500 AE Enschede, Education On location drinks. 0031 53 489 2810 0031 53 489 1068 Tree years into TOM What is this? it’s smaller [email protected] 6 33 Afer the Lustrum, December started. And we all know of December, the most Material News Junction expensive and stressful of the [email protected] year. Sinterklaas, Christmas, and new 8 News for the electrical engineer Mark Bentum 35 year. All fun activities, but all costly due to shopping, presents and timewise due All members of Scintilla receive De to the traveling. Vonk free of charge by post. Main article Solarteam 3D printing of functional structures Red One Go But what about 2016? First of all I Nothing in this magazine may be du- 10 39 would not want to break my ankle plicated or copied without explicit again, and I am not going to think of permission from the editorial team of Symposium Column all the stressful days in December at the De Vonk. . I am also not the person who Impressions of a feshman 21 41 makes all kind of new years resolutions, Te editorial team reserves the right to but for this editorial I will try to think change or exclude material provided Photopage Column of some things I would like to achieve or by third parties, in part or in whole. accomplish. On of the most important Te opinions expressed in the articles What next? things is getting some nice ECTS. Sadly, are not necessarily shared by the edi- 22 42 this has proven to give me some trouble. torial team. But who can blame me? I just like to do New Board Puuzle fun activities with friends. ISSN 0925-5421 year 34 year 34 4 Te 86th board edition5 1 edition 1 24 43 Guusje Greenteam Setting course for a victory in 2016 28 year 34 yearyear 34 34 5 4editionedition 1 1 edition 1 main article main article 3D printing of functional structures

Fig. 1: A few examples of 3D printed objects. (a) Te 3D printed car ‘Blade’ by Divergent Microfactories. (b) CAD drawing of a 3D printed hand exoskeleton for rehabilitation purposes [6]. (c) Rolls Royce uses 3D printing for engine parts [6]. (d) Stent like structure printed by stereophotolitho- graphy. Note the scale bar. [3]. (e) House printed by the Chinese company Yingchuang. (f ) CAD drawing of a 3D printed LED [7] Te technology colloquial known as ‘3D printing’ has developed materials can be found in [5]. Some printing most ofen the powder (aerospace industries, robotics, in such diversity in printing technologies and application felds examples of (to be) 3D printed objects not used in a print can be reused medical devices (surgery, prosthe- that meanwhile it seems anything is possible. However, clearly the are shown in Fig. 1(a)–1(f ). in the next. tics)) where tooling costs would ideal 3D Printer, with high resolution, multi-material capability, r Integration: functional and struc- forma major part of the total costs. fast printing, etc. is yet to be developed. Nevertheless, one can al- 3D printed objects tural parts may bemonolithically r Crowd-sourced brainpower, since ready start to wonder what possibilities for electrical engineering integrated. AM is based on digital designs everywhere. Really? r Metamaterials: like with chemis- they are easy to distribute and applications will become available in the near future. Here I try to try and nanotechnology 3D (mul- share and therefore one can bene- give a brief and balanced overview of current developments and a 3D object, not withstanding gravity and With so much press coverage 3D prin- ti-material ) printing may enable ft from a large intellectual efort few examples of the frst small steps towards 3D printed transdu- other deal-breakers [1]. Te amounts ting is hot, and likely overhyped. So we new meso-scale material proper- (compare open source sofware). cers. of material added are tiny with respect could safely put it aside and concentrate ties. Tink of pseudo piezoelectric Also benchmarking materials, pro- to the overall scale of the object to be on other things, e.g. what to do during materials, negative poison ratio cesses and equipment is relatively made, but in absolute terms this may the European soccer championship this materials, anisotropic thermal straight forward. Introduction mean something completely diferent summer, how to found the next inter- conducting materials, host loa- r On the fy quality control using ca- form. For example by jetting small clods when e.g. talking about 3D printed net blockbuster company, etc. But this ded printable materials (e.g. with mera’s or other near-feld-metrolo- of material, by solidifying particles by a concrete houses [2] or about the sub- would be beside the reality as much as quantumdots [7]), etc. gy produced parts can be directly By now, anyone that has some interest in highly focussed laser beam, by excreting micron voxels solidifed by two-photon assuming that everything will be printed r Mass customisation: objects can compared to the geometrical de- how things are made, and who has not a long, thin wire and dressing it nicely in stereo-photolithography in a Nanoscri- in the near future. Let us look at some of be customised on a per device ba- sign specs. Material faults can be been hibernating in his cave, will have place, much like a glorifed glue pistol, be 3D printer [3]. the bare characteristics of 3D printing: sis, just by design (e.g. 5 diferent monitored. Performance testing, heard something about 3D printing, or by using thin sheets ofmaterial (e.g. sensors for 5 diferent robotic fn- of course mostly, requires of-line or more posh ‘AdditiveManufacturing’. paper), cutting them in the right shape Te technology behind 3D printing can r Enabling: things which can’t be gers...) approaches. Actually, the latter is quite des- and putting them on top of each other be classifed in 7 main fabrication-types made by any other method, becau- r Adding value: think of smart pac- criptive, especially when put opposite (much like the 3D post-cards that keep [4], each with numerous members dif- se of their inherent 3D nature or kagingwith integrated functiona- Sure enough the above may sound much ‘Subtractive Manufacturing’. Bluntly youngsters busy for the better while of a fering somewhat from manufacturer to the range of materials that can be lity (sensing, stress-release, over- like preaching to the choir. And indeed, put, many classical fabrication methods birthday party). manufacturer (if not for a diference in used seamlessly, may in principle pressure protection, etc. of Si dies, while the above is true in principle, ac- are characterised by removing material quality, then at least to circumvent in- be made by 3D printing [1]. or other components, inside) tual practical fabrication can be hampe- from a given chunk of material, e.g. by What all 3D printingmethods have in tellectual property rights). With each r Limited use of materials: In 3D r Prototyping can be extremely fast. red by: milling, eroding, abrading, grinding, common is that structures are built layer of the 7 methods comes a range of prin- printing you only need material r Fabrication can be speeded up since etc. In additive manufacturing, on the by layer froma digital description of the table materials, minimum feature sizes, to add to the object and virtually no tooling is required. Tis is espe- r Lack of resolution. Although vari- other hand, parts get shaped by adding object. It can be shown mathematically physical properties, etc. A brief over- there is no waste, like e.g. with mil- cially valuable for industries that ous printing methods can deliver tiny amounts of material to a developing that such a method can built any kind of view of these methods and printable ling. Even in powder-bed based operate on small series markets print resolutions from sub-micron

1: Not withstanding the z-weakness, some companies claim really large strengths and even replace metal part by printed carbon fber year 34 and Kevlar [8]. year 34 11 10 edition 1 edition 1 main article main article

Ok, so 3D printing may not be the holy grail, but it certainly has produced some imaginative products and solutions. Let us have a look at some of the developing application felds. Medical

In the feld of medical applications 3D printing has been shown to deliver very attractive solutions for problems that Fig. 3: Lef: 3D printed robotic hand, fom [15]. Right: 3D printed ‘RoBird’ fom Clear Flight Solutions require ultimate customisation: pros- thetics. Tere are plenty of examples technology would also be interesting for nautics ‘Rutherford’ rocket engines that contain of fngers, hands [9], lower and up- robotic applications. mostly 3D EBM printed metal parts, per limbs that have been printed to be Until recently mostly plastic printed amongst them the most essential ones. functional, aesthetic and well ftting the Robotics parts, for non fight essential purposes, body. Also, some of the artifcial hip and found their way into airplanes. Tink The 3D printing hype knee replacements are nowadays 3D of parts around the windows, seats, etc. printed. Dental applications form ano- In robotics 3D printing has been adop- Te main advantage here is the high Fig. 2: (a) Afordable desktop 3D FDM printer. (b) Professional 3D FDM printer. ther important feld where 3D printing ted quite well, especially in research en- strength to weight ratio that can be So, overrated expectations on the one to millimeter size, none have both from a source and need forms a cost vironments; just have a look at all things obtained by freeform structures. Metal hand and some tangible demonstration a high resolution and a large build to be removed aferwards. Tis efective alternative to hand made arti- printed in the Robotics And Mechatro- printing processes increasingly help to of 3D printing possibilities on the other volume. Limited resolution also removal may pose its own limita- fcial tooth for example. Te use of 3D nics group of our own EE faculty! Te move 3D printing into fight essential hand seem to strive for equal attention. may result in large surface rough- tions to the printed object. printing technology for the fabrication technology is interesting since it allows parts. Rolls-Royce has developed the Gartner tried to make some sense out of ness, excluding specifc applicati- r Lack of reproducibility. Many of of mock-ups of body parts to allow sur- for a sufcient large materials selection XWB-97 engine with some large tita- all of this by projecting the technology ons. the more afordable 3D printers geons to visualise, prepare and train for for the envisioned purposes, for the free nium parts printed by electron beam against a maturity model [17]. In this r Lack of printable materials. Not all and used materials have limited operations is yet another example.Me- formfabrication of structures, some of melting (EBM). Te part measures no model some applications of 3D prin- materials can be printed, limiting environmental control leading anwhile some of these applications ha- which cannot be made otherwise (at less than 1.5 m diameter times 0.5 m ting are still well before the ‘expectati- the range of what can be made to limited reproducibility of the vematured quite signifcantly and lead least without assembly) and delivers thickness! New Zealand based Rocket- ons peak’ of the hype, to which I hap- for specifc purposes (other than printed parts. Good reproducibi- to large economic activities. E.g. have a results with very short lead-times. On Lab has developed the ‘Electron’ and pily dedicate the printed transducers of the bling-bling and smart-phone lity is generally only obtained by look a the medical page of the website the transductive side, integration of sen- covers). far more expensive professional of the Belgian additive manufacturing sors starts to be addressed increasingly, r Mechanical properties. Te me- machines. service Materialise [10]. where medical and robotic applications chanical properties of most prin- r High per part cost. 3D printing is More scientifcally driven, 3D printing sometimes almost merge. I.e. an or- ted objects showlarge anisotropy mostly competitive for single or is investigated as a means to print hu- thosis (exoskeleton) to assist in patient as the layer by layer deposition small series products. Te advan- man tissues [11] or scafolds on which movements may come close to a robotic basically introduces structured tage is that no tooling is required natural tissues can grow optimally. part as far as function and hardware is inhomogeneities and associated and lead times can be extremely Tink of veins, cartilage, etc. And by ex- concerned, though the required control variations in virtually every physi- short. Te disadvantage that the tension of the concept of tissue printing may difer signifcantly. cal property of the material. Note- needed to print a product one also fndswork on printing of entire Particularly interesting from a design worthy is the problem of reduced is relatively long, certainly com- organs [12,13]. point of view is that 3D printing al- strength in the z-direction, i.e. the pared to techniques like moul- A Stanford group lead by Zhenan Bao lows for a strong degree of biomimetic direction perpendicular to the ding, spray-casting, punching, [14] has developed artifcial skin in the design. Now, not only can principles layers, due to limited adhesion etc.,making 3D printing less suit- form of thin layers with printed elec- from nature be used in robotic designs, between the consecutive layers. 1 able for large series products. trodes and organic transistors which but even the used shapes can be virtually r Need for support structures. Alt- r High energy consumption. Te transduce pressure signals into fre- recreated. Te ‘RoBird’, developed by hough any object can be 3D technology has much to ofer but quency modulated digital pulses. It was Clear Flight Solutions, is a nice example printed in principle, gravity may this comes at a price of using (far) subsequently shown in vitro that these of the latter. require additional internal and/ more energy than for regular fa- pulses could optically stimulate optoge- or external supports. Tese need brication, for example moulding. netically engineered mouse somatosen- Aeronautics & astro- Fig. 4: Lef: 3D printed bearing housing of a Rolls-Royce XWB-97 engine [6]. Right: the ‘Ru- to be co-printed with the object sory neurons. Obviously, the developed therford’ rocket engine developed by Rocketlab [16].

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Over the last two computing pic they have drafed a roadmap [18] in and communication has seen an incre- order to assess the future needs for sen- dible development. With the internet sor as well as to address their fabrication. in the palm of our hands it is hard to Interestingly, the resulting matrix shows believe that it is only 15 years back that 3D printing to be thought capable of Google was founded! And sure enough fabricating sensors for all applications. many more developments are still So this poses the question: ‘how will ahead of us. High expectations about 3Dprinting become a viable technologi- the future connectedworld have been cal platform for transducers?’. condensed in catchy phrases like Te internet of things or even Te internet A technology preceding 3D printing is, of everything, Industry 4.0 and Real of course, 2D printing. Although this computing2. What all these concepts is an entire subject of its own, it is inte- have in common is that they heavily rely resting to see howmuch meanwhile has on a variety of sensors to obtain infor- become possible with printed electron mation from the environment, machi- ics. Probably one of the most imagina- nery, humans, engines, etc. Tis has led tive examples is the work by TNO. Tey Fig. 7: (a) An 8 bit electronic digital processor a consortium of people engaged in sen- have demonstrated an 8 bit electronic with printed-programmable memory by TNO. (b) A quadcopter with included electri- sor research and development to think digital processor based on organic tran- cal wiring printed by a Voxel8 printer. about the future of sensor fabrication. sistors with inkjet print-programmable Considering the age of abundance3 they memory [19]. this article as well, whereas others have predict that somewhere between 2020 reached a more stable expectation pla- and a few years later the number of sen- Obviously, 3D printing of electrical and Fig. 5: Maturity model in the analysis of the 3D printing market according to tech research company Gartner [17]. teau. In the report Gartner emphasi- sors employed in our smartphones, cars, electronic structures is nowhere near ses the scale and speed by which 3D utility devices, environmental sensor as developed as to where silicon tech- TApps 9. Smart energy generation generation control energyand Smart 9. monitoring health Minimally invasive 4. printing is being introduced in the networks, medical equipment, etc. will nology or even printed circuit board 10. Digital manufacturing, 3D 3D printing Digital manufacturing, 10. TSensors Roadmap medical world, leading to (too) high exceed accumulatively a trillion sensors. technology is nowadays. However, there Precision aquacultureagriculture and 3. Noninvasive health Noninvasive monitoring 3.

DNA/Genome/RNA/Protein based DNA/Genome/RNA/Protein expectation, but also stresses that the Hence they have aptly called themselves is a, for those anticipating, slow, but cer- . Education:sensorsandIoE 2. fabrication of customised hearing aids the Trillion Sensors Roadmap group. tain development of technologies for a Environmentalsensing 7a. 7b. Infrastructure Infrastructure sensors 7b. Quality, pollution, freshnesspollution,Quality, Harsh Harsh sensorsenvironment 8. Smart foodproduction Smart 8. Home Home energy management disease Chronic monitoring diseaseChronic monitoring Autonomy brain fordrones Autonomy brain

Autonomy brain forrobotsAutonomy brain and dental products by 3D printing Organising various summits on the to- the printing of electrically conductive Bridges,roads, buildings Biometric Biometric authentication Petrochemical pollution Petrochemical Planthealth monitoring 6. Computer Computer senses 6. 5. Personal Personal imaging 5. has already frmly settled. Knee and hip Explosivesdetection Agricultural pollution Digestible pill basedpillDigestible Water management Water Smart Smart grid sensors Smart City sensing Body fluid analysis fluidBody Radiation pollution replacements are expected to become Table 1: Overview of resistivities of some conductive (print) materials Body fluid basedfluidBody Livestock Livestock health Assets Assets tracking ae pollution Water Emotion based Contact-based

Breath-based mainstream playground for 3D prin- Voice-based Non-contact Air pollution ting due to positive trials and the scale Touch Vision Taste Smell of the market. For a variety of applica- Sensor Technology Feel tions the graph indicates the current Platforms maturity with respect to 3D printing Spectrometer opportunities. Clearly, some are ahead Gas chromatograph Chemical sensors of the curve andmay be overhyped, but Lab-on-Chip others have become mainstream in their Lab-on-CMOS Paper Microfluidics respective markets. Disposable cameras Acoustic imaging Hyperspectral imaging Thermal imaging Printed electronics Ultrasound imaging Xray imaging and transducers THz imaging Radiation sensors Brainwave sensors The internet of everything 3D printed sensors 3D printed ICs & 3D printing Graphene sensors High temperature sensors 2: Meaning that whatever we have in the shape of digital designs in our computer can take on real shape using digital fabrication methods like ad- Fig. 6: Te sensor needs versus fabrication technologies matrix as produced by the Trillion Sensor Roadmap group, fom [18]. Yellow marking by the ditive manufacturing, CNC, etc. author. 3: Abundance is the termto denote that fabrication of products will become increasingly cost-efective, productivity growing faster than the world populations demand such that all products will become in reach of each person on the planet.

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6000 electrodes. Tis implies that actuation is Water of the ions in the moving fuid in com- going to be hampered. However, sensing Acetone bination with manually assembled mag- generally requires far less power and 5000 Potassium Hydroxide nets. Te sensor is made out of two 3D Ethanol therefore is still possible. Comparing printed parts which, when put together,

the diferent solutions for electrically 4000 form a channel and which allow for easy conductive printing we can observe that mounting of the permanent magnets the range of conductivities is large. and electrodes to measure the fow in- 3000 duced potential diference. Experiments Clearly standing out is, of course, cop- indeed showan acceleration dependent per. Reason for theMacDonalds group Material loss (mg) 2000 output voltage.However,we fnd strong of the University of El Paso to concen- contributions from other than electro-

trate on a diferent approach. In their 1000 magnetic sources which, due to their na- 3D printed electronics work they use ture and magnitude, are interesting for Fig. 8: Various phases in the 3D printing of a motor. Afer each phase some parts are embedded robots to lay down tracks of copper further research. (fom [29]) 0 by a robot in a stop-and-go process 0 0.5 1 1.5 2 2.5 3 Time (s) 4 materials. Some are based on doping of devised a process in which they use sa- [27,28]. Tis way it is even possible to x 10 Printing of intricate structu- well-known print materials like polylac- crifcial material, i.e. they print with 3D print motors [29], cube sats, elec- tic acid (PLA, an organic environment (at least) two materials, one of which tronic dice, etc., admittedly using some res friendly and bio-degradable material) is non-destructively and selectively assembly as well. In an another project we have investi- or acrylonitrile butadiene styrene (ABS, soluble afer printing [21]. Once the gated the 3D printing material jetting- the stuf that Lego bricks are made sacrifcial material is dissolved they im- 3D printed transducers process for the fabrication of intricate from). Other manufacturers design and pregnate the resulting channels with sil- structures [31]. Normally, any required market printers and materials that are ver particle based ink and let it solidify. In the Transducers Science & Techno- support material is removed by brute specifcally meant to print conductive Tey show that it is possible to use this logy group we conduct research on 3D force water jetting. We investigated the inks, mostly based on silver particles. technology to make LC-tank oscillator printed sensors. Te idea is that to start chemical dissolution of Fullcure 705 z x E.g. Voxel8 [20] is such a start up. In type sensors for measurement of the die- making sensors one only needs the capa- 1 mm support material their commercial material they show lectric constant of dairy products. bility to print structural, dielectric and while minimally afecting Fullcure 720 how a quadcopter is made by a stop- conductive materials. By allowing struc- 800 structural material. From several sol- and-go print process, i.e. the printing is In printing of electrically functional tures to be deformable a transductive vents ethanol turned out to be the best 700 stopped various times to embed electro- structures one of the important points operation is obtained. Tis way one can with respect to selectivity and dissoluti- nic components but the electrical wiring is the conductivity of the electrodes, easily envision e.g. piezoresistive, capaci- 600 on speed. We found that the dissolution is by 3D printing of silver ink. see table 1. Obviously, low conductivity tive, magnetic and other sensors. process can be theoretically accurately does not allow for high current densi- 500 described by the Noyes-Whitney equa- Recently researchers from Berkeley have ties since Joule heating will destroy the tion, implying that the development of 400 various structures can be predicted quite well. Te fabrication process was used 300 to make various 5 mm diameter mem-

200 branes, ranging in thickness from 112 Membrane defection to 768 μm and their mechanical perfor- 100 Plate defection mance was characterised, see Fig 10(c). Measurement Data Te theoretical shapes for membrane 0 0.5 1 1.5 2 2.5 3 3.5 (blue) and plate (green) behaviour are Fig.10: (a)Material loss for Fullcure 705 support material forWater, Acetone, PotassiumHy- compared with the shape of the realised droxideand Ethanol. Te dissolution process can be described using the Noyes-Whitney equation membrane that was pressurised by 300 [32]. (b)Cross-section of a 112 &mmembrane under optical microscope afer gold deposition and mbar (red dots). Clearly the structure slicing. (c) Measured membrane shape under a uniform load of 300mbar (red dots). Angular acceleration sen- behaves like a membrane. and fsh [30]. Te sensor consist of a sor fuid flled circular channel. When ex- 2D force sensor In the MSc. work of Joël van Tiem we posed to angular accelerations the fuid have investigated a biomimetic angular fows relative to the channel. Read-out For robotics and rehabilitation purpo- acceleration sensor inspired by the ves- is based on electromagnetic fowsensing ses, the sensing of interaction forces, tor- Fig. 9: (a)Design of the two separately 3D printed parts that formthe sensor (lef) and the assembled sensor (right). (b) Voltage as a function of angular acceleration. tibular system, as found e.g. in mammals using the pseudoHall efect by means ques and pressures on sof materials that

year 34 year 34 17 16 edition 1 edition 1 main article main article

C /C versus number of wires tot ref 1.5 C /C tot pp C /C tot ww

1 ref /C tot C

0.5

0 1 2 3 4 5 6 7 8 9 10 # of wires

Fig. 11: (a) CAD rendering of a proposed Normalforce 3D printed 2-DOF force sensing system. (b) Normalised capacitance versus number of Fig. 12: (a) Te frst transistor, invented in 1947. (b) A printed, bulky capacitive sensor, 2015. Shearforce wires for a structure of 10mm x 10mm size, materials. Understanding, model- a gap of 2mm and a wire diameter of 1mm. ling & application of the various the free-formcapabilities to make DOI: 10.1109/BIBE.2013.6701672 (c) Fabricated prototype sensor parts using AM technologies for transducers new, exciting transducers, charac- NinjaFlex FDM material and a MakerBot [2] TU Eindhoven starts using king- research. terise them, etc. Replicator 2 3D printer. size 3-D concrete printer: http://phys. r Single material printing: Form- r Systems integration and applica- org/news/2015-10-tu-eindhoven-king- fdelity, adhesion, anisotropy, ma- tion: Of course, one of the promi- size-3d-concrete.html sity. Initial results show a sofer material terials properties, small structures ses of 3D printed transducer is to such as NinjaFlex (Fig. 11(c)) may prove (e.g. membranes), etc. need to be embed them in other structures, [3] Nanoscribe, information retrieved- to be the most compatible with this sen- understood, modelled and opti- RoBirdwings, robotic hands, hand March 2015: http://www.nanoscribe. sing system. mised protheses, etc. where they will be de/en/technology/additive-manufactu- : Te ex- exposed to mechanical/thermal Interdigitated r Multi material printing ring/ TopElectrode Conclusion tension to using multi-material loading, fouling, chemical attack, ElectrodePattern prints implies many additional etc. [4] I. Gibson l D.W. Rosen l B. Stucker, Pattern question regarding form-fdelity, ‘AdditiveManufacturing Technologies; If you have made it to here, I hope by adhesionbetween dissimilar ma- All in all, it is clear that exciting things Rapid Prototyping to Direct Digital- now you have a somewhat better over- terials, optimisation of printing become possiblewhen merging 3Dprin- Manufacturing’, 2010, Springer, ISBN: view of sense and nonsense of 3D prin- conditions, diferences in layer ting with electronics tomake transdu- 978-1-4419-1119-3 ting. Hopefully you have gotten excited thicknesses, etc. that will cause un- cers. At the moment this seems challen- [5] Free 3D printing basics guide stretch on movements are required [33]. plate) capacitance can be obtained. Tis about future possibilities, meanwhile desired topological features, stress, ging but there are sufcient indications from 3Dprintingindustry.com: To this end, initial investigations are is an important encouraging result for appreciating the challenges that lie anisotropy etc. of progress in the 3D printing landscape http://3dprintingindustry.com/3d- underway for embedded sensing using fabrication methods where both high ahead of us in terms of technology that : to start this endeavour now. And, lets r Conductive material printing printing-basics-free-beginners-guide/ novel commercial fexible elastomer ma- wire density and continuous metal sheet has to be developed, device principles How can we get sufcient conduc- face it, who would have been able to terials such as NinjaFlex [34]. In order embedding are challenging. that have to be investigated, etc. To ma- tivity while still keeping the con- predict the course of semiconductor [6] Some pictures in this article were to create normal and shear force sensing terialise any of the high expectations on ductors small, fexible, etc.? What development when confronted with the taken from news items that appeared on with one device, a multiwire structure is With a fully characterised sensor model 3D printed transducers, much research to do with anisotropic conducti- frst transistor? www.3Dprintingindustry.com. investigated, such as that in Fig. 11(a). (Fig. 11(b)), a multilayer wire capaci- still has to be done, luckily!, as it pro- vity. With respect to external in- Using elementary expressions [35], for tive system was designed within a 3D vides for ideas for research grants, ba- terfacing we need to sort out how References [7] Y. Kong, I. Tamargo, H. Kim, B. the electrical felds of pairs of opposi- printed structure. Initial proof of con- chelor and masters projects and exciting to connect printed conductive Johnson, M.Gupta, T.-W. Koh,H.- tely charged wires, it is possible to cal- cept structures were fabricated from a future applications. Some of the materials to e.g. platinum, copper, [1] A. Anastasiou, C. Tsirmpas, A. A. Chin,D. Steingart, B. Rand culate the capacitance of collections of variety of materials. Materials such as research that is going to be addressed in solder, silver-ink or glue, etc. Rompas, K. Giokas,D. Koutsouris, &M.McAlpine, 2014, ‘3D Printed wire pairs. Te results are shown in Fig. ABS, NinjaFlex, and ULTEM 9085 the near future in the TST group: r Printed transducers: Once the “3DPrinting: Basic concepts Mathema- QuantumDot Light-Emitting Diodes’, 11(b) and indicate that even for a wire were used in the fabrication process in above challenges have sufciently tics and Technologies”, IEEE 13th Inter- Nano Lett., 2014, 14(12), pp 7017- density of only 50%, a capacitance of order to determine the optimal correct r Technology: Selection of the most been addressed we need to use national Conference on Bioinformatics 7023, DOI:10.1021/nl5033292. 85% or more of the fully dense (parallel stifness, flling factor, and printing den- promising print technologies and our imagination to optimally use and Bioengineering (BIBE), 2013, p1-4, [8] Markforged web pages, visited No-

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