SmartSeam

Editor: Rike Brendgen & Theresa Junge Editorial Welcome to SmartSeam Magazine. We take you with us and look back on the last two and a half ye- ars of project work in the field of smart textiles. We present you smart con- cepts, smart materials up to smart textile products, always looking at the ent- ire textile value chain. The last few years have been ups and downs with some setbacks isolated working during the covid- pandemic but also many bright spots and succes- ses. We have learned a lot and want to share with you what we came to un- derstand, because only shared knowledge ensu- res that people can conti- nue to develop and grow. Anne Schwarz-Pfeiffer Kerstin Zöll Thomas Weide Rike Brendgen Katalin Mengler Carsten Graßmann like 3

Content 6_The motivation How can functional threads be integrated into clot- hing by means of the joining technology „sewing“? 8_The SmartSeam sewing machine A lockstitch sewing machine with special laying thread device 10_Hollow spindle spinning A spinning process that can do much more than simply produce ordinary yarns 12_Yarn coating can do more than just coat Functional coatings make simple yarns intelligent 14_Hybrid functional yarns From sketch to the sensory yarn 22_From yarn to finished seam Integration potential of sewing for smart textiles 4

28_Now it matters What can the developed yarns and seams really do? A detailed report on testing the sensitive properties 50_Let‘s move Motion analysis with the help of smart textiles 56_Sweet sweat Sweat level monitoring - knowing your body physiology 62_Safety first Integration of active light elements to improve visibility in the workwear area. 66_The end Acknowledgements to project partners and sponsors 5

The motivation Using seams for functional integration in garments? Digitisation, security and individualism are three megatrends that dominate the fa- shion industry. In the SmartSeam project we saw an opportunity for the textile and clothing market to address these trends by developing smart clothing products. Smart garments can interact with the wea- rer, increase the security level and can mea- sure individual data - all important points to meet consumer needs. A few smart products are already in the market. However, the market is rather scattered as most likely not the traditional textile and clothing industry comes up with new, smart products on the market, but more and more start-ups co- ming from diverse disciplines, such as me- dicine, sports or electronics, enter the mar- ket with innovative solutions and products. Hence, the question arises what are the current bottlenecks and problems that hinder the textile and clothing industry to increase forces to develop smart texti- les and clothing? The issues are manifold, but one major contention is a lack of inte- rest in abolishing well-established proces- ses and replacing them by new processes or adding new processing steps in existing production lines. Effectivity and flexibili- ty can be achieved by using a technology that has to be applied anyhow for a pro- duct to be produced for multiple purposes. One example is the joining of pattern pie- ces to manufacture a textile product. Most often, sewing is the method of choice for clothing as well as for technical texti- le products in the medical and automotive industry, as it allows a precise matching to the properties of the fabric pieces to be joined by combining different threads and by adjusting the seam stitch type. Another example is spinning. In order to produce textile structures, such as woven or knit- ted structures, and for sewing, yarns are needed. Most often, yarns are produced by ring spinning and twisting processes. These processes are meant to combine dif- ferent fibrous materials and can therefore be perfectly explored to process functional materials combined with traditional fibres. From this background our motivation aro- se: We want to use well-established tech- nologies in the textile and clothing industry and add functionalities into textile products with no additional processing steps. There- fore, we focused on spinning and coating of functional hybrid yarns and processing these hybrid yarns into functional seams using commodity or adapted sewing ma- chines. With this we demonstrate scala- ble, flexible and effective textile techno- logies to meet the demands of tomorrow. 7

The SmartSeam sewing machine The basic sewing machine that was used throughout the entire SmartSeam pro- ject is the model M-Type 857 from the company Dürkopp Adler. This is a two-needle lockstitch machine with triple feed. By the addition of two seperate laying thread de- vices and an operating panel for targeted control of the laying thread devices from the company Habraken B.V. the two-needle-lockstitch machine becomes a decorative stitching machine. It enables the processing of most diverse yarns and braids, from smooth to barely twisted yarns. This way, electrically conductive yarns, functional fi- bres or hybrid spun yarns can be placed on a base fabric by the thread laying devices and fixed by the use of the sewing needles without damaging those delicate materials - smart sewing made simple. 9

FantaOne The laboratory frame for the production of high quality speciality fan- cy yarns Gualchieri e Gual- chieri & C. S.r.l. User-friendly, modular, The machine is easily multifunctional. These terms controlled by the company‘s describe the hollow spindle spinning machine FantaOne from the Itlaian company Gua- own software allowing applica- tion-specific settings thanks to its simple handling. licheri e Gualicheri. With two drafting units, double hollow spindle, ring rail and winding unit, it is possible to produce classic yarns for weaving and knitting, as well as technical yarns and unusual fancy yarns for technical, expe- rimental or design applications. Different yarn structures can be created by controlling the yarn feed, the number of hollow spindles, the unwinding and bobbin take-off. Perfect for the fast and easy de- velopment and pro- duction of intelligent yarns making texti- le materials a little smarter. With that, hybrid yarn structures can be created that combine traditional fibres and functional yarns to serve as yarn-based sensors. Source: https://gualchieriegualchieri. it/en/machinery/fanta-one/ 10 10

Dyeing, printing, impregna- ting? No, we want to coat! Coating is a well-kown fi- nishing technology for tex- tiles to reduce wear of the coated material, to re- pair material defects or to create necessary surface properties for decoration, conductivity, thermal or electrical insulation. In the SmartSeam project, the coating process is used to apply delicate coating mate- rials onto yarn-based subs- trates. Not only an electri- cal conductive coating made from carbon black but also a coating containing ther- mochromic pigments was ap- plied onto yarns to create hybrid sensory yarn struc- tures. Mostly, textiles are coated as fabrics but the novelty here is that the coating set-up is especi- ally designed for yarn-ba- sed substrates, saving high material costs for special coatings and yarn materi- als. 12

HumY Hybrid functional yarns by hollow spindle spinning ently, their permeability to electric fields. A dielectric can be any isolating, polar or un- polar material, but note that different mate- rials do have a different dielectric constant. If a material is introduced into a capacitor as a dielectric, the forces of the electric field between the electrodes also act in it. The electric field causes a shift of the positive and negative charges within the material. This process is called polarisation. If the molecules of the dielectric are dipoles, as is the case with water, they align themselves accordingly. As a result of the polarised particles, additional charges reach the electrodes. An electric field opposing that of the capacitor is formed in the dielectric and the capacity increases. The better molecules and atoms can be polarised, the higher the permittivity. To measure humidity, a hygroscopic material is needed as dielectric that takes up water molecules from the environment. The ab- sorption of moisture by the sensor results in an increase in sensor capacity as water has a rather high dielectric constant due to its dipo- le character. Humidity is the content of water in air. The more water content is dissolved in air, the more the hygroscopic dielectric can Electrode Dielectric Electrode 14 M Moisture sensitive yarns When developing smart textile sensors, we like to reproduce electronic components on a textile basis. A widely used electronic com- ponent is a capacitor, which can be used for humidity measurement. Basically a capacitor consists of a dielectric material placed bet- ween a pair of electrodes - a pretty simple structure to be rebuilt by metal yarns and cellulosic material to serve as dielectric. But what does a capacitor do and how does it measure humdity exactly? A voltage can be applied to the electrodes, causing them to become electrically charged. Positive charges accumulate on one electrode and negative charges on the other - a phenomena, which is also known as electric field. The performance of a capacitor is defined by capacity, which is the amount of electrical charge it can hold and store at an applied voltage. In between the electrodes is the dielectric. Dielectrics are defined by their permittivity, or named differ-

d e p p a r w n r a y e r o c - Z n i e c w i i t g n d n w i i y t i d m u h e v i t i c a p l a t e m - r e y a l l e g n i s A l y b d e t a o s i r e t t e B - a c - e s n e s o t y d a e R For further processing we wrapped a protection layer of either the same material as the dielectric or of text- urised polyester around the capacitor structure. This layer is especially necessary for further pro- cessing during sewing and ensures that the loosely wrapped outer electrode does not unwind. . n o i t c e r i d - Z n i e c n o . n o i t c e r i d - S n i d n a . n r a y e v i t i s n e s Hybrid functional yarns adsorb from the environment. In this way, changing capacity can provide information about present relative humdity. We produced this capacitor structure by using the hollow spindle spinning machi- ne Fanta-One. With that we were able to process silver coated yarns (Highflex 7077, HC40), stainless steel fibres (Bekinox) and a copper wire (Polysol 155) as inner electrode as core yarn. The different core yarn materials were wrapped single or twice by cellulosic material, where we used conventional viscose yarn but also super absorbent viscose, modal and lyocell (Len- zing). The cellulosic material was wrapped twice in S and in Z direction to ensure isolation and seperation of both electrodes. Subsequently, we loosely wound another electrode consisting of a silver coated yarn (Silvertech 50) around the cellulosic layer. And ready is our hu- midity sensitive hybrid yarn HumY. 15

TempY Hybrid functional yarns by hollow spindle spinning ] m h O [ e c n a i t s s e R Iron Copper Constantan Carbon Temperature [°C] Source: https://vorsam.uni-ulm.de/vs/ Versuche/EM/html/EM083V00.htm TTemperature sensitive yarns This spinning technology enables the creation and manufactering of further sensory yarn structures. Next to observing humidity levels, also temperature monitoring is of interest. Just imagine an athlete being able to track his/her bodyphysiological parameters during training in a simple T-shirt. Or think of wor- kers in impermeable protective clothing get- ting a notification when they are overheating and need to take a break. Many conceivable scenarios that require a smart solution. Temperature expresses quantitatively the perceptions of hotness and coldness and is measured usually by thermometers. One prin- ciple for operating a thermometer is based on the change of resistance of certain materials as a function of temperature. This is a typical behaviour that we observe for metals. Pure metals show a strong change in resistance when temperature varies. Next to metals also ceramics and semi-conductors exhibit this behaviour and have higher temperature coeffi- cients than metals, with which higher sensiti- vities can be achieved. Unfortunately though, these materials are not available as yarn-like threads or fibres. Materials that change their resistance upon varying temperature are called thermistors and can be distinguished in hot and cold conductors. Hot conductors (NTCs) have a negative temperature coeffi- cient, which means that current is better con- ducted at high temperatures. Cold conductors (PTCs), on the other hand, have a positive temperature coefficient, meaning that current is better conducted at cold temperatures. 16

Copper changes its electrical resistance in dependence of temperature. Resistance in- creases with rising temperature, which makes copper a PTC. As copper is also available as yarn-like material, we chose it for the development of the tem- perature sensitive hybrid yarn TempY. Resistance rises with increasing length of the material. This prompts the question if an overall higher resistance also increases the sensitivity of the TempY yarns by making changes in resistance caused by varing tem- perature more evident. This is the point at which the spinning machine comes into play once again. This is because it enables us to get a longer length of copper yarn to a defined length of core yarn by winding it as tightly as possible without contacting around a conven- tional cellulosic yarn. Therefore, we developed 3 different hybrid yarns having the copper yarn Amberstrand as core yarn and as wrap- ping yarn around one or two strands of visco- se yarn. The thicker the core yarn, the more length of copper yarn is needed for winding and that hopefully improves the sensitivity towards temperature. Hybrid functional yarns The sketch - what we are trying to do. The basis - copper yarn as temperature sensitive material. We need more copper! Therefore we wind the copper yarn around a strand of visco- se. Viscose x2 to raise core yarn thickness and thereby length of wrapped yarn. 17

StrainY Hybrid functional yarns by coating StrainY is a strain sensitive yarn for strain ranges as little as 1%. It is made from conven- tional electrically conductive yarns coated with an elastic carbon filled silicone. This coating is crucial, as it compresses the yarn structure, thereby reinforcing the change in geometry upon strain, which in turn causes a change in electrical resistance. We coated many different electrically con- ductive yarns made from different materials (copper, steel, silver) but also with different finenesses and resistances. As the carbon filled silicone coating is rather viscous, we couldn‘t use the conventional ring-slot-die for coating but had to develop a 3D printed coating bath for vertical dip coating. The elctrically conduc- tive yarns are easily pulled through and the- reby take up the coating mass. Gravity and a narrowed opening that wipes off excess coating compound ensure uniformity of the coating. StrainY fills the lack of easy-production, highly-sensitive textile based sensors at small strains. SStrain or pressure sensitive yarns Strain sensors are of interest for many smart textile products and they have been investiga- ted by research and industry a lot. A decisive performance characteristic of strain sensors is the Gauge factor, which is the ratio of relative change in electrical resistance to the mechani- cal strain and provides information on sensiti- vity of the sensor. Another decisive property is the strain range, in which the sensor is able to detect changes. Most textile sensors are able to detect large strains with a high sensitivity and are used for motion detection like arm or leg movement. Only few are reported having a high sensitivity at small strain ranges ( <5%) that could be used for detecting feeble human motions. And this is the beginning of the development of StrainY. f o n o i t a r a p e r p - l l e w t i x i m r e t t e b u o Y . e t s a p g n i t a o c e n o c i l i s d e l l fi n o b r a c 18

TherchromY Hybrid functional yarns by hollow spindle spinning and coating AActive heating and temperature sensitive yarn Now let‘s combine spinning and coating and add more than just a sensory function. Becau- se what if the yarn in your garment could not only sense but also give direct feedback to you? This question Theresa Junge dealt with in her Bachelor thesis. Herein, Theresa developed a hybrid yarn that cannot only actively heat a garment but also show its wearer when the desired temperature is reached. Next to this visual feedback, the yarn is also capable of measuring the temperature by little changes in its electrical resistance. To achieve all of that, she had to combine two functional materials. 20 Theresa spinning around for her Bachelor thesis. The whole process in micrographs. Each strand shows a processing step - from plain texturised poly- ester to wrapped stain- less steel fibre to final coated and wrap-spun hybrid yarn.

The first one is the stainless steel fibre, Be- kinox, that is wrapped with polyester on the hollow spindle spinning machine. A setting was chosen, so that the core yarn is comple- tely wrapped. Bekinox filaments are used for signal transfer, power transfer and also ther- mal conductivity. The latter is exactly, what Theresa was looking for. But up to now, the hybrid yarn can simply heat up when voltage is applied - not much more though. And this is where the coating comes into play, because Theresa inserted thermochromic pigments into a polyurethane coating making it a thermoacti- ve material. Thermochrome pigments lose their colour when a defined temperature is reached and become transparent - a property that can be used as clear and direct feedback. By combining two types of smart functional ma- terials by means of spin- ning and coating tech- nology the hybrid yarn TherchromY is produ- ced. However, Theresa quickly had to find out that production of TherchromY was not that simp- le, because lots of parameters were unknown. Starting for example with the order of produc- tion steps; should she coat the polyester yarn with thermochromic pigments before spinning or should she coat the wrapped Bekinox yarn? Theresa found that the coating is rather sticky and thus the coated yarn cannot be processed in the spinning machine - she had to spin first and then coat. Another challenge was finding the ideal viscosity of the coating, because too liquid coating mass had as consequence that the mass runs out of the vertical dip bath, too viscous meant that not enough coating mass sticked to the yarn. The viscosity of the coating was adjusted by thickening agent and adapted to be processable in the self printed dip coating Hybrid functional yarns nozzle. In another trial Theresa investigated which wrapping material is working for her application. In the end she decided for slightly texturised polyester yarn, taking up the coa- ting nicely with few irregularities. Theresa produced a hybrid yarn with dual functionality that cannot only actively heat but also show the user that desired temperature is reached. Active textile heating systems find already applications in car seats, but with the additional sensory and feedback function new possibilities open up. All I see is pink - but if temperature chan- ges, it turns white. 21

From yarn to finished seam U sing the intersection points of a seam for function integration. this Clearly technology opens up more possibilities than simply se- wing on hybrid sensitive yarns. What if the seam could be sensitive itself ? We also pursued this question and as we looked at the seam, many inter- section and crossing points jumped right at us. We realised that we could leverage those points by selectively combining electrically conductive ma- terials and creating sensor points by that. A promising stitch variation is the D-stitch, for which both thread layers are working simultaneously and per- form a sweeping movement. The result is a seam pattern with intersecting lay- ing threads. Loads such as pressure or strain have an influence on these cros- sing points and change the electrical properties of the yarns processed in the seam. But also other stimuli like tempe- rature are likely to have an influence on the electrical performance of the seam so that this sewing technology opens the possibility to directly create gar- ment-integrated sensors without an in- termediate spinning or coating process. 23 I ntegration of hybrid yarn structures into the seam. Hybrid functional yarns were pro- duced that somehow need to be integ- rated in a garment - but how? Those de- licate yarns, which include not only our self-produced hybrid yarns but also elec- troluminescent wires and polymer opti- cal fibres for active lighting in garments, are hardly integratable by common textile technologies such as weaving, knitting or classic sewing, as mechani- cal stress damages the susceptible yarn structure. Luckily, we own the modified two-needle lockstitch machine with the laying thread device that makes placing and integration of such yarn structu- res very simple. For integration of the functional yarns the stitch variation of the laying thread devices L or R can be used, which means that just one thread layer is working and moves in swin- ging motions from right to left. A pret- ty seam pattern is created in which the guided thread runs in a sinuous shape.

From yarn to sensory seam. Inte- gration of hybrid sensory yarns into the seam structure. Let‘s light up the world. Active lighting elements for integration in garments. Pursuing these approaches we created many seam sam- ples, that we tested and evaluated to find the best set- tings for integration of smart functions in garments. This work resulted in humidity-sensitive seams, whereby the sewing process does not damage the capacitor-structure of the produced hybrid yarns. Also the wavy seam struc- ture ensures that more sensory yarn can be incorpora- ted in the seam, which improves measurement accuracy. On top of that, we succeeded in integrating electrolumine- scent (EL-)wires and polymer optical fibres by sewing tech- nology - which, to our knowledge, has not yet been achieved. EL-wires and polymer optical fibres are hardly bendable, which makes them unprocessable for ordinary textile pro- cessing technologies but with the right settings of the sewing machine integration becomes possible without breakage. 24

s m a e s e v i t i s n e s n i a r t s e t a e r c o t s d a e r h t g n i y a l e h t f o s t n i o p g n i s s o r c e h t g n i s U . s m a e r t S - some Nowadays, electrical- ly conductive yarns are available on the market. Most of them are thinly coated with silver, but also copper or stainless steel yarns are available. All of them are suita- ble for smart textile applications, though the yarns differ in fineness, number of twisted filaments, ri- gidity and conductivity. Some of them were originally developed by sewing thread manufacturers, while others were developed by manufacturers in the technical- electronic field. However, we used a wide range of commerci- ally available conductive yarns to create a sensory seam - Stream - for strain or pressure sensing and find the best material and set- ting for this application. Some of the used commercial yarns are ea- sily processable, which are espe- cially those produced by sewing thread manufacturers for applicati- ons such as embroidery or sewing (Silvertech, HC40, Shieldex). For others, we were happy to have the thread guiding devices on the lock- stitch machine, which allows us to handle thicker conductive yarns (Highflex, Bekinox) in the seam. On top of that, we also int- 26

From yarn to finished seam s n o i t c n u j l a c i r t c e l e g n i t a e r c s l a i r e t a m l a t e m t n e r e f f i d o w t - n o i a n i b m o c t r a m S . e l p u o c o m r e h t a m r o f o t egrated our self-produced StrainY yarn and luckily found that the pro- cessing in the thread layers does not damage the coating. All yarns were processed by the D-type stitch va- riation, that creates crossing points between the two strands of metal yarns. Loads act on these cros- sing points and this changes the electrical resistance of the seam. As we dove deeper into the sub- ject, we realised that we could le- verage these crossing points for more than just strain and pressure measurement. A selected combi- nation of metallic materials that intersect at one (or more) points is also known in electrical parlance as thermocouple (thermo chain). If you are not familiar with how a thermocouple works, here is a very short and simple explana- tion: When the junction of the two metals is heated or cooled, a voltage is created that can be correlated back to temperature. We used a combination of a cons- tantan wire and a Silvertech yarn (silver) or a Bekinox yarn (steel) to create this structure. In this way, we have not only created a thermo chain and demonstrated that we are able to process delicate yarn materials but also to process even stiffer materials such as thin wires. We named those seam samples Thermoseam. 27

StrainY Reporter: Rike, you work with smart textiles. Can you tell us what exactly are smart textiles? Rike: Smart textiles are textile materials that ex- ceed their usual functionali- ties. Those functional yarns, fabrics or ready-made clothings are able to acti- vely sense or react to en- vironmental conditions and external stimuli. Reporter: Can you show us some examples? How do they work? Rike: Of course. Let me start with textile materials that can detect strain or pressure. Those materials are often used for e.g. moti- on detection and for that we developed the hybrid sen- sory yarn, StrainY, but also some sensory seam sam- ples that we call Streams. Reporter: Alright, but how do they measure strain or pressure exactly? Rike: Well, we work a lot with electrically conducti- ve materials and electrical resistance is an important performance characteris- tic. Resitive materials, like StrainY or our seam sam- ples here, actually change their resistance upon loa- ding. We investigated which seam samples react best to strain or pressure by mea- suring the change in elect- rical resistance under load. Reporter: Oh, that‘s inte- resting. But it sounds like you need special equipment for that, is that right? Rike: Yes, absolutely. For StrainY we developed a completely new measure- NOW IT MAT- TERS ment set up. Two pieces of StrainY were intertwined and clamped in an adjus- table measuring rail. The clamps are then connected to an ohmmeter and so we can measure the resistance as we load the entangled pieces of yarn. We carried out four subsequent loa- ding cycles to test the re- peatability and investigated possible hysteresis effects. For StrainY, we found that especially small loads, we applied 1% load, can be de- tected and that resistance drops upon loading. That was quite suprising be- cause mostly textile based strain sensors are able to detect large strains and that mostly by an increasing resistance. Reporter: I understand. Can you give us some pre- cise figures and explain why your results were surpri- singly different from previ- ous studies? Rike: I am glad you ask. Well, for StrainY you need to know, that we developed this hybrid yarn from seve- ral conventional conductive yarns coated with a carbon filled silicone and compa- red them to each other and their uncoated equivalent. Of course, we had to test not just one sample, but at least 5 and calculated the mean value from those re- sults. On the next page you see the results of the resis- tance measurement and as you can see all yarns cle- arly reduce their electrical resistance upon loading. 28

StrainY How it really looks then. StrainY clamped in measuring rail ready to be stretched about 1%. Testing the samples in 4 successive cycles, also pro- ves that the StrainY yarns recover after loading. Reporter: Ok, so looking at the diagram, the StrainY yarn made from Highflex 3981 as base material wor- ked best? Rike: One could assu- me so, but for us not only the absolute values are of interest but also things like standard deviation. I won‘t bore you with the detailed diagram of each substrate showing the standard de- viation, but let me tell you this: The standard deviation was quite high for all thi- cker metal yarns that we tested. Those were Bekinox, and both Highflex yarns and because of the high de- viation we were not really satisfied with the results of those yarns. Reporter: So, if Highflex 3981 wasn‘t the best, which one was then? Rike: We calculated the fac- tor of resistance change from our measurement and with that we were actually able to make a statement about which hybrid yarn worked best. Looking at the bar chart, you will certainly notice that one substrate, Bekinox, is missing. This is because the calculated results were actually quite different from the others and didn‘t fit in the scale. But despite Highflex 3981, the coating definetly increa- ses the factor of resistance change. Before coating, all samples had a factor of around 1, which means that Gauge Factor Substrate uncoated coated -13.0815 -69.6716 Highflex 7077 Highflex 3981 -65.5768 -41.9042 Shieldex 0.2092 -77.4867 0.590 -72.2907 Silvertech Silvertech+ 4.9875 -89.0990 nearly no resistance change is observable upon loa- ding. But with the coating we could at least triple the factor and thereby triple the sensitivity. Best results were obtained with Silver- tech+, where we increased the factor from 0.95 to 9.21 simply by coating. A factor that is a com- mon measurand in research is the Gauge factor (GF), which is the ratio of relative change in electrical resis- tance to mechanical strain. Of course we calculated this as well and could actually prove the findings. Reporter: Well, that sounds really interesting but it is also a lot to re- member. Is there any chan- ce to read more about your work with textile strain sensors? Rike: Yes, absolutely! You can just check out our pu- blication on this topic. Paper: Textile Strain Sensor Enhancement by Coating Me- tal Yarns with Carbon-Filled Silicone 30

Streams Rike showed me around university and despite StrainY I got to know other ways to detect strain or pressure with textiles. Rike and her team also developed the previous- ly mentioned strain sensitive seam sam- ples - Streams. For that they used a special sewing machinery and placed conventional electrically conductive yarns as well as StrainY in a wavy, intersecting structure. Those samples were then loaded in a tes- ting equipment that is well-known in textile world, the tensile testing machine of Zwick Roell. But this machine at university had a special modification making it possible to not only measure strain but simultaneous- ly electrical resistance. The seam samples were placed between the clamps of the machine and stretched about 10% in 10 suc- cessive cycles. Rike and her team found that the seam in this configuration is actually capable of de- tecting strain by reducing is electrical resis- tance. The reduction of electrical resistance explains the SmartSeam team by the appro- aching crossing points and thereby better contacting of the conductive yarns. Stretched state. Stretching forces the con- tact points to get closer together - resis- tance goes down. The new testing set-up for strain sensing in the tensile testing machine - unstretched state. The diagram shows only the mean values of all cycles, but Rike told me that the sam- ples had a good recovery and strain could be sensed over all cycles. The higher resis- tance values compared to those of the mea- surement set-up of StrainY can be explained by the different clamping method. The elec- trically conductive yarns in the clamps of the tensile testing machine are only contac- ted at one side as the whole fabric needs to be fixed in the apparatus and thus isolates the back side. Some samples had better sensitivity than others, which is slightly implied by the trendlines. Gauge Factor Amberstrand Bekinox Silver coated PA 6.6 Gütermann HC40 Shieldex Silvertech+ StrainY -0.21 -1.31 -0.71 -1.35 -0.36 -0.25 -1.48 32

250.00 200.00 ] m h O k [ e c n a t s i s e R l a c i r t c e E l 150.00 100.00 50.00 0.00 Now it matters Amberstrand Bekinox Silver coated PA 6.6 Gütermann HC40 Shieldex Silvertech+ StrainY 0 10 Strain [%] Also Streams are able to detect strain. Resistance decreases when the samples are being loaded about 10%. For Stream with HC40 for example, one can clearly see a decrease in resistan- ce when the sample is loa- ded. But only the calculation of the Gauge factor gives a clear indication of sensitivi- ty. Rike and her team found that their self-developed hybrid yarn StrainY actually shows highest sensitivity in this testing set-up as well and were quite satisfied with this result. But also the commercially available con- ductive yarn HC40 works quite well and has the se- cond highest Gauge factor. In this way a strain sen- sor can be produced direct- ly by sewing and although the coating of StrainY im- proves sensibility, it is not especially necessary to have this additional proces- sing step. Stream with Shieldex produced by the SmartSeam sewing machine with two laying thread devices. 33

Streams Not its original purpose but it works. A measurement setup for pressure sensing utili- sing a thickness measurement device. Factor of Resistance Change F(Rc)= R0/R1 If Streams are able to detect strain, are they able to detect pressure as well? The SmartSeam team asked themselves the same question and developed a test setup for this purpose. They applied a quantifiable pressure with a thickness measurement device for textiles. By weights they adjusted the applied pres- sure to 2 Kg that were pressed onto the Streams for 30 seconds and released for 30 seconds as well. During that time the sample was connected to an ohmmeter and resistance was continously recor- ded. This cycle was repeated 3 times. d e n fi e d h t i w s m a e r t S f o g n i d a o L : r e s o l c t i b A . t h g i e w Factor of resistance change of Streams upon loading Amberstrand Bekinox StrainY HC40 Shieldex Silvertech Silver coated PA 6.6 Gütermann 1.01 1.00 1.01 1.04 1.02 1.02 1.04 34

The diagrams show exemplarily some of the results Rike and her team found for this measurement. Streams with HC40 and a silver coated polyamide 6.6 yarn from Gü- termann actually worked best, which is also proven by calculating the factor of resis- tance change upon loading. The diagrams clearly visualise the 3 cycles that have been carried out and that resistance decreased during loading. The application of pressure results in a better contacting of the crossing points in the seam and this reduces the re- sistance. Other silver coated sewing threads also showed sensitivity towards pressure, but unfortunately the team got not quite Stream with HC40 under pressure. Now it matters successful with the copper (Amberstrand) and Bekinox (stainless steel) yarn, which only delivered poor results. Summing up, Streams can be produced by a variety of conductive yarns; some work better for strain sensing others work better for pressure sensing. If they are to be used in a close-to-the-body application, a mixtu- re of pressure and strain will most likely act on the samples. Therefore, the samples with the silver coated embroidery thread HC40 seem to be a suitable choice. In both mea- surment setups they showed the highest sensitivity and will therefore perform nicely in future applications. HC40 ] m h O [ e c n a t s i s e R 43.5 43 42.5 42 41.5 41 40.5 40 39.5 0 2 0 2 0 2 Loading [kg] Stream made with silver coated PA6.6 from Gütermann works equally good and shows a clear decrease in resistance when pressure is exerted. Silver coated PA 6.6 Gütermann ] m h O [ e c n a t s i s e R 6.35 6.3 6.25 6.2 6.15 6.1 6.05 6 5.95 5.9 5.85 5.8 0 2 2 0 Loading [kg] 0 2 35

The deployment of two layers of visco- se increases capacity and also sensitivity compared to those yarns with just one layer of viscose. Those results were consistent for all yarns independent of the core mate- rial. Highest capacity was reached with the Highflex 7077 as core yarn, twice wrapped. The reason for that can be found in the geo- metry of the yarns, because from all tested yarns, Highflex 7077 is by far the thickest. When wrapping this thick yarn, more visco- se as well as more of the second electrode will be needed compared to thinner core yarn materials - this increases the perfor- mance of the capacitive yarn. But also here Rike told me not simply to look at the absolute numbers. Sensitivty is of greater interest. S= ∆C / ∆rH = (C-C0) / (rH - rH0) HumYs Another large study that the SmartSeam team carried out was about humidity sensi- tive yarns - HumYs. Those yarns were tes- ted for their sensitivity towards relative hu- midity in a climate chamber. This chamber is able to run through a defined programme controlling temperature and humidity. As HumY is not a temperature sensitive yarn, that variable was held constant but relative humidity was increased from 20% to 80% in steps of 10% and backwards. During that time, HumY was connected to a measurment device detecting the change of capacity in the yarn structure. Rike made a sketch for me to better understand what the set-up looked like. Rike told me that they developed quite a lot of yarns, but firstly the influence of one, respectively two layers of hygroscopic vi- scose as dielectirc between the two elec- trodes was investigated. Moreover different core yarn materials were tested. Rike and her team found that all yarns actually show sensitivity towards humidity, thus can be used as moisture sensor. But also differences in capacity between various hybrid yarns did occur. Let‘s see what HumY is able to do. Measurement set-up for humidity-sensitive yarns. 36

] F p [ y t i c a p a C 220 200 180 160 140 120 100 80 60 40 30 40 50 60 70 80 Rel. Humiditiy [%] HighFlex once HighFlex wrapped einfach umwunden Bekinox once wrapped Bekinox einfach umwunden Polysol once Polysol wrapped einfach umwunden HighFlex twice HighFlex wrapped doppelt umwunden Bekinox twice wrapped Bekinox doppelt umwunden Polysol twice wrapped Polysol doppelt umwunden Now it matters - e m t i e s u a c e b , n g i s d o o g a s i s i h t d n a - g n i s i r l l a s ‘ t I . y t i d i m u h o t t c a e r y l l a u t c a s n r a y e h t t a h t s n a The calculation of sensitivity actually proved what was suspected before. HumY with Highflex is the most sensitive. For all HumYs, the SmartSeam team observed that the sensitivity is higher at moist conditions. Meaning that the yarns reliably detect humidity from 50% rel. humidity onwards. Sensitivity - always important to consider when judging the performance of textile sensors. twice Bekinox once Bekinox twice Elektrisola Elektrisola rel. Hum. once % twice HighFlex Highflex once wrapped wrapped wrapped wrapped wrapped wrapped 0.02 0.08 0.12 0.19 0.31 0.60 0.04 0.08 0.11 0.16 0.25 0.43 0.12 0.20 0.25 0.35 0.70 2.31 0.04 0.05 0.06 0.12 0.18 0.34 0.10 0.16 0.19 0.26 0.49 1.11 0.15 0.17 0.21 0.37 0.61 1.87 30 40 50 60 70 80 37

HumYs Rike also told me that they observed something called hysteresis. Scientifical- ly speaking, it is is the dependence of the state of a system on its history. For HumY that meant that at same humidity content, the measured values are higher during de- sorption than before during adsorption. So they react differently depending on whether they come from a low or high humidity en- vironment. Looking at the diagram at page 37, one could imagine that hysteresis is bigger for twice wrapped yarns, but when we actually put the hysteresis per humidity level in relation to the change in capacity, we actually see that a double layer of vi- scose slightly reduces hysteresis. The hys- teresis effects are particularly effective at high humidity. Rike told me that the hyste- resis of the HumYs is due to the adsorption behaviour of viscose towards water. Due to intramolecular hydrogen bonds between cellulose and water molecules, more water remain in the fibre during desorption than during adsorption at same humidity con- tent. So actually, Rike and her team expec- ted that hysteresis effects would occur. To be usuable in clothing the HumYs should not only detect humidity but also ac- tual wetness. Because if you imagine inte- Hysteresis effect of HumYs ] % [ A C - D C / C ∆ 25 20 15 10 5 0 24,4 18,5 11,2 5,6 2,0 24,0 20,5 12,6 6,7 2,8 23,2 15,4 7,4 3,9 2,0 23,1 15,2 9,2 4,6 2,1 22,1 18,6 14,6 8,0 4,5 22,4 19,2 10,7 5,5 3,1 HighFlex HighFlex Bekinox Bekinox Polysol Polysol once wrapped twice wrapped once wrapped twice wrapped once wrapped twice wrapped 30 rH 40 rH 50 rH 60 rH 70 rH 38

grating those yarns in a T-shirt to monitor sweat levels, it should certainly be able to detect watery media. So therefore the team developed a rapid test ex- amining if the yarns react to droplets applied to them. Three drops were applied subsequently waiting 2 min. in between. The team found that at least two layers of viscose are needed for iso- lation. Of course, this ob- servation does not hold true for the samples with Po- lysol, as this is an isolated material already. However, when water was applied to the unisolated samples with just one layer, it created an electrical contact between the electrodes, which re- sulted in an overload and this was not measurable. The diagrams at the bottom show the results of that ex- periment for twice wrapped samples. All of them show a Now it matters Rapid test for HumYs to check wether they react to wetness as good as they reacted to humidity. clear rise when water was applied and therefore proof to be useful as moisture sensors. All the presented findings were actually established in the Bachelor thesis of the student Laura Hegers, whom the SmartSeam team supported and supervised. Polysol twice wrapped Bekinox twice wrapped Highflex twice wrapped ) F p ( y t i c a p a C 450 400 350 300 250 200 150 100 50 0 0 0 : 0 0 3 : 0 0 0 : 1 0 3 : 1 0 0 : 2 0 3 : 2 0 0 : 3 0 3 : 3 0 0 : 4 0 3 : 4 0 0 : 5 0 3 : 5 0 0 : 6 Time (min) ) F n ( y t i c a p a C 50000 40000 30000 20000 10000 0 ) F n ( y t i c a p a C 8000 7000 6000 5000 4000 3000 2000 1000 0 0 0 : 0 0 3 : 0 0 0 : 1 0 3 : 1 0 0 : 2 0 3 : 2 0 0 : 3 0 3 : 3 0 0 : 4 0 3 : 4 0 0 : 5 0 3 : 5 0 0 : 6 0 0 : 0 0 3 : 0 0 0 : 1 0 3 : 1 0 0 : 2 0 3 : 2 0 0 : 3 0 3 : 3 0 0 : 4 0 3 : 4 0 0 : 5 0 3 : 5 0 0 : 6 Time (min) Time (min) Twice wrapped HumYs show a reaction - also towards wetness. So nothing stands in the way of its use in a sports undershirt. 39

HumYs Further experiments were carried out with super hygroscopic cellulose yarns as dielectric. On top of that another protection layer of polyester or of the same material as used for dielec- tric was wrapped around the yarn structure. This extra wrapping was needed as during sewing the team observed that the outer electrode easily unwinds and is shifted. Rike exemplarily showed me the results of Bekinox wrapped with a super ab- sorbent viscose and quickly it becomes clear why the material is called super ab- sorbent. Especially at high humidity a steep increase in capacity is observable for the sample wrapped twice with viscose as dielectric and then again as outer protection. The increase at 80% relative humidity is ac- tually that high, that the Sensitivity of HumYs with superabsorbent Viscose. BVSV BVVSV BVSP BVVSP 0.38 0.18 0.44 0.66 0.56 1.03 0.95 2.51 3.70 75.99 35.48 8776.20 9.78 809.97 0.09 0.23 0.25 0.42 0.70 0.25 0.44 0.68 1.61 14.95 rel. Hum. [%] 30 40 50 60 70 80 BVSV = Bekinox + 1xViscose + Silvertech + Viscose BVSP = Bekinox + 1xViscose + Silvertech + Polyester BVVSV = Bekinox + 2xViscose + Silvertech + Viscose BVVSP = Bekinox + 2xViscose + Silvertech + Polyester changes at lower humidity are not visable due to the scaling. But looking at the sensitivity one can see that changes in humidity are already detected at lower moisture levels, mere- ly with lower sensitivity. Compared to the samples wrapped with normal vi- scose, sensitivity as well as absolute numbers in- creased. Bekinox wrapped with normal viscose twice has a capacity of ~160 pF at 80% rel. hum. This value is already exceeded by the sample with one layer of super absorbent viscose and polyester as outer pro Super absorbent viscose takes up a lot - especially at high humidity. Bekinox-Viscose 10000 8000 6000 4000 2000 ] F p [ y t i c a p a C 0 30 40 50 60 70 rel. Hum. [%] BVSV BVVSV BVSP BVVSP 80 40 40

tection layer with ~186 pF. The team also concluded that the material of the outer protection layer has an imapct on the measu- rement. Polyester as outer layer does not increase sensitivity as much as viscose does. At 80% rel. hum. the HumY BVVSP has a capacity of ~8360 pF, whereas BVVSV has a capacity of ~88660 pF. Rike told me that comparable results have been found for other super absorent ma- terials such as Modal and Lyocell yarns of the compa- ny Lenzing as well. To sum up, it can be noted that super absorbent cellu- losic materials increase the moisture take-up and the- reby increase capacity. The more of that super absor- bent material was proces- sed in the yarn structure, the higher the amplitude. But the multiple deployment of super absorbent viscose exponentially icreases ca- pacity, which must be con- sidered for further use and evaluation of the yarns. Measuring range and desired sensitivity should be known and accordingly materials should be chosen. The choice of material and layout of yarn structure has a huge impact on perfor- mance of the sensors. HumYs can and must be de- signed taking their future application into account. Now it matters 41

TempYs Next to moisture also temperature monitoring is of interest for body physio- logical applications. There- fore, the SmartSeam team developed TempYs. Tem- perature sensitive yarns based on a resitive princi- ple. For testing the yarns, they were put in the climate chamber again but this time the programm was set so that temperature increases from 10°C to 60°C. The yarns were exposed to that tem- perature and simultaneous- ly their change in electrical resistance was recorded. To previously determine if the length of the copper yarns has an influence on sensitivity, the team tested a commercially available copper yarn Highflex 3981 in different lengths (40, 80, 120 cm). As expected the length definetly has an impact on resistance and increases for the longer samples. But that does not automatically mean that sensitivity in- creases. To check this, Rike and her team calculated the sensitivity of the samples for the complete measuring range from 10°C to 60°C. S= ∆R / ∆T = (R-R0) / (T - T0) Sensitivity is nearly dou- bled when the length is doubled and increases from 0.0013 at 40 cm to 0.0024 at 80 cm. Further enlarging still increases sensitivity but not to the same extent. Based on this pre-trials, it was clear that the wrapping of copper yarn around a ce- ] m h O [ e c n a t s i s e R 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Highflex 3981, 40 cm Highflex 3981, 80 cm Highflex 3981, 120 cm 10 20 30 40 50 60 Temperature [°C] Preliminary tests for TempY - Does the length have an impact on sensitivity? 0.0030 0.0025 y t i v i t i s n e S 0.0020 0.0015 0.0010 0.0005 0.0000 llulosic core yarn should have a positive effect on sensitivity of the TempYs and that was tested of course. TempYs wrapped with the copper yarn Amberstrand were tested in the climate chamber in the same way. The diagrams look really similar to those of the pre- liminary tests and this is a good sign, as it means that Rike and her team were able to increase sensitivity with wrap spinning. Looking a bit closer, she Highflex 3981, 40 cm Highflex 3981, 80 cm Highflex 3981, 120 cm 42

] m h O [ e c n a t s i s e R 2.60 2.50 2.40 2.30 2.20 2.10 2.00 1.90 Amberstrand wrapped with viscose Single viscose wrapped with Amberstrand Double viscose wrapped with Amberstrand 10 20 30 40 50 60 Temperature [°C] Now this is what TempY can do and, yes, wrapping does increase sensitivity. y t i v i t i s n e S 0.0050 0.0045 0.0040 0.0035 0.0030 0.0025 0.0020 0.0015 0.0010 0.0005 0.0000 Amberstrand wrapped with viscose Single viscose wrapped with Amberstrand Double viscose wrapped with Amberstrand told me that we can obser- ve an inconsistency for the absolute numbers of the TempY with single viscose as core yarn and wrapped with Amberstrand. Actually, Rike expected the resistan- ce of the wrapped yarn to be higher than the resis- tance of the yarn having the copper yarn as core yarn. Because the length of the copper material becomes longer by wrapping and that increases resistance. But they quickly found the rea- son for this discrepancy in Now it matters the contacting of the yarns; it was challenging to con- tact those fine metal yarns with the rather big croco- dile clamps of the measur- ment device, so that con- tact resistances occur and cause irregularities. Though the absolute numbers are somehow unexpected, the calculation of the sensitivity was satisfying for Rike and her team. Here again, sen- sitivity increases by wrap- ping the copper yarn around one or two strands of visco- se and thereby increasing its length. For the TempY with two strands of viscose wrapped with Amberstrand sensitivity is at 0.0043 and the absolute numbers show that resistance linearly increases with rising tem- perature. The team showed that it is easily possible to pro- duce thermistor yarns and steer- ing their sen- sitivity towards temperature by hollow spindle spinning. 43

Thermoseam Next to thermistors, the team also produced ther- mocouples by sewing two different metal yarns in a wavy, crossing structure. Those crossing points serve as sensors for temperatu- re. The seam samples were placed in the climate cham- ber and temperature was again increased from 10°C to 60°C and backwards. Si- multaneously thermoelec- tric voltage was measured. In total, three samples of each combination were measured. The first diagram shows the correlation of thermoelectric voltage and temperature set/real. The- reby it becomes clear that firstly, thermoelectric volta- ge changes in dependence of different temperatures. Secondly, there is an offset between temperature set and temperature real, whe- reby thermoelectric voltage rather follows the curve of temperature real, albeit a slight time delay. However, thermoelec- tric voltage significantly increases from 0 mV to approximately 53 mV. This increase is reversible and so voltage decreases again when temperature drops. Unfortunately, the curve of thermoelectric voltage at decreasing temperatures shows some more irregula- rities, such as an increase between 30 and 40°C. Those irregularities can possibly be attributed to material properties. However, if the diagram is simplified by considering only the mean values at every given tem- perature state, the irregula- rities can be eliminated. It‘s getting hot and measurable by a seam based thermocouple. ] V m [ e g a t l o v c i r t c e e o m r e h T l 60 50 40 30 20 10 0 60 50 40 30 20 10 ] C ° [ e r u t a r e p m e T Constantan + Silvertech Temperature real [°C] Temperature set [°C] 44 44

Now it matters . m a e s o m r e h T d e h s i n fi . s v h c t e k S : n o s i r a p m o C The team calcualculated the mean value at every given temperature step and came up with a rat- her exponential curve. For the SmartSeam team that means, that higher tem- peratures (30-60°C) can be detected with a higher accuracy than lower tempe- ratures (10-20°C). Moreover, a slight hys- teresis becomes visible depending on the tempera- ture state the sensory seam comes from. Nevertheless, also with this temperature sensing principle it is possible to create simple textile based sensors that require no complicated technologies. Though, further research could be carried out on which material combinati- ons work best. Simplification for better visualtisation. ] V m [ e g a t l o v c i r t c e e o m r e h T l 45.00 40.00 35.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00 -5.00 Constantan + Silvertech 10-60 Constantan + Silvertech 60-10 10 20 30 40 50 60 Temperature [°C] 45 45

TherchromY The final development of the SmartSeam project was the production of a tempe- rature-sensing hybrid hea- ting yarn with colour-chan- ging function, TherchromY. The three functions, tem- perature sensing, colour changing and heating, were tested by different charac- terisation methods. For the sensory charac- terisation, the SmartSeam team placed the Therchro- mY yarn in the climate chamber. During the mea- surement, it was connected to a multimeter, which re- cords the resistance values during a specially-written temperature programme. In this programme, tempera- tures between 20 and 60°C are reached with a reten- tion time of 30 minutes and a 10°C interval. The temperature mea- surement was carried out on both the pure stainless steel yarn and the finished coated yarn. This was to show whether the additio- nal layers, blank polyes- ter yarn and coating layer, had an influence on the sensitivity of the resistan- ce thermometer. As there can always be random or systematic errors in such measurements, the mea- surement was repeated five times. The average was then calculated from the measured values. After evaluating the mea- surement, Rike and The- resa, the Bachelor student who developed this yarn, talked about the result and agreed that the stainless TherchromY at glance - different layers for different functions. steel yarn is able to detect temperature changes by increasing its resistance. Thereby, the resistance cur- ve runs almost linear with the temperature increase and decrease. Also, the ad- ditional wrapped polyester yarn and coating layer has no negative influence on sensory function. The wrap- ping and coating just slight- ly increases resistance and runs parallelly to the pure Bekinox yarn. Furthermore, There- sa investigated the colour change function by a co- lourimetric measurement. Colour measurement is an important part of dyeing and printing of textiles, as it can be used to optimise dyeing recipes, measure colour differences and carry out quality controls. In the case of Therchro- mY, the measurement was used to check the colour intensity of the thermochro- mic dyes and to analyse the colour gradient from pink to white. For the colour mea- surement, Theresa manu- factured a piece of woven fabric from the hybrid yarn and analysed it underneath the high-performance spec- trophotometer of Datacolor. By increasing the voltage using a laboratory voltage device, the conductive core material can be gradually heated and the resulting temperature is displayed by a multimeter. According to the manufacturer (Kremer) of the thermochromic pig- ments, a complete colour change should take place at a temperature of 31°C. To verify this, the SmartSe- am team tried to increase the temperature from 23°C (room temperature) to 35°C in 1°C steps. 46

Now it matters TherchromY showing sensitivity towards temperature by changing its electrical resistance and can therefore be used as tempera- ture sensor. From the measured va- lues, they created a reflec- tion spectrum, from which conclusions can be drawn about the colourfulness at the applied temperatures. Due to the large gap bet- ween 28 and 29°C, it beco- mes clear that the colour change takes place at these temperatures. At the same time, Theresa explains to me that the function of the curve makes it possible to draw conclusions about the colourfulness. According to this, at temperatures bet- ween 23 and 26°C the co- lour is pink, where a strong reflection takes place in the red range (600-700nm). At higher temperatures, especially between 30 and 35°C, there is also a strong reflection in the blue and green range. The func- tion approaches an almost straight line, from which it can be concluded that the woven fabric becomes al- most white. Theresa also calculated the colour difference, ∆E, between the temperatures, which describes the colour difference between two co- lours. The ∆E value is cal- culated from the tempera- ture-dependent Lab values and is calculated as follows: ∆E=√(∆L2+∆a2+∆b2 ) Colour measurement of Therchromy showing the colour change ef- fect at 28-29°C. 47

Now it matters The heating function of TherchromY is a At the same, the time needed for heating little more difficult to measure, as the quan- tity heat is subjectively evaluated. For the heating performance, Theresa has charac- terised the yarn by a thermal imaging ca- mera at different voltage values. and cooling was also interesting for the heating performance. For this purpose, a voltage of 2.09V was connected to the yarn three times and the time to heat up to 45°C and cool down to 23°C was measured. A flexible heating element should opti- The yarn takes an average of 28 seconds mally be able to approach different heating levels in order to heat the wearer depending on the situation and to save electricity. The outcomes of this measurement method ac- tually show that the TherchromY yarn is able to do this. Different temperatures could be achieved at different voltages of 1.01, 1.67 and 3.01V, which are particularly visible through the thermochromic colour change. At 1.01V, in contrast to the other voltages, no colour change took place. to heat up to 45°C and 24 seconds to cool down to the ambient temperature. Thus, the SmartSeam team concluded that the Beki- nox yarn has a very good heating perfor- mance. By thoughtful combination of diverse functional materials and the deployment of different textile technologies, Theresa was able to produce this smart hybrid yarn with triple functionality. Thermal imagimg of TherchromY showing the hea- ting function of the hybrid yarn. 49

L Lets move! From the strain sensitive seam samples a sports outfit was crea- ted but this time with the covering stitch 602. This stitch is formed by four threads, two needle threads, one looper thread and one top co- vering thread. It was chosen due to its nicer handling on elastic and thin sports jersey and was investi- gated a lot by our project partners Hogent. But we also carried out some investigations and tested the seam samples in the tensile testing machine loading them about 10% and measuring the change in elec- trical resistance. Thereby, actual- ly the electrically conductive yarn HC40 of Madeira worked best. When the seam is stretched, the metal yarns integrated as looper and top covering thread get com- pressed as strain puts load on the needle threads. This compression results in a decrease of resistance. It is conceivable that not just me- chanical stretching performed by a tensile testing machine but also stretching caused by body move- ments result in such a decrease. Let‘s move ] m h O k [ e c n a t s i s e R 13 12.8 12.6 12.4 12.2 12 11.8 11.6 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 Strain [%] Tensile testing and resistance measur- ment of smart seams made with stitch type 602 and the electrical conductive yarn HC40. Sensitive seam with conductive thread HC40 produced by covering stitch 602. 51

Movement puts a lot of pressure on our clothings - especially on tight garments that we find often in women‘s sport clothing. If we were able to quantify those loads, it would be possible to correlate it back to the movement. And this is exactly what we are trying to do by making the seams smart. But of course, those sensitive seams were not just placed randomly on a sports jersey but with thoughtful consideration about where loads actually occur during e.g. a home work out. Besides, we had to consider connecting pos- sibilities to an evaluation unit. As both yarn ends need to be con- nected to be able to measure resistance, the seam had to be placed in such a way that it begins and ends at the same position - a con- ventional cut was not an option. For the leggings, sensory seams were placed over the knees to detect movements such as squatting. Moreover, a seam was placed around the buttocks to detect moti- ons like sitting. Those seams started and ended in a small pocket, known from conventional sports leggings as a mobile phone pocket. 52

Let‘s move For the sports upper part, seams were mainly placed on the back- side to detect back roundings that occur for instance during stret- ching. Another seam was placed over the elbow to allow detection of arm movements that take place e.g. during pull- or push-ups. Here again, small pockts are sewn between the shoulder blades or on the upper arm for connection to an evaluation unit and power supply. The sports outfit is made from elastic jersey and the sen- sory seams are either dividing seams or simply decorative seams depending on their position. By that we, we do not only use com- mon textile technologies for adding functionality but are also able two complete two steps in one - joining plus functional integration. 53

Of course the sports outfit was tested while worn as well. Diffe- rent movements, such as push- ups and squats, have been carried out while change in resistance was recorded. Resistance actu- ally drops when areas are loaded and recovers well when going back into the resting position. The tests show that if further field studies are conducted on what mo- vements cause what change in re- sistance, this bodysuit, developed exclusively with common textile technologies, can be used for mo- tion detection. It easily enables the clothing manufacturers to adapt to consumer needs without large investments in new technologies. Changes in electrical resistance cau- sed by push-ups. Changes in electrical resistance caused by lunges. 54

Sweet sweat HumY was integrated in a clot- hing demonstrator as well. Her- efore, a T-shirt for an under- garment was designed and manufactured. The undershirt should be able to detect human sweat, which is useful to know for e.g. athletes. Therefore, the sensory seam was placed along the spine and HumY was applied with the SmartSeam sewing machine in a wavy structure. We used a white, elastic, polyester jersey as base fabric and trans- fer-printed a watery pattern on it. As sewing thin elastic fabrics with the SmartSeam sewing machine is rather challenging, we decided to simply apply a de- corative stitch rather than using the seam for joining and func- tional integration at the same time. Although this causes us to introduce an additional process step, we can at least show that purely textile technologies were used to create the demonstra- tor. For a smoother seam surfa- ce a fabric lining was placed as reinforcment underneath the sensory seam. When applying the seam, contacting had to be considered as well. Therefore, the sensory seam was applied in a U-shape, so that start and ending are in the same position. For contacting, the two electro- des were unwrapped and pulled to the inside of the T-shirt. 56

The integrated HumY yarn is connected to an evaluation unit that is able to send a signal to a mobile phone or a laptop via internet. From the measured capacity, conclusions can be drawn about the ambient hu- midity and thus about the swea- ting state. This way, the wearer can continuouisly monitor his/ her sweat level. We simulated a sweat test by wearing the T-shirt and enriching the environment with moisture using a spray ne- buliser. Capacity slowly increa- ses as humidity surrounding the sensory T-shirt rises. Though, we prove that T-shirt integrated sweat monitoring is possible, large-scale field stu- dies are needed to make reliable statements about sweat levels. Therein, the correlation of swea- ting on the body surrounding humidity needs to be establis- hed. However, we prove that we successfully produced and in- tegrated an all-textile based hu- midity sensor - HumY. Therefore we used a commercial spinning machine as well as a modified double lockstitch sewing stitch. 60

Safety in the workwear area is a huge topic. Especially streetworkers are subjected to high risks in poor lighting conditions. There are different func- tional materials on the market to increase visibility, those are mainly retro- reflective materials or fluorescent materials, known for example from safety vests. However, active lighting materials are not wide spread; might be a real game changer though to increase visibility and thereby safety. Active lighting materials are for example electroluminescent (EL-)wires and polymer optical fibres. EL-wires are thin copper wires coated with phosphor that produce light through electroluminescence when an alternating current is applied to them. Safety first Polymer optical fibres are thin, flexible polymer fibres drawn to a diameter slightly thicker than human hair. Optical fibres are able to transmit light but not actually produce light. They need and external light source and function as a waveguide by internal reflection. Both materials have in common that they are delicate to handle and common textile manufacturing techniques of- ten do not allow to process those special materials. But with the SmartSeam sewing machine it was actually possible to apply these materials as laying thread in a decorative seam. A modular safety vest was developed in a final thesis of a student, Theresa Grümpel. The modularity is created by zip, snap and velcro fastener connections. In this way, sleeves, pockets or luminous strips can be de- and attached easily. Also the vest can be transformed in a cropped version by a detachable hem. 62

Theresa Grümpel first worked with EL-wires, whereas we developed fur- ther modular clothing parts with polymer optical fibres. EL-wires need to be connected to inverters. The advantage here is, that the EL-wire can be of any length without light intensity loss. For those, Theresa Grümpel has provided small pockets between the shoulder blades. Polymer optical fibres need to be connected by a laser. The problem here is, that the light intensity in the fibre decreases the longer the fibre. This ultimately means, that the light source should be as close to the area that should be illuminated as possible. This was realised by small straps, onto which the portable light source can be attached. In this way, we created a modular safety vest that cannot only be chan- ged in style but also mode of active lighting. As we used detachable lighting elements, washing of the base jacket does not cause a problem. Workers can choose their individual prefrences. Thereby, we hope to make the roads brighter and the people safer. 64

The endThe end We would like to dedicate this last page to you - all our project partners that have supported and accompanied us through the SmartSeam project. This is first and foremost our project funder AiF/iGF, without whose funding the project would not have been possible in the first place. Secondly, we would like to thank our project partner Hogent for the mutually enriching cooperation on this project. Alexandra de Raeve, Sheilla Odhiambo, Simona Vasile, Ingeborg Rottiers, Jochen Sarrazyn, Anna De Coene, Joris Cools, Charlotte Moer- kerke, Svea Thienpondt. We had a delightful exchange about achievements and challenges and could learn and profit from each ot- hers knowledge. Moreover, we would like to thank all our student research assistants and students, who wrote their final theses with us. They have done a gre- at job and were largely involved in the achievements of the project. Theresa Grümpel, Michèle Lemper, Theresa Junge, Laura Hegers, Rebecca Faber, Lina We- ber, Finja Petersen. Last but not least we would like to thank the project committee, that has supported us with their wide knowledge and material. We hope that we can give something back to you with this magazine and that you benefit from the cooperation as much as we do. Amann & Söhne GmbH & Co. KG., Gütermann GmbH, Hexonia GmbH, Ferd. SCHMETZ GmbH, Sta- tex Produktions- und Vertriebs GmbH, HANZA Beyers GmbH, Trans-Textil GmbH, PW Krystain GmbH, KAYA&KATO GmbH, Ergobaby Europe GmbH, KOB GmbH, Paul H. Kübler Bekleidungswerk GmbH & C0. KG. Without all of you the SmartSeam project would not have been possible in the way that it was. 66