Flexible and stretchable wearable biomedical devices provide a platform for continues long-term monitoring of biological signals during neutral body movements thus enabling early intervention and diagnostics of various diseases. This thesis evaluates novel flexible and stretchable bio interfacing medical devices based on microneedle patches and split ring resonator for healthcare diagnostics. Flexible and stretchable microneedle patches were realized by integrating a soft polymer substrate with sharp stainless steel microneedles. This was realized using a magnetic assembly technique. Investigations have shown that the flexible microneedle patch can provide conformal and reliable contact with wrinkles and deformations of the skin. In addition, transdermal monitoring of potassium ions using the proposed flexible microneedle patch have been demonstrated by coating the microneedles with a potassium sensing membrane. Ex-vivo test on the microneedle potassium sensor performed on chicken and porcine skin was able to detect change in potassium concentration in the skin. Furthermore, a novel flexible bio-interface spilt ring resonator (SRR) for the monitoring of intera cranial pressure (ICP) is demonstrated. The sensor was fabricated by depositing a 500 nm gold film on a thermoset thiolene epoxy polymer substrate. The flexible sensor was able to clearly detect the pressure variation that might be an indication of increased ICP in the skull. The proposed methodology of heterogeneous integration of hard materials on a soft and flexible substrate demonstrates a first proof of concept of flexible wearable bio-interfacing devices with vastly different material properties with the potential for continuous and real-time health monitoring. / <p>QC 20190306</p>

In this research, we aimed to develop thin-film devices on a polymer substrate and an alternative 3D-printed device with macroelectrodes for treating gastrointestinal (GI) conditions. First, the fabrication of thin-film devices was demonstrated on a softening thiol-ene/acrylate polymer utilizing titanium nitride (TiN) as electrode material. This was achieved by utilizing cleanroom fabrication processes such as photolithography, wet and dry etching. The functionality of the device was shown by performing electrochemical characterization tests, mainly cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transient. We synthesized a novel thiol-ene/acrylate polymer based on 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), trimethylolpropanetris (3-mercaptopropionate) (TMTMP), and polyethylene glycol diacrylate (PEGDA). We show that this stretchable shape memory polymer substrate is well suited for cleanroom processes. Finally, for the high throughput of the wearable devices with electrodes size 10 mm in diameter, we implemented single electrode fabrication using printed circuit boards (PCBs) and depositing gold (Au) and TiN on the plated side of PCBs utilizing the sputtering tool. This step was followed by the assembly of those single electrodes on the flexible 3D printed device. We showed that the TiN electrode material performed better in terms of charge storage capacity and charge injection capacity than the widely used stainless steel electrode material for wearables.

The hands and feet account for half of the complexity of the musculoskeletal system, while the skin of the hand is specialised with many important structures. Much of the subtlety of the mechanism of the hand lies in the soft tissues, and the tactile and proprioceptive sensitivity depends on the large number of mechanoreceptors embedded in specific structures of the soft tissues. This thesis investigates synthetic materials and manufacturing techniques to enable building robots that reproduce the biomechanics and tactile sensitivity of vertebrates – histomimetic robotics. The material and mechanical anatomy of the hand is reviewed, highlighting difficulty of numerical measurement in soft-tissue anatomy, and the predictive nature of descriptive anatomical knowledge. The biomechanical mechanisms of the hand and their support of sensorimotor control are presented. A palate of materials and layup techniques are identified for emulating ligaments, joint surfaces, tendon networks, sheaths, soft matrices, and dermal structures. A method for thermoplastically drawing fine elastic fibres, with liquid metal amalgam cores, for connecting embedded sensors is demonstrated. The performance requirements of skeletal muscles are identified. Two classes of muscle-like bulk MEMS electrostatic actuators are shown theoretically to be capable of meeting these requirements. Means to manufacture them, and their additional application as mechanoreceptors are described. A novel machine perception algorithm is outlined as a solution to the problem of measuring soft tissue anatomy, CAD/CAE/CNC for layup of histomimetic robots, and sensory perception by such robots. The results of the work support the view that histomimetic robotics is a viable approach, and identify a number of areas for further investigation including: polymer modification by graft-polymerisation, automated layup tools, and machine perception.

Cette thèse propose tout d’abord une méthode originale, appelée 2 en 1, de construction contrôlée, couche-par-couche, de films de polyélectrolytes, basée sur le dépôt d’un unique complexe polycation-polyanion. Détaillée dans le cas du poly(éthylènedioxythiophène)-poly(styrènesulfonate) PEDOT-PSS, la méthode est ensuite étendue avec le même succès à d’autres complexes (poly(éthylèneimine) branché-poly(4 styrènesulfonate), poly(diallyldiméthylammonium)-poly(4 styrènesulfonate) et poly(allylamonium)-poly(4 styrènesulfonate)).Les films 2 en 1 de PEDOT PSS sont robustes vis-à-vis d’un recuit thermique et possèdent une conductivité électronique indépendante de leur épaisseur. Cette conductivité peut être améliorée en utilisant un composite contenant des nanoparticules d’or Au Np PEDOT PSS. Des superstructures alternant dépôts de PEDOT PSS et de composite ont, en outre, pu être construites.La construction est contrôlée non seulement sur des substrats rigides (verre, wafer de silicium) mais également sur des substrats élastomère de type silicone (polydiméthylsiloxane PDMS). Le traitement du PDMS par polymérisation plasma d’EDOT sous vide permet le dépôt subséquent de films 2 en 1 de PEDOT PSS. Par ailleurs, la pulvérisation cathodique d’or sur le PDMS permet d’obtenir des conducteurs étirables, de surcroît utilisables comme substrats de films 2 en 1 de PEDOT PSS.Enfin, de nouveaux complexes aqueux synthétisés par voie chimique à partir d’EDOT et d’un polysaccharide (sulfate de chondroïtine A) ont conduit à des films présentant une très bonne conduction qui peut être augmentée par inclusion de nanoparticules d’or. Ces nouveaux composés sont porteurs d’un potentiel très prometteur. / This thesis proposes firstly an original method, called 2 in 1 method, for controlled, layer-by-layer, polyelectrolytes film buildup, based on the deposition of a sole polycation-polyanion complex. Detailed on the case of poly(ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS), the method was then extended with the same success to other complexes (branched poly(ethyleneimine)-poly(4 styrenesulfonate), poly(diallyldimethylammonium)-poly(4 styrenesulfonate) and poly(allylamonium)-poly(4 styrenesulfonate)).The 2 in 1 PEDOT PSS films are robust regarding thermal annealing and have an electronic conductivity independent of their thickness. This conductivity can be improved by using a composite containing gold nanoparticles Au Np PEDOT PSS. Superstructures alternating PEDOT PSS and composite depositions were also obtained.Film buildup is controlled not only on rigid substrates (glass, silicon wafer) but also on elastomeric substrates of the silicon type (polydimethylsiloxane PDMS). The treatment of PDMS by vacuum plasma enhanced chemical vapor deposition (PECVD) of EDOT allows subsequent deposition of 2 in 1 PEDOT-PSS films. Besides, gold sputter deposition on PDMS reaches stretchable conductors. Gold sputtered PDMS can further act as a substrate for 2 in 1 PEDOT-PSS films.Finally, new aqueous complexes, chemically synthesized from EDOT and a polysaccharide (chondroitin sulfate A), lead to films which exhibit a very good conduction, which can be improved by the inclusion of gold nanoparticles. These new complexes are very promising in the field of conductive biomaterials.

The purpose of this thesis is to develop a simple Direct Ink Writing (DIW) method for fabricating intrinsically stretchable microsupercapacitors as ef- fective on-chip energy storage devices for the emerging stretchable electron- ics. Using the printing method for fabricating intrinsically stretchable elec- tronic components remains a novel approach. In this thesis, interdigitated structures of intrinsically stretchable electrodes were printed on a stretchable thermoplastic polyurethane (TPU) substrate using a formulated ink based on Poly(3,4-ethylenedioxythiophene):Polystyrene Sulfonate. Formulated elec- trolytes based on Poly(4-styrene Sulfonic Acid) and Phosphoric Acid were applied to the electrodes to complete the fabrication of microsupercapacitors. Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Elec- trochemical Impedance Spectroscopy (EIS) were used to characterize the per- formance of the devices. The stretchability of the electrodes was also mea- sured. Results from CV-measurements revealed a maximum capacitance of740 µF cm−2 at a scan rate of 5 mV s−1. GCD-measurements showed a capaci- tance of 952 µF cm−2 for the same device and an equivalent series resistance of approximately 7 kΩ. The printed electrodes exhibited a stretchability of 80%. The results show the feasibility of fabricating intrinsically stretchable energystorage devices using commercially available materials and a simple 3D print- ing technique. This method could be used as a high-throughput and low-cost method for stretchable electronics applications. / Syftet med detta arbete är att utveckla en simpel Direct Ink Writing (DIW) metod för framställning av intrinsiskt sträckbara mikrosuperkondensatorer som effektiva on-chip energilagrinsenheter i kommande sträckbar elektronik. Användandet av DIW för att tillverka intrinsiskt sträckbara elektroniska kom- ponenter är ett nytt tillvägagångssätt. I detta arbete trycktes interdigiterade strukturer av intrinsiskt sträckbara elektroder på ett sträckbart termoplastiskt polyuretan (TPU) substrat genom att använda ett formulerat bläck baserat på Poly(3,4-etylendioxitiofen):Polystyren Sulfonat (PEDOT:PSS). Formuler- ade elektrolyter baserade på Poly(4-styrensulfonsyra) och Fosforsyra applicer- ades på elektroderna för att färdigställa tillverkningen av mikrosuperkonden- satorer. Cyklisk Voltammetri (CV), Galvanostatisk uppladdning-urladdning (eng. GCD) och Elektrokemisk Impedansspektroskopi (EIS) användes för att karaktärisera enheternas prestanda. Bläckets sträckbarhet uppmättes också. Resultaten från CV-mätningar visade att den maximala kapacitansen var 742µF cm−2 vid skanningsfrekvensen 5 mV s−1. Kapacitansen från GCD-mätningar var 952 µF cm−2 för samma enhet och den ekvivalenta serieresistansen var cirka 7 kΩ. Sträckbarheten som de tryckta elektroderna uppvisade var 80%. . Re- sultaten påvisar möjligheten att kunna framställa intrinsiskt sträckbara en-ergilagringsenheter genom att använda kommersiellt tillgängliga material och en simpel metod för friformsframställning. Denna metod skulle kunna använ- das för att framställa sträckbara elektroniska komponenter till låg kostnad och med hög produktionstakt.

Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems. Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures. In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties. To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.

This thesis presents various integrated antenna solutions for different types of systems and applications, e.g. wireless sensors, broadband handsets, advanced base stations, MEMS-based reconfigurable front-ends, automotive anti-collision radars, and large area electronics. For wireless sensor applications, a T-matched dipole is proposed and integrated in an electrically small body-worn sensor node. Measurement techniques are developed to characterize the port impedance and radiation properties. Possibilities and limitations of the planar inverted cone antenna (PICA) for small handsets are studied experimentally. Printed slot-type and folded PICAs are demonstrated for UWB handheld terminals. Both monolithic and hybrid integration are applied for electrically steerable array antennas. Compact phase shifters within a traveling wave array antenna architecture, on single layer substrate, is investigated for the first time. Radio frequency MEMS switches are utilized to improve the performance of reconfigurable antennas at higher frequencies. Using monolithic integration, a 20 GHz switched beam antenna based on MEMS switches is implemented and evaluated. Compared to similar work published previously, complete experimental results are here for the first time reported. Moreover, a hybrid approach is used for a 24 GHz switched beam traveling wave array antenna. A MEMS router is fabricated on silicon substrate for switching two array antennas on a LTCC chip. A concept of nano-wire based substrate integrated waveguides (SIW) is proposed for millimeter-wave applications. Antenna prototypes based on this concept are successfully demonstrated for automotive radar applications. W-band body-worn nonlinear harmonic radar reflectors are proposed as a means to improve automotive radar functionality. Passive, semi-passive and active nonlinear reflectors consisting of array antennas and nonlinear circuitry on flex foils are investigated. A new stretchable RF electronics concept for large area electronics is demonstrated. It incorporates liquid metal into microstructured elastic channels. The prototypes exhibit high stretchability, foldability, and twistability, with maintained electrical properties. / wisenet

In this work, stretchable magnetic sensorics is successfully established by combining metallic thin films revealing a giant magnetoresistance effect with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved by specific morphologic features (e.g. wrinkles), which accommodate the applied tensile deformation while maintaining the electrical and magnetic integrity of the sensor device. The entire development, from the demonstration of the world-wide first elastically stretchable magnetic sensor to the realization of a technology platform for robust, ready-to-use elastic magnetoelectronics with fully strain invariant properties, is described. The prepared soft giant magnetoresistive devices exhibit the same sensing performance as on conventional rigid supports, but can be stretched uniaxially or biaxially reaching strains of up to 270% and endure over 1,000 stretching cycles without fatigue. The comprehensive magnetoelectrical characterization upon tensile deformation is correlated with in-depth structural investigations of the sensor morphology transitions during stretching. With their unique mechanical properties, the elastic magnetoresistive sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally. Various application fields of stretchable magnetoelectronics are proposed and realized throughout this work. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking and touchless control capabilities. A variety of novel technologies, like smart textiles, soft robotics and actuators, active medical implants and soft consumer electronics will benefit from these new magnetic functionalities.

In this work, stretchable magnetic sensorics is successfully established by combining metallic thin films revealing a giant magnetoresistance effect with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved by specific morphologic features (e.g. wrinkles), which accommodate the applied tensile deformation while maintaining the electrical and magnetic integrity of the sensor device. The entire development, from the demonstration of the world-wide first elastically stretchable magnetic sensor to the realization of a technology platform for robust, ready-to-use elastic magnetoelectronics with fully strain invariant properties, is described. The prepared soft giant magnetoresistive devices exhibit the same sensing performance as on conventional rigid supports, but can be stretched uniaxially or biaxially reaching strains of up to 270% and endure over 1,000 stretching cycles without fatigue. The comprehensive magnetoelectrical characterization upon tensile deformation is correlated with in-depth structural investigations of the sensor morphology transitions during stretching. With their unique mechanical properties, the elastic magnetoresistive sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally. Various application fields of stretchable magnetoelectronics are proposed and realized throughout this work. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking and touchless control capabilities. A variety of novel technologies, like smart textiles, soft robotics and actuators, active medical implants and soft consumer electronics will benefit from these new magnetic functionalities.:Outline List of abbreviations 7 1. INTRODUCTION 1.1 Motivation and scope of this work 8 1.1.1 A brief review on stretchable electronics 8 1.1.2 Stretchable magnetic sensorics 10 1.2 Technological approach 11 1.3 State-of-the-art 12 2. THEORETICAL BACKGROUND 2.1 Magnetic coupling phenomena in layered structures 14 2.1.1 Magnetic interlayer exchange coupling 14 2.1.2 Exchange bias 15 2.1.3 Orange peel coupling 16 2.2 Giant magnetoresistance 17 2.2.1 Electronic transport through ferromagnets 17 2.2.2 The GMR effect 19 2.2.3 GMR multilayers 20 2.2.4 Spin valves 21 2.3 Theory of elasticity 22 2.3.1 Elastomeric materials 22 2.3.2 Stress and strain 23 2.3.3 Rubber elasticity 25 2.3.4 The Poisson effect 26 2.3.5 Viscoelasticity 27 2.3.6 Bending strain in a stiff film on a flexible support 27 2.4 Approaches to stretchable electronic systems 28 2.4.1 Microcrack formation 28 2.4.2 Meanders and compliant patterns 29 2.4.3 Surface wrinkling 30 2.4.4 Rigid islands 32 3. METHODS & MATERIALS 3.1 Sample fabrication 34 3.1.1 Polydimethylsiloxane (PDMS) 34 3.1.2 PDMS film preparation 35 3.1.3 Lithographic structuring on the PDMS surface. 36 3.1.4 Magnetic thin film deposition 38 3.1.5 GMR layer stacks 40 3.1.6 Mechanically induced pre-strain 43 3.1.7 Methods and materials for the direct transfer of GMR sensors 45 3.1.8 Materials used for imperceptible GMR sensors 47 3.2 Characterization 48 3.2.1 GMR characterization setup with in situ stretching capability 48 3.2.2 Sample mounting 50 3.2.3 Electrical contacting of stretchable sensor devices 51 3.2.4 Customized demonstrator electronics 52 3.2.5 Microscopic investigation techniques 53 4. RESULTS & DISCUSSION 4.1 GMR multilayer structures on PDMS 54 4.1.1 Pre-characterization 54 4.1.2 Thermally induced wrinkling 55 4.1.3 Self-healing effect 57 4.1.4 Demonstrator: Magnetic detection on a curved surface 60 4.1.5 Sensitivity enhancement 61 4.1.6 GMR sensors in circumferential geometry 64 4.1.7 Stretchability test 67 4.2 Stretchable spin valves 69 4.2.1 Random wrinkles and periodic fracture 70 4.2.2 GMR characterization 73 4.2.3 Stretching of spin valves 74 4.2.4 Microcrack formation mechanism 76 4.3 Direct transfer printing of GMR sensorics 81 4.3.1 The direct transfer printing process 82 4.3.2 Direct transfer of GMR microsensor arrays 84 4.3.3 Direct transfer of compliant meander shaped GMR sensors 86 4.4 Imperceptible magnetoelectronics 89 4.4.1 GMR multilayers on ultra-thin PET membranes 89 4.4.2 Imperceptible GMR sensor skin 92 4.4.3 Demonstrator: Fingertip magnetic proximity sensor 93 4.4.4 Ultra-stretchable GMR sensors 94 4.4.5 Biaxial stretchability 99 4.4.6 Demonstrator: Dynamic detection of diaphragm inflation 101 5. CONCLUSIONS & OUTLOOK 5.1 Achievements 102 5.2 Outlook 104 5.2.1 Further development steps 104 5.2.2 Prospective applications. 105 5.3 Technological impact: flexible Bi Hall sensorics 106 5.3.1 Application potential 106 5.3.2 Thin and flexible Hall probes 107 5.3.3 Continuative works and improvements 108 5.4 Activities on technology transfer and public relations 108 Appendix References 110 Selbständigkeitserklärung 119 Acknowledgements 120 Curriculum Vitae 121 Scientific publications, contributions, patents, grants & prizes 122