Mechano-electrical signal transductions based on interparticle quantum tunneling in polymer matrix composite system are widely used in various fields of biomedical healthcare monitoring, energy converting electronics, wearable devices, and human-machine interfaces due to the enormous potentials, enabling to realize integrated sensing electronic system. Piezoresistive type pressure sensors can be upmost candidates as befitting components for mechanical sensing devices thanks to the feasible merits. However, existing strategies for the formation of percolative signal transductions which are composed of non-featured electroactive particles have shown low sensitivity, membrane rigidity, and opaque device in despite of the fact that piezoresistive pressure sensors act as the key sensitizer layer in sensing system. Here, we demonstrate synergistically combined spike-stimulated dendritic networks leading to the sig- nificantly reinforced-quantum electron tunneling effect between interparticle microchannels on geometrically dendritic surface. Polymer-based composite layer composed of electroactive metal particles and elastomeric matrix shows standout capability to transport electrical distribution and signal transduction from the dynamic external stimuli into digital signal driving multifunctional device performance on the human skin and display touch screen. Our approach provides a remarkable improvements in sensing performance and operation stability such as ultrahigh sensitivity (160.3 kPa-1), device flexibility, and even high optical transparency (75.4 T%, 100). In addition, the flexible and transparent PU composite layers were demonstrated as a multifunctional pressure sensor for signal detection of the physical movement of the skin and a transparent touch panel with flexibility, mechanical/chemical stability (> 30000 cycles), and short response/recovery time (< 21 ms).
Table Of Contents
I. Introduction 1 1.1 Emerging fields of soft electronics 1 1.1.1 Soft electronics for integrated sensing component 4 1.1.2 Piezoresistive pressure sensor in flexible electronic applications 5 1.2 Design nanomaterials for multifunctional sensing device 9 1.2.1 Novel active materials 1. Gold Nanostar 10 1.2.2 Novel active materials 2. Siliver Fractal Dendrite 11 1.2.3 Spike-stimulated Dendritic Networks (SDN) in polyurethane 12 II. Theoretical Background 14 2.1 Mechano-electrical signal transduction 14 2.1.1 Piezoresistive effects based on quantum electron tunneling 14 2.1.2 Neuro-mimetic percolative conducting microchannels 18 2.2 Active materials for piezoresistive type pressure sensor 19 2.2.1 (In)organic nanomaterials and conducting polymers 21 2.2.2 Polymeric composite for elastomeric matrix 21 2.3 Multifunctional nanocomposite film for practical applications 22 2.3.1 1 Mechanical, electrical, and optical properties of SDN-based composites 22 2.3.2 Flexible and transparent pressure sensor 23 III. Experimental section 24 3.1 Chemicals and materials 24 3.2 Synthetic method of electroactive fillers 24 3.3 Fabrication of SDN-based piezoresistive pressure sensor 26 3.4 Characterizations of the piezoresistive pressure sensor 28 3.5 Mechano-electrical measurement and device characteristics 29 3.6 Biomedical and optoelectrical applications 30 IV. Results and Discussion 32 4.1 Enhanced-quantum electron tunneling effect (QTE) 32 4.1.1 Optical and geometrical characteristics for SDN 34 4.1.2 3D finite element analysis of pressure sensor 38 4.1.3 Mechano-response behavior of nanocomposite film 39 4.2 SDN-based piezoresistive pressure sensor 49 4.2.1 Piezoresistive sensing performance 49 4.2.2 Electrochemical impedance analysis 53 4.2.3 Applicability for multifunctional pressure sensor 56 4.2.4 Mechanical and enviornmental stability 59 V. Applications and Demonstration 61 5.1 Biomedical applications for physiological signal processing 61 5.2 Force touch panel for transparent display 63 VI. Conclusion 66 References 67 Summary (in Korean) 73