Smart Patches

Author : Akanksha Rohit
Publisher :
ISBN 13 :
Total Pages : 220 pages
Book Rating : 4.:/5 (13 download)

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Download or read book Flexible Sensors and Smart Patches for Multimodal Sensing written by Akanksha Rohit and published by . This book was released on 2021 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emerging wearable technologies are creating a major impact in the area of health monitoring, aerospace, prosthetics and robotics to monitor crucial information in real time which could not be achieved using conventional electronics only. The demand for multifunctional wearable systems is set to grow exponentially in the next decade and low cost multimodal sensor patches that can be closely coupled to the skin define the success of this new era of digital health and robotics. Accordingly, this dissertation focuses on developing a wireless multi-modal sensor patch that can be directly placed on the skin or integrated into clothing to monitor multiple biophysical and structural signals simultaneously. Serving both as a multimodal sensor as well as a compact integration platform for smart textile development, the proposed patch is ideally suited for complex body performance monitoring, realistic worker training and for high-risk patients. The foundation of this research is based on parallel plate capacitive sensors with elastomeric dielectrics (Ecoflex/PDMS) and conductive textile electrodes. The patches are highly stretchable (100%) with a gauge factor of 0.64 with pure silicone (Ecoflex) as the dielectric layer. The gauge factor of the capacitive strain sensor is enhanced two-fold with the inclusion of high-k (or relative dielectric constant) barium titanate (BTO) nanoparticles dispersed in the silicone dielectric layer without sacrificing its linearity and durability easily exceeding 2000 cycles. To further improve the capacitive performance and capabilities for multi-modal sensing, the elastomer dielectric layer is modified with highly flexible polyurethane (PU) foam. With a foam-based dielectric, the change in capacitance is not only due to the change in the thickness of the dielectric but also due to the change in the permittivity of the micropores due its porous structure. In addition to bending and stretching, the foam-based dielectric had a high-pressure sensitivity (0.0198 kPa-1) in the range of 0-4.5 kPa making it capable to monitor phonation, pulsatile flow and respiration. The piezoelectric properties of films, including the nanoparticles of barium titanate (BTO), lead zirconate titanate (PZT) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) was systematically studied at different weight ratios by bending and motor vibrational tests. On corona poling the nanocomposite films at high field (6 kV/cm), the voltage output of all the piezoelectric sensors increased by two-fold. Therefore, with a few modifications in the dielectric layer, the patches are sufficiently sensitive to detect multiple stimuli such as strain, pressure, temperature, bending, vibration, and acoustic feedback. Due to limitations with high poling voltages that can cause arcing, triboelectric sensing was also explored in this work. While charge generation in piezoelectric materials is due to deformation and shift of ions in the crystal structure, triboelectricity is the charge generated due to friction between the two materials. Amongst all the material studied, polyurethane foam was used as the positive frictional layer and PDMS mixed with expandable microspheres was used as the negative frictional layer. The high sensitivity of the triboelectric sensors were capable of sensing small movements such as blinking and chewing, breathing rate and pulsatile flow which could not be detected with the piezoelectric sensors. Three different designs of multimodal patches were developed by combining the different dielectrics into a single patch