Flexible Self‐Repairing Materials for Wearable Sensing Applications: Elastomers and Hydrogels

Abstract

related operations, and destroy the operation of the whole equipment (system). Bao and his colleagues developed a novel self-healing and mechanical force-sensing flexible sensor using micro-structured elastomeric dielectrics, which served as a foundation to improve the stability and lifetime of flexible sensors. [8] Self-healing flexible materials can be divided into two categories, one is solvent-less or water-free after curing and high degree of polymerization of elastomers, such as polyamide, polyurethane, etc., the other is hydrogels, low degree of polymerization, structural cross-linking. In self-healing flexible elastomer sensors, the structure of elastomer is mostly linear structure or semi-cross-linked structure; the elastomer of cross-linked structure is poor flexibility and fragile due to its high degree of polymerization. The elasticity of semi-crosslinked structure has excellent resilience and great potential in the field of flexible flexural sensors. In the past two years, self-healing flexible hydrogels have attracted extensive attention due to their excellent stretchability and resilience, as well as outstanding performance in the preparation of sensors with high sensitivity and fast response. [9,10] Sensors with elastomers and hydrogels as flexible matrices face great difficulties in conductivity, which affects the sensitivity and stability of the sensors. Filling conductive materials is the most commonly method, in which organic conductive polymers (polyaniline, [11] polypyrrole [12]) are filled to construct conductive networks, and good interfacial compatibility results in uniform conductive polymer elastomers, but the inherent color fillers affect the transparency of flexible sensors, limiting their applications in the biomedical field. [13-17] Flexible materials filled with inorganic conductive particles (graphene, nano-silver wire) have high conductivity, but phase separation between filler and matrix usually reduces the tensile, toughness and fatigue resistance, and even affects the self-healing ability of flexible materials. Modified fillers are often required to improve affinity for flexible matrices and inhibit phase separation. However, many hydrogel matrices are intrinsically weak and cannot withstand cyclic loadings. [18] Although surface modified fillers can improve strength and toughness, it is difficult to compensate for the inherent weaknesses. For self-healing flexible elastomers, conductive flexible materials can still be endowed with conductivity by scraping or printing conductive particles on the Flexible pressure and strain sensors have great potential for applications in wearable and implantable devices, soft robots, and artificial skin. The introduction of self-healing performance has made a positive contribution to the lifetime and stability of flexible sensors. At present, many self-healing flexible sensors with high sensitivity have been developed to detect the signal of organism activity. The sensitivity, reliability, and stability of self-healing flexible sensors depend...

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Artificial Intelligence in Medical Sensors for Clinical Decisions

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