Strain sensors with ultrahigh sensitivity under microstrain have numerous potential applications in heartbeat monitoring, pulsebeat detection, sound signal acquisition, and recognition. In this work, a two-part strain sensor (i.e., polyurethane part and brittle conductive hybrid particles layer on top) based on silver nanowires/graphene hybrid particles is developed via a simple coprecipitation, reduction, vacuum filtration, and casting process. Because of the nonuniform interface, weak interfacial bonding, and the hybrid particles' point-to-point conductive networks, the crack and overlap morphologies are successfully formed on the strain sensor after a prestretching; the crack-based stain sensor exhibits gauge factors as high as 20 (Δε < 0.3%), 1000 (0.3% < Δε < 0.5%), and 4000 (0.8% < Δε < 1%). In addition, we demonstrate the sensing mechanism under strain results in the high gauge factor of the strain sensor. Combined with its good response to bending, high strain resolution, and high working stability, the developed strain sensor is promising in the applications of electronic skins, motion sensors, and health monitoring sensors.

Flexible electronic skin (e-skin) have been widely researched due to their potential applications in wearable electronics, robotic systems, biomedicines, et al. For realization of lower cost of the e-skin, copper nanowires (CuNWs) are often served as conductive fillers since their high conductivity and flexibility. However, CuNWs are very sensitive to oxygen that greatly hinders their developments. To solve this issue, a facile galvanic replacement reaction without any heating, stirring or dispersant was performed to coat a thin layer of silver (20 nm) on the surface of CuNWs and Cu-Ag core-shell nanowires (Cu-Ag NWs) with excellent oxidation resistance were obtained and served as conductive fillers for e-skin. To further increase the sensitivity and reduce the response time and detection limit, micro-structure of the surface of rose petal was replicated and introduced onto 2D polydimethylsiloxane (PDMS) surface. The bio-inspired piezoresistive e-skin demonstrates high sensitivity (1.35 kPa -1 ), very low detection limit (< 2 Pa), very low response time and relaxation time (36 ms and 30 ms) and outstanding working stability (more than 5000 cycles). The high performance e-skin has extensive applications in voice recognition, wrist pulses monitoring and detection of spatial distribution of pressure.−1 ), fast response (<500 ms) and low detection limit (20 mg). 29 Wang, et al. replicated the surface of silk and constructed a piezoresistive e-skin, which can be used as voice The defining feature of our design is that the length of the CuNWs should not larger than 20 μm. Therefore, a lower EDA concentration (95 mM) and shorter reaction time (<1.0 h) was performed to synthesis shorter CuNWs. Fig.1a and b show the

A highly stretchable strain sensor with a graphene/silver nanoparticle synergic conductive network and a sandwich structure was fabricated.

A compliant, self-adhesive and self-healing epidermal strain sensor that shows excellent sensing performance at ultra-low and high strain.