Most stretchable film strain sensors generally present nonlinear electrical responses to applied strain, leading to an inaccurate acquisition of sophisticated signals, difficult signal processing, and zero-calibration, which hampers practical applications severely. Here, a Janus hetero-structured microarray film sensor is developed by in-situ growth of silver nanoparticles on the surface of micro-patterned elastomer films fabricated via low-temperature imprinting followed by scraping-induced particle trapping. Heterogeneous property designs in both modulus and electrical conductivity via introducing polymer microarrays enable modulating the electron transport manner in the conductive layer of elastic Janus films upon stretching, allowing to tune signal linearity effectively. Therefore, such a hetero-structured film sensor shows good signal linearity (fluctuation of gauge factor [GF] below ±0.02) and relatively high sensitivity (GF > 10) within 55% strain, a detection limit of 0.2% strain, and a response/recovery time of 16.3/46.9 ms, respectively. Correspondingly, it enables monitoring human respiration and body motion with higher resolution compared with the nonlinear one, meanwhile, it is capable of detecting tiny pressure to discriminate braille alphabets via touch identification. Overall, it unveils a simple strategy to fabricate film strain sensors for high-resolution healthcare and body motion monitoring, as well as electronic skins toward tactile sensing and touch identification.
Elastomer-based resistive super-thin film strain sensors show great application potentials in electronic skins, human–machine interaction systems, wearable devices for healthcare, and machine learning algorithms. However, it is challenging to accurately monitor the deformation of human body joints and organs with curved surfaces (e.g., knees, throats, finger joints) by only taking advantage of material thickness and elasticity of conventional 2D film strain sensors. Herein, a simple strategy is developed to fabricate conformal elastomeric thin film sensors with periodic 3D microstructure inspired by the ridges and valleys of human skin for accurate signal acquisition. Specifically, an 8-micrometer-thick elastic film strain sensor with 3D microstructure is fabricated via thermoforming followed by in situ chemical growth of silver nanoparticles. The 3D film strain sensors exhibit excellent signal linearity (R 2 = 0.99) and relatively high sensitivity (gauge factor = 14) over a relatively wide strain range (≈43%), with an ultra-low strain detection limit of 0.025%, enabling potential applications in human healthcare monitoring and air leakage detection. Thus, this study unveils a simple methodology to process microstructure-enabled conformable 3D film strain sensors, which show good conformability and multiple mechanical sensing functions for advancing the development of next-generation flexible strain sensors.
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