Breathable and Skin-Mountable Strain Sensor with Tunable Stretchability, Sensitivity, and Linearity via Surface Strain Delocalization for Versatile Skin Activities' Recognition.

Metal film/elastomer-based strain sensors usually exhibit small rupture strain (<5%) because of the strain localization and necking effect of the metal film under tension. To achieve both high stretchability and wide linear region is still challenging for metal film-based strain sensors. Here, we propose a low-cost yet effective strategy for fabricating ultrathin, breathable, and skin-mountable strain sensors with high sensitivity (gauge factor from 7.2 to 474.8), high stretchability (up to 140%), and good linearity by regulating the surface strain delocalization in the metal film on elastomer substrate. On the basis of this phenomenon of strain delocalization, the sensitivity and linearity are further enhanced based on a novel diffraction-induced Au film with gradient thickness. Meanwhile, by means of the strain redistribution and Poisson effect, a novel biaxial strain sensor is designed for recognition of complex human motion. On the basis of the enhanced stretchability, linearity, skin-mountable, and breathable properties, the low-cost metal film-based strain sensors can be broadened as disposable wearables for human motion detection, emotional expression recognition, human interaction, and virtual reality.