(Invited) Flexible Electronic Skins for Wearable Sensors

Flexible electronic skins with high tactile sensitivities have gained great attentions in the fields of wearable sensors, robotic skins, and biomedical diagnostics. Here, we introduce highly-sensitive, multifunctional, and stretchable electronic skins based on interlocked design of micro- and nanostructured hybrid materials. Inspired by the interlocked microstructures found in epidermal-dermal ridges in human skin, piezoresistive interlocked microdome arrays are employed for stress-direction-sensitive, stretchable electronic skins. We show that the interlocked microdome arrays possess highly direction-sensitive sensitive detection capability of various mechanical stimuli including normal, shear, stretching, bending, and twisting forces. We also demonstrate that the bioinspired e-skin design of hierarchical micro- and nanostructured ZnO nanowire (NW) arrays in an interlocked geometry shows a highly-sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. Finally, we show that the stretchable electronic skins attached on the human skin can be used as wearable healthcare monitoring devices, which are able to distinguish various mechanical stimuli applied in different directions, selectively monitor different intensities and directions of air flows and vibrations, and sensitively monitor human breathing flows and voice vibrations.