Fingertip-inspired electronic skin based on triboelectric sliding sensing and porous piezoresistive pressure detection

Fingertip is the region with the largest density of mechanoreceptors in human body. Inspired by its complicated anatomical structure, we design a fingertip-like electronic skin (e-skin) that can simultaneously detect the movements from lateral and vertical directions. The device includes three parts that correspond to fingerprint, epidermis and dermis of the human being, respectively. The fabricated double spiral carbon nanotube-poly-dimethylsiloxane (CNT-PDMS) electrodes and substrate mimic the structure of fingerprint and epidermis, respectively. Based on triboelectrification effect, the double spiral CNT-PDMS electrodes can generate alternating voltage with different frequencies when sliding across different rough surfaces, which behaves like fast adapting (FA) in real skin. Porous CNT-PDMS is used for detecting pressure, mimicking the function of slow adapting (SA) and the structure of dermis. A cost efficient way to fabricated porous CNT-PDMS is adopted and it can modulate the porosity and resistance at the same time, which provides a way to modulate its sensitivity. With the help of both sliding sensing and pressure sensing, this device can execute many complicated tasks such as differentiating roughness of surfaces and holding-releasing execution, which greatly expands the application fields of e-skin.