Wearable, washable and ultra-high environmental tolerant solid-liquid composite sensor based on IL@PU microcapsules

Abstract

Tactile sensors are typically rigid restricting various natural motions and subjected to failure under pressure which compromise their conformability and durability. Here, we exploit the fluidity of ionic liquid (IL) which was encapsulated within a polyurea (PU) shell before being directly incorporated into flexible water-borne polyurethane (WPU) matrix. This approach not only ensured IL stability in the composite by preventing IL leakage but also low dielectric losses beneficial for low-power consumption. Such design yielded high sensitivity (0.083 kPa-1), fast response (40 ms), and excellent stability under cyclic pressure (3000 cycles). The sensor also demonstrated potential for robot gripping, e-skin and real time motion detection by accurately detecting pressure distribution and perceiving real time signals. Moreover, our sensor exhibited long-term sensing stability under complex environments, particularly upon repeated washing, which adequately addressed the poor washability of liquid-based sensors. As such, IL@PU/WPU capacitive sensors not only meet the low-power but washability requirements of wearable devices.