A Single‐Channel Capacitive Sensor for Sequential Discrimination of Proximity, Pressure, and Shear With High Sensitivity in All Three

ABSTRACT

Emulating human skin tactile perception with pre‐touch awareness would enable safer, more dexterous robotic manipulation, yet integrating proximity, pressure, and shear sensing into one device remains challenging. Here, we report an all‐in‐one Proximity–Pressure–Shear capacitive sensor: a porous CNT/Ecoflex nanocomposite (PNC) and an ultrathin insulating layer between coil‐shaped electrodes. The electrodes project fringing fields outward for proximity detection, while lateral misalignment reduces overlap under shear. The CNT‐doped PNC behaves as a lossy medium and the ultrathin insulating layer blocks this charge transport, triggering Maxwell–Wagner–Sillars interfacial polarization that markedly amplifies effective permittivity and pressure‐induced capacitance change. Together, these coupled geometric and material effects yield high sensitivity across all three modalities: a proximity capacitance change of 0.46 pF, a pressure sensitivity of 0.44 kPa ^{− 1} (0–10 kPa), and a shear response of Δ C / C ₀ = 0.28 (γ  =  1, 50 kPa pressure). In a robotic manipulation cycle, the sensor sequentially identifies approaching, gripping, and lifting phases from the sign of a single capacitance output, which decreases upon approaching, increases upon gripping, and decreases again upon lifting. This sequential, sign‐based logic leverages the known temporal order of manipulation rather than decoupling the three modalities independently.