High-performance flexible tactile sensor enabled by multi-contact mechanism for normal and shear force measurement

Flexible tactile sensors are essential components of pressure monitoring in the fields of electronic skin, health care, and robotic hands. Currently, there is a great demand for tactile sensors that exhibit high sensitivity, linearity, and a wide dynamic range, as they play an increasingly vital role in information exchange. However, it is still challenging to achieve a synchronous improvement in performance through a simple strategy. Theoretically, we present the multi-contact mechanism for sensing enhancement by changing the contact mode and the initial state. Specifically, the curved polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (MWCNTs) surface ensures the continuity of contact deformation, leading to a wide dynamic range. Besides, the discrete resistor pillars on the micro-honeycomb electrodes (MHEs) depress the initial current, and thus enhance the sensitivity. Experimentally, we utilize microelectromechanical systems (MEMS) technology to fabricate the MHEs, mainly including patterning and micro-electroforming processes. By adjusting the resistor distribution density and the curvature of PDMS contact, the extraordinary sensitivity is tuned from 25.88 kPa^-1 to 64.68 kPa^-1, and the maximum detection pressure switches between 500 kPa and 1400 kPa, which is consistent with the physical model. Furthermore, a proof-of-concept of the flexible three-axis tactile sensor demonstrates the possibility of realizing normal and force measurement. These results reveal the great application prospect of tactile sensors based on multi-contact mechanism in future wearable electronics.