Highly sensitive and robust soft tri-axial tactile sensors enabled by dual inductive sensing mechanisms

Abstract

Tri-axial tactile sensors that provide real-time information on both normal and shear forces are enabling technologies for tactile perception, which open up new possibilities in robotics, human-machine interfaces, environmental sensing, and health monitoring. Among tri-axial tactile sensors based on different mechanisms, inductive sensors possess good robustness against environmental contamination. Their low sensitivity to normal and shear loads, however, is a critical barrier. This work presents the rational design of soft inductive tri-axial tactile sensors that are capable of distinguishing static or dynamic normal and shear loads, with exceptional tactile sensitivity. Dual mechanisms of Biot-Savart law and Eddy current effect are explored to overcome the long-standing sensitivity issue. In addition, a hybrid coil with non-uniform spacing is designed to generate uniform magnetic fields, addressing the limitations of traditional uniform coils and significantly improving the sensor’s tactile sensitivity. The picosecond pulsed laser scribing technique makes it possible to pattern silver nanowires into inductive coils with high fidelity. A porous compressible layer is adopted to enable adjustable sensitivity and sensing range to meet diverse application demands. Finally, the sensor is integrated between the user’s leg and the orthosis, showcasing the sensor’s capability for real-time monitoring of tri-axial forces and its robustness against environmental objects.

Keywords

Tri-axial tactile sensors / pressure sensing / shear sensing / soft electronics / silver nanowires

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