Design, Fabrication, and Validation of a Flexible Tactile Sensor for a Hand Prosthesis

Abstract

This article presents the development, fabrication, and validation of a flexible tactile sensor designed for integration into a hand prosthesis. The proposed sensor design encompasses two distinct prototypes: a fingertip tactile sensor and a palm tactile sensor. Employing a dual-layer structure composed of liquid metal (LM) and elastic fibers, these sensors exhibit enhanced sensing capabilities in multiple axes while retaining the capability to deform. The fabrication process includes mold preparation and silicon formulation, body sensor fabrication, Galinstan injection, wire assembly, and creation of a shaped cover for enclosing the tactile palm sensor. A dedicated signal processing circuit is implemented to accommodate the typically small-magnitude and noisy output signals that are characteristic of resistor-based sensors. To enable this signal processing, a filter and programmable gain amplifier-analog-to-digital converter (ADC) are used for signal conditioning. Finally, experimental data are collected through a computer-microcontroller communication link and displayed through a user interface (UI). The results of the sensor validation experiment demonstrate that the finger tactile sensor can provide 1.557, 0.944, and 1.412 mV/N of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${F}_{x}$ </tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${F}_{y}$ </tex-math></inline-formula>, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${F}_{z}$ </tex-math></inline-formula>, respectively, with low-drifting error (0.0265, 0.0145, and 0.0198 mV) and multiaxis sensing capacity, aligning effectively with the operational requisites of a hand prosthetic robot.