Skin-Inspired Magnetoresistive-based Tactile Sensor for Force Characterization in Distributed Areas

Touch is a crucial sense for advanced organisms, particularly humans, as it provides essential information about shape, size, temperature, and texture. In robotics and automation, the integration of tactile sensors has become increasingly relevant, enabling devices to properly interact with their environment. This study aimed to develop a biomimetic, skin-inspired tactile sensor device capable of sensing applied force, characterizing it in three dimensions, and determining its point of application.

The device was designed as a 4x4 matrix of magnetoresistive sensors, wire-bonded to a PCB and encapsulated in epoxy. These sensors detect the magnetic field from an overlayed magnetorheological elastomer, composed of Ecoflex and 5 μm neodymium-iron-boron ferromagnetic particles. Structural integrity tests showed that the device could withstand forces above 100 N, with an epoxy distribution of 0.12 mL per sensor chip.

A 3D movement stage equipped with an indenting tip and force sensor was used to collect device data, which was then used to train neural network models to predict force parameters. The magnitude-sensing model was trained on 31260 data points, being able to accurately characterize force with a mean absolute error between 0.07 and 0.17 N. The spatial sensitivity model was trained on 171008 points and predicted the location of applied pressure with a mean absolute error of 0.26 mm, and 0.63 mm for points outside the testing range.