Wearable Pressure Mapping Through Piezoresistive C-PU Foam and Tailor-Made Stretchable e-Textile

Abstract

Pressure mapping e-skins and e-textile have applications in robotics, human movement and grasp analysis, rehabilitation, and health monitoring. Especially, e-textiles can be tailor-made and sized as a human <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula> robot-specific wearable garment, with multiple tactile sensing nodes. Nevertheless, it has been challenging to achieve a good combination of wearable functionality and good quality pressure measurement, i.e., high sensitivity, high range, and repeatability. In this work, we demonstrate materials and methods for printed pressure sensing films. A low-cost, easy-to-replicate piezoresistive foam is prepared by carbon-filled PU (C-PU), using sugar as sacrificial material. This foam shows extreme sensitivity in the < 5 kPa range (0,18 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ) but is able to measure pressures up to 500 kPa. It as well presents good repeatability and a stable electromechanical response allied to a long lifetime (15000 sequential compression cycles). The developed piezoresistive foam was integrated into a stretchable circuit backplane with electrodes and interconnects that were printed over a TPU film and transferred to a textile substrate. We demonstrate a pressure sensor matrix, a smart thimble for texture discrimination, and a pressure mapping glove for human grasp taxonomy evaluation. The possibility of integrating the developed foam in wearable health monitoring is also showcased by a respiration monitoring patch using the same architecture.