Analysis of Embroidered Strain Sensors in the Presence of Dynamic Forces

It is estimated that at least 66% of stroke survivors will present some condition that impair their ability to perform well during their activities of daily living. This is the reason why stroke survivors engage in rehabilitation therapies to improve their quality of life. To aid in their recovery process, robot-assisted technologies in the form of soft wearable devices have been proposed as a complementary method to traditional rehabilitation sessions. Within these soft devices, great attention has been placed on their sensing mechanisms. Among the different sensing modalities used to provide feedback to the soft wearable mechatronic device, force sensing stands out due to them being easier to integrate within the wearable system. However, one flaw with these sensors is that most of the times they are used as pressure sensors due to their nonstretchable characteristics. Therefore, in this study, a novel stretchable Kirigami-based force sensor is presented. This force sensor was created by embroidering a silver-plated conductive onto an elastic band (EB). To test the performance of the sensor in terms of sensitivity, linearity, hysteresis, and repeatability, three sensor samples were fabricated and stretched at a slow, medium, and high speed, while force data were being collected. After these tests, the sensor showed high repeatability, an average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} ^{{2}}$ </tex-math></inline-formula> of 0.9782, an average 10.27% hysteresis, and an average 0.03-V/N gauge factor. These results show that embroidered force sensors have the potential to be used to detect interaction forces within soft wearable robot-assisted therapies.