Skin-Inspired Bimodal Magneto-Dielectric-Based Flexible and Sensitive Capacitive Sensor for Limb Motion Tracking

Abstract

Flexible devices featuring bimodality finds wide application in wearable electronics for tracking simple-to-complex human activities. Such tracking requires high sensitivity and broad working range which is still a concern for wearable electronics. Herein, a magneto-dielectric layer (MDL)-based bimodal sensing (strain and proximity) device with a broad working range and higher sensitivity is proposed. Nanoparticles in MDL (magnetic nanoparticles (MNP) within the PDMS matrix) change their position dynamically ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}{\rightarrow }{g}^{\prime }$ </tex-math></inline-formula> ) according to different bending load conditions. Increased sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{ST}~\approx ~4\text{x}$ </tex-math></inline-formula> -times and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{Prox}~\approx ~1.5\text{x}$ </tex-math></inline-formula> -times) and wider working range (from 6 to 20 mm) are achieved in contrast to regular devices with PDMS as a dielectric. Linear device response (0.99 coefficient of linearity), long-endurance (1000 cycles), and rapid detection (200 and 250 ms) features add further advantages. Single capacitive readout and standard interdigitated electrodes (IDEs) simplify the device implementation. Moreover, IDE design automates contactless sensing along with identification of the nature of the sensing object (conducting/nonconducting), which is applied directly when it comes to object-sensitive human perception (e.g., visually impaired person).