Wearable Inductive Sensing of the Arm Joint: Comparison of Three Sensing Configurations

Abstract

Currently, there is a rapidly growing interest and demand for wearable textile sensors that can monitor human motions in a naturalistic environment. Some potential applications for this technology include research on measuring the motor skill performance of patients with motor disabilities such as autism spectrum disorder, Parkinson’s disease, cerebral palsy, and stroke and evaluating the efficacy of applied treatments. Among wearable sensors, inductive sensors that are made from highly conductive threads are attractive due to their easy development process, high reliability, and low cost. In this study, we analyzed and compared the performance of three inductive wearable sensor configurations—(1) single planar rectangular coil, (2) two separated coils connected in series, and (3) two helical coils connected in series—in terms of the change in the resonant frequency of the tank circuit they comprised as a result of the change in elbow joint angle through simulations. Three parameters of length, width, and the number of turns were considered to calculate sensor sensitivity to the joint angle. The coil with the highest sensitivity was then fabricated and measured, and its performance was compared with the simulation results. The proposed methodology can be extended to sensing other joints in the body such as the shoulders, fingers, and knees.

Two‐Terminal Deformable Induction Array Sensor Capable of Recognizing Non‐Contact Dynamic Motions of Various Objects

“…The dependence of the human skin could be predicted with the capacitive coupling. [ 33 ] The positive inductance change by the finger increased proportionally to the L foil (Figure S6, Supporting Information). It is noteworthy that the positive inductance change by the finger was not affected when the hand was covered with a tribopositive layer (nylon glove) and a tribonegative layer (PDMS) (Movie S1, Supporting Information).…”

“…[31] Very recently, induction-based soft sensors using printed liquid metal have demonstrated the possibility of high-precision bending angle sensing, [4,32] and a theoretical work on inductionbased sensor proposed the possibility of exclusive sensing of human skin. [33] Inductive soft sensor may solve the technological hurdles encountered in the previous approaches if an induction-based array sensor operates with only a small number of signal terminals and recognizes the stimuli from all directions.…”

Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance

“…Induction-based sensors offer good sensitivity with magnetic resolution on the scale of nT [29,30] and simple fabrication, and are capable of wireless transmission [26,33]. However, inductive sensing requires conductive or ferromagnetic objects for detection and is less sensitive to humans or passive objects [34].…”