Abstract
Wearable health monitoring smart systems based on flexible metal films are considered to be the next generation of devices for remote medical practice. However, cracks on the metallic surface of the films and difficulty in repeatability are the key issues that restrict the application of such wearable strain sensors. In this work, a flexible wearable strain sensor with high sensitivity and good repeatability was fabricated based on a patterned metal/polymer composite material fabricated through nanoimprint lithography. The mechanical properties were measured through cyclic tension and bending loading. The sensor exhibited a small ΔR/R0 error line for multiple test pieces, indicating the good mechanical stability and repeatability of the fabricated device. Moreover, the sensor possesses high sensitivity with gauge factors of 10 for strain less than 50% and 40 for strain from 50% to 70%. Various activities were successfully detected in real-time, such as swallowing, closing/opening of the mouth, and multi-angle bending of elbow, which illustrates the proposed sensor’s potential as a wearable device for the human body.
Highlights
A flexible wearable strain sensor with high sensitivity and good repeatability was fabricated based on a patterned metal/polymer composite material fabricated through nanoimprint lithography
Wearable strain sensors attached to the human body have been explored recently as key components for potential applications in human motion detection and personal healthcare devices [1,2,3]
To solve the problem of circuit breaking caused by metal cracks, metal nanowires spin-coated on the polymer substrates were used instead of a deposited metal film [18,19]
Summary
Wearable strain sensors attached to the human body have been explored recently as key components for potential applications in human motion detection and personal healthcare devices [1,2,3]. Under external load conditions, cracks on the metallic surface and difficulty in repeatability are the key issues that restrict the application of wearable strain sensors [13,14]. External stresses can lead to the initiation of cracking in the surface of metal films, which results in a loss of durability, stability, and sensitivity for the device [16,17]. The materials of nanowires and wrinkled patterns are irregular and difficult to be reproduced, resulting in the need for the performance detection and calibration of each device before use, thereby illustrating that these materials are unsuitable as wearable strain sensors. The mechanical stability was investigated by measuring the surface resistance change (∆R/R0) for initial state and cyclic loads These experiments were explored on multiple repetitive tests to investigate repeatability. The patterned wearable strain sensor was evaluated via attaching it to a human body to detect various activities
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