Wearable flexible electronic strain sensor devices have developed rapidly in recent years due to their potential capacity to detect human motion in various situations. However, it still remains still a big challenge to fabricate strain sensors with high sensitivity over a wide workable strain range. In order to meet this challenge, a new type of strain sensor based on elastomer/carbon nanotube composite fiber is reported in this work. Elastomer fibers are initially prepared via the electrospinning of styrene ethylene butene styrene block copolymer (SEBS). The resultant SEBS fibers are then functionalized by sequentially coating with dopamine (DA) coating and carboxyl group (‐COOH) grafted multi‐walled carbon nanotubes (MWCNTs) under vacuum filtration and ultrasonication. Scanning electron microscopy (SEM) and thermogravimetric analysis reveals that a large amount of MWCNTs is firmly bonded onto the SEBS fibers and evenly distributed. SEBS@PDA/MWCNTs composite fibers based strain sensors exhibit excellent performance, including a high gauge factor of 3717 and large workable strain range up to 530%. Furthermore, the developed sensors demonstrate excellent washing fastness and superior sensitivity in monitoring both small strains (e.g., pulse beats and vocal cord vibrations) and large strains (e.g., finger, elbow, and knee bending).

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To date, a majority of polymer-based wearable flexible strain sensors are non-biodegradable, which inevitably causes environmental pollution at the end of their service life. In this work, biodegradable polyurethane (BPU) was synthesized and then processed with carbon nanotubes (CNTs) via wet spinning into BPU/CNT composite fibers used as strain sensors. The synthesized BPU showed excellent biodegradability with a 19.45% weight loss in 42 days in a phosphate buffered saline (PBS) solution. Compared with previously reported strain sensors made from silk, cellulose, and polylactic acid, the BPU/12%CNT fibers achieved a much wider strain-sensing range (0−250%) and a high sensitivity (gauge factors of 15 at 100% strain and of 2468 at 250% strain respectively) while exhibiting reliable stability. These properties allow strain sensors based on BPU/CNT fibers and knitted fabric to be successfully used for monitoring various human motions. Moreover, biodegradability of the BPU/CNT strain sensor in a PBS solution was verified. In consequence, this work provides insights into the development of biodegradable wearable electronic devices.

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