Highly Sensitive Strain Sensor with Aligned Fibrous Base and Patterned Biphasic Metal Sensing Layer

Abstract

Great progress has been made in the development of liquid-metal-based wearable devices. However, the sensitivities of the liquid-metal-based strain sensors are still limited in an inadequate range. Herein, a highly sensitive and stretchable strain sensor constructed with an aligned electrospun thermoplastic polyurethane (TPU) fibrous base and a patterned biphasic metal sensing layer was developed. The patterned biphasic metal sensing layer was composed of liquid metal (LM) Galinstan as “islands” and solid metal silver (Ag) as “sea”. Ag “sea” prevented the formation of a continuous LM conductive pathway. The sensitivity was enhanced significantly based on the crack propagation mechanism of the Ag conductive region. Additionally, the alignment of fibers ( horizontally or vertically aligned ) weakened fiber rearrangement, and enlarged the deformation of the sensing layer. Results showed that, the sensitivity of the sensors composed of a single LM layer or a pure Ag layer with a vertically aligned fibrous base increased by 1. 09 and 33. 19 times compared to that with the randomly oriented fibrous base, respectively. The final patterned biphasic metal strain sensor with a vertically aligned fibrous base could achieve an ultrahigh sensitivity (gauge factor up to 952. 20) and a wide sensing range (up to 59. 33%). This design shows a great potential for a wide variety of wearable devices.

Keywords

high sensitivity / strain sensor / fiber alignment / biphasic metal / patterned sensing layer

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Funding

Fundamental Research Funds for the Central Universities, China(2232022D-13); Fundamental Research Funds for the Central Universities and Graduate Student Innovation Fund of Donghua University, China(CUSF-DH-D-2022034)