Abstract
A wearable, low-cost, highly repeatable piezoresistive sensor was fabricated by the synthesis of modified-graphite and polyurethane (PU) composites and polydimethylsiloxane (PDMS). Graphite sheets functionalized by using a silane coupling agent (KH550) were distributed in PU/N,N-dimethylformamide (DMF) solution, which were then molded to modified-graphite/PU (MG/PU) composite films. Experimental results show that with increasing modified-graphite content, the tensile strength of the MG/PU films first increased and then decreased, and the elongation at break of the composite films showed a decreasing trend. The electrical conductivity of the composite films can be influenced by filler modification and concentration, and the percolation threshold of MG/PU was 28.03 wt %. Under liner uniaxial compression, the 30 wt % MG/PU composite films exhibited 0.274 kPa−1 piezoresistive sensitivity within the range of low pressure, and possessed better stability and hysteresis. The flexible MG/PU composite piezoresistive sensors have great potential for body motion, wearable devices for human healthcare, and garment pressure testing.
Highlights
Piezoresistive sensors which transduce stress imposed on the sensor into a resistance signal have been applied in extensive fields such as sensitive e-skin, wearable health care devices, and human motion detection [1,2,3,4,5]
The results indicate that hydrolysate silanol of the silane coupling agent has been grafted graphite
The results indicate that hydrolysate silanol of the silane coupling agent has been grafted successfully onto the surface of the graphite sheets
Summary
Piezoresistive sensors which transduce stress imposed on the sensor into a resistance signal have been applied in extensive fields such as sensitive e-skin, wearable health care devices, and human motion detection [1,2,3,4,5]. Rubber-like materials, which have low modulus, high elasticity, and good flexibility, are commonly used as a substrate matrix for supporting and fixing conductive fillers in composites such as nitrile-butadiene rubber (NBR) [8,9,10], silicone rubber (SR) [11], styrene-butadiene rubber (SBR) [12,13,14], polydimethylsiloxane (PDMS) [15], and segmented polyurethane (PU) [16,17]. Yao et al [19] reported that a piezoresistive sensor was fabricated with graphene and a polyurethane sponge, which enhances the pressure sensitivity in order to reach a desired magnitude for artificial electronic skin applications. According to the previous studies, carbon materials have been researched as main filler components to improve the electrical and mechanical properties of polymer composites, such as carbon black [20], graphite [21,22], carbon nanotubes [23,24], and graphene [25]. The electrical conductivity of the NBR/graphite nanoplates was changed by more than five orders of magnitude under the condition of
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