Highly Sensitive Graphene/Polydimethylsiloxane Composite Films near the Threshold Concentration with Biaxial Stretching

Abstract

Uniformly dispersed graphene effectively improves the strain-sensing capability of the composite film under a low graphene load in nanocomposites prepared with polydimethylsiloxane (PDMS) and graphene (GNP) monolayer powder. The threshold concentration of graphene was determined by loading nanocomposites at different temperatures. For different concentrations, when using traditional uniaxial stretching, the rate of resistance change of films near the threshold concentration is five times higher than the rate of films with a high concentration. Compared with traditional uniaxial stretching, the biaxial stretching we introduced can effectively improve the sensitivity of the film by an order of magnitude. The change in the resistance of the film near the threshold concentration is due to the change of the tunnel length and the cross-section of the tunnel, whereas the high concentration of the film is due to the change of the conductive path inside the film. Biaxial stretching has different effects on films with different concentrations, but the final effect of increasing sensitivity is the same. This study provides guidance for improving the strain-sensing sensitivity of GNP/PDMS composite films and the application of biaxial tension in detecting human motions.

Biaxial Stretching of Polymer Nanocomposites: A Mini-Review

“…Biaxial stretching was shown to efficiently improve the sensitivity (gauge factor (GF) 687.43) of the GNP/PDMS composite compared with uniaxially stretched sample (GF 68.81). Furthermore, the biaxially stretched sensor showed excellent signal responses to various bending degrees of knee joint (Liu et al, 2020). The application of nanocomposite films assisted by biaxial stretching in EMI shielding has been studied recently.…”

“…A biaxially stretched GNP/HDPE nanocomposite exhibited a 63% enhancement to Young's modulus, with the oxygen permeability coefficient reduced to only 4.1 × 10 −16 cm 3 cm/cm 2 s Pa at SR 3, as shown in Table 1. Liu et al (2020) prepared a polydimethylsiloxane (PDMS)/GNP composite film near the threshold concentration, finding that biaxial stretching effectively enhanced the sensitivity of the PDMS/GNP composite film by an order of magnitude compared with traditional uniaxial stretching. Traditionally prepared (Wu et al, 2015).…”

Direct ink writing of a graphene/CNT/silicone composite strain sensor with a near-zero temperature coefficient of resistance

“…15,16 Nevertheless, the increase of resistance with an increase of temperature was observed for GNP-based strain sensors, which is described by a PTC effect. [17][18][19] Intuitively, it is possible to prepare wearable strain sensors with a small or near-zero TCR by combining GNPs and CNTs. From this perspective, Luo et al fabricated a CNT/GNP hybrid thin film sensor with a close-to-zero TCR through recognizing the different TCRs in CNT-and GNP-based composites.…”

Tuning Thermal and Mechanical Properties of Polydimethylsiloxane with Carbon Fibers

“…In order to overcome the mechanical and thermal shortcomings of PDMS, extensive research has focused on improving the material properties using different fillers. Carbon nanofibers and nanotubes [ 18 , 19 , 20 ], graphite [ 21 ], graphene [ 22 ], nanodiamond [ 23 ], carbon black [ 18 ], silica [ 24 ], nanoclay [ 25 ], and other fillers have all been used to improve the properties of PDMS and other polymer materials. Specifically, carbon fibers have several qualities that make them an appropriate filler for polymer materials.…”