# Underwater Highly Pressure-Sensitive Fabric Based on Electric-Induced Alignment of Graphene
## 3 Results and Discussion
As a conductive material, graphene sheets lap each other and build a conductive network, which can reduce the resistance of composite fabrics effectively. However, when the additional amount of graphene is low, the distance between graphene sheets in the fabric is large, and they do not lap well with each other to form a complete conductive path. Thus low sensitivity and high resistance are caused. In contrast, the excessive amount of conductive material covering the fabric's three-dimensional (3D) structure prevents the pressure sensor  
Figure 2: (**a**) Response/recovery time of the sensor at 50 kPa before and after electric field induction. (**a(i)**) is the response and response time of the unapplied electric field, (**a(ii)**) is the response and response time of the applied electric field. (**b**) The cross-sectional morphology of the coating before and after the electric field induction: (**b(i)**,**b(ii)**) are the cross-sectional morphology before the electric field induction; (**b(iii)**,**b(iv)**) are the cross-sectional morphology of the coating after the electric field induction. (**b(i)**,**b(iii)**) scale bar: 50 \(\upmu\)m; (**b(ii)**,**b(iv)**) scale bar: 25 \(\upmu\)m. (**c**) Schematic diagram of graphene nanosheets being twisted by force in an electric field. from producing large changes in contact resistance under pressure. This is because the conductive pathways have reached saturation and the number of conductive pathways no longer increases when external forces are applied [26]. The sensing performance test results of the sensor with different graphene contents at 30 kPa pressure showed that 3 g/L was selected as the best dispersion concentration for subsequent sensing performance tests. As shown in Figure 3b, the I\(-\)V curves of the graphene fabric pressure sensors showed a linear relationship under dynamic pressure. The resistance (obtained from the slope) is stable under different external pressures, indicating that the electrochemical performance of the sensor obeys Ohm's law and has good piezoresistive performance. This has great potential for detecting changes in human surface pressure. In addition, the hydrophobicity of the fabric was tested. The results show that when the graphene concentration is 3 g/L, the interpenetrating cross-linking reaction between PDMS and polyester remained unaffected, and the coating can reach a superhydrophobic state. The static contact angle reached 153.96\({}^{\circ}\), and the dynamic contact angle reached 9\({}^{\circ}\) (Figure 3c). The mechanical stability of superhydrophobic surfaces is also important in practical applications. This is because sensors inevitably rub against each other and other devices during service. The contact angle was measured to evaluate the mechanical durability of the sensor after different numbers of abrasion cycles. As illustrated in Figure 3c, the contact angle decreased from 153.9\({}^{\circ}\) to 149.3\({}^{\circ}\) after 50 abrasion cycles (Clamp the fabric in the radial weave direction to the standard wool tack cloth for experiments. Fix the white standard friction cotton backing fabric on the grinding head. The running speed is 2 s per friction cycle. The dynamic range of friction on the specimen is 50 mm.). The degradation of superhydrophobicity is due to the weaker bonded part of the PDMS coating being broken or peeled off from the fabric surface during external friction or mechanical rubbing. The electric field was then introduced into the fabric treatment process, and the impregnated fabric was immediately placed in a DC electric field for directional twisting of graphene. As shown in the inset of Figure 3d, the I\(-\)V curves of the single-layer fabrics  
Figure 3: (**a**) \(\Delta\)I/I\({}_{0}\) value of the flexible pressure sensor at 50 kPa; the inset is the I\(-\)V curve of the single-layer fabric at different graphene concentrations. (**b**) I\(-\)V curves of the flexible pressure sensor under different static pressures.