Abstract:

Objective Because of superior wearability and comfort, fabrics have drawn a lot of attention as a substrate for flexible sensors. In the fields of health monitoring and smart clothing, their close fit to human skin and capacity to give continuous monitoring and feedback are significant and attractive. However, in practical applications, these fabric-based sensors typically struggle with limited strain range and low sensitivity. Furthermore, the stability and durability of fabric-based sensors must be taken into account so as to increase their applicability. The performance and dependability of the sensors may be impacted by frequent use and cleaning.
Method Layer-by-layer electrostatic self-assembly was utilized to create fabric-based polystyrene/reduced graphene oxide (PS/rGO) microsphere composites. Using styrene (St) as the monomer, azobisisobutyronitrile (AIBN) as the initiator, and polyvinylpyrrolidone (PVP) as the stabilizer in a mixture of ethanol and water, polystyrene microspheres (PS) were prepared via the dispersion polymerization technique. PS/GO microsphere composites were prepared by loading graphene oxide (GO) onto the PS surface via the electrostatic self-assembly technique. PS/GO was reduced to polystyrene/reduced graphene oxide (PS/rGO) using ascorbic acid (Vc). Ultimately, PS/rGO was applied to the spandex fabric surface with the aid of ultrasonic technology to create PS/rGO microsphere composite materials.
Results When the rGO content was 1%, the conductivity of the PS/rGO microsphere composite textiles was nearly zero. The electrical conductivity gradually increased as the rGO level was raised from 1% to 10%. The conductivity was 68.2 S/m and the conductivity curve tended to be stable at 15% rGO mass fraction. It demonstrates that in this content range, the PS microspheres formed an efficient conductive network and are suitably coated with rGO. In the strain range of 0%-70%, the PS/rGO microsphere composite textiles exhibited a constant linear connection with Ohm's law, indicating that they may be employed as strain sensors to track changes in resistance. By using linear fitting, the G_F value of PS/rGO microsphere composite fabric with 15% GO mass fraction was found to be 4.29 at 40%-90% strain and 10.44 at 0%-40% strain. Additionally, the PS/rGO microsphere composite fabric with 15% GO mass fraction demonstrated outstanding cyclic stability at all strains from 5% to 90%. The prepared PS/rGO microsphere composite fabric with 15% GO mass fraction had good stability, as evidenced by the PS/rGO microsphere composite fabric with 15% GO mass fraction' stable resistance change behavior at varying stretching rates when the strain was 10%. In contrast, the composite textiles showed nearly no change in the resistance change rate during 100 tensile cycles when the stresses were 20% and 60%, showing good durability. At 5-20 V, the electrical and thermal characteristics of PS/rGO composite textiles were examined. With an increase in voltage, the PS/rGO composite textiles' surface temperature rose noticeably. The surface temperature of the PS/rGO microsphere composite textiles increased dramatically as the voltage was raised. The fabric's surface temperature were raised from 19 ℃ to 64.2 ℃ at 20 V within 87 s, demonstrating good electrothermal performance. In the meantime, the detecting electrothermal fabric's resistivity shift showed good resistance to rubbing and washing, changing only little under 0-500 rubbing cycles and 0-60 min washing. The constructed fabric-based PS/rGO microsphere composite sensors showed good sensing capability with strain detection of 0%-90% and sensitivity G_F of 10.44, when compared to other reported fabric-based sensors.
Conclusion Smart textiles with strain sensing and electrothermal properties were prepared by loading PS microspheres and rGO onto spandex elastic fabric using the electrostatic self-assembly technique. The microsphere-nanosheet layered structure provides the sensors with excellent cycle stability, permeability, water washing resistance, and a wide strain detecting range. When the applied voltage is 20 V, the fabric can rise from 19 ℃ to 64.2 ℃ with in 87 s, which has good electrothermal performance. The G_F value can reach 10.44 at the 0%-90% strain range, and the resistance change rate is almost unchanged at different strains and different tensile speeds as well as 100 cycles, which shows excellent cyclic stability. Additionally, the sensing electrothermal fabric is very resistant to washing and rubbing, ensuring its dependability in practical applications. Future research can further examine the possible userange of these flexible sensors in a variety of industries, including motion tracking, health monitoring, and smart apparel. Their uses can be broadened through the optimization of material combination, structural design, and preparation procedure. It is anticipated that flexible strain sensors will play a major role in the development of an intelligent society, bringing convenience and creativity to daily existence.

Key words: polystyrene microspheres, graphene oxide, flexible sensor, electrical and thermal property, sensing performance, polyester/spandex fabric