Abstract:

Objective With the development of the times, more and more attention are paid to health issues. Wearable technology is also slowly approaching the lives of the public, and compared with conventional rigid sensors, flexible wearable technology has the advantages of better wearing comfort, human body fit and lightness. In order to deal with high manufacturing cost, complex manufacturing process and difficult integration of some flexible sensors into textiles, which limits the further development and application in flexible pressure sensors, a flexible pressure sensor with simple preparation process is studied.

Method The spacer fabric selected is composed of outer fabrics and a monofilament in the middle. Firstly, the toner, copper powder, PDMS and its curing agent and organic silicon are mixed in a ratio of 10 g∶13 g∶18 g∶2 g∶20 g, stirred on a digital display constant speed mixer for 20 min, the speed is 300 r/min, and 2 g of carbonic acid is added during the stirring process. The warp knitting spacer fabric is cut into 1×1 cm, which is put into the mixed conductive material to soak and press. After the warp knitting spacer fabric fully absorbs the conductive material, it is dried in an oven at 80 ℃ for 2 h. After drying, it was encapsulated with conductive silver cloth to prepare a resistive flexible pressure sensor based on warp knitted spacer fabric.

Results The flexible pressure sensor was identified to have a sensing range of 0-160 kPa and a sensitivity of 1.304 kPa in the low pressure range (0-20 kPa). Owing to the three-dimensional structure and microporous structure of the sensor. The sensor was also able to undergo large deformation under the action of small external forces, and the change of conductive path leads to a large change in its resistance. The response time of the flexible pressure sensor is only 140 ms, which is enough to monitor human movement signals. The resistance change remained stable for 2 000 cycles, indicating that the flexible composite piezoresistive material had good recovery and wear resistance. At the same time, the flexible sensor prepared based on textile matrix exhibited good air permeability and moisture permeability of 180 mm/s and 1 850 g/(m²·24 h), respectively.

Conclusion A flexible pressure sensor with excellent sensing performance was prepared. The 3D structure and excellent elasticity of the warp knitted spacer fabric was shown to provide excellent structural advantages for the preparation of the resistive flexible pressure sensor. The spacer fabric can not only absorb more conductive materials more firmly, but can also allow diferent compressible space and be more sensitive to external mechanical stimuli. In the preparation process, carbonic acid is added to make it porosity, so that the internal air increases, and the compressibility is improved, so the performance in the sensitivity including taking performance is improved, the response time of the flexible pressure sensor is 140 ms, and the recovery time is 166 ms. Reliable sensing stability and cycling durability (>2000 cycles) all contribute to the sensor's good electrical performance. Spacer fabrics inherently have good air and water permeability, while PDMS is malleable, biocompatible, easy to process, and relatively low in cost. It is proved that the sensor prepared can sensitively make signal changes to human motion changes, and has certain advantages compared with piezoresistive sensors of the same type and realizes a simple process and low cost.

Key words: warp knitted spacer fabric, pressure sensor, flexible electronic fabric, polydimethylsiloxane, sensing performance