Abstract:

Flexible piezoresistive pressure sensors were prepared through assembling the surface⁃microstructural and the flat thermoplastic polyurethane sensing substrates. The surface of the microstructural substrate with a size of 10 mm×10 mm was sprayed with diffe⁃rent masses of multi⁃walled carbon nanotubes （MWCNTs） （0.02， 0.05 and 0.1 g）. The surface morphology of the microstructural flexible sensing substrate and the performance of the sensors were characterized and analyzed. The results demonstrated that there was a carbon nanotube layer with a certain thickness formed on the top surfaces of the microcolumns on the microstructural substrate. The sensor based on the microstructural sensing substrate sprayed with a greater mass of MWCNTs exhibited a higher sensitivity and a lower detection limit. This may be attributed to greater increments in the pressure⁃induced overlap degree of the MWCNTs network and the contact area between the sensing substrates. The sensor based on the microstructural sensing substrate sprayed with 0.1 g MWCNTs presented a higher sensitivity of 0.143 kPa^-1 （0~3 kPa）， a lower detection limit of 100 Pa， together with a certain piezoresistive response in the wide pressure range of 3~200 kPa. Moreover， the sensor maintained a stable piezoresistive response during the 4 000⁃cycle compression/release test with a peak pressure of 200 kPa， and had an accurate detection capability toward the piezoresistive responses generated by typical human motions. The sensor exhibits great application potential for intelligent wearables.

Key words: thermoplastic polyurethane, multi?walled carbon nanotube, flexible pressure sensor, microcolumn