Abstract: A novel approach is proposed to rapidly prepare dual-level microstructured flexible pressure sensors with micro-papillae,which are applied in weak physiological signals detection. The flexible thermoplastic polyurethane sheets with the dual-level and single-level microdomes array and the flat surface are rapidly prepared by using compression molding. Then the gold-sprayed microstructured sheet and the graphite-coated flat sheet are assembled into flexible piezoresistive pressure sensors face-to-face. It is demonstrated that the dual-level microstructured pressure sensor(D-Sensor) with micro-papillae distributed on the surface of microdomes exhibits a higher sensitivity(0.061 kPa^-1) and obviously higher linearity(with a linear correlation coefficient of upto 0.996) in linear low-pressure region(0~11 kPa) than the pressure sensor with the single-level microdomes array. This is attributed to the fact that the deformation of the dual-level microdomes under pressure obeys the Archard theory, and the area of the contact regions is increased largely with raising pressure. The D-Sensor has a short response time(100 ms) and maintains a stable piezoresistive response during 1000 cycles of cyclic compression/release tests(under 9 kPa pressure). The D-Sensor can accurately monitor some physiological signals corresponding to weakly mechanical stimulation, such as wrist pulse, pronunciation, and respiration. The results demonstrate that the dual-level microstructured sensors fabricated by the proposed rapid approach has high sensing performance and so can be applied in health detection field.

Key words: flexible pressure sensor, microdomes array, microdeformation, thermoplastic polyurethane, compression molding