Flexible piezoresistive pulse sensor using biomimetic PDMS mold replicated negatively from shark skin and PEDOT:PSS thin film

Abstract

We propose a newly designed and fabricated flexible piezoresistive pulse sensor (FPPS) using a biomimetic PDMS mold replicated negatively from shark skin and PEDOT:PSS thin film. Its feasibility to measure physiological signals from the human body using FPPS was tested. The FPPS consists of a sensor element with PEDOT:PSS film coated on the PDMS substrate and two electrodes with copper tape as a counter electrode almost covering the surface of the sensor element and an Ag paste electrode on the edge of one side of the sensor element. The PDMS substrate was negatively replicated from shark skin as a biomimetic mold, and the PEDOT:PSS sensing film was coated on the replicated PDMS substrate to fabricate the sensor element of the FPPS. The unique geometry of shark skin remarkably affects the decrease of contact resistance by about 700-fold until the pressure range of ˜500 Pa compared to using PEDOT:PSS film on the planar PDMS substrate. The reason why the contact resistance decreases with increasing pressure is that the conducting points increase in the PEDOT:PSS chains with increasing pressure. In the low pressure range (<0.7 kPa) and high pressure range (0.7 through ˜6 kPa), the sensitivities were 62.56 kPa−1 and 8.32 kPa−1, respectively. For the feasibility test, physiological pulse signals were measured from a human subject’s body using the FPPS, the S.I. of 6.73 m/s and R.I. of 64.03% were close to the normal range of S.I. and R.I., which are 5.72 ± 0.28 m/s and 48.19 ± 9.51%, respectively. The calculated vascular age, 24.5 years old, was similar to 24.9 years old, the actual age of the subject.