A porous PDMS pulsewave sensor with haircell structures for water vapor transmission rate and signal-to-noise ratio enhancement

We present a porous polydimethylsiloxane (PDMS) pulsewave sensor with haircell structures that improves both water vapor transmission rate (WVTR) and signal-to-noise ratio (SNR). The conventional planar PDMS pulsewave sensors have the problems of low WVTR and low SNR for real-time and long-term pulsewave monitoring. In order to improve WVTR, we fabricated a porous PDMS layer with the thickness of 40 μm and high porosity of 45% by crystallizing and dissolving citric acid powders in PDMS. On the porous PDMS layer, we form haircell structures to increase the skin contact area, thus enhancing SNR. The porous PDMS pulsewave sensor with haircell structures achieved an enhanced WVTR of 486.17 g−1 d−1 m−2 and an SNR of 22.89, respectively, 72% and 757% higher than those of the conventional PDMS pulsewave sensors without haircell structures. Furthermore, the enhanced WVTR is 13% higher than the human skin sweat rate of 432 g−1 d−1 m−2. The present pulsewave sensor shows strong potential for applications in real-time and long-term pulsewave monitoring with the lower skin irritation and the enhanced SNR.