Reusable and Porous Skin Patches with Thermopneumatic Adhesion Control Capability and High Water Vapor Permeability.

We present a reusable and porous skin patch (RPS patch) capable of controlling adhesion force with a thermal-pneumatic method for repetitive use as well as improving moisture permeability for long-term use without skin troubles. Previous skin patches cause skin troubles due to high adhesion force (∼30 kPa) and low moisture permeability (∼382 g/m2/day), hindering them from repeatable and long-term use. We control the skin adhesion force of the RPS patch using thermopneumatic pressure generated by an embedded heater on multiple chamber arrays. The RPS patch controls the adhesion force ranging from 8 to 29 kPa on both dry and wet skin while keeping the stable adhesion force for 48 h. It shows repeatable adhesion up to 100 times, and the adhesion force is restored after the RPS patch is washed with water, thus enabling repetitive skin adhesion. We improve the moisture permeability of the RPS patch to 733 g/m2/day while maintaining the adhesion force by making the RPS patch with porous materials. The RPS patch shows no skin troubles for 7 days of attachment, thereby being available for long-term skin attachment. The RPS patch, having adhesion control capability and high moisture permeability, shows potential for use in daily life in biomedical applications, including wearable sensors, medical adhesives, and rehabilitation robots.

Wearable porous PDMS layer of high moisture permeability for skin trouble reduction.

The present research proposes the present porous polydimethylsiloxane (PDMS) layer for the skin trouble reduced daily life skin attachable devices. The present research proposes the new pores forming method in the PDMS by crystallization and dissolution of the citric acid in the PDMS for fabricating high uniform and small size pores. The present porous PDMS layer (i) decreases the pore size 93.2%p and increases the pore size uniformity 425%p compared to the conventional porous PDMS layer of mixing sugars and PDMS; (ii) is able to be fabricated in the thickness of 21-101 µm by spin-coating; (iii) has the 2.2 times higher water vapor transmission rate (947 ± 10.8 g/day•m2) compared to the human skin water vapor transmission rate. The present porous PDMS layer reduces the skin trouble effectively by having the high water vapor permeability, therefore is applicable to the human daily-life skin attachable devices.

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.