Laser-Engraved Porous Breathable Hydrogels for Wearable Electrocardiogram Monitoring

Abstract Accurate diagnosis of cardiovascular diseases relies on reliable electrocardiogram (ECG) monitoring. However, conventional hydrogel electrodes exhibit poor air permeability, and prolonged application tends to result in problems including degraded signal quality and skin discomfort. In this study, a polyelectrolyte double-network (PAD) hydrogel was fabricated via UV-initiated free radical polymerization using acrylic acid (AA) and acryloyloxyethyl trimethylammonium chloride (DAC) as main monomers, polyethylene glycol diacrylate (PEGDA) as cross-linker, combined with poly(vinyl alcohol) (PVA) and tannic acid (TA). The PAD hydrogel exhibits favorable mechanical strength, self-adhesion, and ionic conductivity. Subsequently, a 4×4 micropore array was constructed on the PAD hydrogel using a 455 nm laser at 5 W power, yielding a highly breathable PADH hydrogel electrode. The PADH hydrogel retains adequate flexibility (elastic modulus of 23.81 kPa, matching human skin) and achieves a high-water vapor transmission rate of 1176.25 g·m–2 ·day–1, a strain-sensing sensitivity (gauge factor) of 2.54, and a rapid response time of 143 ms. When employed for electrocardiogram (ECG) monitoring, the PADH hydrogel allows clear capture of P waves, T waves, and QRS complexes, showing broad application prospects in cardiovascular health monitoring and intelligent medical fields.