DLP-printed microstructured sensors with enhanced sensitivity for wearable physiological monitoring

Flexible capacitive pressure sensors have attracted significant attention owing to their simple structure and performance. However, the limited volumetric deformation of traditional planar dielectric layers under pressure severely restricts sensitivity improvement. In this study, we developed a high-performance flexible sensor based a 3D-printed microstructured hydrogel composed of polyethylene glycol diacrylate (PEGDA), N-hydroxyethyl acrylamide (HEAA), and lithium chloride (LiCl). An exposure regulation strategy maintained optimal curing energy (100–200 mJ/cm 2 ) by reducing exposure time by 30–50 % with every 5 mW/cm 2 increase in light intensity. By precisely engineering the microneedle aspect ratio (H/D = 2:1), synergistic optimization of sensitivity across broad pressure ranges was achieved: 0.31 kPa −1 in the low-pressure regime (0–6 kPa) and 0.11 kPa −1 in the high-pressure regime (30–160 kPa), which was 3–5 times higher than that of the flat structure. Notably, the cross-sectional shape has a significantly impacts on sensitivity. The triangular cross-sectional design exhibited an enhanced sensitivity of 1.03 kPa −1 in the low-pressure range and maintained 0.56 kPa −1 in the high-pressure region—representing a 400 % enhancement over elliptical or square structures. The sensor also demonstrated environmental adaptability from −40 °C to 40 °C, long-term durability (600 cycles), and fast response times (65 ms). These features enable real-time monitoring of diverse physiological signals (e.g., pulse, respiration, and muscle motion), as well as individual identification through handwriting pattern recognition—highlighting its potential for personalized health monitoring, smart wearables, human-machine interfaces, and secure authentication systems.