Gradient Porous PVA/CB Composites for High-Performance Flexible Piezoresistive Sensors

Flexible piezoresistive sensors often face a trade-off between sensitivity and working range. In this work, a gradient porous poly(vinyl alcohol)/carbon black (PVA/CB) composite was fabricated via a simple sugar-templating method. The bilayer structure consists of a small-pore layer and a large-pore layer, enabling sequential deformation under external pressure. As a result, the sensor exhibits a sensitivity of -3.05 kPa^-1 in the low-pressure range (0-20 kPa) and maintains a stable response up to 120 kPa. Compared with uniform porous structures, the gradient design shows improved performance in the medium- and high-pressure ranges. The sensor also demonstrates good repeatability, fast response, and stability over 1000 cycles. Practical applications including respiration monitoring, vocal vibration detection, and motion sensing are demonstrated. This work provides a simple and scalable approach for developing flexible pressure sensors.