A Hierarchical Contact-Electrification Interface Based on Gradient Micro-/Nanostructured Hydrogel for Cardiovascular...

Accurate monitoring of pulses is essential for assessing cardiovascular health. However, the specificity of the pulse wave depends on prestress applied to a wearable sensor. Here, we introduce a progressive contact area compensation strategy, which greatly extends the detection range of the sensor's high-sensitivity region. It features a hierarchical flower surface structure and a gradient micro-/nanostructured hydrogel as the dielectric layer, compensating for the output decrease resulting from pressure hardening by gradually increasing the contact area between the contact-electrification interfaces. Consequently, the gradient micro-/nanostructured hydrogel, fabricated via electric field induction, enables the sensor's high-sensitivity region to reach 1.1-52.2 kPa, a 5-fold improvement over that of comparable sensors. By integrating prestress adaptive units, signal processing modules, and a peak seeking algorithm, we develop a wireless wristband for continuous monitoring of cardiovascular status and blood pressure. Importantly, a preliminary 10 day blood pressure test on 22 volunteers showed an error margin of less than ±5 mm Hg, demonstrating its potential as a cardiovascular health product.