High-performance transparent pressure sensors based on sea-urchin shaped metal nanoparticles and polyurethane microdome arrays for real-time monitoring

An ultra-sensitive and transparent piezoresistive pressure sensor based on a sea-urchin shaped metal nanoparticle (SSNP)-polyurethane (PU) composite with microdome arrays is successfully fabricated for the first time. The piezoresistive pressure sensor with microdome arrays was prepared using a nanoimprinting process based on an intermediate polymer substrate (IPS) replica mold. It showed a superior sensitivity (71.37 kPa^-1) and a high optical transmittance (77.7% at 550 nm) due to the effective quantum tunneling effect even at small concentrations of conductive SSNP filler (6 mg mL^-1). The high-performance characteristics of the piezoresistive pressure sensor are attributed to the geometric effects of the microdome structure, especially the stress concentration at small contact spots and the deformation of the contact area. The piezoresistive pressure sensor with microdome arrays also exhibited a fast response/relaxation time (30 ms), ultra-low pressure detection (4 Pa), and excellent long-term stability under harsh conditions. In addition, the effectiveness of the piezoresistive pressure sensors in various sensing applications including sensing mapping, human arterial pulse monitoring, and the detection of muscle movement is also successfully demonstrated. It is anticipated that this novel transparent pressure sensor based on a SSNP-PU composite with microdome arrays will be a key component in the development of integrated transparent sensing applications.