Biomimetic-inspired micro-nano hierarchical structures for capacitive pressure sensor applications

Capacitive pressure sensors are an important part of flexible/stretchable electronic skin applications. The fabrication of most of the reported polydimethylsiloxane (PDMS) based capacitive pressure sensors involves complex techniques and expensive tools. To improve the capacitive sensing properties of PDMS, a bio-mimicking hierarchical micro- and nanostructure that are facile, cost-effective, and scalable is presented in this work. Red rose petals are known to consist of hierarchical micropapillae and nanofolds. So, the artificial fabrication of these micro- and nanostructures provides a necessary roughness for pressure sensors. The sensors comprise both single and double layers of well-defined PDMS structures with indium tin oxide (ITO) electrodes. This capacitive pressure sensor allows the sensitive detection of both static and dynamic external stimuli. By successfully mimicking rose petals whose hemisphere contains micropapillae and nanofolds, ultra-sensitive capacitive pressure sensors show a sensitivity of 0.055 kPa⁻¹ over a wide pressure range (0.5–10 kPa) with a fast response time (<200 ms) and high stability. The sensing performance also checked for capability to accurately pulse monitoring at the human wrist which demonstrated the bilayer pressure sensor has promising application in wearable electronics.