Enhanced Piezocapacitive Response in Zinc Oxide tetrapod–poly(dimethylsiloxane) Composite Dielectric Layer for Flexible and Ultrasensitive Pressure Sensor

Touch sensing has found immense applications ranging from mobile communication and display to various wearable devices for advanced health monitoring. Thus, there is a tremendous demand for more accurate, delicate pressure sensing elements that can be implemented into health care and medical diagnosis systems, as well as electronic skins. Future artificial robots or amputees wearing flexible pressure sensors could feel the sense of touch or the texture of the fingertip. In this regard, flexible piezocapacitive pressure sensors with high sensitivity and low limit of detection, which can function in human skin perception, fine touch, weak interaction, and gentle manipulation, are highly desired. Recently, elastomeric polymer, such as poly(dimethylsiloxane), has been regarded a promising material of choice as dielectric layer, because of its superior flexibility, elastic properties, and biomedical and human tissue compatibility. However, upon very small pressure this type of elastomer is not able to produce enough deformation; after removal of pressure the relaxation time back to initial thickness is inactive. Although several methods of introducing microstructures or micropores into the dielectric layers have been discussed, they are generally complex and expensive.<br/>Here, we demonstrate polymeric piezocapacitive pressure sensors based on a novel composite dielectric film of poly(dimethylsiloxane) elastomeric silicone with zinc oxide tetrapod. Electrical characterization results from these composite devices with an appropriate loading of tetrapods show remarkable sensing performance in capacitance change and pressure sensitivity of 2.55 kPa⁻¹ over that of pristine polymer sensors, enabling a minimum detectable pressure of only 1.0 Pa. Further, the operational stability, reliability and demonstration of the device for monitoring human physiological movements are also discussed. It is expected that the proposed piezocapacitive pressure sensors incorporating stress-sensitive additives of zinc oxide nanostructures may open up a promising means for potential applications in ultrasensitive touch sensing, wearable device and electronic skin.