Manufacturing methods of stretchable liquid metal-based antenna

Abstract

Stretchable electronics for wearable applications are a highly researched topic over the past decade in application areas such as health and fitness. The use of stretchable rather than rigid materials enables the device to conform to the human body allowing wireless sensor patches to be integrated into clothing or bonded to skin. However, to have a completely functional system, all the components need to be stretchable at the micro-scale and methods of making the components should be compatible with standard MEMS fabrication methods. This paper investigates the use of liquid metal as a stretchable conductor to be used as an antenna. Silicone-based elastomers were investigated to enhance elongation of the device. Methods of integrating the liquid metal with microfabricated devices were investigated along with corrosion of metal interconnects and liquid metal fill factor effects due to stretching using 3D X-ray imaging. Results demonstrated that a macro-scale monopole antenna was able to tune the frequency with an elongation of > 40%. Increased elongation affects the electrical resistance of the liquid metal and the resonant frequency of the antenna and should be accounted for in the circuit design. A new spiral shaped device was fabricated using Parylene-C with dispensed liquid metal which demonstrated complete filling and potential elongation up to 200%. This new thin film liquid metal device has excellent stretch ability, is microfabrication friendly, and has an excellent fill factor.