Flexible and Stretchable Microwave Electronics: Past, Present, and Future Perspective

Abstract Microwave electronics have evolved from bulky waveguide and vacuum tube‐based format to smaller and lighter board‐based electronics, and then to the highly miniaturized, chip‐based solid‐state form. Spurred by the advent of high‐performance flexible inorganic single‐crystalline semiconductors, a new opportunity of technology evolution from rigid microwave electronics to flexible and/or stretchable microwave electronics has emerged. The new forms of microwave electronics are expected to provide novel functions to be achieved with advanced materials, device, and system design considerations and innovative fabrication methods. Over the last years, some microwave components, modules, and systems with operation frequency greater than or equal to 1 GHz in the flexible/stretchable form factors are demonstrated. These demonstrations have alluded to the prospects of the new stage of microwave electronics evolution. Herein, a comprehensive review of the microwave/flexible microwave electronics that are demonstrated up to date is provided. An introduction to the need of flexible/stretchable microwave electronics emphasizes the motivation and potential influences of this new growing field. This review also highlights important developments in transistors, diodes, various passives, antennas, circuits, and system demonstrations, all in flexible or stretchable forms. Finally, an outlook for specific technical gaps at both the fundamental and applications levels is presented.