Circular Wireless RF Systems With Recyclable and Degradable Components Based on Additively-Manufactured Liquid Metal Interconnects

Fabricating sustainable circuits with low-waste end-of-life is crucial for enabling an electronics circular economy. Here, we present the first circularity-driven fabrication flow for sustainable wireless circuits based on recyclable liquid metals and degradable dielectrics. The proposed recyclable radio frequency (RF) circuits consist of 3D-printed substrates with fluidic channels, e.g. using polylactic acid (PLA), filled with Galinstan interconnects. At their end-of-life, the ICs and liquid metal interconnects are recovered and re-used in functional circuits, over multiple iterations. The printed dielectrics are degraded, with under 2% by weight waste produced. Various RF circuits are demonstrated, up to 4 GHz, including transmission lines based on Coplanar Waveguides (CPWs), with high-performance DC/RF control and filtering, and broadband high-efficiency radiation in a CPW antenna. Active microwave systems are then demonstrated including a voltage-controlled oscillator (VCO), and a multi-layered design for a broadband power amplifier (PA). The circuits maintain a stable performance across over 9 metal and 3 IC re-use cycles. The reliability of the circuits is verified by continuously operating months-old circuits for over 30 hours as well as under-water storage, demonstrating their reliability. Our results pave the way for multi-function, green wireless circuits, reducing waste electrical and electronic equipment (WEEE) and allowing component circularity.