MEMS liquid metal through-wafer microstrip to microstrip transition

A novel approach for creating an RF MEMS switch in the form of a microstrip-to-microstrip liquid-metal transition is presented. A slug of non-toxic liquid metal that controllably fills a through-wafer via is the key component of the switch. The large contact area between this slug and the solid microstrip lines renders this design an excellent candidate for high-power switching and particularly for hot-switching applications. With the slug inside the via the switch presents a measured insertion loss of 0.24 and 1.1 dB up to 5 and 10 GHz respectively. When the slug is removed from the via the switch isolation is measured to be more than 20 dB up to 7 GHz. The fabrication technology and critical trade-offs between RF and microfluidic performances are discussed in the paper. The slug movement is controlled by an external micropump. The recent advances in microfluidics have resulted in a large variety of practical micropumps that may be monolithically integrated with such switching designs.