Electrostatic Liquid-Metal Capacitive Shunt MEMS Switch

In this paper we report the first high-frequency MEMS capacitive switch based on a liquid metal droplet that controls the impedance of a coplanar waveguide line. The droplet forms an RF short or open circuit depending on its distance from the transmission line. The range of the droplet movement is approximately 370μm perpendicular to the line and requires 110V. Unlike conventional MEMS capacitive switches, this switch relies on a conformal liquid-metal contact that results in a very high on-state capacitance. Additionally, the off-state capacitance is negligible since the droplet does not load the coplanar waveguide when it is moved away from it. The switch is successfully and repeatedly actuated with 110V and demonstrates an off-state loss of less than 0.6dB up to 20GHz, which is solely due to the transmission line underneath the droplet at 20GHz. The switch isolation is 15.7 and 21.1dB at 10 and 20GHz respectively.