Reconfigurable coupled-line bandpass filter with electrically actuated liquid-metal tuning

Electrocapillary actuation is presented as a novel liquid-metal tuning mechanism in a reconfigurable radio-frequency device. Applying a voltage directly across the liquid-liquid interface between a liquid-metal slug and an electrolytic carrier fluid locally alters the surface tension, creating a pressure imbalance between the liquid metal and the electrolyte. Trapping the bulk of the liquid metal in a reservoir creates a “stretching” effect that elongates the liquid-metal tuning element in response to a low-voltage electrical signal. A prototype tunable coupled-line bandpass filter that uses this technique to achieve frequency tuning is demonstrated.