Pump-free feedback control of a frequency reconfigurable liquid metal monopole

We demonstrate a pump-free method to control the length of liquid metal in a capillary as a means to change the operating frequency of a monopole antenna. An applied DC voltage controls the surface tension of the liquid metal filament, causing it to lengthen or contract, varying the antenna´s resonant length. A closed-loop feedback system tracks the antenna´s operating frequency and adjusts the applied voltage to shape the liquid metal towards the desired response. Measurements show that the process is controlled and fully reversible, dynamically adjusting to a programmed frequency.