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.