Liquid metal actuation-based reversible frequency tunable monopole antenna

Abstract

We report the fabrication and characterization of a reversible resonant frequency tunable antenna based on liquid metal actuation. The antenna is composed of a coplanar waveguide fed monopole stub printed on a copper-clad substrate, and a tunnel-shaped microfluidic channel linked to the printed metal. The gallium-based liquid metal can be injected and withdrawn from the channel in response to an applied air pressure. The gallium-based liquid metal is treated with hydrochloric acid to eliminate the oxide layer, and associated wetting/sticking problems, that arise from exposure to an ambient air environment. Elimination of the oxide layer allows for reliable actuation and repeatable and reversible tuning. By controlling the liquid metal slug on-demand with air pressure, the liquid metal can be readily controllable to connect/disconnect to the monopole antenna so that the physical length of the antenna reversibly tunes. The corresponding reversible resonant frequency changes from 4.9 GHz to 1.1 GHz. The antenna properties based on the liquid metal actuation were characterized by measuring the reflection coefficient and agreed well with simulation results. Additionally, the corresponding time-lapse images of controlling liquid metal in the channel were studied. V

Stretchable and Soft Electronics using Liquid Metals

“…Another method is to simply remove the oxide. The oxide can be removed using acid (such as HCl, or base, such as NaOH), which allows the metal to move without leaving residue, but requires caustic chemicals (Figure c,d) . Likewise, droplets of metal can be forced in and out of molds using pressure in the presence of acid vapor (Figure e) …”

“…d) In the presence of acid, the metal is oxide‐free and moves freely in response to pressure through channels. Reproduced with permission . Copyright 2014, American Institute of Physics.…”

Liquid Metal Droplet and Graphene Co‐Fillers for Electrically Conductive Flexible Composites

“…Such an interesting second‐order behavior can be associated to the existence of free flow of liquid metals within the connected tunnels, with the possibility of flow in both directions till a stable condition is reached. However, this behavior is not seen at higher loads since the increased pressure via the pressing of the material changes the natural resonance frequency, leading to stable conductivity of the material …”

Electromagnet polarity dependent reversible dynamic behavior of magnetic liquid metal marble

“…However, it is very challenging to deform the gallium-based liquid metal as its surface is easily oxidized in oxygen-rich environment [1]. Many researches have been focused on the way to deform the liquid metal's shape on-demand for various applications such as tunable antenna [2][3][4], metamaterial [5,6], electrical switch [7,8], energy harvester [9], microvalve [10,11] and pressure sensor [12,13]. In order to deform the shape of the liquid metal, a variety of methods such as pneumatic [14,15], electrochemical [16][17][18][19], magnetic [20][21][22], slip layer insertion [23] and electrowetting [24,25] were utilized.…”