A multiple liquid metal switching mechanism in a single flow microfluidic channel as a reconfigurable bandpass filter

Abstract

We propose a novel microfluidic channel wherein three different liquid metal switches can be operated via a single fluidic flow. Liquid metals with movable metallic properties have been used in antenna filters, sensors, etc. In previous works of the liquid metal switch, each switch requires each channel with an inlet and outlet. For instance, three liquid metal switches must employ three channels with three flows. However, the proposed mechanism needs only single flow for three liquid metal switches. The proposed mechanism applies to a novel filter that achieves the frequency reconfigurability by using the variation of inductive coupling of a half-mode substrate-integrated waveguide (HMSIW) rather than capacitive coupling. The proposed filter consists of three layers, namely, top microfluidic channel, middle conductive, and bottom ground layers. The middle conductive layer has an HMSIW with two microstrip step impedances (SIs) and two microstrip 50-Ω feeding lines. A pair of defected ground structures (DGSs) was realized on the bottom ground layer. The HMSIW and DGS were designed to determine the low-cutoff and high-cutoff frequencies, respectively. Because two of the liquid metal switches are located above the SI lines with the DGSs, they enable switching of the high-cutoff frequency. However, as the remaining liquid metal switch is located on the HMSIW to change its width, it enables switching of the low-cutoff frequency. For instance, when the SI switches are on, the 1-dB passband of the filter is 2.95 GHz–4.76 GHz, and when the HMSIW switch is on, the 1-dB passband of the filter is 4.8 GHz–6.6 GHz.