Liquid metal antenna-based pressure sensor

In this paper, a centre-fed, finite-length, infinitesimally thin dipole antenna is presented as a pressure sensor to monitor pressure changes in geotechnical engineering. The antenna consists of a liquid metal (eutectic gallium–indium alloy) injected in microfluidic channels, which are enclosed in the elastic material polydimethylsiloxane (PDMS); therefore, the liquid antenna is stretchable and frequency reconfigurable and can thus be used as a pressure sensor when the length of the elastic material PDMS is changed under pressure. The effects of the geometrical parameters of the dipole antenna on its resonant frequency are investigated using the finite-element software HFSS. Based on the numerical results, the liquid-metal antenna is designed, fabricated and measured, and its resonant frequencies are recorded under different pressures. According to the experimental results, the relation between the resonant frequency of the liquid antenna and the applied pressure is defined, and it is consistent with the numerical and theoretical results. Moreover, the experimental results show that the relation between the displacement and the resonant frequency is in good agreement with the numerical and theoretical results. Thus, there is a linear relation between the resonant frequency of the antenna and the applied pressure as well as between the resonant frequency and the displacement. Therefore, this frequency-reconfigurable liquid-metal dipole antenna is suitable for use as a pressure sensor.