Liquid metal microcoils for sensing and actuation in lab-on-a-chip applications

Abstract

The use of metals and alloys with melting point near room temperature, called here as liquid metals, allows the integration of complex three-dimensional metallic micro structures in lab-on-chip devices. The process involves the injection molten liquid metal into microchannels and subsequent solidification at room temperature. The paper reports a technique for the fabrication of three-dimensional multilayer liquid-metal microcoils by lamination of dry adhesive films. The adhesive-based liquid metal microcoil could be used for magnetic resonance relaxometry (MRR) measurement in a lab-on-a-chip platform. Not only that the coil has a low direct-current resistance, it also has a high quality factor. In this paper, we investigate the sensing and actuating capabilities of the liquid metal microcoil. The sensing capability of the microcoil is demonstrated with the coil working as a blood hematocrit level sensor. In a MRR measurement, the transverse relaxation rate of the blood sample increases quadratically with the hematocrit level due to higher magnetic susceptibility. Furthermore, a vibrating adhesive membrane with the embedded coil was realized for electromagnetic actuation. A maximum deflection of approximately 50 堡t a low resonance frequency of 15 Hz can be achieved with a maximum driving current of 300 mA.