Abstract
This study presents a dielectrophoresis-based liquid metal (LM) droplet control microfluidic device. Six square liquid metal electrodes are fabricated beneath an LM droplet manipulation pool. By applying different voltages on the different electrodes, a non-uniform electric field is formed around the LM droplet, and charges are induced on the surface of the droplet accordingly, so that the droplet could be driven inside the electric field. With a voltage of ±1000 V applied on the electrodes, the LM droplets are driven with a velocity of 0.5 mm/s for the 2.0 mm diameter ones and 1.0 mm/s for the 1.0 mm diameter ones. The whole chip is made of PDMS, and microchannels are fabricated by laser ablation. In this device, the electrodes are not in direct contact with the working droplets; a thin PDMS film stays between the electrodes and the driven droplets, preventing Joule heat or bubble formation during the experiments. To enhance the flexibility of the chip design, a gallium-based alloy with melting point of 10.6 °C is used as electrode material in this device. This dielectrophoresis (DEP) device was able to successfully drive liquid metal droplets and is expected to be a flexible approach for liquid metal droplet control.
Highlights
IntroductionDroplet manipulation is the base of digital microfluidics in which the droplet control is of most importance
Droplet-based microfluidics, known as “digital microfluidics”, has become a hot spot in the chemical and biological sciences [1,2], benefitting from its advantages, such as no cross-contamination, small sample size, and potential of high throughput analysis [3].Droplet manipulation is the base of digital microfluidics in which the droplet control is of most importance
By applying different voltages on six square electrodes in this device, a non-uniform electric field is formed inside the manipulation pool; liquid metal (LM)
Summary
Droplet manipulation is the base of digital microfluidics in which the droplet control is of most importance. Among all active manipulation methods, electric-based ones are most popular because there are diverse and convenient ways to apply the electrical field inside microchannels. Room temperature liquid metal (LM) has been introduced into droplet microfluidics as well [13]. Some metals, such as mercury, or alloys, most known as gallium-based alloys, have melting points lower than the room temperature and could form droplets at room temperature [14,15]
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