Development of a novel electrotaxis tweezer for enhancement of droplet manipulation

Electrotaxis, a method that utilizes an electric field to direct the motion of particles or droplets, typically involves a droplet on a flat surface being guided by an electrically charged tweezer above it. Traditional electrotaxis methods have relied on voltages over 1.5 kV for droplet control, but this has several disadvantages, such as high voltage demands, the danger of electric discharge to the droplet, possible adhesion of the droplet to the tweezer, and issues with droplet oscillation and overshoot, which impede its broader application. The present study proposes an innovative tweezer design that not only operates at reduced voltages but also reduces droplet oscillation relative to traditional tweezers. This tweezer features a coaxial tubular sheath encircling the electrode, which modifies the electric field’s influence on the droplet. Numerical simulations were employed to obtain the tweezer’s ideal dimensions and shape. The empirical evidence indicates that the new tweezer can adeptly steer droplets at a markedly lower voltage of 620 V, ensuring a more stable trajectory and significantly diminishing overshoot. The tweezer’s distinctive design also decreases the possibility of electric discharge to the droplet, thus improving the safety of the system for managing delicate droplets. In the experiment, the maximum droplet translation speed attained was 105 mm/s at an applied voltage of 1.2 kV. This represents a 29.6% increase in speed and a 70% decrease in the required voltage compared to the previously highest reported droplet speed.