Programmable two-dimensional actuation of ferrofluid droplet using planar microcoils

This paper reports the concept and the device for two-dimensional magnetic actuation of a ferrofluid droplet. Four planar microcoils were etched on one side of a printed circuit board (PCB). The magnetic field was digitally controlled by adjusting the magnitude and the polarity of the driving current in the coils. A computer programme generates the control signals, which are conditioned by an external amplifier circuit and transferred to the coils. The ferrofluid droplet is attracted to the field maximum. With the controlled magnetic field, the location of the field maximum can be changed electronically allowing the droplet to move in a closed loop on the planar platform. The concept presented in this paper can have a variety of applications in digital microfluidics such as sample transport or mixing.