One-dimensional actuation of a ferrofluid droplet by planar microcoils

This paper discusses the simulation of a device for actuation of a ferrofluid droplet using planar microcoils. The device with two pairs of planar microcoils was designed and fabricated on a double-sided printed circuit board (PCB). Each pair is placed on each side of the PCB. The coils on the bottom actuate the droplet along the line connecting their centres. The coils on the top create a virtual channel to confine the motion of the droplet along a straight line. The paper first formulates the model of the magnetic field of the coils. With the modelled magnetic field, the corresponding forces acting on the droplet were calculated. The equation of the motion of a ferrofluid droplet immersed in silicone oil is solved numerically. The influence of different parameters such as driving current, droplet diameter and viscosity of the carrier fluid is investigated. Theoretical and experimental results agree well quantitatively and qualitatively. Both theoretical and experimental results show that a higher magnetic field, a lower oil viscosity and a bigger droplet size will increase the peak velocity of the droplet.