Ferrofluid Valve Operated By the Magnetic Field of a Straight Current-carrying Wire

Abstract

Integrated valves produce increased control and make up an essential part of different devices, especially in microfluidics. The use of ferrofluid in valves is one of actuation methods. Different magnetic fields could be used to operate a ferrofluid valve. In the present paper, we propose to use the magnetic field created by a straight current-carrying wire to operate a ferrofluid valve which can open the channel formed by two coaxial cones and a cylinder. Numerical modelling of the valve behaviour for different values of ferrofluid volumes and currents in the wire is done for two cases: when the ferrofluid wets and does not wet surrounding solid boundaries. It is shown that the presence of limiting cones allows the ferrofluid to sustain the pressure drop which is much bigger in case of non-wetting than in case of wetting. In case of wetting the ferrofluid cannot sustain any pressure drop at small currents, but in case of non-wetting the ferrofluid can do it even at zero current. It is found that in case of non-wetting spasmodic and hysteresis phenomena are possible for some values of ferrofluid volumes and currents in the wire.