Multiaxial fields drive the thermal conductivity switching of a magneto-responsive platelet suspension

Abstract

We demonstrate the ability to change the thermal conductivity of a magnetic platelet suspension from insulating to conducting by using either uniaxial or multiaxial ac magnetic fields to control the suspension structure and dynamics. The equivalent thermal conductivity of the suspension can be modified either by creating static particle structures that facilitate or block heat transfer, or by using multiaxial ac fields to drive emergent particle dynamics that create vigorous, organized, non-contact flow. The equivalent thermal conductivity of a single suspension can be varied over a 100-fold range, and an equivalent thermal conductivity as high as 18.3 W m⁻¹ K⁻¹ has been achieved in an aqueous suspension containing only 2.0 vol% platelets. This value is more than twice the conductivity of liquid mercury.