Liquid mirrors deform magnetically

A unique liquid mirror has been developed by researchers at Université Laval (Quebec, QC, Canada) that combines a surface film of silver particles with a magnetic fluid. To prepare the mirrors, 6 mL of ferrofluid were placed in a 7-cm-diameter aluminum dish. The ferrofluid consisted of iron oxide nanoparticles suspended in ethylene glycol with a weight percentage of particles of 19%. Silver particles, once extracted and concentrated from an aqueous suspension, were sprayed over the ferrofluidic surface using a commercial spray gun with nitrogen assist.

The method of preparation of the ferrofluid and silver film results in a very smooth mirror surface (with a root-mean-square surface roughness of approximately λ/20 at 624 nm) compared to previous experiments with silver films on water or other nonoptimized suspensions. Manipulation of the mirror’s surface shape is possible by controlling the ferrofluid with a magnetic field. Prototype magnetically deformable liquid mirrors were demonstrated in the Université Laval laboratory by the research team. Contact Ermanno Borra at ermanno.borra@phy.ulaval.ca.