"Stick and slide" ferrofluidic droplets on superhydrophobic surfaces

The authors report the suspension and movement of ferrofluid droplets on superhydrophobic surfaces in the presence of strong external magnetic fields. The system allows the quantitative evaluation of friction between droplet and substrate surface. It represents an enabling example for the development of microferrofluidic devices and a breakthrough in the remote actuation of droplets on surfaces, which cannot be achieved using conventional microfluidics, or inkjet printing, electrowetting, or light-driven motion.