Open surface droplet manipulation and mixing by ferrofluid instabilities

Open surface droplet manipulation is a powerful technique for many microfluidics applications.  Here, we present how ferrofluid spikes, which show soft matter behavior due to magnetic field instabilities, were used to manipulate and mix water droplets.  The droplet mechanism was integrated within a paper-based microfluidic device for magnetic manipulation of digital microfluidics. As a proof of concept, two droplets were mixed together using the physical action of ferrofluid spikes generated by magnetic forces.