A ferrofluid microrobot for manipulation in multiple workspaces

Ferrofluid droplet has wide applications in bioanalysis manipulation. This study presents a ferrofluid microrobot for manipulation in different workspaces. Based on the deformation character of droplet, the ferrofluid microrobot has the capabilities of climbing the 3D (3-dimensional) surface, splitting in the channel, and transporting large particles. To manipulate in multiple workspaces with the capabilities, the size and magnetic force of ferrofluid are studied for suitable scenes. It shows that the diameter of 0.5 μl ferrofluid is around 980 μm. The manipulation force of different ferrofluid microrobots ranges from micronewton to millinewton. Subsequently, we have verified the manipulation of the ferrofluid microrobot on a 3D chip by permanent magnet. The ferrofluid microrobot can climb the stairs only when the height of the magnetic fluid is higher than twice the height of the stairs. Meanwhile, splitting of ferrofluid microrobot in the microfluidic chip has been successfully demonstrated. It indicates that the splitting influenced by the magnetic field and large magnetic force is easier to split the microrobot. Finally, the transportation of large polystyrene microparticles (150 μm) is confirmed by the ferrofluid microrobot. These capabilities show that the ferrofluid microrobot has the potential application advantage in biomedicine's micro-drug testing.