Figure 15.

Magnetic tweezer manipulation of a swarm of magnetised fluorescent-magnetic microspheres in a droplet. The 250 μm iron wire magnetic tweezers were placed above the droplet to aggregate the magnetic microspheres into a swarm. The iron wire was then abruptly moved above the swarm to observe the velocity profile of the swarm. (a) Simultaneous bright field and fluorescence image of swarm and iron wire above. (b) Fluorescence image of swarm before moving the wire. (c) Moving the swarm left. (d) Moving the swarm right. (e) Holding wire still. (f) Moving the wire and swarm down. From [73]

Corr et al. Nanoscale Research Letters 2008 3:87-104   doi:10.1007/s11671-008-9122-8