Magnetically Actuated Assmbly of Anistropic Colloidal Structures

Speaker: 
Hui Son
Date of Seminar: 
Fri, 2008-04-04 12:00
Semester & Year: 
Spring 2008
Seminar Location: 
Hudson Hall Room 207
Seminar Contact(s): 
Elizabeth Irish eri@duke.edu or Justin Jaworski jwj@duke.edu
Special Instructions: 
Lunch and beverages will be served
We demonstrate a convenient method for assembling ring-shaped colloidal structures by applying uniform magnetic field to a mixture of paramagnetic beads, non-magnetic polystyrene beads, and a fluid dispersion of 10-nm iron oxide nanoparticles (i.e., ferrofluid). The ferrofluid serves as a magnetic contrast medium and induces dipole moments in both the paramagnetic and non-magnetic beads when an external magnetic field is applied. We discovered that for various relative bead sizes, the smaller beads form ring structures around the larger bead. This method differs from similar self-assembly techniques in that the ring structures form solely through highly specific magnetic forces, rather than depending on random motion and patterned bonding.