Thursday, November 11, 2010: 2:10 PM
Topaz Room (Hilton)
Microfluidic devices offer the ability to finely control physical and chemical conditions which is advantageous for materials synthesis. Several groups have used multi-phase microflows to produce microparticles and capsules. Surface tension limits these particles to be spheroids. The Doyle group recently showed that more complex shapes and also patterned chemistries within a particle can be attained by coupling microfluidics to photolithography. Continuous-flow lithography (CFL) and the more refined stop-flow lithography (SFL) can generate 2-D extruded particles of any desired shape. Colloidal polymeric particles that have been synthesized using a variety of techniques including SFL, have been envisioned as atoms and molecules of future materials. The tuned assembly of microparticles can find applications in a variety of fields such as in photonics, for generating scaffolds and tissue engineering. External fields, specifically electric and magnetic fields have been used to tune assembly widely in the past. In this work, we generate super paramagnetic microparticles using two different methods. Anisotropic magnetic hydrogels are obtained by direct encapsulaton of magnetic nanoparticles using SFL or by growth of magnetic nanoparticles in hydrogels synthesized using SFL. Also we study their assembly in a reservoir by the application of a uniform magnetic field, trying to highlight the dependence of structure evolution on the shape of the microparticles.