Patterned Surface Energy in Elastomeric Molds as a Generalized Approach to Polymer Particle Fabrication.

We present a generic fabrication scheme to produce polymer microparticles with engineerable, complex shapes. The polymer particles are made from polyethylene glycol based hydrogels using a poly(dimethylsiloxane) (PDMS) molding technique. A simple surface treatment is used to pattern the surface energy of the PDMS molds, engendering the recessed wells in the molds with a higher surface energy than that of the surface. The contrast in surface energy causes hydrogel precursor to wet only the inside of the molds, creating isolated particles after curing with UV light. This eliminates the formation of an interconnecting "scum" layer and allows for fabrication of well-defined, independent particles. We discuss resolution limits for the approach and present a simple strategy for releasing the particles. Finally, to show how the fabrication technique is inherently compatible with further particle modifications, we also demonstrate magnetic functionalization of particles.