Softening into Shape

Polymer particles with nanometer and micrometer dimensions have been applied to fields ranging from medical imaging to fluid rheology, but controlling particle shape during synthesis has been challenging. Champion et al. have devised a simple method for manipulating spherical polystyrene particles into a diverse array of shapes and sizes (including the bicones shown left). The particles were embedded in a sheet of polyvinyl alcohol and then either softened (by solvent or heat) and stretched, or else softened after first stretching the film (which created voids filled by the softened particles). Dissolution of the film then afforded the shaped free particles. Stretching was possible in either one or two directions, and it was possible to combine or repeat the two techniques. — MSL