(401c) Directed Assembly of Non-Equilibrium Structures Utilizing Optical Trapping and Surface-Modified Colloids

Colloidal particles modified with photo-sensitive polymeric brushes exhibit reversible phase transformation properties allowing for the development of switchable particle aggregation and rheological response. By manipulating photo-sensitive particles using optical trapping, it is possible to assemble 2D and 3D microstructures. The system of interest consists of 2 micron borosilicate particles, coated with polymethyl methacrylate/spirobenzopyran polymeric brushes, suspended in toluene. Particle structures are assembled in the solvent using time-shared optical traps and then exposed to ultraviolet light. The light induces a polarity change in the polymer brushes causing particle-particle adhesion. The resulting 2D structure is then attached to a substrate. The process is repeated to assemble three dimensional microstructures with multiple particle layers. Research activities to develop this assembly capability will be presented related to the material requirements needed in optical trapping systems, their application in this photo-sensitive system, and developments in particle assembly.