Simultaneous polymerization and patterning: A one step acoustic directed assembly method

Processing materials to form microstructures in the least possible number of steps is desired in order to reduce cost and processing time. In this work, we propose a new approach where standing surface acoustic waves are used to order materials prepared in-situ rather than preformed materials, providing a new method for one-step (simultaneous polymerization and patterning) directed assembly. We demonstrate this concept on products of an ongoing chemical reaction such as polymerization of polydimethylsiloxane (PDMS). We have found that by directed coalescence of nano-sized intermediate nucleation sites, continuous polymeric microstructures are formed. A systematic study of the parameters that control this directed coalescence (cross-linker ratio, salt concentration and acoustic field strength) was performed. Acoustic forces can influence almost all dispersed systems, require low power densities and can be scaled up. Combining chemical synthesis with the patterning processes as shown here, could therefore be beneficial for directed assembly of soft matter.