Staged Assembly of Colloids Using DNA and Acoustofluidics.

Assembly of DNA-coated colloids (DNACCs) provides a practical route to programming complex self-assembled materials at the micro/nanoscale. So far, the programmability of DNACC assembly has been extensively exploited internally using different DNA sequences or colloid geometry so that the assembly is mainly manipulated with single-particle spatial resolution such as in crystallization. In this Letter, we present an acoustic approach to externally programming the DNACC assembly with control of spatial resolution over larger scales. We demonstrate assembly of the DNACCs under different acoustic frequencies from stage to stage to produce hierarchical structures that are difficult to fabricate when using DNA coating alone. By programming the acoustic wave frequency, amplitude, and phase, colloidal structures with different morphologies can be assembled. The nonspecific driving force based on acoustic radiation forces at each stage allows our approach to be adopted for most colloidal systems without specific requirements on particle or medium properties.