Ultrasonically assisted deposition of colloidal crystals

Sabine Wollmann, Raj B. Patel, Achim Wixforth, Hubert J. Krenner

Applied Physics Letters 105, 031113 (Jul 2014) DOI: Applied Physics Letters

Colloidal particles are a versatile physical system which have found uses across a range of applications such as the simulation of crystal kinetics, etch masks for fabrication, and the formation of photonic band-gap structures. Utilization of colloidal particles often requires a means to produce highly ordered, periodic structures. One approach is the use of surface acoustic waves (SAWs) to direct the self-assembly of colloidal particles. Previous demonstrations using standing SAWs were shown to be limited in terms of crystal size and dimensionality. Here, we report a technique to improve the spatial alignment of colloidal particles using traveling SAWs. Through control of the radio frequency power, which drives the SAW, we demonstrate enhanced quality and dimensionality of the crystal growth. We show that this technique can be applied to a range of particle sizes in the m-regime and may hold potential for particles in the sub-m-regime.