Optically Induced Electrokinetic Trapping and Sorting of Colloids

Recently, we have demonstrated electrothermal hydrodynamics with an external heating source of a highly focused 1,064 nm laser beam [1]. This phenomenon, when coupled with particle-electrode electrokinetic interactions, has led to the rapid and selective concentration of suspended colloids [2–6]. This technique, termed Rapid Electrokinetic Patterning (REP) was demonstrated without any additional surface modification or patterning of the electrodes. This dynamic, optically induced fluid and particle manipulation technique could be used for a variety of lab-on-a-chip applications. However, there are additional effects that have yet to be investigated that are important for a complete understanding of REP. This paper showcases experimental particle-particle behavior observations by varying particle diameter, electrode material, and preliminary results of varying fluid electrical conductivity.