Method and apparatus for forming multi-dimensional colloidal structures using holographic optical tweezers

摘要

Holographic optical tweezers are used to position charge stabilized colloidal particles within a flow cell. Once the particles are positioned, fixation is accomplished by pumping an electrolyte solution or pH adjusted solution (or a combination of the two) into the sample cell. In the former, the Debye length is reduced and aggregation caused by the van der Waals attraction takes place. In the latter, the surface charge density of the suspension is reduced and aggregation caused by the van der Waals attraction takes place. This technique can be applied multiple times, and allows for the formation of two and three dimensional structures composed of multi-colloid types to be formed on or away from a substrate. The technique relies upon forces acting on virtually all colloidal dispersions making it applicable to a wide variety of colloid types and compositions, such as formation of photonic crystals, colloidal electronics, and bioengineered materials.