We report our work of binding microscopic particles into three dimension structures through a novel layer-by-layer approach. Multi-beam interferometry was used to form a two dimensional periodic optical field. Such optical landscape was used to trap colloidal particles into a single layer of 2-d colloidal array. A second optical tweezers setup was combined to offset such single-layer 2-d colloidal arrays in the third dimension. A strong electric field was found at the vicinity of each single layer with carefully calculated experimental parameters. Our numerical results suggest that with practical parameters, the strong electric field resulted from the diffraction of trapped particles should trap colloidal particles into a new layer of identical 2-d arrays, thereby offering an alternative approach to optically bind microscopic particles into three dimension periodic structures. Preliminary experimental results of this method demonstrating trapping with secondary diffracted light are also presented.
"Layer-by-layer optical assembly of colloidal particles", Proc. SPIE 6644, Optical Trapping and Optical Micromanipulation IV, 664417 (5 September 2007); doi: 10.1117/12.733199; https://doi.org/10.1117/12.733199