Nano-engineering of colloidal particles, synthetic biomimetic blood cells, synthetic opals, photonic crystals and the physics of self-assembling nanostructures.

摘要

Lithographically patterned substrates serving as geometric guides that force colloidal spheres to assemble into a face centered cubic (FCC) crystal lattice vertically along the [100] direction are demonstrated. The self assembly of spherical colloidal particles and their interaction forces are also described. Colloidal silica spheres are shown to sediment over large areas in a way that is similar to that of uncharged particles and to self assemble along the [100] direction of the FCC crystal lattice under the described conditions. The liquid phase in colloidal silica dispersions is shown to be a collection of partially interacting granulated regions and not a global network of interacting spheres resulting from strong horizontal forces. The experimental data is tied together with the traditional interaction forces from colloidal theory to explain the self assembly process for large populations of charged spheres. This new understanding resulted in the formation of opalescent crystallites (1.2cm x 8mm x 4mm) with 250nm diameter silica spheres and was used to create 1 mm wide opalescent crystallites with sphere diameters up to 2.3mum. The model predicts that under certain laboratory created conditions, polystyrene spheres will sediment vertically along the [100] direction of the FCC crystal lattice with sphere volume/volume fractions as high as 10%. Experimental verification was achieved using polystyrene spheres with various diameters between 200--500nm. Metallic, metallodielectric, chalcogenide and electro-luminescent polymer photonic crystals were made from synthetic silica opal templates with various sphere diameters between 200nm and 2.3mum. Hollow colloidal discs 1.5mum thick with 4mum diameters were fabricated using human red blood cells as templates. The blood cells were chemically encapsulated in a thin golden shell of controllable thickness. Control of the osmotic pressure during the encapsulation process allowed control over the shape of the resulting particles.