New advances in 3D micro-fabrication of polymer nanocomposites (3/11/2008)

Fluorescent bull and lizard sculptures

With the technique they have developed, as reported on-line on January 30 by the journal of Advanced Materials, the researchers are successful in making fluorescent bull and lizard sculptures not much bigger than red blood cells. The tiny creatures luminesce either green or blue.

Due to the constraints of traditional optical theories on diffraction limits, it is difficult to carry out the nano-scale 3D structure microfabrication via a conventional lithography technique. By applying the nonlinear optical theorems, however, the multiphoton technology provides a new approach and method for overcoming the limits and raising its nano-scale resolution. Based on this, Prof. Duan's research team had already developed an ultra-fine fabrication system with the aid of nanophotonics.

In collaboration with co-workers at home and abroad, the team realized the fabrication with nanometer scale resolution by taking advantage of femtosecond laser direct writing technology. At the same time, they observed the lasing phenomenon in a 3D nanowire structure of materials with fluorescence dyes.

The semiconducting nanomaterials are noted for their unique optical, electrical and magnetic properties. However, the high viscosity of the photoresist, which is widely used in 3D multiphoton microfabrication, makes it difficult to evenly disperse the previously synthesized nanomaterials.

To overcome the technical snag, Prof. Duan put forward a new approach for realizing the processing of a 3D microstructure through component preparation which involves the material's precursors. Then, the 3D reprocessing mode was introduced with the aid of the in-situ synthesis to fabricate the nano-composites. In this way, he obtained the lab preparation of the nanocomposites of TiO and CdS in the form of 3D photonic crystals, including the successful observation of the reinforced photonic bandgap effect in the 3D photonic crystals.

Furthermore, the research team realized the size control of the CdS nanoparticles in the in-situ synthesis by regulating the crosslinking molecule's networking density in the light-etching glue and the nanocomposite's fluorescent wavelength might be tunable in the scope between 450mn and 530nm. By making use of the above-listed expertise, the team prepared a lot of 3D microstructures from multicolor nanocomposites in the shape of mini-cattle and discovered that, the lighting intensity becomes stronger in sections with smaller dimensions. The journal Nature makes the following comment in its research highlight published in 21 February, 2008: Their animal creations are offered as proof of principle for a means of making miniature light-emitting electronics.

Note: This story has been adapted from a news release issued by Chinese Academy of Sciences

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