New Self-Assembly Process Produces Amazing 3D Structures

Scientists at the University of Illinois in Urbana-Champaign (UIUC) announce that they recently managed to complete a new method of fabricating self-assembling nanostructures. The technology, they say, combines two different approaches, namely photolithography – the same process used in producing integrated circuits for computer processors – and a capillary interaction-driven self-folding process. This resulted in what can be described as an ultra-high-tech set of origami, three-dimensional, single-crystalline silicon structures that have amazing properties. The new formations, which are only a few microns thick, are capable of performances that their thicker cousins simply cannot fathom.

“This is a completely different approach to making three-dimensional structures. We are opening a new window into what can be done in self-assembly processes,” says the UIUC G. L. Clark Professor of Chemistry Ralph G. Nuzzo. The new formations, he adds, can be bent to a degree that thicker materials cannot even approach. This alone makes the new structures very suitable for use inside future bendable and twisting electronics. This field of research is at this point garnering a lot of attention, but most research groups are either investigating carbon nanotubes – which still have a long way to go – or silicon, which is too brittle to allow for massive improvements.

In order to demonstrate their new construction method, Nuzzo and his team began developing spherical- and cylindrical-shaped silicon solar cells. After the synthesis process was complete, the team put the new devices to the test. At the same time, the team also developed a predictive computer model, which allows them to throw in data such as the type of thin film to be used, its mechanical properties, and the desired structural shape, and to come up with a solution. Details of the amazing work appear in the November 23 early online issue of the respected journal Proceedings of the National Academy of Sciences (PNAS). Nuzzo was the corresponding author of the paper.

“The model identifies the critical conditions for self-folding of different geometric shapes. Using the model, we can improve the folding process, select the best material to achieve certain goals, and predict how the structure will behave for a given material, thickness and shape,” adds K. Jimmy Hsia, who is a mechanical science and engineering professor at the University. “The resulting photovoltaic structures, not yet optimized for electrical performance, offer a promising approach for efficiently harvesting solar energy with thin films,” concludes the Director of the UIUC Frederick Seitz Materials Research Laboratory, Jennifer A. Lewis. She is also the Thurnauer Professor of Materials Science and Engineering at the university.