U.S. scientists say they have developed and successfully tested a method of making three-dimensional, single-crystalline silicon structures from thin films.

The researchers, led by Professor Ralph Nuzzo of the University of Illinois, said their method begins by using photolithography, and is completed by capillary interactions that drive a self-assembly process. As a demonstration of the new method, Nuzzo and his colleagues constructed silicon solar cells having spherical and cylindrical shapes, and then evaluated their performance.

"This is a completely different approach to making three-dimensional structures," Nuzzo said. "We are opening a new window into what can be done in self-assembly processes."

The researchers said they also created a predictive model that describes the interactions among the type of film used, the film's mechanical properties and the shape of the desired structure.

"The model identifies the critical conditions for self-folding of different geometric shapes," said Professor K. Jimmy Hsia, a member of the research team. "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."

The team's findings appear in the Proceedings of the National Academy of Sciences.