Ying Diao, an assistant professor of chemical and biomolecular engineering at the University of Illinois’ Beckman Institute for Advanced Science and Technology. Photo: L. Brian Stauffer, University of Illinois at Urbana-Champaign
Ying Diao, an assistant professor of chemical and biomolecular engineering at the University of Illinois’ Beckman Institute for Advanced Science and Technology. Photo: L. Brian Stauffer, University of Illinois at Urbana-Champaign

Researchers at the University of Illinois at Urbana-Champaign, in collaboration with a team from Purdue University, have discovered that certain crystals are more flexible and stretchable than current materials used for electronic applications. These new materials could prove useful for making sensors and in robotics. The researchers report their findings in a paper in Angewandte Chemie.

Typically, silicon and germanium are used for making electronics. But using these brittle materials on human skin or in robotics is challenging, because they break apart when stretched too much.

"Researchers use two ways to make stretchable electronics," said Ying Diao, an assistant professor of chemical and biomolecular engineering at the University of Illinois’ Beckman Institute for Advanced Science and Technology. "Either they carve intricate patterns out of silicon or they design new polymer materials. However, these approaches either involve complicated processes or they compromise the perfect order of the molecules."

To overcome this limitation, the Diao group looked for single crystal materials that could be stretched easily. The researchers were inspired by nature in their search. "This mechanism is found in a virus called the bacteriophage T4 virus," Diao explained. "The tail of this virus is a single crystal of protein molecules and it is compressed over 60% when the virus injects its DNA into the bacteria. The compression occurs without losing structural integrity."

"We discovered that bis(triisopropylsilylethynyl)pentacene crystals can be stretched over 10%, which is 10-fold that of the elastic limit of most single crystals." said Sang Kyu Park, a postdoctoral researcher in the Diao group.

"The molecules in the single crystals can cooperatively glide and rotate to accommodate mechanical strain beyond their elastic limit." said Hong Sun, a graduate student in the Kejie Zhao group at Purdue University.

"This mechanism also is found in shape memory alloys that are available in retail stores," Park said. "You can distort the wire and then restore it back into its original shape by heating it. However, we are the first to discover this phenomenon in organic electronic crystals."

This story is adapted from material from the University of Illinois at Urbana-Champaign, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.