A team of researchers from the University of California, Berkeley, has developed a new technique to study how soft materials, such as rubber and Silly Putty, react to deformation at the molecular level. The findings, published in the journal Nature Materials, could lead to new ways to design and engineer materials with improved properties for a wide range of applications.

"Soft materials are everywhere around us," said study lead author Ting Xu. "They're used in everything from tires to toys, from medical implants to food packaging. But until now, we haven't had a good way to study how these materials behave at the molecular level when they're deformed."

The new technique, called "single-molecule force spectroscopy," uses a tiny glass needle to probe the mechanical properties of individual molecules. By attaching one end of a molecule to the glass needle and the other end to a surface, the researchers can apply a force to the molecule and measure how it responds.

The researchers used single-molecule force spectroscopy to study a variety of soft materials, including rubber, Silly Putty, and gelatin. They found that these materials all exhibited a similar response to deformation: they became stiffer as they were stretched.

"This was unexpected," said Xu. "We thought that soft materials would become more compliant as they were stretched, but we found the opposite to be true."

The researchers believe that the stiffening of soft materials under deformation is due to a change in the way that the molecules interact with each other. When these materials are stretched, the molecules become more aligned and form stronger bonds with each other. This makes the materials stiffer.

The findings of this study could lead to new ways to design and engineer materials with improved properties for a wide range of applications. For example, the researchers say that their findings could be used to create new materials that are more resistant to wear and tear, or that can be used in medical implants to promote tissue repair.

"We are excited about the potential of this new technique to help us understand the mechanical properties of soft materials at the molecular level," said Xu. "We believe that this knowledge could lead to the development of new materials with improved properties for a wide range of applications."