Animals and electronic devices aren’t the only things with memory. Materials can retain memories of past deformations in their microscopic structure. A common example is a crease in a sheet of paper that has been folded then unfolded. Understanding this type of memory could benefit the design of materials that respond to changes in their environment in predictable ways.

It can also be a source of ideas about the various types of memory studied by neuroscientists, including how short-term and long-term memories interact and influence each other. Now, researchers at Penn State have shown that two different types of material memory can coexist in a simple mixture of small particles suspended in a viscous liquid. Like long-and short-term memories, these material memories interact and compete.

A paper describing the research was recently published and highlighted as an editors’ suggestion in the journal Physical Review Letters.