Researchers have developed tiny flexible lasers that can be used to measure forces inside living cells. The new lasers could help illuminate various biological processes, including those involved in early development and tumor progression.

“Biological forces inside and between cells play an important role in many diseases,” said research team leader Marcel Schubert from the University of Cologne. “For example, when cancer cells invade tissue, they have to squeeze through the other cells. Our tiny lasers make it possible to measure forces on the scale of individual cells, which has previously been very difficult to accomplish.”

In the journal Optical Materials Express, the researchers describe their new spherical whispering gallery mode microbead lasers, which measure just 20 microns, about the width of a human hair. Whispering gallery mode lasers trap light in circular paths—in this case, inside a tiny elastomer bead doped with fluorescent dye—where the light circulates and amplifies until it emits coherent laser light.