One of the least-studied factors in traumatic brain damage and other soft-tissue injuries is the focus of a new, four-year, $2.6 million grant from the Office of Naval Research. A team led by polymer scientist Alfred Crosby at the University of Massachusetts Amherst, with others at the University of Pennsylvania and the University of California, San Diego, will study cavitation, the sudden expansion of bubbles in a material.
As Crosby explains, the creation and collapse of bubbles in liquids is well known and has been studied extensively for the past century. When cavitation bubbles collapse, they force liquid into a smaller area, causing a pressure wave and increased temperature. In a pump, for example, cavitation can cause wear and erode metal parts over time. Cavitation inside artificial heart valves can damage not only the parts but the blood. Microcavitation in the brain as a result of high-impact blows or being near an explosion is suspected as a factor in brain injury.
Cavitation can also occur in solids and gels, but few scientists have studied this, he notes. Crosby and chemical engineer Shelly Peyton, mechanical engineer Jae-Hwang Lee and polymer scientist Greg Tew at UMass Amherst, with chemical engineer Rob Riggleman at UPenn and mechanical engineer Shengqiang Cai at UCSD have formed “CAVITATE,” a team at the UMass Amherst’s Center for Evolutionary Materials, to study the phenomenon.
By focusing on how cavitation causes damage and materials failure, that is, the breakdown of materials, they plan to combine new experimental instruments with creation of new gels and new theoretical models to change the way this failure is understood in biological tissues and gels and turn it toward new uses. “We hope this will lead to advances in medical devices for diagnosing disease, novel devices for protective gear and new sustainable approaches for cleaning materials,” Crosby says.
He adds, “While cavitation is often thought of as something to be avoided, we aim to use it to benefit medicine and the development of new materials.” For example, cavitation rheology, an experimental tool he invented, uses cavitation to measure the stiffness of living tissues at very small scales, as small as a single cell, measurements that are difficult to achieve with any other method.
CAVITATE team members Peyton, an expert on tissue mechanics, and Tew, a leading chemist of new polymer gels, with Crosby have shown that this approach offers significant promise but it also faces challenges before it can be used widely.
In other CAVITATE projects, Lee will further explore methods to cavitate materials with lasers to learn about how materials stretch and fail at extremely high rates, and Riggleman and Cai, are developing theoretical models of materials from the molecular level to macroscopic size scales to discover new opportunities for using cavitation.