Meredith Silberstein at Cornell University thinks outside the box to create polymers with targeted functionality. Many of the concepts she explores are bio-inspired. (Photo Credit: Beatrice Jin; Jason Koski, Elizabeth Nelson)

Creating Materials That Mimic Nature

by Jackie Swift

Materials That Switch States, Heal Themselves

In one project, Silberstein and Xinyue (Joy) Zhang, PhD ’22 Materials Science and Engineering, are working with the United States Office of Naval Research to develop an antifouling material that can be applied to ship keels. The material would be able to switch between two states: hydrophobic (repelling water) and hydrophilic (mixing with water). Hydrophobic materials are good for forcing organisms such as barnacles and seaweed to release their hold, whereas hydrophilic materials tend to stop organisms from growing in the first place.

“A lot of mechanochemical concepts are bio-inspired because we’re trying to make materials that do more, adding multifunctionality by embedding it into the chemistry of the polymers.”

“This work is based on charged interactions within polymers — what we call metal coordination bonds,” Silberstein says. “In a lot of the concepts we’re working with, dissipation will happen and then the bonds will reconnect. You can keep pulling and breaking and reconnecting. There are a variety of chemistries you can do this with, but our system is special because of the amount of tailoring we can do on these bonds. We can modulate their environment, and that will change how easily they break and how easily they reform, which is critical if you want to have full control over the mechanical properties of your material.”

Electric Fields to Drive Changes in Mechanical Properties

Working with metal coordination bonds, or charged ions, led the researchers to wonder whether they could use electric fields to modulate the polymers to change their mechanical properties or their ability to heal, Silberstein says. “This is also a very bio-inspired concept,” she points out. “In biology, in human cells, healing and property modulation is based on small electric fields. Neurons, for example, are an ionic charge firing.”

Bio-Inspired Circuits

Recently, Silberstein looked at how the human body depends mostly on ionic-based transport and wondered if the ionic materials she and her lab were developing for other uses could also have bio-like conductivity. “In the synthetic world there are people who look at electronic-like components based on ionic transport, but they’re all mimicking electronics,” she says. “My idea is to stop doing that and explore, instead, what’s inherently good about stretchable materials that have ionic capabilities.” Such materials could give excellent ability to interact directly with biology — for instance, allowing for direct interfacing with the brain.

Modeling the Physics of Materials

Along with developing new materials, the Silberstein lab also creates models — sets of equations that describe the physics of a material. Together with Michael R. Buche, PhD ’21 Theoretical and Applied Mechanics, Silberstein is currently working on a model describing the changes mechanical properties go through as bonds break. The researchers are attempting to create the model both for force-dependent bonds that are irreversible and for those that can be reversed.

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