A prototype of a new material that could advance protection qualities of armor and other biomedical inventions has been created by UNH mechanical engineering Assistant Professor Yaning Li and a group of five former and current UNH students: Yunyao Jiang, Shengguang Jin, Emily Hunchison, Stephanie Medicke and Carolyn Przekaza.

According to Li, this new material is unique due to its elevated internal rotation caused by auxetic effects, meaning that, when the material is stretched, it becomes thicker perpendicular to the applied force. This particular dynamic of the material engages advanced protection from forces of impact or tension, which would make the material useful for armor or headgear.  

“If you put [the material] in tension vertically, it’s going to expand horizontally,” Li said. “That’s odd. This material is odd.”

Chiral cells are asymmetric and function differently than typical cells in the sense that they don’t have the capacity to expand and rotate like chiral cells. Li noted that softer corners and a harder core would amplify the auxetic effect.

This five year study to create this material was proposed in spring 2015, and the project began development that summer. Due to the material’s complexity, the team used a 3-D printer in Kingsbury Hall to prove this concept beyond the theoretical level and create a successful prototype.

“Because of the chiral geometry, when I press it, each side [of the material] is going to rotate,” Li said. “The rotation is the major reason for the identic effect.”

According to Li, there is a lack of the material left in the database that helped create the prototype. The 3-D printer uses polymers to create the material, which consists of a specific hard plastic and rubbery-like substance.

“Our major product is knowledge,” Li said. “The goal is to create new material that can go beyond the theoretical level.”

 Li said that due to this material’s features, it has unique applications in terms of biomedical advancements. She said that if the material is used as armor, it would cause particles to sit in the cells of the interior of the protective gear and it would then give damaged cells different doses of repair. The repair of the doses would be initiated by the sliding of the respective materials against one another

According to Li, if the material were to  be responsive to light or color, the cells could automatically open or close to save the user energy, and that the color change would respond to variations in volume and temperature.

“Think of it like an octopus,” Li said. “The octopus can change its skin color because they have multiple layers, but only one layer has cell-like pixels. Their biological system allows the cells to locally stretch or shrink.”