Ingenious: Engineered Healing

Engineering professor Shelly Zhang draws inspiration from natural structures like spider webs. (Image by Fred Zwicky)

If computers can be programmed to perform a myriad of functions, then why can’t materials be programmed to do the same? And how could those programmed materials be applied to orthopedic medicine?

These are the questions Shelly Zhang, a David C. Crawford Faculty Scholar and assistant professor of civil engineering, is investigating with her team at the Grainger College of Engineering. A programmable-materials pioneer, Zhang is working on a computational framework to produce a bone-mimicking material to repair broken femurs. She and her team also are using programmable materials to create “soft robots” that can be implanted beneath the skin to heal soft-tissue injuries.

Femur fractures are often mended using titanium plates and screws, but they don’t always provide the right stress distribution, Zhang explains. This can result in “stress shielding,” in which the metal plate unevenly distributes stress on the bone and “interrupts the bone-healing process,” she says.

To correct that imbalance, Zhang’s team is developing a computer-generated material that replicates the functionalities of human bone. “The material can be programmed to have a specific stress distribution, boosting the healing process,” she says. It’s the first-ever use of programmable materials for bone repair, she adds.

The team devised in-house algorithms to program and “virtually grow” the programmable material. They then employed 3D printing to create a full-scale resin prototype of the bio-inspired material and attached it to a synthetic model of a fractured human femur. The researchers now are seeking medical doctors to conduct the next stage of research.

To help heal soft-tissue injuries, Zhang’s team is programming small robots made of a rubber-like material called elastomer. The miniature robots can be implanted beneath the skin, where they are placed directly on injured tissue to “massage” it.

To initiate the process, magnetic particles are distributed throughout the elastomer material. A wireless controller is then used to magnetize the robot, enabling it to move and massage tissue where directed.

By performing “very controlled and specifically designed motions on the injured tissue,” the soft robot can accelerate tissue repair, Zhang says.

As an example of the emerging redefinition of “mechanotherapy,” these robots have the potential for use with all types of soft-tissue injuries, including those suffered by athletes and soldiers. They represent the first wireless devices to provide mechanotherapy directly to soft tissue.

Zhang’s motivation to program materials comes from her lifelong pursuit of structure and device optimization. Her inspirations derive from both natural structures, such as spider webs and bones, to man-made oness like skyscrapers.

“Optimization has a huge potential to improve the functionality of many engineered structures and devices,” she says.