Researchers present programmable materials to help heal bone fractures

Natural materials such as bone, bird feathers and wood, despite their irregular architecture, have an intelligent approach to physical stress distribution. However, the relationship between the modulation of stresses and their structures is difficult to understand. A new study integrating machine learning, optimization, 3D printing and stress experiments has enabled engineers to gain insight into these natural wonders by developing a material that replicates the functionalities of human bone for orthopedic femur restoration.

The study, led by University of Illinois Urbana-Champaign civil and environmental engineering professor Shelly Zhang and graduate student Yingqi Jia in collaboration with professor Ke Liu from Peking University, introduces a new approach to orthopedic repair that uses a fully controllable computational framework to produce a material that mimics bone.

Conventional treatment of femur fractures often involves surgically attaching metal plates to stabilize the fracture, but this can lead to complications such as loosening or chronic pain. The technique developed by Zhang’s team could offer an innovative alternative. Based on an extensive material database and a computer-aided optimization algorithm, the team was able to model a virtual material that optimizes both the architecture and the stress distribution in the bone.

“We started with materials database and used a virtual growth stimulator and machine learning algorithms to generate a virtual material, then learn the relationship between its structure and physical properties,” Zhang said. “What separates this work from past studies is that we took things a step further by developing a computational optimization algorithm to maximize both the architecture and stress distribution we can control.”

In the laboratory, a prototype of the material was produced from synthetic resin using 3D printing and attached to a synthetic model of a broken human femur. The practical tests confirmed the effectiveness of the new material by showing that it mimics the natural structure of biological systems and could therefore support the healing process.

“Having a tangible model allowed us to run real-world measurements, test its efficacy and confirm that it is possible to grow a synthetic material in a way analogous to how biological systems are built,” Zhang said. “We envision this work helping to build materials that will stimulate bone repair by providing optimized support and protection from external forces.”

Zhang said this technique can be applied to various biological implants wherever stress manipulation is needed. “The method itself is quite general and can be applied to different types of materials such like metals, polymers — virtually any type of material,” she said. “The key is the geometry, local architecture and the corresponding mechanical properties, making applications almost endless.”

The results of the study were published in the journal Nature Communications and offer a promising outlook for the future development of materials that not only mimic the function of bone, but could also optimize the healing process.