Engineers at the Massachusetts Institute of Technology (MIT) have designed a pliable, 3D-printed mesh material whose flexibility and toughness can emulate and support muscles and tendons in ankle and knee braces. The tough yet stretchy fabric-like mesh can be tailored for personalized, wearable supports.
As a demonstration, the team printed the mesh for use in an ankle brace. They custom-made the mesh’s structure to prevent the ankle from turning inward while allowing the joint to move freely in other directions. The researchers also fabricated a knee brace design that could conform to the knee even as it bends. A study about the development was published June 19 in the journal Advanced Functional Materials.
“3D-printed clothing and devices tend to be very bulky,” said Sebastian Pattinson, PhD, the lead author of the study. “We were trying to think of how we can make 3D-printed constructs more flexible and comfortable, like textiles and fabrics.”
Inspired by the molecular structure of collagen, which makes up much of the body’s soft tissues and is found in ligaments, tendons, and muscles, Pattinson designed wavy patterns, which he 3D printed using thermoplastic polyurethane as the printing material. He then fabricated a mesh configuration to resemble pliable fabric. The taller he designed the waves, the more the mesh could be stretched at low strain before stiffening—a design principle that can help to tailor the mesh’s degree of flexibility and helped it to mimic soft tissue.
The researchers printed a long strip of the mesh and tested its support on the ankles of several healthy volunteers. For each volunteer, the team adhered a strip along the length of the outside of the ankle, in an orientation that they predicted would support the ankle if it turned inward. They measured each volunteer’s ankle stiffness in 12 directions, and then measured the force the ankle exerted with each movement, with the mesh and without it, to understand how the mesh affected the ankle’s stiffness in different directions.
In general, they found the mesh increased the ankle’s stiffness during inversion, while leaving it relatively unaffected as it moved in other directions.
“The beauty of this technique lies in its simplicity and versatility. Mesh can be made on a basic desktop 3D printer, and the mechanics can be tailored to precisely match those of soft tissue,” said A. John Hart, PhD, an associate professor of mechanical engineering at MIT and a study author.
Editor’s note: This story was adapted from materials provided by MIT.