Engineers 3-D Print Flexible Mesh for Ankle and Knee Braces


MIT engineers 3-D-print elastic mesh, with personalized patterns developed to be flexible yet strong, for usage in ankle and knee braces.Image: Felice Frankel

Listening devices, oral crowns, and limb prosthetics are a few of the medical gadgets that can now be digitally developed and personalized for private clients, thanks to 3-D printing. Nevertheless, these gadgets are normally developed to change or support bones and other stiff parts of the body, and are frequently printed from strong, reasonably inflexible product.

Now MIT engineers have actually developed flexible, 3-D-printed mesh products whose versatility and strength they can tune to replicate and assistance softer tissues such as muscles and tendons. They can customize the detailed structures in each mesh, and they picture the difficult yet elastic fabric-like product being utilized as customized, wearable assistances, consisting of ankle or knee braces, and even implantable gadgets, such as hernia fits together, that much better match to an individual’s body.

As a presentation, the group printed a flexible mesh for usage in an ankle brace. They customized the mesh’s structure to avoid the ankle from turning inward — a typical reason for injury — while enabling the joint to move easily in other instructions. The scientists likewise produced a knee brace style that might comply with the knee even as it flexes. And, they produced a glove with a 3-D-printed mesh stitched into its leading surface area, which complies with a user’s knuckles, offering resistance versus uncontrolled clenching that can happen following a stroke.

“This work is new in that it focuses on the mechanical properties and geometries required to support soft tissues,” states Sebastian Pattinson, who performed the research study as a postdoc at MIT.

Pattinson, now on the professors at Cambridge University, is the lead author of a research study released today in the journal Advanced Practical Products. His MIT co-authors consist of Meghan Huber, Sanha Kim, Jongwoo Lee, Sarah Grunsfeld, Ricardo Roberts, Gregory Dreifus, Christoph Meier, and Lei Liu, along with Sun Jae Teacher in Mechanical Engineering Neville Hogan and associate teacher of mechanical engineering A. John Hart.

Riding collagen’s wave

The group’s flexible meshes were influenced by the flexible, conformable nature of materials.

“3-D-printed clothing and devices tend to be very bulky,” Pattinson states. “We were trying to think of how we can make 3-D-printed constructs more flexible and comfortable, like textiles and fabrics.”

Pattinson discovered even more motivation in collagen, the structural protein that comprises much of the body’s soft tissues and is discovered in ligaments, tendons, and muscles. Under a microscopic lense, collagen can look like curved, linked hairs, comparable to loosely braided flexible ribbons. When extended, this collagen at first does so quickly, as the kinks in its structure correct. Once tight, the hairs are more difficult to extend.

Influenced by collagen’s molecular structure, Pattinson developed wavy patterns, which he 3-D-printed utilizing thermoplastic polyurethane as the printing product. He then produced a mesh setup to look like elastic yet difficult, flexible material. The taller he developed the waves, the more the mesh might be extended at low stress prior to ending up being more stiff — a style concept that can assist to customize a mesh’s degree of versatility and assisted it to imitate soft tissue.

The scientists printed a long strip of the mesh and checked its assistance on the ankles of a number of healthy volunteers. For each volunteer, the group adhered a strip along the length of the beyond the ankle, in an orientation that they anticipated would support the ankle if it turned inward. They then put each volunteer’s ankle into an ankle tightness measurement robot — called, realistically, Anklebot — that was established in Hogan’s laboratory. The Anklebot moved their ankle in 12 various instructions, and then determined the force the ankle applied with each motion, with the mesh and without it, to comprehend how the mesh impacted the ankle’s tightness in various instructions.

In basic, they discovered the mesh increased the ankle’s tightness throughout inversion, while leaving it reasonably untouched as it relocated other instructions.

“The beauty of this technique lies in its simplicity and versatility. Mesh can be made on a basic desktop 3-D printer, and the mechanics can be tailored to precisely match those of soft tissue,” Hart states.

Stiffer, cooler drapes

The group’s ankle brace was used reasonably elastic product. However for other applications, such as implantable hernia fits together, it may be beneficial to consist of a stiffer product, that is at the exact same time simply as conformable. To this end, the group established a method to integrate more powerful and stiffer fibers and threads into a flexible mesh, by printing stainless-steel fibers over areas of a flexible mesh where stiffer residential or commercial properties would be required, then printing a 3rd flexible layer over the steel to sandwich the stiffer thread into the mesh.

The mix of stiff and flexible products can offer a mesh the capability to extend quickly as much as a point, after which it begins to stiffen, offering more powerful assistance to avoid, for circumstances, a muscle from overstraining.

The group likewise established 2 other methods to offer the printed mesh a practically fabric-like quality, allowing it to adhere quickly to the body, even while in movement.

“One of the reasons textiles are so flexible is that the fibers are able to move relative to each other easily,” Pattinson states. “We also wanted to mimic that capability in the 3-D-printed parts.”

In standard 3-D printing, a product is printed through a heated nozzle, layer by layer. When heated polymer is extruded it bonds with the layer below it. Pattinson discovered that, once he printed a very first layer, if he raised the print nozzle a little, the product coming out of the nozzle would take a bit longer to arrive at the layer listed below, providing the product time to cool. As an outcome, it would be less sticky. By printing a mesh pattern in this method, Pattinson had the ability to produce a layers that, instead of being totally bonded, were totally free to move relative to each other, and he showed this in a multilayer mesh that curtained over and complied with the shape of a golf ball.

Lastly, the group developed meshes that included auxetic structures — patterns that end up being larger when you pull on them. For example, they had the ability to print meshes, the middle of which included structures that, when extended, ended up being larger instead of contracting as a regular mesh would. This home works for supporting extremely curved surface areas of the body. To that end, the scientists made an auxetic mesh into a possible knee brace style and discovered that it complied with the joint. 

“There’s potential to make all sorts of devices that interface with the human body,” Pattinson states. Surgical fits together, orthoses, even cardiovascular gadgets like stents — you can picture all possibly gaining from the sort of structures we reveal.”

This research study was supported in part by the National Science Structure, the MIT-Skoltech Next Generation Program, and the Eric P. and Evelyn E. Newman Fund at MIT.

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