Artificial Muscles
| Researchers have created a low-cost, programmable soft actuated material that they used to replicate the complex motion of the heart, along with a matching 3D computer model. The development sets the stage for new possibilities in the emerging field of soft robotics. |
Three dimensional action is known to be more appropriate to describe the action of muscles in the body, especially in the heart.
Healthy hearts actually experience a twist motion while pumping as if they were wringing a wet towel. The bottom of the heart twists as it contracts in a counterclockwise direction while the top twists clockwise.
Scientists call this the left ventricular twist—and is used as an indicator of heart health.
The human body is full of other examples of soft muscular systems that bend, twist, extend, and flex in complex ways. Designers have long sought to design robotic systems with the requisite actuation systems that can perform similar tasks, without much success.
Now, a team of researchers at Harvard's Wyss Institute for Biologically Inspired Engineering and Harvard's School of Engineering and Applied Sciences (SEAS) has developed a low-cost, programmable soft actuated material holds a lot of promise. They demonstrated the material's potential by using it to replicate the biological motion of the heart, and also developed a matching 3D computer model of it, as reported in the journal Advanced Materials.
What's missing is the essential twisting motion that the heart uses to pump blood efficiently.
"We drew our inspiration for the soft actuated material from the elegant design of the heart," said Wyss Core Faculty member Conor Walsh, Ph.D., the senior author, who is also an Assistant Professor of Mechanical and Biomedical Engineering at SEAS and founder of the Harvard Biodesign Lab. "This approach could inspire better surgical training tools and implantable heart devices, and opens new possibilities in the emerging field of soft robotics for devices that assist other organs as well."
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The researchers then embedded several of these artificial muscles within a matrix made of the same soft silicone elastomer. By changing their orientation and configuration within the matrix and applying pressure, they were able to achieve various motions in more than one direction, mimicking the complex motion of the heart.
They calculated the force and strain values for an array of PAM arrangements and used them to develop a new computer model that simulates their associated movement patterns in 3D.
Of the heart's three layers of muscle fibers, the outermost layer is the one most responsible for the dominant global twist — so the team used their computer model to identify a PAMs configuration within a cup—shaped matrix that most closely mimicked the fibers in the outermost layer of the heart. They built the prototype and attached motion trackers to see how it would respond when the PAMs were subjected to various pressures.
Their experimental results closely matched the computer model predictions and also corresponded to the available clinical data on the action of the ventricular twist.
"That was a great moment," Roche said. "It means that now we have proof of concept that we can in fact mimic the heart's natural 3D motion." In short, they got their model hearts to do the twist.
What's more, by selectively deactivating certain PAMs within the matrix, the team mimicked the kind of damage that happens to the heart muscle under certain disease conditions. For example, a diseased heart after a heart attack exhibits a less pronounced left ventricular twist due to local damage that extends through the heart wall.
Eventually the team hopes to develop biocompatible versions of the matrix as one of several next steps toward a new kind of implantable cardiac device, said Roche.
SOURCE Wyss Institute
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