The bottom of the heart twists counterclockwise, while the top twists clockwise. The image on the right is the team's model of the heart, which has tube-like pneumatic artifical muscles (PAMs) that act like striated muscle fibers.
Replication of a human heart in 3D by Harvard researchers goes beyond the action of pumping blood—it circulates the blood and twists the heart, too. Conventional 2D heart models typically can’t reproduce those functions. In the new 3D model, the lower half of the heart twists and contracts blood counterclockwise, while the top half twists clockwise. This motion, called the left ventricular twist, can be used as an indicator for heart health.
Harvard’s Wyss Institute for Biologically Inspired Engineering and Harvard’s School of Engineering and Applied Sciences (SEAS) reproduced the heart’s biological motion and created the matching 3D computer model. This data was reported in Advanced Material’s article “A Bioinspired Actuated Material.”
The research team developed a modified pneumatic artificial muscle (PAM) to imitate muscle fibers. PAM is made from a soft, silicone elastomer with braided mesh, and connected through tubing to an air supply. When pressurized, PAMs shorten in only one direction. Researchers embedded many artificial muscles into a matrix made of the same material, and were able to achieve various motions in multiple directions to mimic heart motion.
The outermost layer of the heart is responsible for the dominant twisting motion. The team, using their computer model, was able to shape the matrix in order to mimic the fibers in this region. Then they built a prototype that, after being tested, matched their computer model predictions. During the experiment, the team even replicated heart muscle damage by deactivating certain PAMs.
They will look to develop biocompatible versions in the future. It’s their hope that this innovation opens up the field of soft robotics to more organ-centric devices.