Harvard scientists may have just found a way to repair a heart after it sustains damage during a heart attack: using a layer of heart cells that replicate the way that natural heart muscle beats.

Human hearts are susceptible to damage after major problems such as a heart attack. After the damage is done, it is often irreversible. Currently, the only option for many is an organ transplant, but with so many on the waiting list for organs, and the high chance of complications for those who do receive transplants, it’s not always a positive outcome.

Repairing the heart tissue is the best solution but scientists have been searching for years to find a way to effectively do this. Previous attempts have fallen through when it comes to the material since it is hard to match the heart tissue. Human hearts are almost like elastic, and all attempts at a patch were gelatin like – meaning the materials didn’t resemble the heart closely enough to work.

The elastic material of the heart plays a key role in the functioning of the heart, which is where 3D printing has come in. After developing a new family of gels that resemble the material of the heart in a stretchy, elastic way, scientists then turned to 3D printing. Once the material was designed, scientists and researchers used 3D printers to create the right patterns using the gels.

The 3D printed patterns coaxed new heart cells to grow the way researchers wanted them to, resulting in heart muscle cells lining up neatly and beating in sync within the grooves of the 3D printed elastic substrates.

Scientist now believe these patterns can one day be used as “cardiac patches” and possibly lower the amount of people on the waiting list for new heart organs.