With a squishy embrace, a new soft robot can keep a weak and failing heart pumping. So far, it’s only been tested in pigs. But if it works in humans, it could one day keep people with heart failure alive.

Researchers at Harvard developed a new soft robot that is basically a sleeve with silicone muscles that twist into a heart shape — much like the muscles in the heart itself. Compressed air makes these soft muscles contract, squeeze, and twist, according to a paper published last week in Science Translational Medicine. The sleeve wraps around the heart and syncs up with the heart’s existing rhythm. When the researchers tested it in pigs suffering from cardiac arrest (induced by drugs), the soft robot was able to get the pig’s hearts pumping blood again.

The soft robot was able to get the pig’s heart pumping

Right now, it’s just a prototype and needs a lot more testing in pigs and people. But the idea is that it could replace devices called ventricular assist devices, or VADs that keep blood flowing as people await transplants — or in people ineligible for transplants.

Around the world, 41 million people suffer from heart failure. Heart transplantation is the best option for people with end-stage heart failure that has stopped responding to medication. There aren’t enough donors out there, so many patients have to rely on VADs that basically re-route the blood around the heart to the blood vessels leading to or away from it.

But blood tends to clot inside this artificial plumbing, which can stop the pump from functioning. If they come loose, clots can block blood vessels and cause strokes. As a result, people using VADs need to stay on blood thinners, which put the patients at risk of dangerous bleeding, and don’t completely eliminate the risk of clots.

This new soft robot it doesn’t actually touch any blood. That means that if it eventually makes its way to human patients, the people who use it might not have to be kept on blood thinners for the rest of their lives.

The device isn’t perfect — for example, it did cause inflammation from all the squeezing, twisting, and friction. But by cushioning the space between the soft robot and the pig heart with a hydrogel, the researchers were able to somewhat reduce the inflammation. With longer term studies and tests in more chronic, complicated cases of heart failure, this soft robot could one day keep human hearts pumping long after they’ve failed.