The foam heart is off to a promising start, but it’s not ready to be put into humans quite yet. The foam heart only contains two chambers, unlike typical human hearts, which have four. The researchers didn’t test if the foam’s property changes at higher temperatures like those that might be found in the body. And even though the device pumps more fluid than any other soft artificial heart, the speed at which it does so is still limited—and if the heart overinflates, the foam tears. In future work, the researchers will change some of the foam’s ingredients to make it less susceptible to tearing and make the air pathways simpler so that the heart can inflate more quickly.