The machines save lives, but because they come in direct contact with blood, the patient has to be on blood thinners to avoid clots that gum up the works. The soft robotic pump doesn't come into contact with blood. The thin sleeve slips over the outside of the heart, twisting and contracting to mimic the muscle's natural movements. To test it, the researchers induced cardiac arrest in six pigs, then used the sleeve to get their hearts pumping blood again for 15 minutes or more. That's promising news, but several challenges lie ahead.

Three years later, they emerge with a funnel-shaped robot that enfolds the mammalian heart, then actively compresses and twists it to restore normal blood flow after heart failure. Okay, so that's not how it actually happened, but the robot is real. Today, a team of researchers at Harvard University and Boston Children's Hospital, among other participating institutions, published details on an implantable, soft-robotic device that could help failing hearts pump blood without ever touching the blood. The work, including a proof-of-concept experiment with live pigs, was published this week in Science Translational Medicine. Traditional ventricular assist devices (VADs) are used to bypass a failing heart.