Batteries are the weak link for wearable and implantable devices. But what if you could harvest energy from the heat, sweat or vibrations of the wearer?

In “I Sing the Body Electric,” poet Walt Whitman waxed lyrically about the “action and power” of “beautiful, curious, breathing, laughing flesh.” More than 150 years later, MIT materials scientist and engineer Canan Dagdeviren and her colleagues are giving new meaning to Whitman’s poem with a device that can generate electricity from the way it distorts in response to the beating of the heart.

Electronics are now so powerful that a smartphone has more computing power than all of NASA did when it put the first men on the moon in 1969. The extraordinary advances technology has made over time have raised hopes that devices worn on, or even implanted within, the body can also become ever more capable.

A key drawback of most wearable and implantable devices still remains their batteries, whose limited capacities restrict their long-term use. The last thing you want to do when, say, a pacemaker runs out of power is to open up a patient just for a battery replacement. The solution to this problem may rest inside the human body — rich as it is in energy, in its chemical, thermal and mechanical forms. This has led scientists to investigate a plethora of ways for devices to harvest energy from the bodies that host them, detailed by Dagdeviren and her colleagues in the 2017 Annual Review of Biomedical Engineering.