A team of engineers led by the University of Massachusetts Amherst has designed an ultrathin, flexible mesh that seamlessly integrates electronics with human cells to provide a continuous, reliable, powerful electrical supply. The study, published in Science Advances, provides a potential solution to one of the most difficult problems in the wearable and implantable electronics effort—how to get rid of batteries?

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“Humans have long dreamed of a future where certain electronics can augment our abilities,” says Jun Yao, associate professor in UMass Amherst’s Riccio College of Engineering and the paper’s senior author. One can think of famous examples from science fiction’s cyborgs, but there are also plenty of everyday examples that have nothing to do with Star Trek: pacemakers and implantable defibrillators, for example, or deep brain stimulators, cochlear implants and various health monitors. Every one of these needs a power source.

Unfortunately, the dominant power source—batteries—are bulky and eventually run out of juice, and making them smaller and more flexible reduces the charge they can store.

“But,” says lead author Siqi Wang, a Ph.D. student in UMass Amherst’s Riccio College of Engineering, “our bodies are 24/7 power plants. Every single cell produces its own power.” Some of this power is electrical—think of nerve impulses—and some is mechanical, like the contracting of muscle tissue.

Harvesting that cellular power requires a paradigm shift in electrical engineering—a shift that Yao, who has previously demonstrated a mesh that can grow with and monitor heart tissue, built an artificial neuron that can communicate directly with human cells and discovered how to harvest clean energy from thin air, is leading.
 

The beginning of that shift lay in thinking about how the body is powered. Everything battery powered relies on a centralized supply of energy, but that’s not how the body works.

Instead, each cell in a human body is its own power plant, and the power is distributed throughout the entire system.

“We wanted to shift this traditional, centralized paradigm to something more distributed and modeled on biology,” says Yao.

The team began with an array of thin ribbons of lead zirconate titanate, or PZT, which converts mechanical energy into electrical energy. They then devised a technique for putting them on an ultrathin, ultraflexible polymer platform. Next, they seeded this platform with human cardiac cells which, as they grew, meshed seamlessly into and around the PZT-loaded platform. The result is a device that moves and looks like human tissue but works like a battery that never needs to be replaced.

Yao, who is quick to point out that their research so far exists only in the lab, says that their device generated 10-times more power density—or the amount of energy that can be produced in a given volume—than those systems that rely on a centralized power source. And that’s just the start. Because these films are ultrathin, they can be stacked in layers, drastically increasing the amount of power on tap while remaining noninvasive.

“The beauty of this system is how noninvasive and powerful it is,” says Yao. “Our bodies want to reject systems that come with bulk batteries, but when the device exists at the cellular level, you get vastly improved biocompatibility.”