The device, which the team calls a biohybrid mesh harvester, addresses what many in the field consider the single most difficult problem in wearable and implantable electronics: how to get rid of the battery altogether. Batteries, for all their ubiquity, impose a punishing set of trade-offs. They are bulky, they eventually run out of charge, and shrinking them or making them flexible enough to conform to living tissue reduces the amount of energy they can store. For implanted devices, that means larger surgeries, shorter device lifetimes and a constant negotiation between power and size. The UMass Amherst team, led by senior author Jun Yao, an associate professor in the university’s Riccio College of Engineering, argues that the solution is not to build a better battery but to abandon the centralized energy paradigm that batteries represent.

That paradigm shift begins with a simple observation about how the human body is powered. Every battery-powered device relies on a single, centralized reservoir of energy that is distributed outward to wherever it is needed. The body does the opposite. Each of the trillions of cells in a human body is, in effect, its own miniature power plant, generating energy continuously and distributing it throughout the entire system. Some of that power takes electrical form, most visibly in the nerve impulses that race through the nervous system, and some takes mechanical form, as in the rhythmic contraction of muscle tissue. “Our bodies are 24/7 power plants,” says lead author Siqi Wang, a Ph.D. student in the Riccio College of Engineering. “Every single cell produces its own power.”

Capturing that distributed cellular energy required the researchers to rethink electrical engineering from the ground up. “We wanted to shift this traditional, centralized paradigm to something more distributed and modeled on biology,” Yao says. The result is a device architecture in which energy generation is not a separate component bolted onto the body but a property woven into the tissue itself. The mesh does not sit beside the cells it powers; it grows with them, moves with them and harvests their mechanical activity as its fuel.

The construction of the harvester reflects that philosophy. The team began with an array of thin ribbons of lead zirconate titanate, or PZT, a piezoelectric ceramic well known for its ability to convert mechanical energy into electrical energy. Piezoelectric materials generate a voltage when they are deformed, which makes them natural candidates for harvesting the mechanical work performed by contracting muscle. The challenge was that conventional piezoelectric devices tend to be stiff and brittle — the opposite of what living tissue tolerates. The researchers therefore devised a technique for transferring the PZT ribbons onto an ultrathin, ultraflexible polymer platform, creating a scaffold that could bend and flex without losing its energy-converting function.

The next step is what makes the device truly biohybrid. The researchers seeded the PZT-loaded polymer platform with human cardiac cells and allowed them to grow. As the cells proliferated, they meshed seamlessly into and around the piezoelectric ribbons, enveloping the platform in living tissue. The finished device moves and looks like human tissue but works like a battery that never needs to be replaced. Every beat of the cultured cardiac cells deforms the embedded PZT ribbons, and every deformation is converted into usable electrical energy. The power source and the power consumer are, in effect, the same living system.

The performance figures reported by the team are striking. Yao, who is quick to emphasize that the research so far exists only in the laboratory, says the device generated ten times more power density — the amount of energy that can be produced in a given volume — than systems that rely on a centralized power source. That advantage arises precisely because the harvester is distributed: instead of one dense energy reservoir competing for space with the electronics and the tissue, energy is generated everywhere the device touches, from countless small conversion sites working in parallel.

And the design leaves room to grow. Because the harvesting films are ultrathin, they can be stacked in layers, drastically increasing the amount of power available while the device remains noninvasive. This stacking strategy means that power output is not fixed by the geometry of a single film but can be scaled up by adding layers, a flexibility that conventional implantable batteries, constrained by chemistry and packaging, cannot match. For applications that demand more energy — a more power-hungry sensor suite, a stimulator with higher output — the answer is simply more film, not a bigger implant.

Biocompatibility, often the quiet killer of implantable technologies, is another area where the distributed approach pays dividends. “The beauty of this system is how noninvasive and powerful it is,” Yao says. “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.” A device that is mechanically indistinguishable from the tissue around it avoids many of the immune and mechanical stresses that plague rigid implants, from inflammation to the formation of scar tissue that can degrade performance over time. By dissolving the boundary between device and tissue, the mesh harvester sidesteps problems that battery-centric designs have struggled with for generations.

The work builds on a broader research program by Yao’s group at UMass Amherst, which has been steadily assembling the pieces of a bioelectronics toolkit. Yao and colleagues previously demonstrated a bioelectronic mesh capable of growing with and monitoring cardiac tissue, an artificial neuron that can communicate directly with living human cells, and a technique for harvesting clean energy from the moisture in ambient air around the clock. The mesh harvester adds the missing element — power — to that toolkit, suggesting a future in which sensing, computation, communication and energy generation are all integrated into tissue-like devices that live comfortably within the body. If the laboratory results can be translated into clinical systems, the implications extend well beyond pacemakers: any electronic augmentation of human ability, from the mundane to the science-fictional, ultimately needs power, and the body itself may be the most elegant place to find it.

Subject of Research: Biohybrid piezoelectric mesh devices that harvest energy from living human cells to power implantable and wearable electronics

Article Title: The body electric: UMass Amherst researchers integrate electronics with human cells

Article References: The body electric: UMass Amherst researchers integrate electronics with human cells. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: biohybrid electronics, energy harvesting, piezoelectric, PZT, implantable devices, wearable electronics, cardiac cells, batteries, biocompatibility, UMass Amherst, Science Advances, power density