Revolutionary Materials Inspired by Nature
Jun Yao, associate professor of electrical and computer engineering, looks to nature for his high-impact projects. Drawing inspiration from biosystems, his research group designs electronic devices and sensors with improved performance. In turn, they harness the electronics to more effectively interface with these biosystems.
Influenced by biological tissue networks, Yao’s research team has built a bioelectronic
mesh system with an array of atom-thin graphene sensors that can simultaneously measure both
the electrical and mechanical cellular responses in 3D cardiac tissue. Before Yao’s device, there was no single sensor capable of measuring these dual properties of the heart without interfering with its functioning. And, remarkably, this tissue-like mesh can grow alongside the cardiac cells to form seamless integration, which allows researchers to observe how heart functions change during the developmental process. Yao has a National Science Foundation CAREER award for this project.
Yao’s interdisciplinary team is also working on a related project that aims to develop biosensors that are more resilient to body fluids and can attain better sensing resolution and specificity. The first application the team will investigate will be to apply the sensor technology to the early detection of tick-borne diseases. Yao has a National Institutes of Health Trailblazer award for this project.
But the work in Yao’s lab that has caused the most excitement—receiving coverage from more than 150 news outlets globally, including BBC News, The Guardian, Newsweek, Smithsonian Magazine, The Boston Globe, and The Washington Post—is a device that creates electricity from moisture in the air. The technology, called Air-gen, has significant implications for the future of
renewable energy.
“The air contains an enormous amount of electricity,” says Yao. “Think of a cloud, which is nothing more than a mass of water droplets. Each of those droplets contains a charge, and when conditions are right, the cloud can produce a lightning bolt—but we don’t know how to capture electricity from lightning. What we’ve done is to create a human-built, small-scale cloud that produces electricity for us predictably and continuously so that we can harvest it.”
Remarkably, Yao and his team have demonstrated that nearly any material can be turned into an Air-gen device. The secret lies in being able to pepper the material with nanopores less than 100 nanometers in diameter. This is because of a parameter known as the “mean free path,” the distance a single molecule of a substance travels before it bumps into another single molecule of
the same substance. When water molecules are suspended in the air, their mean free path is about 100 nm; Yao and his colleagues realized that they could design an electricity harvester based around this number.
An Air-gen device can be made from a thin layer of material filled with nanopores that let water molecules pass from the upper to the lower part of the material. Because each pore is so small, the molecules bump into the pore’s edge as they pass through, meaning that the upper part is bombarded with more charge-carrying water molecules than the lower part, creating a charge imbalance, like that in a cloud. This effectually creates a battery—one that runs as long as there is any humidity in the air.
And because humidity is diffusive in vertical space and the Air-gen device is so thin, thousands of them can be stacked on top of each other, thus scaling up the amount of energy without increasing the footprint of the device.
“Imagine a future world in which clean electricity is available anywhere you go,” says Yao. “The generic Air-gen effect means that this future world can become a reality.”