Johns Hopkins APL Harnesses Snake Heat-Sensing Proteins for Next-Generation Sensors

When it comes to seeing in the dark, few animals are better than pit vipers or pythons. And they do it without infrared goggles; the stealthy serpents wield one of nature’s most adept heat sensors: tiny openings under each eye called pits. These specialized organs are filled with heat-sensitive proteins that allow the snakes to detect temperature differences of 0.003 degrees Celsius or less — precise enough to pinpoint warm-blooded prey against even a mildly cooler background.

Researchers at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, are now working to translate that precision into a new type of compact, biologically driven infrared sensor that could support future solid-state devices, such as thermal trip wires or heat-sensing goggles, that operate with little or no conventional electrical power.

The project is part of a broader APL effort to build a new generation of sensing technologies that are smaller, lighter, and less power-draining than current systems but still capable of detecting subtle environmental differences.

“Service members are often stuck carrying hefty equipment, so we’ve focused on developing low-SWaP [size, weight, and power] technologies that will not only meet or surpass current performance capabilities but reduce the power and physical footprint required by them,” said Shanna Ratnesar-Shumate, who leads APL’s Biological and Chemical Sciences program. “We’re looking to biology for inspiration in how to achieve that goal.”

Led by APL biochemist Lizzy Robinson, the research team developed a heat-sensing system that relies on two linked modules: an energy module that serves as a biological battery and a sensing module that detects infrared signals with snake-like precision.

Building a Biological Battery

The energy module solves a central problem for building any biologically derived sensor: How do you power it in a way that the system can use?

The team’s solution was to build a simplified version of a living cell, equipping it with molecular machinery to convert light and chemical gradients into usable energy. In the living world, that energy almost always comes as the molecule adenosine triphosphate, or ATP.

“To match the way an electrical current moves through a conventional circuit, we had to engineer a biological chain of events in which each component passes energy to the next,” said Robinson. “In our system, sunlight is first converted into stored chemical energy, and then that powers a thermal sensing response. It’s essentially a biological energy circuit made up of tightly coordinated molecular steps.”

The system relies on a thin film laced with multiple layers of microbial rhodopsin (a light-sensitive protein) and ATP synthase (a molecular turbine) placed in an acidic solution.

When light strikes the rhodopsin layers, they start pumping protons in the surrounding fluid to one side of the thin film, creating a chemical imbalance. This imbalance is like stashing water behind a dam: As the protons build up, they naturally want to start flowing back to the other side. But they can only do so by passing through ATP synthase, which turns like a turbine to generate ATP.