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Light Powers Butterfly-Inspired Hydrogen Sensor

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Butterfly wings are the inspiration for a light-activated hydrogen sensor device capable of producing ultraprecise results at room temperature. Tests demonstrated the sensor’s ability to detect hydrogen leaks before they develop to a point at which they could pose a safety risk. The sensor additionally performed measurements of minute amounts of the gas on an individual’s breath, giving it the potential to diagnose disorders in the gut. 
Ph.D. researcher Ebtsam Alenezy holds a prototype of the light-activated hydrogen sensor, which can deliver ultraprecise results at room temperature. Courtesy of RMIT University.

PhD researcher Ebtsam Alenezy holds a prototype of the light-activated hydrogen sensor, which can deliver ultra-precise results at room temperature. Courtesy of RMIT University.
Commercial hydrogen sensors require a temperature of 150 °C or higher to achieve functionality. The prototype developed by RMIT University researchers bypasses that requirement; it is powered by light rather than heat.

According to co-lead researcher Ylias Sabri, the prototype was scalable and cost-effective, and it offered a total package of features that could not be matched by any hydrogen sensor on the market today.

“Some sensors can measure tiny amounts, others can detect larger concentrations; they all need a lot of heat to work,” Sabri said. “Our hydrogen sensor can do it all — it’s sensitive, selective, works at room temperature, and can detect across a full range of levels.”

The sensor detected hydrogen at molecular concentrations as low as 10 parts per million for medical diagnoses, to 40,000 parts per million — the level at which the gas becomes potentially explosive.

According to co-lead researcher Ahmad Kandjani, the broad detection range made it ideal for both medical use and to boost safety in the emerging hydrogen economy.

“Hydrogen has the potential to be the fuel of the future, but we know safety fears could affect public confidence in this renewable energy source,” Kandjani said. “By delivering precise and reliable sensing technology that can detect the tiniest of leaks well before they become dangerous, we hope to contribute to advancing a hydrogen economy that can transform energy supplies around the world.”

The sensor’s core structural innovation are photonic crystals, which are physically tiny spheres. Those hollow shapes, similar to the tiny bumps found on the surface of butterfly wings, are highly ordered structures and ultraefficient as light absorbers.
The sensor is made with an electronic chip, which is covered with a thin layer of photonic crystals and then a titanium palladium composite. Courtesy of RMIT University.
The sensor is made with an electronic chip, which is covered with a thin layer of photonic crystals and then a titanium-palladium composite. Courtesy of RMIT University.

That level of efficiency allowed the sensor to draw all the energy it needs to operate from a beam of light rather than from heat.

Researcher and first author Ebtsam Alenezy said the senor was safer and more cost-effective than commercial hydrogen sensors that require temperatures of 150 to 400 °C to perform.

“The photonic crystals enable our sensor to be activated by light and they also provide the structural consistency that’s critical for reliable gas sensing,” Alenezy said. “Having a consistent structure, consistent fabrication quality, and consistent results are vital — and that’s what nature has delivered for us through these bioinspired shapes.”

The well-developed fabrication process for photonic crystals also means that the technology is easily scalable to industrial levels as hundreds of sensors can be rapidly produced simultaneously, she said.

To make the sensor, an electronic chip is first coated with a thin layer of photonic crystals followed by a titanium-palladium composite. When hydrogen interacts with the chip, the gas is converted to water. That process creates an electronic current, and by then measuring the magnitude of the current, the sensor is able to tell precisely how much hydrogen is present.

While current commercial sensors tend to struggle in the presence of nitrogen oxide, the researchers’ sensor achieved a degree of selectivity that enabled the accurate and reliable isolation of hydrogen from other gases that could be present in a setup or real-time setting.
These tiny hollow spheres known as photonic crystals, inspired by the bumpy surface of butterfly wings, are the innovative core of the new hydrogen sensor. Image magnified 40,000 times. Courtesy of RMIT University.
Tiny hollow spheres, known as photonic crystals and inspired by the bumpy surface of butterfly wings, are at the fore of the new hydrogen sensor. Image magnified 40,000 times. Courtesy of RMIT University. 

The technology also has medical applications; elevated levels of hydrogen are known to have connections to gastrointestinal disorders. The current standard diagnostic approach is via breath samples, which must be sent to labs for processing following their acquisition.

Sabri said that the new chip could be integrated into a hand-held device to deliver instant results.

“With gut conditions, the difference between healthy levels of hydrogen and unhealthy levels is miniscule — just 10 parts per million — but our sensor can accurately measure such tiny differences,” he said.

The researchers have filed a provisional patent application for the device, and the team hopes to collaborate with manufacturers of hydrogen sensors, fuel cells, batteries, and medical diagnostic devices to commercialize the sensor.

The research was published in ACS Sensors (www.doi.org/10.1021/acssensors.0c01387).

Photonics Spectra
Feb 2021
Research & TechnologySensors & DetectorshydrogenBiophotonicsbreathbreath analysisbreath testdiagnosticDiagnosisgastrointestinalgastrointestinal diseasegastrointestinal diseasesgas sensinghydrogen gasRMITRMIT UniversityAustraliaTech Pulse

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