Hydrogen sensor inspired by butterflies, powered by light

Inspired by the surface of butterfly wings, RMIT University researchers have developed a light-activated hydrogen sensor that produces ultraprecise results at room temperature.

Described in the journal ACS Sensors, the technology can detect hydrogen leaks well before they pose safety risks and can measure tiny amounts of the gas in people’s breath. Its development follows over two decades of investigation into gas sensing by researchers in RMIT’s Centre for Advanced Materials and Industrial Chemistry (CAMIC), led by Distinguished Professor Suresh Bhargava.

The core of the new sensor is made up of tiny spheres known as photonic or colloidal crystals. These hollow shapes, similar to the minuscule bumps found on the surface of butterfly wings, are highly ordered structures that are ultra-efficient at absorbing light. That efficiency means the new sensor can draw all the energy it needs to operate from a beam of light, rather than from heat — and that it is both safer and cheaper to run than commercial hydrogen sensors, which typically operate at 150 to 400°C.

“Some sensors can measure tiny amounts, others can detect larger concentrations; they all need a lot of heat to work,” said Dr Ylias Sabri, who served as co-lead researcher on the study. “Our hydrogen sensor can do it all — it’s sensitive, selective, works at room temperature and can detect across a full range of levels.”

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.

“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,” added PhD researcher Ebtsam Alenezy, first author on the study.

“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 our technology is easily scalable to industrial levels, as hundreds of sensors could be rapidly produced at once.”

To make the sensor, an electronic chip is first covered with a thin layer of photonic crystals and then with a titanium palladium composite. When hydrogen interacts with the chip, the gas is converted into water. This process creates an electronic current; by measuring the magnitude of the current, the sensor can tell precisely how much hydrogen is present. And unlike many commercial sensors that struggle in the presence of nitrogen oxide, the new technology is highly selective so it can accurately isolate hydrogen from other gases.

The sensor is made with an electronic chip, which is covered with a thin layer of photonic crystals and then a titanium palladium composite.

With elevated levels of hydrogen known to be connected to gastrointestinal disorders, the technology has strong potential for use in medical diagnosis and monitoring. The current standard diagnostic approach is through breath samples, which are sent to labs for processing, but Dr Sabri said the new chip could be integrated into a handheld 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 (ppm) — but our sensor can accurately measure such tiny differences,” he said.

With the ability to detect hydrogen at concentrations from 10 up to 40,000 ppm, co-lead researcher Dr Ahmad Kandjani said the sensor has a broad detection range that makes it ideal for both medical use and boosting safety in the emerging hydrogen economy.

“Hydrogen has potential to be the fuel of the future, but we know safety fears could affect public confidence in this renewable energy source,” he 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.”

Top image: PhD researcher Ebtsam Alenezy holds a prototype of the light-activated hydrogen sensor.

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