Butterfly wings propel hydrogen sensor powered by light

Butterfly wings are the inspiration behind a light-activated hydrogen sensor that can produce ultra-precise results at room temperature. While commercial hydrogen sensors can only work at temperatures of 150­°C or higher, the prototype developed by researchers at RMIT University is powered by light instead of heat. The technology can detect hydrogen leaks before they pose safety risks and can measure tiny amounts of the gas on people’s breath, for diagnosing gut disorders. The sensor is based on bumpy microstructures that imitate the surface of butterfly wings, with a core that is made up of tiny spheres known as photonic or colloidal crystals. Co-lead researcher Dr Ylias Sabri said the prototype is scalable, cost-effective and offers a range of features.

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. Image credit: RMIT

“Some sensors can measure tiny amounts, others can detect larger concentrations; they all need a lot of heat to work,” Dr 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 can detect hydrogen at concentrations from as little as 10 parts per million molecules (for medical diagnoses) to 40,000 parts per million (the level where gas becomes potentially explosive). Co-lead researcher Dr Ahmad Kandjani said the broad detection range makes the sensor suitable for medical use, while enabling it to boost safety in the emerging hydrogen economy. Dr Kandjani noted that hydrogen could be the ‘fuel of the future’, but safety fears could affect public confidence in the renewable energy source.

“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,” Dr Kandjani said. The photonic crystals that make up the sensor’s core are similar to the miniscule bumps found on the surface of butterfly wings, and are highly ordered structures that are ultra efficient at absorbing light. This means the sensor can draw all the energy it needs to operate from a beam of light, rather than from heat. PhD researcher and first author Ebtsam Alenezy said the room-temperature sensor is safer and cheaper to run, compared to commercial hydrogen sensors. Alenezy added that the photonic crystals provide the structural consistency that is needed for reliable gas sensing.

“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,” Alenezy said. “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.” The sensor is made by covering an electronic chip with a thin layer of photonic crystals, followed by a titanium palladium composite. When hydrogen interacts with the chip, the gas is converted into water. This process creates an electronic current and by measuring the magnitude of the current, the sensor can tell exactly how much hydrogen is present. Unlike many commercial sensors that struggle in the presence of nitrogen oxide, the technology is highly selective, enabling it to 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. Image credit: RMIT

The technology has many applications in medical diagnosis and monitoring. Currently, the standard diagnostic approach for gastrointestinal disorders is through breath samples, which are sent to labs for processing. Dr Sabri believes the chip can be integrated into a handheld device for 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,” Dr Sabri said. A provisional patent application has been filed for the technology and the research team hopes to collaborate with manufacturers of hydrogen sensors, fuel cells, batteries or medical diagnostic companies to commercialise the sector.

Top image: PhD researcher Ebtsam Alenezy holds a prototype of the light-activated hydrogen sensor, which can deliver ultra precise results at room temperature. Image credit: RMIT