Australian researchers have developed a tiny, electrically tunable infrared filter that could help shrink bulky thermal sensing systems onto portable chips – potentially opening the door to handheld pollution detectors, compact multispectral cameras and next-generation chemical sensing devices.

The technology, developed by researchers from The University of Western Australia (UWA) and The Australian National University (ANU) through the Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, works in the long-wave infrared region – the part of the spectrum associated with thermal radiation emitted by objects that are near room temperature.

Their results were published in Advanced Materials Technologies.

While conventional thermal cameras mainly measure heat intensity, the new device was designed to help infrared systems distinguish between different materials and gases based on their spectral ‘fingerprints’.

Lead author, UWA PhD candidate Oleg Bannik, says one useful way to think of the technology “is as ‘colour vision’ for thermal imaging.”

“Instead of seeing only hot and cold, a camera could compare several carefully selected infrared bands, similar to how the human eye combines red, green and blue wavelengths to perceive colour,” Bannik says.

“That could allow systems to tell the difference between gases, chemicals or materials that look identical in ordinary thermal images.”

For decades, infrared spectroscopy was restricted to labs, military systems and expensive industrial equipment. These were machines with mirrors, lenses and moving parts – but were often too bulky and power-hungry to leave controlled environments.

The device itself is a microscopic ‘sandwich’ of suspended gold and silicon membranes perforated with nanoscale holes.

By electrically changing the tiny gap between the layers – across distances smaller than a micron – the researchers could continuously tune which infrared wavelengths passed through the structure.

The work relies on a phenomenon known as ‘extraordinary optical transmission,’ where light passes through tiny holes in metallic films far more efficiently than expected.

In the team’s device, nanoscale movements strongly alter the infrared response of the system.

“The most counterintuitive part is that changing a gap by only a few hundred nanometres can strongly tune infrared light with wavelengths around ten microns,” Bannik says.

“Tiny nanoscale motions end up controlling much larger infrared waves through near-field plasmonic interactions.”

In laboratory testing, the researchers tuned the transmission peak from around 8 micrometres to 9.8 micrometres in wavelength using voltages below 10 volts. Simulations suggest the tuning range could eventually extend beyond the long-wave infrared region.

Unlike many existing infrared filtering systems, which rely on comparatively large moving optical components, the new approach operates using extremely small membrane motions and low power consumption.

“It is important to understand that, by itself, the device is only a tunable spectral filter, not a complete sensing system,” Bannik says.

“However, when combined with a thermal detector, it can add entirely new capabilities to infrared cameras and sensing platforms.”

He says environmental monitoring is one of the strongest potential applications, particularly for detecting methane leaks and industrial emissions.

“The technology could also benefit industrial safety, thermal imaging, medical diagnostics and defence systems where identifying materials matters more than simply measuring temperature,” Bannik says.

The paper points to the possibility of medical application, with spectrally selective thermal imaging systems capable of detecting subtle physiological changes invisible to conventional thermal cameras.

“The most realistic applications are non-contact diagnostics and advanced thermal imaging,” Bannik says.

“Different tissues emit infrared radiation differently, so spectrally selective thermal imaging could potentially help identify inflammation, monitor wounds or detect subtle physiological changes invisible to standard thermal cameras.”

These lightweight, low-power infrared sensors could also be especially useful in drones and portable field systems.

“Drones are probably the most realistic near-term platform because they benefit enormously from lightweight, low-power sensors,” he says.

Still, significant engineering challenges remain before the technology leaves the lab, particularly around manufacturing reliability and contamination control at extremely small scales.

“One of the hardest engineering challenges was maintaining extremely flat suspended membranes separated by gaps smaller than a micron,” Bannik says.

“At these scales, even dust particles only a few hundred nanometres wide can block membrane motion or distort the optical response.”

“The physics works well, but turning delicate laboratory devices into robust commercial products is a major engineering challenge.”

He says the work points to a future where bulky infrared spectrometers could eventually be replaced by compact, chip-scale systems.

“What makes this work exciting is the combination of advanced physics with a very practical goal,” Bannik says.

“The idea that nanometre-scale motion can give machines a richer understanding of the thermal and chemical world is both scientifically fascinating and potentially very useful in real-world sensing systems.”

Tunable Extraordinary Optical Transmission in the Long‐Wavelength Infrared Range Using Electrostatic MEMS Actuation

Oleg Bannik, Fedor Kovalev, Michal Zawierta, Dilusha Silva, Lorenzo Faraone, Ilya Shadrivov, Mariusz Martyniuk

Advanced Materials Technologies, 2026, https://doi.org/10.1002/admt.202502605

ABSTRACT: We present a continuously tunable long wavelength infrared (LWIR) spectral filter that enables chip-scale, on-demand spectral selection in a spectral range traditionally dominated by bulky optics. The device leverages extraordinary optical transmission (EOT) effect in a dual-membrane stack: two suspended, patterned gold and silicon membranes separated by a dynamically adjustable air gap. Because the EOT resonance is highly sensitive to the intermembrane spacing, microscale gap modulation enables broadband, continuous spectral tuning. Numerical simulations predict a redshift of the transmission peak from 8 to 11 µm as the gap is reduced from 600 to 50 nm, while maintaining peak transmittance above 74% across the range. Mechanical tunability is achieved through integration into micro-electro-mechanical system (MEMS) actuator that provides smooth, pull-in-free sub-micron displacement at voltages below 10 V, enabling practical, low-power operation. We developed dual-membrane device fabrication strategies facilitating membrane flatness, high fabrication yield and broad spectral tuning range. Experiments validate continuous LWIR tuning with measured spectra in close agreement with simulations. The resulting platform is compact, scalable, and highly compatible with integration into portable LWIR sensing hardware, opening a clear path to low-power, reconfigurable filters for gas detection, chemical analysis, and thermal imaging.