A passive, light-responsive material for intelligent windows
A new Danish breakthrough points to "smart" windows that work entirely without wiring, sensors or electronics. Scientists at Aarhus University's Interdisciplinary Nanoscience Center (iNANO) have developed a transparent layer embedded with silver nanorings that automatically adapts to sunlight intensity and controls how much heat enters through the glass—without dimming the view or using any electricity.
How it works.
The silver nanorings act like microscopic antennas for near-infrared (NIR) light, which carries the majority of solar heat. When exposed to intense sunlight, they heat up via a thermoplasmonic effect and reduce NIR transmission. Because the mechanism is triggered directly by light, it self-regulates in real time: more sun means stronger response and less NIR gets through; less sun weakens the effect. Visible light passes largely unaffected, keeping interiors bright without the midday heat load.
What's new.
Unlike electrochromic or mechanically adjustable smart windows, this passive solution needs no wiring, power supply, sensors, or control systems. The NIR-blocking effect intensifies with solar irradiance, while visible transmittance remains high—preserving both daylight and clarity. The response is reversible and has been demonstrated under controlled lab conditions.
Why it matters.
Modern buildings with large glass façades often consume more energy on cooling than heating. A window coating that selectively filters heat-producing radiation at peak times—without blocking light—could lower cooling demand and CO₂ emissions, contributing to energy-efficient architecture and improved indoor comfort.
"We have developed a combination of materials whose optical properties change in response to sunlight. It allows heat to enter when the sun is low, but reduces heat radiation at midday—exactly when the need for cooling otherwise increases. And it all happens without any electricity,"
— says PhD student Xavier Baami González, first author of the study.
"These types of solutions are crucial if we want to build in a more climate-friendly way without compromising on comfort and daylight. Our hope is that the hybrid material can eventually be integrated into smart window solutions and find its way into commercial use,"
— adds project lead Professor Duncan S. Sutherland.
The university has filed a patent application covering aspects of the technology.
Publication
Thermoplasmonic Nanorings for Passive Solar-Responsive Smart Windows in Energy-Efficient Building Applications , Advanced Functional Materials (2025).
Authors: Xavier Baami González
