Self-regulating silver nanorings enable power-free smart windows
by Robert Schreiber
Berlin, Germany (SPX) Oct 06, 2025

A new Danish innovation could soon make "smart" windows that automatically manage heat and light - without power, wiring, or electronics - a practical reality. Scientists at Aarhus University's Interdisciplinary Nanoscience Center (iNANO) have created a transparent coating filled with silver nanorings that dynamically adjusts how much solar heat passes through glass while keeping it clear to the eye.

The nanorings act as microscopic antennas for near-infrared (NIR) radiation, which carries most of the Sun's heat. When exposed to intense sunlight, they warm up through a thermoplasmonic process that reduces NIR transmission. Because this mechanism is directly driven by light, the coating self-regulates - stronger sunlight triggers stronger reflection of heat, while lower light reduces the effect.

Unlike electrochromic or mechanically controlled systems, the material functions entirely passively. It requires no sensors, wiring, or external power, yet maintains high visible light transmission, allowing buildings to stay bright without excessive heat gain. The effect is fully reversible and has been confirmed in controlled laboratory experiments.

Researchers note that buildings with extensive glazing often spend more energy on cooling than heating. A passive window layer that selectively blocks heat-producing radiation during peak sunlight could reduce cooling loads, carbon emissions, and overall energy consumption while improving indoor comfort.

Research Report:Thermoplasmonic Nanorings for Passive Solar-Responsive Smart Windows in Energy-Efficient Building Applications

Related Links
iNANO, Aarhus University
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