Environmentally friendly buildings are highly attractive for sustainable development and efficient energy consumption. Recently, scientists have made significant strides towards the development of energy-efficient smart windows—with features such as optical modulation, high transparency, low thermal conductivity, and ultraviolet (UV) blocking and heat shielding capabilities—to replace traditional glass windows. The smart windows are a lucrative technology to protect household items as well as human health from the adverse effects of UV radiation.
In a recent breakthrough, a team of researchers from the Republic of Korea, led by Professor Sung Ho Song from Kongju National University and Assistant Professor Jin Kim from the Department of Materials Science and Engineering at Hanbat National University, has developed switchable thermochromic transparent woods (TWs) for smart windows by utilizing UV-curable polymer-dispersed liquid crystal (PDLC) into modified woods for the first time. Their novel findings were made available online and have been published in Volume 8, Issue 393, of the journal Advanced Composites and Hybrid Materials on October 16, 2025.
The PDLC/TW-based "passive" smart window fabricated in this study adjusts its visible light transmittance based on temperature at no extra energy cost. Balsa PDLC/TW exhibits a slowly increasing transmittance based on temperature—switching between opaque (28% transmittance) at room temperature and transparent (78% transmittance) at 40 °C—at 550 nm. In this way, it demonstrates energy-autonomous light regulation while requiring zero external electricity.
Moreover, balsa PDLC/TW exhibits near-total UV shielding with outstanding UV-blocking performance. The material blocks nearly 100% of UVA radiation through a unique "J-aggregation" effect, protecting skin and interiors without sacrificing visible light. It also shows almost five times lower thermal conductivity than that of the glass. "With a thermal conductivity of 0.197 W m⁻¹ K⁻¹, our novel bio-composite is nearly five times more insulating than conventional glass, significantly slowing heat loss or gain in buildings," highlights Dr. Kim.
He further points out the diverse potential applications of their work. "Our innovation is a direct, eco-friendly replacement for glass that provides privacy at night and natural illumination during the day while slashing HVAC energy costs. It is ideal for smart greenhouses to prevent crop scorching by automatically regulating sunlight and maintaining stable internal growing temperatures. Furthermore, the present technology is promising for the development of intelligent wearable health monitors. It can be used as a flexible skin patch that turns transparent when body temperature exceeds 38°C, providing an instant visual health alert without the need for batteries or electronics," says Dr. Kim.
In the long term, this work can open the doors to carbon-neutral living by making carbon-neutral homes affordable for the average family by replacing power-hungry smart windows with self-managing, wood-based panels. It can further revolutionize food security; smart greenhouses using the proposed next-generation material could stabilize food production in harsh climates by providing optimal, energy-free thermal and light management. Lastly, this technology is expected to pave the way for a new class of low-cost and disposable battery-free medical wearable devices—such as fever-monitoring wristbands—that provide critical health data with zero charging or syncing requirement.
