Dynamic Refractive Index-Matching for Adaptive Thermoresponsive Smart Windows

Area of Science:

• Materials Science
• Optics
• Energy

Background:

• Thermoresponsive smart windows (TRSWs) offer energy efficiency but face limitations like poor transparency and fixed critical temperatures.
• Existing TRSWs often rely on single-material phase transitions, hindering practical application.

Purpose of the Study:

• To develop an adaptive TRSW with tunable optical properties and improved performance.
• To overcome the limitations of fixed critical temperatures and poor transparency in conventional TRSWs.

Main Methods:

• Fabrication of TRSWs by embedding ethylene glycol solution (EGS) microdroplets into polydimethylsiloxane (PDMS) via one-step emulsification.
• Utilizing dynamic refractive index (RI) matching between EGS and PDMS for temperature-responsive optical modulation.
• Tuning the critical temperature (Tc) by adjusting EGS concentration.

Main Results:

• Achieved high luminous transparency (≈92%) and significant bidirectional transparency-temperature response (≈20% at 73°C, ≈40% at 8°C).
• Demonstrated wavelength selectivity due to RI dispersion, varying with temperature.
• Successfully tuned the optical-temperature response over a wide range (13-68°C) by altering EGS concentration.

Conclusions:

• The dynamic RI matching strategy enables TRSW construction beyond phase-transition materials.
• This approach broadens the applicability of TRSWs for smart optical devices, including smart windows and anti-counterfeiting applications.
• The developed TRSWs show promise for energy-efficient buildings and advanced optical functionalities.