Dynamically transparent microfluidic layers for adaptive thermal management and energy efficiency in smart façades and windows

Façades and windows significantly contribute to the energy inefficiency of buildings due to heat gain and loss, accounting for approximately 40 % of total energy costs. This study introduces an innovative multi-material microfluidic glazing layer made of a polydimethylsiloxane(PDMS)-paraffin composite, designed to be integrated with glass windows or façades to manage thermal loads and adaptively modulate light. The composite microfluidic glazing layer is fabricated using a 3D-printed scaffold removal method and facilitates convective cooling by using water as a coolant. The microfluidic glazing layer was further integrated into a 10 × 10 cm² prototype window, and both experimental and numerical analyses were employed to evaluate its effectiveness. Experimental results demonstrated that water maintained at room temperature, flowing at 240 µL/min, could lower the average temperature of the window prototype by approximately 14 °C within the first 5 min. Additionally, the PDMS-paraffin layer transitions from a transparent to opaque state by absorbing heat from the carrier fluid within a short period, highlighting its potential as switchable haze. Numerical analysis revealed an intrinsic harvesting efficiency of 80 % for the proposed prototype with optimal flow tuning. Beyond its primary application in smart glass window and façade cooling, the PDMS-paraffin layer has potential applications in battery thermal management, microfluidic heat sinks, and lab-on-a-chip systems.