Optofluidic Smart Glass System Is Cost-Efficient, High Performing

Smart glass panels that can switch between allowing light in and blocking it out could one day be used in eco-friendly windows, windshields, roof panes, and building envelopes to absorb light and heat in cold weather and reflect heat away from buildings and vehicles when the weather is hot.

Researchers at the University of Delaware have developed a form of smart glass that is about one-tenth the price of other versions. According to researchers, it is also more transparent and more reflective than other versions of smart glass.

The Delaware team’s technology uses two sheets of plastic separated by a thin cavity. The chamber is filled with a fluid that has optofluidic properties. The team has improved on its initial prototype, which incorporated tiny cube-shaped structures into the plastic sheets to make them retroreflective. The new design relies on the total internal reflection of one-dimensional structures layered perpendicularly. It is highly reflective at up to a 60° angle of incidence.

Electrical engineers at the University of Delaware developed their version of smart glass technology. It starts opaque but turns transparent when filled with index-matching fluid, as shown in the bottom portion of this pane. Courtesy of University of Delaware.

Although the team uses 3D printing to make its prototypes, the technology could eventually be manufactured at a high volume and low cost using injection molding. The team, led by professor Keith Goossen, is now testing the system over a wide range of temperatures to see how it performs, especially as it approaches temperatures between 3 and 16 °F, which could cause the fluid to freeze.

The team believes that optofluidic smart glass exhibits superior transmittance in the light-transmitting state compared to other commercially available smart glasses, such as electrochromic, polymer dispersed liquid crystal and suspended particle devices. A cycling experiment showed that optofluidic smart glass performs well over time with only slight deviation in light transmittance.

The team demonstrated its latest prototype at the SPIE Smart Materials and Nondestructive Evaluation for Energy Systems IV conference held in Denver in March. The research was published in Optics Express, a publication of The Optical Society (doi: 10.1364/OE.26.000A85).