Heating and cooling a building uses a lot of energy, but a new dynamic shading system developed by University of Toronto (U of T) researchers may help significantly. The system, inspired by the skin of krill, uses blooming pigment cells that can block light on demand.
Krill are tiny sea crustaceans typically translucent but can rearrange the pigments in the cells beneath their skin, enabling them to darken to counteract UV ray damage in direct sunlight. The U of T team believed that having this capability would be beneficial for building facades and windows.
The team’s krill-inspired prototype consists of optofluidic cells that can quickly transition between being transparent and opaque while consuming minimal energy. A 1-mm layer of mineral oil sandwiched between two sheets of plastic makes up the cell’s interior. It can be made darker by injecting a tiny amount of water into the cell through a linked tube that contains a pigment or dye. This results in a “bloom” of the darker hue.
The bloom size depends on how much pigment is injected, and the flow rate can control the shape it takes. For example, a circular pattern results from low flow rates, whereas high flow rates produce branching tree-like formations. Later, the pigment can be pushed back out, restoring the cell’s transparency.
Ben Hatton, the study’s lead author, said:
“We are interested in how ‘confined fluids,’ of green, sustainable chemistries, can be used to change material properties. It’s very versatile: not only can we control the size and shape of the water in each cell, but we can also tune the chemical or optical properties of the dye in the water. It can be any color or opacity that we want.”
The group imagines a network of these optofluidic cells utilized in windows or building facades as a low-energy temperature-regulating system. For example, the cells could be configured to become opaque during a hot summer day to block sunlight and then transition back to transparency at night.
The researchers simulated how effectively such a system might operate at the size of a building and contrasted the potential energy savings with two alternative technologies, such as electrochromic windows or motorized blinds, which alter the transparency of a glass coating using voltage changes.
Raphael Kay, the study’s corresponding author, concluded:
“What we found is that our system could reduce the energy required for heating, cooling and lighting by up to 30% compared with the other two options. The main reason for this is that we have much finer control over the extent and timing of solar shading.
Our system is analogous to opening and closing hundreds of tiny blinds at different locations and times across a facade. Moreover, we can achieve all this with simple, scalable and inexpensive fluid flow.”
The group also suggests that optofluidic displays could make massive artistic creations. The study was released in Nature Communications on July 15, 2022. The video below shows the cells in action.
