Microfluidic system cuts energy costs for buildings

Developed by a team at University of Toronto Engineering, the platform was inspired by the dynamic colour-changing skin of organisms such as squid. Compared with existing technologies, it offers much greater control while keeping costs low due to its use of off-the-shelf components.

“Buildings use a ton of energy to heat, cool and illuminate the spaces inside them,” said Raphael Kay, lead author on a new paper published in PNAS. “If we can strategically control the amount, type and direction of solar energy that enters our buildings, we can massively reduce the amount of work that we ask heaters, coolers and lights to do.”

So-called ‘smart’ building technologies including automatic blinds or electrochromic windows can be used to control the amount of sunlight that enters the room, but Kay said these systems are limited because they do not discriminate between different wavelengths of light, nor control how that light is distributed spatially.

The system developed by Kay and the team — led by Professor Ben Hatton, and including PhD candidate Charlie Katrycz and Professor Alstan Jakubiec — utilises microfluidics.

Their prototypes consist of flat sheets of plastic filled with an array of millimetre-thick channels for fluids to be pumped through. Customised pigments, particles or other molecules can be mixed into the fluids to control what kind of light gets through and in which direction the light is distributed.

According to the University, these sheets can be combined in a multi-layer stack, with each layer responsible for a different type of optical function: controlling the intensity, filtering the wavelength or tuning the scattering of transmitted light indoors. The system can reportedly optimise light transmission with a small, digitally controlled pumps to add or remove fluids from each layer.

“It’s simple and low-cost, but it also enables incredible, combinatorial control. We can design liquid-state, dynamic building facades that do basically anything you’d like to do in terms of their optical properties,” said Kay.

The work builds on another system that uses injected pigment, developed by the same team earlier this year, and published in Nature Communications. While that study drew inspiration from the colour-changing abilities of marine arthropods, the current system is more akin to the multilayered skin of squid.

Many species of squid have skin that contains stacked layers of specialised organs, including chromatophores, which control light absorption, and iridophores, which impact reflection and iridescence. These elements work together to generate unique optical behaviours that are only possible through their combined operation.

While the University of Toronto Engineering researchers focused on the prototypes, Jakubiec built computer models that analysed the potential energy impact of covering a hypothetical building in this type of dynamic facade.

These models were informed by physical properties measured from the prototypes. The team also simulated various control algorithms for activating or deactivating the layers in response to changing ambient conditions.

“If we had just one layer that focuses on modulating the transmission of near-infrared light — so not even touching the visible part of the spectrum— we find that we could save about 25 per cent annually on heating, cooling and lighting energy over a static baseline,” said Kay. “If we have two layers, infrared and visible, it’s more like 50 per cent. These are very significant savings.”

The control algorithms for this study were designed by humans, but Hatton said the challenge of optimising them would be an ideal task for artificial intelligence.

“The idea of a building that can learn, that can adjust this dynamic array on its own to optimise for seasonal and daily changes in solar conditions, is very exciting for us,” he said.