Optofluidic Skins for Sustainable Buildings

Indoor climate control is among the most energy-intensive activities conducted by humans; more than 25% of the energy and 50% of the electricity we consume globally is spent heating, cooling, and lighting interior spaces to keep humans comfortable. At the core of this footprint is a fundamental design flaw in architecture: human comfort is predominantly curated internally, using air conditioners, furnaces, and electric lights. As an entirely different approach to keeping humans comfortable, a building ‘skin’ capable of achieving climate control directly could drastically reduce the use of the indoor heating, cooling, and lighting systems that drive energy consumption and greenhouse gas emissions globally. However, to date, the development of such a universally configurable building platform remains an unresolved scientific challenge.<br/><br/>Looking orthogonally to typical solid-state approaches, we have turned to a new class of material to achieve versatile climate control along the surfaces of buildings: liquids. Compared to solids, liquids have two important functional advantages. First, they flow. Liquids can be easily transported, overlapped, and exchanged, while quickly and reversibly filling the extents of their containers. Second, liquids can much more readily be tuned, and are able to hold a range of particles and molecules relevant to the manipulation of solar radiation. Taken together, the versatility of liquids allows us to explore a new set of optofluidic strategies for more comprehensively controlling environmental sunlight.<br/><br/>We develop simple fluidic devices capable of general solar configurability, and we treat rationally selected liquids as injectable solar filters, introducing them in different combinations and sequences to spatiotemporally regulate temperature and daylight distributions indoors. Altogether, using optical experiments and simulations, we demonstrate how a simple fluidic platform can synergistically control the amount, color, and position of transmitted sunlight over time – a universal solar toolkit not realized in traditional building technologies.<br/><br/>Importantly, because this fluid-based toolkit can curate much of the internal climate at the external skin, the need for indoor operational energy usage can be massively reduced. Compared to available alternatives, models demonstrate that our liquid wrappings can decrease heating, cooling, and lighting energy consumption in buildings by over 40%, suggesting the emergence of a liquid design paradigm toward net-zero buildings.