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Transformative Underwater Structures: Reimagining the Future of Coral Reef Conservation
The nereids are underwater structures, designed to safeguard coral reefs from the escalating threat of rising temperatures.
The structures provide active cooling for endangered areas over extensive durations, by harnessing the intrinsic properties of their materials.
Each structure is made up of a thermoresponsive, biocompatible hydrogel called NIPA.
As temperature rises, the gel undergoes a phase change, causing it to absorb heat, whiten and shrink.
This phase change enables the nereids to synergistically employ two cooling mechanisms.
Firstly, the active cooling of the gel itself - each gram of NIPA possesses the ability to cool down 10 grams of water by up to 1 degree Celsius. Secondly, leveraging the gel's transformative nature, I designed the structures to fold and encapsulate water within the gel sheets during each phase change. This strategic folding amplifies the cooling impact by creating a responsive geometry. In normal temperature, the leaves are open, allowing water to freely flow through them. When heated, the leaves contract, and fold - encapsulating cool water within them, forming a cooling vessel that maintains a balanced temperature over extended durations.
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Programming thin sheets composed of gel and a constraining layer to exhibit heat-induced geometric variations.
As the NIPA gel shrinks when heated, while the constraining layer does not,
the thin sheet undergoes a transformative shift from 2D to 3D.
By altering the pattern of the constraining layer,
an array of customizable morphologies can be generated to meet specific design needs.
Similar to ice, when exposed to heat, NIPA gel undergoes a phase change, resulting in heat absorption, whitening, and shrinkage.
Each phase transition of NIPA allows it to exhibit a cooling capacity
of 1 degree Celsius per gram of gel for every 10 grams of water.
However, in contrast to ice, which undergoes a phase transition to a liquid state and disperses within the watery medium, NIPA gel remains in the form of a thin, coherent sheet after its phase transition. This unique property enables NIPA gel to be repeatedly activated for heat absorption upon encountering even slight temperature fluctuations within its watery environment.
NIPA gel exhibits repeated phase changes in response to temperature fluctuations, transitioning between cooler temperatures (e.g., 27°C) and higher temperatures (e.g., 32°C). When immersed in the ocean, the gel can be continually reactivated by brief streams of cooler water, allowing for repeated cycles of heat absorption and geometric transformation.
The phase transition temperature of NIPA gel, occurring at around 32°C, coincides with the emergence of another critical event. However, this particular occurrence brings with it a deeply concerning and potentially catastrophic consequence, posing a grave threat to one of the most vital ecosystems on Earth.
This phenomenon is commonly known as "Coral Bleaching," where coral species worldwide confront the consequences of rising ocean temperatures. As a result, they expel the essential algae residing within their cells, leading to irreversible damage and, in many cases, outright mortality.
Driven by the convergence of the two processes, I embarked on the quest to design underwater structures made up of NIPA gel that serve as local temperature balancers, protecting the coral reefs from the rising temperatures.
The genesis of my design process lay in the pursuit of an optimal base unit, meticulously tailored to bring the nereid into being. This foundational unit needed to fulfill two essential requirements. Firstly, in normal temperatures, it had to facilitate unrestricted water flow around the structure, ensuring the prevention of sedimentation and the unimpeded transport of nutrients to the corals. Secondly, when subjected to heat, I aimed for the gel to contract and fold, creating a protective enclosure that would encapsulate cool water within its confines.
Throughout the process, careful deliberation was given to the possible performances of various optional base units when subjected to water flow. Certain units appeared rigid and posed a potential hindrance to the smooth passage of water, raising concerns of possible sediment accumulation within their structures (e.g., the "Skirt unit"). Other disk-shaped units demonstrated only a slight folding response to the flow, showcasing a promising absence of sediment entrapment (e.g., the "Spider unit").
In the pursuit of achieving optimal water flow, base units constructed from multiple leaf-like structures emerged as the most promising contenders. The softness of each leaf enabled it to easily fold in alignment with the flow direction, ensuring unimpeded passage of water.
Throughout the process, I assessed the cool water encapsulation capacity of different geometries formed when the unit was heated. While some designs showed promise in effectively encapsulating water, they were disregarded due to their vulnerability to sediment accumulation in normal temperatures (e.g., the "Skirt Unit"). Conversely, other units that avoided sedimentation concerns in normal temperatures failed to retain cool water within their secondary shapes when heated (e.g., the "Spider Unit"). Hence, these designs were deemed unsuitable for the intended purpose.
Base units constructed from multiple leaf-like structures demonstrated dual promise, excelling as effective cool water encapsulators when exposed to high temperatures while facilitating unrestricted water flow in normal conditions.
The design process of the optimal base unit was not solely driven by its geometric potential to create cooling vessels through water encapsulation. It also took advantage of the inherent heat-absorbing property of the NIPA gel. As a result, the goal was to maximize the surface area of the gel leafs, thus amplifying the cooling effect. To surpass the limitations imposed by sedimentation risks, an abundance of vertically arranged leafs facilitated multidirectional water flow, successfully forming efficient cooling capsules when exposed to heat.
The selected optimal base units were designed to be assembled one on top of the other, increasing the number of cooling vessels formed and maximize the quantity of NIPA gel leafs available for absorbing heat from the surrounding environment during temperature elevation - thus forming the final shape of the NEREIDS structures.
Each NEREID can be anchored to the ocean floor using conventional ecological mooring methods that vary according to the ground type. Each base unit is equipped with a buoy attached to it, which allows the entire structure to rise tall and yet remain soft and bend according to the stream.
At present, the assembly of each NEREID takes place on a boat and requires manual deployment by personnel in the field. However, I envision a future where the manufacturing of NEREIDS can be achieved through autonomous underwater 3D printing of NIPA gel.
The Nereids are designed to be installed in areas that have been analyzed as common paths for hot ocean currents, forming underwater forests that provide local cooling of hot streams that are heading towards endangered reef areas.
Scientists predict that by the end of the century, coral reefs as we know them will cease to exist. But there is still hope for this valuable ecosystem.
By embracing novel materials and technologies, we can create a world where the beauty and diversity of the Coral reefs flourish for centuries to come.In this envisioned future, the human-made ceases to be a menace, transforming instead into a nurturing refuge for its natural surroundings.