Coral reefs are some of the most diverse and valuable ecosystems on Earth. Coral reefs support more species per unit area than any other marine environment. They occupy less than 0.1% of the world’s ocean area yet they provide a home for at lest 25% of all marine species, including fish, mollusks, worms, crustaeans, echinoderms, sponges, tunicates and other cnidarians. Scientists estimate that there may be millions of undiscovered species of organisms living in and around reefs. This biodiversity is considered key to finding new medicines for the 21st century. Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis, human bacterial infections, viruses, and other diseases.
Apart from that, coral reefs serve as tourist destinations, fishing areas, and protect our coastal shorelines from heavy waves, storms and flooding. So you can see they are very important to our ecosystem.
But because of man’s activities over the year’s, they are under serious threat of extinction; from excess nutrients (nitrogen and phosphorus), rising temperatures, oceanic acidification, over-fishing, and harmful land-use practices, including runoff and seeps (e.g, from injection wells and cesspools).
As a result of fast depleting reefs in some areas, the need for artificial reef structures was inevitable and so; reef structures made out of concrete, plastic’s and some other in-organic materials where introduced which where toxic and non-ecofriendly. But now a much greener alternative has emerged using materials such as clay and ceramics.
The project team from HKU ( University of Hong Kong) uses 3D printing technology to engineer structures that can be customized for specific locations with different environmental challenges (e.g. sedimentation), thus enhancing the success of the ecological restoration. The team of marine biologists and architects has thus developed a series of 3D printed terracotta reef structures to assist in coral restoration, providing structurally complex substrates in a degraded area.
As a solution to the problems mentioned above, 3D printing using clay holds the potential of creating a more viable habitat for corals. In addition to these material parameters, the printing language in this project has been optimized according to a series of factors.
The overall design of the project is based on a strategy that combines a traditional gridded bottom part as a structural platform with a second layer on top that follows an approach of bio-mimicry and serves as the primary surface to attach corals. Several parameters have informed the computational design strategy. Since the structure will be placed underwater and has to accommodate coral growth, local conditions needed to be taken into consideration. For example, the geometry cannot be a full, solid block, but needed to be perforated so that there is no sediment deposition possible, which could potentially suffocate the corals.
For the same reason, the geometry needed to be based on ridges and trenches are created alongside the surface of the geometry – the ridges act as anchors for the corals, while trenches direct sedimentation. To avoid bivalves nesting into empty spaces and to outgrow the initial area, the distances between the ridges needed to be carefully calibrated. The grid cells of the lower part are calibrated so that there is enough perforation to avoid sedimentation, to ensure the shortest possible toolpath and to tense the entire structure, in order to prevent it from cracking. All of the above had to be addressed through a novel robotic printing method that will be explained in this paper.
The 3D printed alphabet of design parameters has been calibrated, optimized, and tested within dry-land conditions. The artificial coral reef structures account for machinic, material, and speculated environment behavior, but further research potential will be generated by the on-site assembly, with the possibility of monitoring underwater situations.