Rise of the robo-coral: 3D printing in conservation

3D printing has found a multitude of uses across education, manufacturing, medicine, construction, art and research.^1–6 Its applications range from producing 3D printed mazes that can be used to investigate ecological phenomena such as predation (à la ‘The Maze Runner’)⁶ to printing prosthetic limbs^4,5 – something we’ve written about previously. Perhaps particularly striking, however, is the use of ‘bioink’ – a substrate containing living cells, biomaterials, or active biomolecules⁴ – to print biological structures, such as tissues and organs.⁴ Although we are still a few years away from seeing patients receive 3D printed livers, it’s undoubtedly an exciting branch of medicine.^4,5

But the promise of bioink is not limited to medicine; as well as potentially saving lives through organ generation, it may also help save the natural world. In a mind-blowing recent development in the world of conservation, scientists from the University of Cambridge have printed a bionic coral reef, by mixing photosynthetic algae with an abiotic substrate designed to mimic the properties of the native coral.^7,8 Simply put, researchers have replicated corals by manufacturing living tissue that is part algae, part man-made polymer. Imagine ‘The Terminator’, but – instead of a lethal killing machine played by a muscular Arnie in his prime – we get a middle-aged gardener wearing an apron that says, “I’m Mister Green Fingers”. But what exactly are coral reefs, and why do they matter? How might cyborg coral save the day? Hold your breath, folks: we’re going for a deep dive to learn more about 3D printing and coral reef conservation.

What are coral reefs?

Coral reefs are underwater ecosystems constructed of living organisms and the shared skeleton of certain species of corals (animals that are related to jellyfish).^9,10 They are found worldwide, but most can be seen in tropical and subtropical waters.^11,12 Many reef-building corals house tiny algal cells (‘zooxanthellae’) inside their bodies in an interaction known as a mutualism, whereby both ‘partners’ cooperate for their common good.¹³ Amazingly, recent evidence suggests that coral reefs may date back to the age of the dinosaurs, up to 160 million years ago.^14,15

What’s so special about coral reefs?

The most recent report from the Intergovernmental Panel on Climate Change (IPCC) has a strong focus on how global warming may impact coral reefs, and reefs continue to be a topic of major interest to ecologists.^16,17 That’s not just because biologists like searching for the natural world’s spookiest creations (coral reefs are essentially giant coral skeletons, after all), or even because the Great Barrier Reef is the largest living structure on the planet¹²; reefs are in fact among the most important biological entities on Earth. Coral reefs support upwards of one third of all marine species of fish¹⁷ – and approximately one quarter of all marine species in general.¹² What’s more, the coral-algae partnership at the core of the reef, together with other so-called ‘photo-symbioses’, are responsible for around one half of all marine photosynthesis.^13,18 So, not only do coral reefs play a huge part in supporting the ocean’s species, but they also help provide the very air that we breathe.

Why do coral reefs need help?

The bodies of reef-building corals and the reefs that they produce provide a secure habitat for their resident algae to thrive^9,13 – you can think of the corals like adoptive parents. The problem arises when climate change threatens the delicate balance of ecological conditions that maintains this relationship; such biological partnerships can be fragile.¹⁹ Sadly, much of the world’s reefs have already been lost – an extremely worrying observation when coupled with the fact that they support one quarter of all marine species.¹²

Could 3D printing help?

A number of recent projects have sought to assist coral reef growth and maintenance using 3D printing.²⁰ The majority of these could arguably be classified as ‘scaffolding’ projects, whereby the primary function of the 3D printed material is to provide additional support for existing corals. Here’s just a snapshot of the pioneering work going on beneath the surface:²⁰

• A concrete ‘skeleton’ for a coral reef was constructed in the Maldives; divers assembled and adhered coral fragments to each piece in the hope that the coral will grow across the infrastructure
• Another 3D printing company collaborated with a design company to 3D print a reef structure mimicking the coral ecosystem of the Mediterranean
• A US project printed structures using calcium carbonate, to which they can embed young coral
• The University of Hong Kong has designed 3D printed tiles to help support reef structure
• Another project has printed settlement substrates – dubbed ‘seeding units’ – that self-attach to reefs and provide shelter for coral larvae

The thing that these projects have in common is the part of the reef they are printing: the reef structure (i.e. the skeleton). However, one recent project has gone beyond this. How? By printing the coral animal itself.

To achieve this, the Cambridge researchers mixed algae with a “photopolymerizable gelatin-methacrylate hydrogel and cellulose-derived nanocrystals”; the latter provides mechanical stability and “allowed tuning of the tissue-scattering properties”.⁷ Erm, what? Did…did they 3D print the person who wrote this? Because this sounds like something a synthetic humanoid might write. Either way, in average human language, this means that they housed algae within 3D printed abiotic material that they had designed to mimic the important light-scattering features of the coral tissue (to ensure that the algae receive similar levels of light compared with living within live coral). Remarkably, they achieved this with micron resolution⁷ – meaning that the synthetic coral ‘matched’ living coral structure down to the microscopic level.

Concluding remarks

While 3D printing projects clearly will not replace the need to safeguard coral reefs in the face of a rapidly changing climate, they represent a fascinating branch of conservation. Beyond this, the technologies in development to accomplish tasks like 3D printing living, bionic matter is pushing in ground-breaking directions. Organ printing, which we mentioned previously,⁴ is a great example of this. Returning to bionic coral, the researchers involved have launched a company that uses their coral-inspired light-harvesting technology to cultivate algae for bioproducts in developing countries.⁸ Further afield, they speculate about the possibility of using such systems in cultivation in long-distance spaceflight – where every centimetre of occupied space within a vessel, and every percent of efficiency, is critical.⁷

So, next time you look at your printer, thank it – for it may just allow humans to reach for the stars.

References:

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