Printing aquatic plants in the fourth dimension

It happened on a hilltop overlooking Wellington Harbour in Te Aro, New Zealand. In 2018, Nicole Hone was finishing her thesis in design innovation at the Victoria University of Wellington. She had just achieved something very few people can lay claim to: leading the creation of an entirely new breed of 4D aquatic plants.

These 4D printed plants had no brain, no consciousness, and weren’t even made up of live cells – but they could move underwater, react to touch, and even mimic tasks live organisms carry out.

These weren’t just pretty forgeries, copycatting for show. One breed was designed to clean harmful algae off coral skeletons. Another to hunt invasive species. And one plant acted as a safe haven where fish could hatch eggs.  

It’s an intriguing blend of synthetic biology and biomimicry, a term derived from Greek words for ‘life’ and ‘imitation’.

Most impressive of all, these prototypes carry the potential to help preserve future marine life, threatened by climate change.  

But their history begins with a 3D printer.

Google the term ‘3D printing’ and your search engine will choke out pages and pages of news headlines. In Michigan, for example, Joshua Harker printed an art exhibition of 3D skulls. An Israeli fashion designer, Noa Raviv, designed an entire line of 3D clothing, inspired by classical Greek sculptures.

Then there are the props film studios commission to cut corners – and subsequently blow to smithereens. Take, for example, that sleek 1960s Aston Martin in James Bond’s Skyfall. It was a dead ringer for the real deal, but watching a replica go up in flames probably doesn’t pack as much cringe as if it had been authentic.

Elon Musk digs 3D printing, too; NASA uses it for its space equipment. Marsha, the utopian beehive designed to house people on Mars, was built with it. It even helped a team of researchers bring a 3,000-year-old Egyptian mummy’s voice back to life – by 3D printing a mould of its voice tract and hooking it up to a voice box. Let’s not forget Grecia, the Costa Rican toucan whose amputated beak was replaced with a 3D-printed prosthetic.  

If you’re unversed in the language of additive manufacturing, here goes: 3D-printed objects are those that have three spatial dimensions, specifically: width, height and depth. During production, 3D printers are fed a blueprint of a conceptual object, and then the machines build it, layer by layer, until it churns out a synthetic skull, or a toucan beak, or – for the extremely meta – a 3D printer.

It all started in 1983, after Chuck Hull came up with the idea of 3D printing when using UV light to harden table top coatings. He patented ‘stereolithography’, known as the solid imaging process, and this innovation endured into the 21st century.  

While the first 3D object he ever printed was, underwhelmingly, an eye wash cup, additive manufacturing proved a hit for automobile companies, the aerospace sector and medical applications. A kidney was 3D printed in 2000, and 13 years later it was transplanted into a patient for the first time.  At around this same time, in 2013, Skylar Tibbit – the architect who founded the Self-Assembly Lab at MIT – introduced the world to a new kind of multimedia printing. At a TED talk, he explained: “(It’s) the use of a 3D printer in the creation of objects which change or alter their shape when they are removed from the 3D printer. The objective is that objects are made to self-assemble when being exposed to air, heat or water. This is caused by a chemical reaction due to the materials used in the manufacturing process.”

Not everyone realised it at the time, but he was referring to something beyond the three dimensions of space we’re all comfortable with. He was talking about the fourth dimension – time. What Tibbit was saying was that he could create an object that could change shape, move and react to its surroundings over time. This is 4D printing.

MIT’s Self-Assembly Lab went on to invent self-assembling boxes, nano robotics and even adaptive clothing – all of which change shape when exposed to a certain element. This is the crucial factor which separates 3D printing from 4D printing – the ability for materials to react to stimuli over time.

In 2016, researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University took 4D printing one step further. Mimicking the way flowers, leaves and tendrils move in nature, they created a series of 4D printed flowers that could swell and change shape under water.  

It was botanical inspiration at its finest. Plants morph organically to respond to changes in their environment – usually for self-preservation. A Venus Fly Trap, for example, has little trigger hairs along its leaves, which when brushed by an insect, cause the two lobes to snap shut and trapping its prey. It then sucks the insect dry, absorbing the nitrogen it needs.

Scientists studied such movements, then used a precise geometric code to dictate how their hidrogel flowers would change shape when coming into contact with outside forces. It was a case of programming physical and biological materials to mimic the properties of other living matter.

Using these capabilities in the context of preserving marine life is still limited to 3D printing - inanimate objects that don’t move. For example, scientists from Cambridge University and the University of California San Diego 3D-printed coral-inspired structures, upon which microscopic algae can grow. They achieved this using a bioprinting technique initially developed for artificial liver cells.

These 3D printed corals have been successfully tested in oceans across Australia, the Maldives, the Persian Gulf and Fiji, but these are still low-scale efforts which barely make a dent in the overall coral deterioration worldwide.

It was Hone who dropped a bombshell. She asked herself: what if she could create 4D plants that could fulfil different functions, within the context of preserving marine life? It’s not unreasonable. After all, scientists could already create 4D-printed nanobots to enter a human’s body and eliminate cancerous cells.  

Hone sees herself as a mediator between technology and society, innovating new applications of current technology and speculating on future uses to share with the population at large. When asked specifically about the Hydrophytes and their potential, she was quick to point out that they were created from an artistic/design perspective, and only a scientist could offer insight into their actual application in the ocean.

She does think, however, that synthetic biological creations will form a valuable part of humanity’s response to adapting to a changing climate. Her research into synthetic biology shows real promise.

But the scientific – and ethical – dilemmas of engineering new life forms are still very real. At a psychological level, we might feel uncomfortable if we can’t tell artificial organisms from real-life ones. That’s why Hone created a unique design language for her Hydrophytes. We can tell they’re not really alive, but we still identify with them on a basic level.

To create the Hydrophytes, Hone used PolyJet technology to print a blend of liquid polymers and digital materials in layers, fleshing out their shape and texture. Each of their specific movements would define their role, which would activate when inflated with pneumatics. She created five breeds: the Arrow Pod, the Haven Flower, the Imp Root, the Feather Nurse and the Nomadic Cleaner.

As pieces of art, they’re astounding. But its their theoretical functions which are truly mind-blowing. The Arrow Pod could absorb harmful carbonic acids caused by excess carbon dioxide. This, she argued, could help regulate the ocean’s dropping PH levels. In turn, the Haven Flower’s petals could open up to provide fish, crustaceans and mollusks with a chemically stable habitat to lay eggs, and whose previous natural habitats had been obliterated by algae.

Her Feather Nurse was designed to help fortify fishes’ immune systems by secreting medicine onto their scales with bristles. To address coral bleaching, the Nomadic Cleaner was designed to fend off harmful algae that smother coral skeletons. Its barbed tendrils could cool heated waters, and could latch onto passing animals to move from coral to coral.  

Finally, the Imp Root took a more aggressive stance. Its tendril could release poison onto invasive species, its stomach layered with spikes to grind up – and digest – its prey.

Of course, 4D printing isn’t cheap, and we don’t really understand yet what these creatures’ life spans are. Hone claims that for one of her hydrophytes to fulfil these functions (and for them to distinguish certain animals from others), she would need to collaborate with scientists to ensure the programming of its cells are carried out properly. She thinks that with continued development – we could bring these forms to life, including cells, muscles and sensors.  

Hone’s designs can help us jumpstart new, biological processes to preserve the ocean’s habitats in future changing climates.

While their applications need further research and testing, that’s one small leap for humans, one giant leap for marine life.  

Elena Alston is a writer and editor living in London. She covers technology, brands, and travel — and anything else under the sun that catches her fancy. You can find more of her writing and what makes her tick on her website.