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FEATURE: Printing the body

Amit Katwala

(Credit: iStock)
(Credit: iStock)

How engineers are building organs, limbs and bones using 3D printing

Additive manufacturing offers the possibility to create shapes that simply couldn’t be made using any other technology. That’s already proving useful in manufacturing, and it could be revolutionary when it comes to medicine and prosthetics, where pioneering engineers are creating techniques and materials to mimic the properties of natural tissue.

They hope to make life a little easier for amputees, or cater to some of the 120,000 people who undergo organ transplants each year, and those on the waiting lists owing to a lack of donors. Commercial giants such as L’Oreal and Procter & Gamble are investigating the technology, along with academics from all over the world.

No matter how complex or intricate the body part, you can be certain that in a laboratory somewhere there’s an engineer trying to print it.

Printing bones

In 2016, a group of researchers at Northwestern University in Illinois led by Ramille Shah developed a new kind of ink. It’s white, so it wouldn’t be much good on paper, but it could change the way surgery is performed. The ink can be used to create flexible bone implants of any size that turn into real bone once they’re inside the body.

That’s because the ink is porous – so blood vessels can grow through it and infiltrate it – the printed part is used as a scaffold for the body to grow. “Porosity is huge when it comes to tissue regeneration, because you want cells and blood vessels to infiltrate the scaffold,” said Shah. “Our 3D structure has different levels of porosity which is advantageous for its physical and biological properties.”

The bones are soft and malleable, so they could be manipulated by surgeons in the operating theatre to make sure they fit in place. Otherwise, they could be printed to the exact specifications required by individual patients. “The turnaround time for an implant that’s specialised for a customer could be within 24 hours,” said Shah. “That could change the world of cranio-facial and orthopaedic surgery, and, I hope, will improve patient outcomes.”

Printing organs

The next step is printing organs. Some companies have already successfully printed viable organs such as ovaries in mice, but there’s a long way to go before they’re ready to be used in humans. The heart could be the first organ to be printed, as it’s relatively simple in biological terms – acting purely as a pump rather than a filter or anything more complex. It would work in a similar way to bones, with a scaffold being printed first, and then imbued with heart tissue cells that would grow around the scaffold and form its working parts.

The problem with growing organs is the blood vessels. Capillaries, which carry blood to the cells, can be thinner than the width of a cell and are therefore difficult to print. NASA has a prize of $500,000 available for the first research group to successfully print a square centimetre of viable ‘vascular’ tissue that stays alive for at least 30 days.

Other companies have printed small pieces of heart, kidney and liver tissue – US firm Organovo’s 3D-printed liver tissue was recently granted “orphan drug designation,” allowing it to be used for treatment in special cases. “This is a critical milestone that supports our ongoing development of 3D bio-printed tissues for therapeutic use,” said the company’s CEO Taylor Crouch, adding that the firm hopes to apply for full approval by the US Food and Drug Administration in 2020.

Printing brains?

This week, a group of researchers at Imperial College London described a new material that could be used to print human lungs, or even brains. Again, their method rests on first making a scaffold. It uses cryogenics alongside 3D printing, and can create scaffolding structures that are soft enough to mimic the mechanical properties of organs.

This could allow the printing of organs where existing scaffolds are too rigid to be practical, such as neuronal cells or the spinal cord. “At the moment we have created structures a few centimetres in size, but ideally we’d like to create a replica of a whole organ using this technique,” said Zhengchu Tan, one of the researchers.

Meanwhile, cosmetics brand L’Oreal has set its sights on printing the biggest organ in the human body: the skin. It’s been working with Organovo, and now has a lab where it produces Episkin, which the company uses to test cosmetics. The technology could also be used to treat burn victims in future with skin grafts, which are often painful because currently the skin needs to be taken from elsewhere in the body.

There seems to be no limit to the possibilities. If Mary Shelley was writing about Dr Frankenstein today, he’d probably use a 3D printer.


Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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