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3D printing: limited only by your imagination?

22 January 2013

This popular rapid prototyping technique seems to have progressed beyond the bounds of everyday product development and into the realms of science fiction.

We're probably all familiar with the science fiction: the interplanetary crew member presses a button and, hey presto, a plate of steak and chips magically appears - with not so much as a cow or potato having any involvement in the process. A flight of fancy? Don't be too sure.....

3D printing — also known as additive manufacturing — is the process of fabricating three-dimensional solid objects from digital computer models. Following computer-generated drawings, 3D printers generally deposit successive layers of various materials to build a physical object from the bottom up. Scale, it seems is not a problem, as the technique can be used to create anything from a single tiny component to a building structure (The D-Shape building process, for example, which can 'print' buildings from the foundation up using a sand/binder combination).

3D printing is hugely popular among product development teams and these days even hobbyists are able to purchase rudimentary machines at relatively affordable prices for model-making at home. However, that's not the end of the story, as far as 3D printing is concerned. Take Jennifer Lewis, for example; the recently appointed professor of biologically inspired engineering at Harvard's School of Engineering & Applied Science has taken 3D printing to a far more sophisticated level - and here the possibilities really start to fire the imagination.

By designing novel inks from diverse classes of materials, as well as high-precision 3D printing platforms with exceedingly small nozzles, her research group is able to create very finely tailored structures with precise electronic, optical, mechanical, and chemical properties. She has demonstrated how to design and manipulate various gels, polymers, and colloidal suspensions and create architectures that mimic those found in nature, such as bone and vascular networks.

Her innovative prototyping platform can pattern a variety of functional materials under ambient conditions with features down to the micron scale over areas approaching a square metre, and all in a matter of minutes. Once deposited, the inks solidify very rapidly, enabling the creation of intricate spanning and self-supporting structures, even at a microscopic scale.

The potential uses for techniques like those developed by Professor Lewis and her team are broad; significantly the generation of 3D polymer scaffolds for tissue engineering - or 'bioprinting', to use the slightly disturbing jargon - is one that could bring huge benefits in terms of wound care, organ regeneration and even food production - specifically meat.

Despite its Frankenstein connotations, the pioneering concept of bioprinting is delivering promising results, according to one of the early champions of the process, Professor Brian Derby of The University of Manchester, who is studying the use of printer technology to build structures in which to grow cells, and thus regenerate living tissue.

Both inkjet and laser printer technology can be used to build the 3D scaffolds within which cells can be grown. Professor Derby says the methods have allowed his team to develop very complex scaffolds which better mimic conditions found inside the body. The scaffold provides a surface to which the cells can adhere, then thrive and multiply. The scaffold material, composition and its internal architecture control the behaviour and well-being of the cells inside.

In an article published in the journal, Science, Professor Derby describes experiments where porous structures are bioprinted, then placed in the body to help act as a scaffold to encourage cell growth. Cells colonise the structure, which either dissolves or becomes part of the body. This type of treatment can help patients suffering from problems such as cavity wounds. Clinical trials are currently taking place around the world to perfect the technology, and Professor Derby says it is moving towards becoming an established form of science.

Professor Derby also describes how stem cells can be grown in printed structures that have been impregnated with certain chemicals. The chemicals are inserted during the printing process and can determine the type of cell the stem cells develop into, such as bone tissue or cartilage. But there are limitations to the technology.

It has proved very difficult to print the cells at the same time as making the structure that will house them. Moreover, the stresses imposed during the inkjet and laser processes can damage the cell membrane. Cell survival rates are variable, ranging from between 40 to 95 percent.

The technology is also some way off progressing from an experimental platform to clinical practice. Whilst scaffolds are undergoing clinical trials, actually transplanting cells grown in an external structure into a patient is a more advanced process. At present, it is not possible to guarantee a consistent quality, as required by medical device regulations.

Meanwhile, the US company, Organovo, which specialises in the manufacture of functional, three-dimensional human tissues for medical research and therapeutic applications, is working with researchers at Autodesk to create the first 3D design software specifically for bioprinting. The software will be used to control Organovo's NovoGen MMX bioprinter, which the company claims can be used to create living human tissues that are three-dimensional, architecturally correct, and made entirely of living human cells.

Autodesk chief technology officer, Jeff Kowalski says bioprinting’s blend of engineering, biology and 3D printing makes it a natural for Autodesk, while Organovo’s chairman and chief executive officer, Keith Murphy, looks forward to a time when customers will be able to use the software to design their own 3D tissues for production by Organovo.

So, what about the artificial production of meat I referred to at the beginning? Well, Organovo co-founder, Professor Gabor Forgacs of the University of Missouri has taken his science beyond regenerative medicine, turning his attention to the production of ‘food grade animal protein’ via bioprinting, with his 2011 start-up, Modern Meadow. The company’s stated aim is to develop cultured leather and meat products which require no animal slaughter and much lower inputs of land, water, energy and chemicals.

And he’s not the only one pursuing this goal. Mark Post of Maastricht University, has been working to develop a synthetic hamburger, which has yet to grace the dinner table.

Moving from regenerative medicine to the production of food poses both technological and regulatory issues for all those involved in the research; consumer attitudes, however, will no doubt prove another matter altogether.

Les Hunt

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