MATERIALS
CREATIVE INKS
3D
printing, otherwise known as additive manufacturing, uses computer-aided design
(CAD) software or 3D object scanners to deposit – or add – melted or partly melted material in layers to form complex shapes. First developed in the early 1980s, this type of digital manufacturing is almost the opposite of traditional methods in which material is ‘subtracted’ through milling, turning and so on. Increasingly, however, 3D
printing research is now focused on developing new additive manufacturing (AM) inks to improve efficiency, speed or sustainable production. As AM processes become ever-more sophisticated, they are finding growing applications in the aerospace, automotive and healthcare sectors, and in industrial production generally. AM inks include many substrates, such as metal powders, thermoplastics, polymers or ceramics.
Some of the most exciting
advances in 3D printing for healthcare are linked to the development of bio-inks. 3D bio- printing, for example, uses bio-inks to fabricate scaffolds to support the growth of body tissues layer-by-layer. These scaffolds mimic the body’s
Imagine printing a human heart using inks derived from nature, or aeroplane components made from high strength polymers? 3D inks can make almost anything possible, Victoria Hattersley reports
3D printing inks promise substantial environmental ben- efits and cost savings through more efficient, lightweight product design – not to mention on-site construction
extracellular matrix by providing structural support, and promoting cell attachment and proliferation. In 2016, Adam Perriman and his research group at the University of Bristol, UK, reported developing a new kind of bio-ink1
containing
two different polymer components: a natural polymer extracted from seaweed; and a sacrificial synthetic polymer used in the medical industry. The former provides structural support, while the latter causes the bio-ink to change from liquid to solid on raising the temperature. ‘The bio-ink is based on a hybrid
hydrogel, which can be crosslinked using temperature or chemicals,’ Perriman explains. ‘This allows us to directly 3D print with cells, but importantly, during the chemical
crosslinking process one of the polymers is removed, leaving behind a microporous hydrogel. Such a 3D matrix has advantages over a normal hydrogel as the cells can get more access to nutrients, eg oxygen, from the media.’
The design of a functioning bio-ink, he tells us, is a materials challenge, constrained by the parameters that define cellular compatibility. Moreover, the formation of bone or cartilage by stem cells within these environments is a great example of biomineralisation. The team’s findings could lead to the printing of complex tissues through using the patient’s own stem cells for surgical bone or cartilage implants. ‘Having the microporosity should
enable larger tissue constructs to be engineered,’ Perriman says. ‘With regard to the wider world, we are already seeing “organ-on-chip” models to test and develop new pharmaceutics and reduce animal testing. The next phase will be 3D bio- printing real tissue for personalised medicine.’
Pushing boundaries All of this leads on to the next step: the 3D printing of entire organs. For example, a team from the University of British Columbia (UBC) in Canada
34 02 | 2018
JAMES KING-HOLMES/SCIENCE PHOTO LIBRARY
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