Manufacturing technology
Despite the maturity of the technology, 3D printing is yet to reach its full potential.
carbide parts, and several others. In each of these cases, and whatever the degree of complexity, the general methodology is the same.
Pores for thought
Although you can create many different items with VIPS-3DP, the researchers say their technique is especially suitable for crafting porous objects – namely those with tiny holes or gaps within the material. This is an important feature of many implants and tissue scaffolds. To achieve this you would simply mix a so-called ‘porogen’ material into the ink and remove it after printing. Through placing the printed parts into a coagulation and porogen dissolution bath, you would induce the polymer to fully solidify while the porogen parts are dissolved.
90%
The percentage of the top 50 medical device manufacturers that use 3D printing to create prototypes
Formlabs 54
This approach lends itself well to objects with ‘multi-scale porosity’ – in which different parts of the material have different degrees of porousness. According to Huang, this could prove to be a real asset when it comes to manufacturing medical implants. “Scaffolds made using VIPS-3DP have multi-scale porosity for better osseointegration,” he says. “The VIPS process introduces intra-filament micropores, while the printing conditions tune the lattice structure, adding inter-filament macropores.” In simple terms, when you’re designing a device that needs to integrate with bone, the porosity serves an important end. For one thing, it helps the implant ‘anchor’ onto the bone, while reducing the risk of stress shielding (a reduction in bone density commonly experienced by those with implants). For another thing, it increases the device surface area, which helps promote cell attachment and growth.
Ideally speaking, you would want a mixture of small pores (helpful for bone regeneration and
protein absorption) and larger pores (helpful for the growth of new bone cells). However, that level of detail wasn’t possible up till now.
“The multi-scale porosity idea has been favoured to have high levels of bone integration around the porous medical implants,” says Huang. “It provides robust and integrated mechanical anchoring. However, there is no economical manufacturing technology to make such multi-scale porosity medical implants.” In tests, the researchers printed a lattice structure with a porous top layer and a much denser bottom layer. They found that their printed structures were not toxic to the body’s cells. What’s more, the porous nature of the scaffold enabled significant cell growth and migration into the porous cavities – a definite advantage when designing the next generation of medical implant. Going forward, the researchers plan on developing a ‘digital twin’ for VIPS-3DP – a virtual model of the technology that looks and functions exactly like its real-world counterpart. This will be useful for running simulations that predict how various manufacturing processes would perform on the factory floor. They also hope to identify more material combinations for VIPS-3DP applications. “Application-wise,” adds Huang, “the next steps mainly include the adoption of VIPS-3D for medical implant printing and utilisation of printed porous parts for substance storage, material filtering, and similar uses.” It’s early days for VIPS-3DP, and it remains to be seen what manufacturers will make of it. All the same, the central proposition of the technology is clearly very attractive. Offering manufacturers unprecedented control over the properties of their printed parts, it could yet cut costs and strengthen products, while helping them reduce their environmental footprint. ●
Medical Device Developments /
www.nsmedicaldevices.com
guteksk7/
Shutterstock.com
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