A shot in the arm: How micro 3D printing could be used to deliver vaccines

A year ago, an industry began responding to one of the biggest pandemics in modern history. Face masks, face shields, ventilator components and nasopharyngeal testing swabs were output in their thousands, hundreds of thousands and millions as 3D printing providers and users mobilised.

At that time, Boston Micro Fabrication (BMF) was just announcing the international roll-out of its Projection Micro-Stereolithography (PμSL) 3D printing technology, which was first introduced in Asia. Such is the profile of PμSL – a technology designed to print micro scale parts at high accuracies and resolutions – it was never likely to play a role as the global 3D printer user base sought to plug the gaps in PPE and medical equipment supply chains. But months later, when it came to plotting the route out of this pandemic and other public health emergencies to come, BMF was invited to take part in a project led by Carnegie Melon University (CMU).

“The concept of microneedles for vaccinations or other drug delivery has been around for a while,” John Kawola, BMF’s CEO, begins. “But COVID has accelerated it. The world is faced with having to vaccinate billions of people. And while the needle and the vial [method has been around] for 75 years, I think we’re all seeing it’s not that easy to scale.”

CMU has thus stepped up its work in the development of microneedle array technology. Microneedle arrays comprise hundreds of tiny needles on a miniature patch that, when applied onto the skin, quickly dissolve and deliver the medication. These devices don't require the same level of cold-chain storage and can allow for 1/100th of the dose of a traditional vaccine to be delivered. CMU’s intradermal delivery device builds on ten years of research and, the university believes, would simplify the transport and storage of vaccines, while also reducing shortages.

BMF has been invited to contribute to the project because of PμSL technology’s capacity to print small parts at very high tolerance requirements. The project will utilise printers from BMF’s 2μm series – the 2μm referring to optical resolution – which are able to achieve layer thicknesses in the region of 5-20μm and surface finishes of 0.4-0.82μm on the top of parts and 1.5-2.52μm on the sides.

“On a two-micron platform, typically you can get a feature size down in the range of 15-20 microns,” Kawola explains. “In this case, for microneedles, that’s the size of the feature they’re trying to get to. Now most of these are cones that’s going all the way up to the tip, and that’s the smallest tip they want to get. And we’re trying to balance geometry with materials properties with the ability to make sure they [pierce the skin] but don’t break.”

Through the research so far, the partners have learnt that the smaller the needles, the easier it is to puncture the skin. Though still undecided, if PμSL is to be used to print the microneedles for direct use, a biocompatible material that has the strength and elongation to puncture the skin will needs to be developed, with a balance between feature size and strength ‘subject to optimisation.’ Alternatively, PμSL could be used to print mould patterns in an existing PDMS material, which has enough strength and the required biocompatibility to be used in the injection moulding of medical devices.

Another aspect of the project - which includes the University of Pittsburgh Center for Vaccine Research, Premier Automation and Tiba Biotech – is a focus on optimising and automating production. While the partners will not be drawn on when the results of this project will be commercially available – and they play down the idea a microneedle vaccine could help guide us out of the COVID-19 pandemic – they do see the last 12 months as a wake-up call, and they do see 3D printing playing a pivotal role in not just responding to global health crises, but in the immunisation of millions of people.

“With dozens of machines or more in a factory, you can certainly be talking about hundreds of thousands, if not millions, a week. That’s the goal,” says Kawola. “If it’s 1,000 a week, that’s not that useful, but if it’s hundreds of thousands approaching millions then that starts to scale. Manufacturing small parts like that at scale the conventional way is expensive. The injection mould is not £25,000, it might be £200,000, so it changes the math in terms of what starts to make sense. Everybody in 3D printing is looking for a way to displace the current way of doing it. If it’s difficult and expensive, then that’s a great target and that’s where we see this sitting.”