Printing progress

3D Printing and Additive Manufacturing remain high on the innovation agenda. With a mission to support SMEs in innovating through digital events, Professor of Additive Manufacturing at the University of Nottingham, Ruth Goodridge, shared some recent developments in the burgeoning industry.

After receiving funding from the Engineering and Physical Sciences Research Council (EPSRC) for healthcare disciplines, Professor Goodridge embarked upon a part-time secondment to the UK NHS to focus on clinical engineering with the aim of investigating where additive manufacturing could be applied to clinical practice, as well as the needs to be considered when introducing new technology and devices into the service.

She also co-founded a special interest group (SIG) in 2014 with the aim of bringing together healthcare professionals, academics, and industry stakeholders to find out where exactly additive manufacturing could fit into the healthcare industry.

“We haven’t held an additive manufacturing SIG for a while,” Goodridge began. “The last one was three years ago so I wanted to kick-off by reflecting on where we are now with the latest technology and its applications in healthcare.”

In terms of commercial machines, Goodridge explained that there have been new colour systems that have provided some fairly significant improvements, particularly for medical models used in clinical practice, either in-house or through the outsourcing of parts. The main players emerging for healthcare appear to be Stratasys and Hewlett Packard. The Stratasys J750, which has just been replaced by an 800 series, came out in 2016. In this process, resin is jetted out of ink heads and cured by UV light: “You can mix six different resins, which gives you 360,000 colour shades,” Goodridge said. “And you can mix resins with different epoxys, e.g. rigid and flexible resins.” Colour- and clarity-wise, Goodridge described the products as “pretty good”.

The release of the HP Multi Jet Fusion Colour System was another recent highlight for Goodridge. “This is a bit like laser sintering using a polymer powder bed,” she added, “and instead of a laser, it uses an ink jet array to selectively apply fusing and detailing agents on the powder bed. The heating elements are then used to fuse the selected areas. So, like polymer laser sintering, the big advantage of this technology is that you don’t need to use support structures, so you can achieve more complex structures than with a lot of other additive manufacturing technologies.”

Progress in process monitoring

Another important thing to happen in terms of machine development is progress in process monitoring. AM systems are increasingly being fitted with this function, and there is a lot of work going on on the research side too, which Goodridge admits is very important in terms of QC: “When it can be developed further I think it will enable more applications for healthcare.”

Another development of the past few years has been the pairing of software materials and machines – particularly where they meet FDA regulatory guidelines, and Point-of-Care in additive manufacturing. Currently, this is mainly being used for physical models for clinical use, Goodridge continued: “This validation system of hardware, software and materials is a really useful step forward.”

Bio-synthesis

Regarding materials, especially where more and more bio-materials are in use, Goodridge admitted to some teething issues: “This, I think, is a bit more worrying,” she said. Not the materials themselves, however, which she added is a great thing to have more of as long as they are complying with standards for medical uses. “I just think the labelling of materials as biocompatible suggests a universal biocompatibility. Given the accessibility of AM technology to a wide range of people, this could be interpreted in the wrong way.”

Several conversations between her, her colleagues and her counterparts have shown a presumption that these biocompatible materials are available for any application.

“However,” Goodridge added, “it’s been good to see material choices improve – particularly for polymers. We’re still a long way off from where we need to be, but progress is being made.”

A special interest group discussion held a few years ago focused on soft flexible materials and included a number of people wanting to focus on silicone especially. There was little choice at the time and there is still much work to be done in that area, but again, there has been progress.

“Most of the companies involved seem to have two things in common – a service to make the parts without selling the machines, and a tendency to be quite secretive about the process. This is something I’m planning to look into much more over the coming months.”

On the research side, polymerisation is used to produce a heart phantom, which has an elastic modulus similar to cardiac tissue with a high tear resistance. This, according to Goodridge, could be a useful device for medical professionals to practise skills such as injection, incision, and suturing.

There have also been some advancements in post-processing and increased recognition of the importance of this step. A polypropylene test piece, for example, has undergone a smoothing process with a surface finish similar to that produced by injection moulding, and Goodridge seemed excited to add that the industry will soon be seeing a lot more progress in this area.

After changing topic slightly to bioprinting, Goodridge added: “3D bioprinting has been an area of significant focus, particularly on the research side, but also in commercial applications … A hydrogel model of a lung was produced by researchers at Wyss University and tackled the challenge of multi-vascularisation. 3D biotherapeutics have developed of 3D bioprinted, living ear-shaped tissue using the patient’s own cartilage cells, which is being approved by the FDA.”

Another development in this area is a hand-held bioprinter being developed by the University of Toronto and designed to print cells directly on to burns and wounds. “Perhaps an area still largely in the research and development stage,” Goodridge admitted, “but with the amount of activity going into it, this is an area we will hopefully see continuing to move forward rapidly.”

COVID-19

It’s impossible to get through a presentation these days without mentioning COVID-19, so it was interesting to see the role of additive manufacturing in both positive and negative ways. These, according to Goodridge, were “mainly good”, but it has highlighted challenges in the field. “The positive was its ability to respond to immediate need before conventional manufacturing could take over,” Goodridge said, “and to provide the only really viable option. Producing face shields has been one of the most publicised functions of AM during the pandemic, with many players pitching in following a shortage. A chaotic response at first, but definitely well-intentioned.”

The are some lessons to be learned, Goodridge concluded, particularly in getting them approved. Seeing what was possible, however, as well as some of the big questions regarding regulations during the pandemic being addressed, were named among the positive outcomes.

Other COVID-related AM successes include nasal swabs, the production of lung models for research, metal filters for respirators and ventilators, Formlabs receiving emergency FDA clearance to produce positive airway pressure adapters, and CRP Technology producing charlotte valves which will link with components for emergency ventilator masks. These were adapted from commercially available snorkelling masks. Ingenuity, working hand-in-hand with innovation, is how we are likely to continue to see additive manufacturing in healthcare applications progressing.