Manufacturing technology
tools, material sciences and multi-material printing technologies, with a view to ironing out some of the challenges. “Collaborative efforts between researchers, clinicians, and regulatory bodies will also be crucial to streamline development and ensure the safe and effective implementation of 4D printing in clinical settings,” he adds.
3D printing (or additive manufacturing) is widely used, while 4D printing has yet to make much of a real-world impact.
ideas and innovations abound, there are many roadblocks standing in the way of widespread commercial application.
“One of the main barriers would be that the 4D printed parts still don’t have a proper way of being certified as safe for use,” says Pei. “Particularly for medical applications, you need to get FDA approval or equivalent, which is very stringent. I think there needs to be a much clearer means for getting certified and fit for use, with the right types of testing and certification processes in place.” In order to pass muster with the regulators, manufacturers would have to show that any device was biocompatible, stable and reliable under physiological conditions. That’s not an easy ask for shapeshifting materials of this kind. “Key obstacles include managing the complex behaviours of materials over time, particularly when in direct contact with physiological solutions or living materials,” notes Mirzaali. “It can be challenging to achieve complex, reliable shape transformations. And ensuring the predictability of responses to external stimuli, especially in vivo, is a significant bottleneck.” After all, 4D printing is a complex field, which requires a deep understanding of the relationship between material properties and shape changes. That, in turn, requires a multidisciplinary approach, spanning materials science, biology, design, modelling and engineering. “This complexity can hinder progress, making the design and fabrication process time-intensive and costly,” says Zadpoor. “What’s more, current computational modelling and 3D printing techniques require better advancements to control material behaviour, enabling more accurate predictions of how 4D printed structures will function within biological systems.”
Playing catch-up
None of that is to say that 4D printing is a write-off; simply that these are early days, and our technologies are still playing catch-up with our ambitions. Mirzaali hopes we will see advancements in computational
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In their own lab, Mirzaali and Zadpoor are working on the three foundational pillars of 4D printing (materials, stimuli and design), with a focus on advanced computational modelling and 4D bioprinting. They are also exploring the miniaturisation of 4D printed structures, which would operate at the micron and submicron scales (70 times smaller than the width of a human hair). At a more fundamental level, they are interested in the physics behind the 4D printing process: for instance, how can defects in the material be harnessed to create shape-morphing structures? “This approach transforms potential drawbacks into functional advantages,” says Mirzaali. Pei, meanwhile, is partnering with industry to understand what types of applications might be derived from his printing technologies. He is also working with standardisation bodies, to try to find a way to harmonise the language that’s being used to communicate 4D printing. “4D printing can be quite hard to visualise because you can’t just draw one shape – you need your technical drawing and the computer models to describe multiple shapes in different phases,” he points out. “It’s like drawing a moving figure. So trying to communicate your designs in technical terms can be very difficult.” Despite the current limitations, Pei, Mirzaali and Zadpoor remain optimistic about what’s to come. Pei thinks that in the near-term future, we will see the world’s first 4D printed parts being certified as safe for use. He also believes that university courses will start to incorporate 4D printing into their curricula. Zadpoor expects that, over the next decade,
we will start to see widespread adoption of 4D printing across various biomedical fields. “That’s particularly true in orthopaedic applications,” he says. “Devices such as self-adjusting casts or shape-adapting splints could become standard, offering more comfort and functionality than current static solutions.”
Of course, there can often be a gulf between research and commercialisation. The kind of designs that are concocted in a lab – or, indeed, dreamed up in a TED talk – are not necessarily going to revolutionise medicine any time soon. That said, the 3D printing boom has more than lived up to expectations. There’s no reason why, further down the line, 4D printing should not do the same. ●
Medical Device Developments /
www.medicaldevice-developments.com
MarinaGrigorivna/
Shutterstock.com
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