Manufacturing technology
As he notes, these dynamic transformations can be one-way – meaning the object changes its shape without referring back to its original configuration – or two-way, meaning the shape change can be reversed. Materials with these properties are known as shape memory materials or SMMs. And while they have been around for decades, it is only recently that scientists have started to approach them through the lens of additive manufacturing. And mastering the associated techniques could pave the way for a host of new applications.
A new wave of possibilities “If you look into medical applications, the first that comes to mind would be for heart stents,” says Professor Eujin Pei, associate dean of the College of Engineering, Design and Physical Sciences at Brunel Design School, who is also the research group leader for 4D printing. “This has been shown by the Australian research agency CSIRO, which has manufactured self-expanding heart stents using a nickel-titanium alloy called nitinol. Through the use of shape memory materials, the stents expand and allow more blood to flow through.” These devices could one day disrupt the global market for stents, worth a staggering $16bn. Not only can they be customised on-site – ensuring that every patient has the stent that best suits their requirements – but they can offer better conformity to blood vessels and improved recovery times. Because nitinol has ‘superelastic’ properties, exhibiting structural changes when stressed or heated, the device expands in the body to keep the vascular structures open.
Another potential application, says Pei, would be 4D printed leg braces. “Let’s say you have an injury and you need to wear a brace,” he explains. “That brace could be controlled not through mechanical approaches, but through shape memory materials.” And the possibilities don’t stop there. As Mirzaali points out, 4D printing is being actively explored across a wide range of adaptable and personalised medical devices. “This includes drug delivery systems that release medications over time or under specific physiological conditions,” he says. “It also includes biodegradable microneedles, which are designed to deliver treatments in controlled doses and safely dissolve after use. In soft robotics, 4D printed materials could lead to the development of minimally invasive surgical tools that adapt to various anatomical structures during procedures. Meanwhile, wearable medical devices that respond to environmental changes could be used to monitor and maintain health parameters.” One further example lies within the field of regenerative medicine. In theory, 4D printing could
42
be combined with 3D bioprinting (printing living cells) to create advanced tissue scaffolds. These could be implanted into the patient at the site of injury or disease, supporting new cell growth and gradually dissolving as new tissue forms. Compared to 3D printed scaffolds, these structures would be better suited to the dynamism of living tissue. “Such scaffolds could adjust their stiffness or shape dynamically in response to the healing process, eventually conforming to the target organ’s form and functionality,” says Mirzaali’s colleague, Professor Amir Zadpoor, chaired professor of biomaterials and tissue biomechanics at Delft University of Technology. “Eventually, 4D printed scaffolds could reduce or eliminate the need for donor organs.”
Barriers to entry
While the list of possibilities is long and tantalising, we’re not there yet. Indeed, 4D printing is a young technology, which has yet to make much of a real- world impact. The term itself dates to February 2013, when MIT scientist Skylar Tibbits debuted the concept during a TED talk. During his talk, Tibbits presented some strand-like structures that, when immersed in water, morphed into complex polygons. These were the earliest true examples of 4D printed objects.
Since then, research has continued apace on 4D printed technologies and materials. As Zadpoor explains, the success of the process relies on three key pillars: stimuli-responsive materials, types of stimuli and structural design. Scientists have made significant progress in all three areas, with a particular focus on biomedical applications. “Several research groups worldwide are focused on developing biocompatible smart biomaterials,” he says. “One significant advancement has been using smart hydrogels, which swell or contract when exposed to moisture or pH, guiding their shape deformation. Regarding structural designs, artistic principles such as origami and kirigami have been adapted to biomedical engineering, inspiring 4D printed structures capable of complex transformations.” It’s no wonder that the market for 4D printing is growing rapidly. According to Precedence Research, the global market is expected to rise to almost $3bn by 2032, from just $137m in 2022. That represents a CAGR of more than 36%. To date, though, most of the work being conducted remains at the experimental stage. Researchers are learning more about the mechanical behaviour of 4D printed parts and how the results might change in response to different printing parameters. They are testing out different types of materials, often in conjunction with computer simulations. But while
Medical Device Developments /
www.medicaldevice-developments.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100
