Additive manufacturing, also known as 3D printing, is the process of transforming digital 3D models into solid objects by building them up layer by layer.
The technology was first invented in the 1980s, but it is only in the past decade that people really began to take notice, especially as the cost of 3D printing drops and becomes more accessible. It is already possible to 3D print in a wide range of materials, for example thermoplastics, metals, ceramics and various forms of food.
One of the most exciting advances in 3D printing technology can be seen in the field of medicine. Medical technologies are often expensive when they enter the market, but many of the new 3D-printed solutions enable cost-efficient manufacturing. The reason for this is found in the design phase: When additive manufacturing processes are used, the respective items can be assembled directly from a digital model, increasing precision and removing room for errors. Moreover, it is distinct from traditional manufacturing techniques, which usually rely on removal instead of addition. With 3D printing this waste and the costs involved can be avoided.
One fairly new technology is called bioprinting. 3D bioprinting is the process of creating biological tissue and organs through the layering of living cells, where cell function and viability are preserved within the printed construct. Although this technology has much in common with typical additive manufacturing processes, there are a number of unique technical and legal challenges to implement the use of bioprinted materials. Bioprinting begins with designing a 3D model based on the composition of the target tissue or organ. The bioprinter uses that model and deposits thin layers of living cells using a bioprint head that moves back and forth in the designed configuration. The living cells are taken from the patient beforehand and then cultivated until sufficient `bio-ink` is created.
Additionally, dissolvable hydrogel will be dispensed during the process to support and protect cells as tissues are constructed vertically, to fill and stabilize empty spaces within the tissues. 3D bioprinting has already been used for the generation and transplantation of several tissues, like multilayered skin, bone, vascular grafts, tracheal splints, heart tissue and cartilaginous tissue. For example, specialists have developed 3D-printed airway splints for babies who are afflicted with tracheobronchomalacia which makes the airways around the lungs prone to collapsing. This new treatment is especially significant since these airways splints are the first 3D implant made for children and designed to grow with the patient. The medical implant had been successfully tested in three children between the ages of three months and 16 months as of April 2015. The production of the splints can be done in a few hours, and costs only about $10 US dollars per unit.
At Princeton University researchers have used 3D printing tools to create a bionic ear during a project to explore the feasibility of combining electronics with tissue. The project was the team’s first effort to build a fully functional organ, and the created ear not only replicated human ability, but also extended it beyond the range of normal human capability.
Just recently, a Japanese research team at Kyoto University developed a novel 3D printing approach to produce artificial silicone tubes for regenerating damaged nerves. As material, the 3D printer uses a lump of cultivated human skin cells to create an conduit about 8mm long and 3mm in diameter. This new technology is supposed to support the rehabilitation of the patient and remove their pain. The team leader, Ryosuke Ikeguchi, explains that around 5,000 to 10,000 people in Japan suffer from nerve-related injuries annually because of work-related accidents and other reasons. The team plans to conduct a clinical trial using of this new 3D printing technology in 2019. So far, the researchers have successfully implanted 3D printed cells into the thighs of rats. Half of the rats were transplanted with a silicone tube, and the other half received the 3D bioprinted tissue vessel to support nerve regeneration. While rats that underwent transplants using the artificial silicone tubes tended to drag their feet, those with the bioprinted tubes promoted faster regrowth of the nerve so that they were able to walk like healthy ones again.
There are several other advances in the field of 3D bioprinting, and many of them have been part of successful surgeries and treatments. One example can be found in cancer treatment. In 2014, researchers developed a fast and inexpensive way to make facial prostheses for patients who had undergone surgery for eye cancer, using facial scanning software and additive manufacturing. In 2015, another team of researchers found that it is possible to print patient-specific, biodegradable implants to more effectively cure bone infections and bone cancer.
At present, bioprinters are still at the very beginning, but first tests are looking promising, creating hopes that this new technology could revolutionize medical practice in the future. The main challenge is that the biomaterial must also be able to thrive and grow in the environment it is intended for. Additionally, the biomaterial needs to remain viable during the entire construction of the tissue or organ.
However, with regards to hearing aids, prosthetics and implants, 3D printing already transforms the medical industry significantly. For example, most hearing aids and dental crowns are produced with additive manufacturing.
The production of hearing aids is a manual, time consuming process as the aids must be customized to fit in the ear. With 3D printing technology, only three steps are necessary, which can be completed in under a day, to manufacture a hearing aid. In the first step, an audiologist scans the recipient’s ear using a 3D scanner in order to create a digital image of the ear´s surface. The scan is sent then to the technician or modeler, who carries out several checks. After the completed scan and a subsequent inspection process for any errors, the hearing aid can be fabricated. 3D printers are used to print out the shell of the hearing aid using resin as a material. Last, the shell is equipped with electronics and acoustic vents. This process is also more comfortable for the patient than traditional methods as it matches the wearer's ear perfectly and results in a higher quality product. At present, more than ten million 3D-printed hearing aids are in circulation.
Another example is the production of prosthetics. The manufacturing process of prostheses is costly because high customization is necessary to fit the needs of the patient. Traditionally, the process of creating a prosthetic limb can take from weeks to months. On average, prosthetics have a lifespan of five years, but especially among younger children who grow quickly and are prone to breaking things, more frequent replacements are required. Although health insurance companies may cover some of the costs, the remaining amount can still be very high so that for many people a prosthesis is not affordable.
Hence, the costs of traditional prosthetics are a significant barrier to those without sufficient resources. The University of Toronto, in collaboration with Autodesk Research and CBM Canada, used 3D printing to quickly produce cheap and easily customizable prosthetic sockets for patients in the developing world, particularly Uganda. A similar project was initiated by Not Impossible Labs based in Venice, California, aiming to create technologies for the sake of humanity. They set up the world's first prosthetic lab and training facility powered by 3D printers in Sudan where war has left its traces behind. Not Impossible Labs trained locals how to use the printers in order to create patient-specific prosthetic limbs.
Medical additive manufacturing is not only for serious medical issues. In fact, it might become part of daily medical practice to treat a wide range of medical issues. 3D-printed ankle replacements, casts, and pills have been developed, with promising success rates. The 3D-printed cast, for instance, heals bones 40 to 80 per cent faster than traditional casts.
As the technology becomes more and more accessible and 3D printing makes customizations much easier, the technology has high potential to revolutionize the medical industry. Nevertheless, some of the more revolutionary applications, such as fully functional and viable 3D printed organs for human transplantation, will need time to evolve. Human organs have a complex web of cells, tissues, nerves and structures that need to be correctly positioned for the organ to function properly so that it is a long and difficult process. Finally, for all new medical treatments, it is required to pass safety tests and proper regulatory processes before they can be made available to the public. Hence, it will still take time until this technology can be used.
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