One of the technologies that has had the greatest impact on advances in medicine in recent years has been 3D printing. In the 1990s it began to be used in the production of dental implants and customized prostheses, surprising even its inventor, Charles Hull, who did not anticipate such a beneficial use in the medical field.

Today, 3D printing makes it possible to create more advanced prostheses, such as artificial organs and prosthetic arms controlled by brain stimuli. It has also improved the precision of surgical procedures thanks to the production of anatomical models and adapted tools, which has helped to optimize the outcome of interventions. As if that were not enough, 4D printing also promises new opportunities in tissue regeneration and reconstructive surgery.
In addition, the fight against cancer has seen significant advances thanks to 3D printing. Recently, the Unit of Advanced Technologies in Design and 3D Printing (UTADI 3D) of the Hospital 12 de Octubre of the Community of Madrid has implemented 3D printed molds in its oncology treatments. These molds improve the precision and safety of radiotherapy treatment, thus offering personalized and cutting-edge care in the field of medicine.

Prostheses with greater adaptability and comfort
In the field of medical prosthetics, the advancement of this technology makes it possible to produce parts adapted to the unique anatomy of each patient, becoming increasingly sophisticated, functional, comfortable, lightweight and aesthetically pleasing.
Recently, researchers at ETH Zurich, in collaboration with the U.S. company Inkbit, reached a milestone by perfecting the manufacturing process, which now allows the creation of artificial organs using a variety of materials. These prostheses feature bio-inspired tendons and have a greater range of motion in the fingers, all achieved through a single printing process.
Meanwhile, a New York-based engineering startup called Esper Bionics has created a prosthetic arm that uses a system called brain-computer interface (BCI) based on electromyography, a technological system that collects brain activity to trigger the movement of the prosthesis.
With the World Health Organization estimating an increasing number of people in need of prostheses, the adoption of 3D printing will improve access for a greater number of individuals, especially in remote areas, reducing cost and production time. The most commonly printed prosthetics include arms, legs, face, eyes, teeth and even limbs for animals.

More accurate models and surgical instruments
3D printing is transforming the way doctors prepare for, plan and perform complex surgical procedures.
By creating accurate anatomical models from medical images, such as MRI or CT scans, surgeons can more clearly visualize the patient's anatomy and practice procedures before performing them in the operating room. This reduces operating times, minimizes risks and improves patient outcomes.
Researchers are already working on producing new, even more accurate and realistic surgical models. The Hangzhou Institute of Medicine (China) is at the forefront of 3D printing customized plastic liver models with self-healing capabilities. Thanks to their self-healing capabilities, these models can help find an optimal cutting path after several attempts for resections or tumor removals. An advance that could significantly improve the safety and efficiency of operations in oncologic surgery.
Likewise, the ability to 3D print surgical instruments means that they can be tailored to the specific needs of each patient and surgery. 3D printing is already being used to produce surgical cutting and drilling guides. These guides play a key role in orthopedic oncology surgeries, allowing precise geometric cuts and minimizing additional exposure and dissection. This in turn reduces reliance on intraoperative navigation systems, which guide the surgeon during the operation.
As a result of increasing demand for technological advancements in surgical instruments, techniques, 3D printed resources and individualized medical care, and due to technological advancements in the medical field, the market for 3D printed surgical models and tools is on the rise. An aging population and global demand for minimally invasive surgery drive industry participation.

Towards 4D printing
Today, bioprinting combines cells and biomaterials for the creation of living tissues and organs that can serve both to replace damaged or aging structures, as well as to replace animal models in drug trials or in the generation of disease models.
In 2020, researchers at Hallym University (Korea) succeeded in printing a light-curable silk fibroin hydrogel that replaced the damaged trachea in an animal model. It contained cartilage tissue cells and stem cells from bone marrow to mimic tracheal tissue. The structure was designed to be able to change its shape, making it easier to implant and repair defects effectively.
The technique, known as 4D printing, makes it possible to print three-dimensional objects capable of self-assembling using external stimuli, such as magnetic fields, and exerting a controlled force on the surrounding tissue.
Currently, at Institute IMDEA Materials of the Community of Madrid, we are working on projects related to the use of 4D printing in medicine. The BIOMET4D project, funded by the European Innovation Council, aims to develop a new generation of implants with dynamic properties to restore tissues, applicable in reconstructive surgeries in conditions such as craniostenosis, in which the bones of a baby's skull close prematurely.
There is no doubt that 3D and 4D printing, with its ability to personalize treatments and improve operational efficiency, is transforming not only how clinicians approach patient care, but also how patients experience their treatment and recovery. As we move forward, it is likely to continue to be a driving force in medical innovation and with each advance we will move closer to a future where personalized medicine is the norm rather than the exception.
Pedro Jesús Navarrete Segado, Postdoctoral Researcher, 3D Printing and Biomaterials, IMDEA MATERIALS
This article was originally published in The Conversation.