How important is 4D Printing to the medical field?
4D Printing is a new manufacturing innovation that allows users to control and program the operation of materials as desired. The materials used in this group are called Smart Materials. Some sources may use the term Intelligence Materials or simply call them Smart Materials in transliteration. Further introductory information can be read in this article.
It is predicted that this technology and these materials will have a significant impact on the medical industry. Due to the complexity of the human body and the variety of internal and external factors, medical treatments must be studied on a case-by-case basis. Consequently, treatments—especially those requiring surgery—take a very long time and demand extreme precision at every step, from planning to the actual procedure. Materials that can change their shape or properties as defined by medical teams will greatly increase the success rate of treatments. This article compiles medical applications that are currently being researched and hold potential for the future for your understanding.
Smart Stent
For heart disease patients with clogged arteries or obstructions in the blood flow, doctors have surgical options such as bypass surgery, which is risky and dangerous, or balloon angioplasty, which is easier because it is non-surgical, to expand the passage and prevent heart attacks. Each patient has different conditions. With 4D printing technology, stents offer the advantage of changing shapes based on defined variables, such as:
- Can expand or contract according to the patient's original vessel shape or the surrounding flow channel.
- Dimensions can be adjusted according to pressure, temperature, and time as appropriate.
Recovery shape stent
Programmed shape stent
For small-scale manufacturing today, using nano and micro-printing technology, ETH Zurich has already successfully simulated artificial blood vessels at the 50-micrometer scale. Therefore, only the development of materials to meet usage requirements remains.
50-micrometer length blood vessel
3D Printed stainless steel, programmable shape
In the long run, humans will live longer because small parts such as blood vessels can be surgically replaced with artificial ones. Although still a distant prospect, it is highly likely that in the future, these innovations will become standard medical treatment procedures.
Airway Splint
In a case study of three infants with tracheomalacia, a condition causing difficulty in breathing (occurring at a rate of 1 in 2,000) and carrying a high risk of mortality, a medical team and engineers designed and produced an artificial airway splint for surgery. This was considered a world-first using 3D printing technology (Source: https://www.livescience.com).
However, 3D printed parts are always produced to a fixed, designed size. As infants grow, everything in the body must grow as well. The implanted artificial airway splint becomes inefficient and poorly sized, requiring replacement according to the infant's age. The introduction of Smart Materials will assist medical teams further because each replacement surgery carries patient risk. If the airway splint could expand in line with growth or have a longer service life, the need for repeat surgeries would be reduced.
Image credit: Morrison et al., Science Translational Medicine (2015)
Tissue and Organ Transplantation
The problem of creating parts to integrate with existing bases or structures is that "size" and "compatibility" are the most important factors. This is especially true for the production of tissues or organs via 3D Printing, which is considered a new field, and still faces many obstacles and ethical principles that require long-term study.
Shape-morphing 3D printed tissue
Source: https://physicsworld.com/a/4d-smart-scaffolds-for-tissue-engineering/
This article discusses the size of produced organs, which must perfectly fit the existing body. Furthermore, compatibility with DNA (genetic code) must also be consistent; for example, blood types must be compatible, not just matched. Therefore, at the start of production, Smart Materials can demonstrate behavior to adjust their size to fit perfectly or allow for flexibility as time passes, such as in the case of joints.
Shape-morphing artificial blood vessel
Color-changing Artificial Skin (Coloring Skin Graft)
Skin transplantation often occurs in patients affected by burns, chemical exposure, or surgery. Currently, there is research using 3D Printing technology to help skin heal better. If left to heal naturally, it would take a long time, and during that period, the patient would endure suffering from wounds, not to mention the potential for subsequent infections. The materials used are Bioinks—technically, these include Keratinocytes, Fibroblasts, and Collagen, which help patients recover faster.
Example of skin transplantation in lab mice
Source: Bioprinting of skin constructs for wound healing
Currently, even if treatment is complete and the patient can lead a normal daily life, the transplanted skin has a different color than the original skin. If Bioprinting materials are used, the color can be defined to change based on the surrounding conditions, helping to achieve a more complete treatment result.
Smart Medical Device
Another obstacle in medicine is the shortage of tools appropriate for specific use. For general tools, manufacturing might not be difficult, just potentially expensive. But in the case of surgery, it is more challenging because human bodies are unique, requiring many types and sizes of equipment. For 4D printing, if materials can change shape, be set with conditions, or be commanded during use, it would be highly essential.
One example of a controllable material that has already been researched is Polyurethane (PU). Many may be familiar with it as an adhesive, insulator, or plastic, which fall into the same group. This PU material can stretch under tensile force and return to its original shape slowly over time, known as Shape Memory. Applications include various gripping tools, depending on the design, or seals/gaskets in medical devices that conform to external factors.
Source: 4D printing of shape memory polyurethane via stereolithography
The Future of 4D Printing
The technology is still in the early stages of research and development, focusing heavily on Material Science to define the relationship between behavior, properties, and shape, which can be controlled by external factors. This is quite difficult. The author's ultimate goal is that we might one day have an Iron Man-style suit that incorporates these programmable materials.
