Incredible new self-healing material innovation

2021-10-26 02:54:11 By : Mr. Jeff Wang

An evolving field of research dedicated to "living materials" can one day achieve impressive functions, such as repairing a bridge that cracks itself or a house that responds to its structural beam breaks through self-repair. The latest example comes from a study by Imperial College London (ICL), which developed tiny 3D building blocks based on bacteria to repair their own damage.

Dr. Patrick Ross of the U.S. Naval Research Global London Office, who funded the research, explained:

The challenge is to mimic and combine the unique characteristics that biology must provide. We are not only trying to imitate these systems, but also trying to obtain more functions through engineering biology in order to better meet the needs we seek without direct intervention.

Ultimately, we hope to extend the life of the product, prevent system failures before the problem is visible to the naked eye, and let the materials think for themselves.

Based on the early work of the team, the ICL team set out to produce engineered biomaterials that can repair their own damage through biologically inspired sensory and response systems.

Professor Tom Ellis, the author of the study, said:

In the past, we created living materials with built-in sensors that can detect environmental cues and changes. Now, we have created living materials that can detect damage and respond through self-repair.

To achieve this goal, scientists genetically engineered a bacteria called Komagataeibacter rhaeticus to produce fluorescent cell cultures shaped like spheres, called spheres. Similar to building blocks, these 3D spheres can be arranged in shapes and patterns. Next, the ICL team tested their self-healing ability in a structural material called bacterial cellulose.

Bacterial cellulose is a naturally occurring scaffold-like material synthesized by certain bacteria. It has great potential in multiple industries and can be used as a wound dressing, high-strength paper, and a filter in speakers in healthcare.

To test the efficiency of this material, scientists punched holes in a thick layer of bacterial cellulose and then planted spheres in the holes. After only three days of incubation, the sphere repaired the damage and restored the consistency and appearance of the original material. "By placing the spheres in the damaged area and incubating the culture, the blocks can sense the damage and re-grow the material to repair it," Ellis added.

Dr. Joaquin Caro-Astorga, the first author of the study, said:

Our discovery opens up a new method in which the grown materials can be used as modules with different functions, such as buildings. We are currently working on accommodating other organisms in the sphere that can live with cellulose-producing bacteria.

The active substances that may be produced are diverse: for example, using yeast cells that secrete medically relevant proteins, we can produce wound healing membranes, in which bandages produce hormones and enzymes to improve skin repair.

The team envisioned integrating the spheres into building materials, allowing them to detect and repair their own damage. This work, published in Nature Communications, may cause potholes in the road, repairing its own cracked windshield, and repairing its own aircraft.

Such a future is far away, but ICL scientists are working to create more complex designs by fusing their spheres with materials such as graphite, wood, cotton, sponge, and gelatin. This can pave the way for new applications such as implantable electronic devices, medical biosensor patches and biofilters.

Ceramic materials can withstand extremely high temperatures, but are very fragile. However, scientists at Texas A&M discovered a previously unknown self-healing mechanism in certain types of ceramics.

Ceramics are prone to cracking when subjected to mechanical stress, resulting in complete failure when the material is broken. Some ceramics can self-heal these cracks, but it usually requires chemical reactions at very high temperatures.

In this study, the team discovered that a special type of ceramic, chromium aluminum carbide, can slow down crack growth and cure them at room temperature, making them very useful in practical applications.

These ceramics are called MAX phases, and they contain alternating layers of material. It is this structure that gives them healing power. For example, when cracks start, defects called kink bands are formed between different layers. When pressure is applied, the crystals in the kinked band rotate, preventing the cracks from propagating further.

Best of all, these rotating crystals actively repair cracks, so once the force on the material is released, they are almost impossible to track. The lead author of the study, Hemant Rathod, points out: "What's really exciting is that this kind of kinking or self-healing mechanism can close newly formed cracks over and over again, thereby delaying material failure."

Scientists envision that this self-healing ceramic can be used to repair cracks formed in materials formed under high stress conditions, such as nuclear reactors, hypersonic aircraft, and jet engines. The research was published in Science Advances on August 11. The video below shows the animation of the kink tape defect.

In April of this year, scientists at Worcester Polytechnic Institute (WPI) developed self-healing concrete that can repair its own cracks by consuming carbon dioxide.

Small cracks in the concrete will not pose a direct threat to the structure of the building, but after a period of time, water will seep in and the crack will spread. This will affect its strength and service life. Self-healing concrete is designed to intervene in the process when the cracks are still small, sealing the material to prevent anything from catastrophic collapse, expensive maintenance or replacement of the entire structure.

The WPI team turned to the human body for inspiration, especially the enzyme called carbonic anhydrase (CA) in red blood cells, and how it quickly transfers carbon dioxide from the cells to the blood.

The scientists added CA enzyme to the concrete powder before mixing and pouring the concrete powder. When cracks are formed in concrete, enzymes interact with carbon dioxide to produce calcium carbonate crystals, which mimic the characteristics of concrete and fill the gaps quickly.

In laboratory tests, the team proved that concrete containing this enzyme can repair its millimeter-level cracks within 24 hours.

Last year, a team at Carnegie Mellon University developed a self-healing material that can restore function after being cut. The material has several impressive applications, some of which include:

The unique characteristics of the composite material enable it to repair itself and enable the equipment made of it to recover its function or acquire new functions after being cut or punctured. What is impressive is that when the cut ends of the material are put together, the pieces reconnect and the seams between them slowly disappear.

In addition, last year, a research team from the National University of Singapore produced a self-healing stretchable electronic material for the next generation of electronic wearable devices and soft robots. The material also emits as bright light as a smartphone screen! Therefore, things such as light-emitting robots can be manufactured, survivors can be quickly located in the dark, and electronic devices can have unbreakable displays.

In addition to enhancing the advantages of robots, the material can also be used in automotive applications, security lighting and special packaging.