For Immediate Release: August 28, 2020
By Felipe Reisch, Office of Naval Research Global
ARLINGTON, Va.—Biology has spent billions of years honing a response system to create healing features in many types of material. From human scarring capacity to the formation and mineralization of mollusk shells to fix cracks, biology has designed diverse ways to have a fast sense-and-respond system for damage. Today, researchers from the Department of Bioengineering at Imperial College London, led by Dr. Tom Ellis, are exploring modularity in engineered living materials, which are based on bacterially made cellulose.
The core objective of this groundbreaking effort is to exploit biology’s distinct ability to sustainably heal, replenish material and respond to constant damage while existing in harsh environments. Researchers are looking to make materials more functional than they are today. While sensors can be incorporated into material, they only send information. In this project, the sense-and-response system is one in the same. When damage occurs and is sensed, the response system kicks in and repairs the material.
In the same way that architecture uses modular pieces that can be assembled into completely different buildings, this research has demonstrated same principle can be applied to the design and construction of bacterial cellulose (BC)-based materials. The Office of Naval Research (ONR) Global, Air Force Office of Scientific Research (AFOSR) and Army Research Office (ARO) are funding this research project.
Dr. Tom Ellis, lead researcher, said, “Using genetic engineering methods, we made bacteria produce fluorescent spheroids to prove the concept of DNA-encoded functionalization. With these spheroids, we built different shapes and patterns, demonstrating the potential of spheroids as building blocks. We also used these modular pieces to repair the material, restoring damage in a piece of bacterial cellulose just by placing the spheres within the damage and incubating the bacteria to regrow the material.”
The growth in popularity of BC for its outstanding properties is the response to the worldwide challenge to find new materials with better-tailored functional behaviors. Dr. Patrick Rose, ONR Global London science director, said, “The challenge is to mimic and combine the distinct features biology has to offer. We are not only trying to emulate those systems, but engineer biology to have additional features that are more amenable to the needs we seek (e.g., fixing a crack in a windshield, a tear in the fuselage of an aircraft or a pothole in the road) without direct intervention. Ultimately, we want to increase the lifetime of a product, prevent failures of systems before the problem is visible to the naked eye and have the material think for itself. We engineer biological systems to do these things by exploiting the platform of synthetic biology.”
Challenges and opportunities for the future
The next step for this group of researchers is to develop new spheroid-like building blocks with different properties. The more types of blocks they can design and make, the more applications will be explored. Spheroids that are composites of BC with other materials is one exciting direction toward the future of this research line, as it will help to create more complex designs.
“This research effort has significant potential to open up a new materials synthesis platform,” said Dr. Stephanie McElhinny a program manager at the Army Research Office, an element of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory. “The system Dr. Ellis’ team has developed provides an opportunity to achieve synthesis of highly tunable cellulose networks that could serve as structural reinforcement in future composite materials—for example, reinforced transparent polymeric materials for vehicle windows or windshields or face shields.”
Combining different types of cellulose blocks with other materials as well could be another way to make interesting composites with different properties. It might also be a possibility to think about designing a 3D printer to assemble the spheroids into the structures automatically.
Dr. Ellis said, “Bacterial cellulose is already attracting a lot of interest in many industries, including textiles, cosmetics, electronics, health, food and architecture and design. For example, cellulose cosmetic face masks could be made from these cellulose blocks and designed to contain different active ingredients placed in patterns, so they activate different parts of the face skin. This same approach would also be appropriate for wound-healing dressings, which can also be made from bacterial cellulose.”
Dr. Jung-Hwa “Aura” Gimm, Air Force Office of Scientific Research program officer for Natural Materials, Systems and Extremophiles, said, “Controlling size, size distribution and mechanical properties of the BC spheroids may allow them to be used as a bio-ink for 3D printing. It may be also possible to engineer spheroids themselves to be inexpensive stand-alone biosensors with more robust mechanical properties, like ‘growing’ living biosensors on the go.”
In other words, instead of having material as a one-off use, or requiring it to undergo regular maintenance cycles, this material can be integrated into windshields, composite materials and clothing. It all undergoes self-healing—extending use and usefulness.
Dr. Rose from ONR Global said, “The hard part is engineering a sense-and-response system into biology that is novel to biology. It requires fine-tuning genetic circuits and understanding how the system responds. Once those pieces are in place, we can integrate the engineered biological pieces into existing materials and demonstrate that the system senses damage (e.g., cracks, crevices) and subsequently heals them within hours without any human intervention. It takes the concept of smart materials to a whole new playing field.”
ONR Global sponsors scientific efforts outside of the U.S., working with scientists and partners worldwide to discover and advance naval capabilities.