Bio-Aerogel Inspired by Cellulose

Innovation: Academia

KTH Royal Institute of Technology

2021

Image: Raymond Culbertson / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Bio-Aerogel from KTH Royal Institute of Technology produced through air-drying method with increased wet stability and ultra-low density.

Benefits

Scalable
Lightweight
Responsive
Biocompatible

Applications

Drug delivery
Soft robotics
Medical diagnosis

UN Sustainable Development Goals Addressed

Goal 3: Good Health & Wellbeing
Goal 9: Industry Innovation & Infrastructure

Bioutilization

Alginate
Cellulose

The Challenge

Aerogels are lightweight, porous materials with many applications, from insulation, to oil spillage clean up, to 3D cellular scaffolds for tissue engineering. Cellulose nanofibril-based aerogels are biopolymer-based and have been studied and applied in many biomedical fields due to their unique characteristics, including ultra-light weight, high porosity, and exceptional strength. These bio-aerogels are also generally non-toxic and biodegradable. However, there is still room for improvement in the production of nanofibril-based aerogels, and aerogels generally. To produce an aerogel, the liquid within a gel must be removed without causing shrinkage. The most common method by which this is done is supercritical drying, which is energy-consuming and expensive. Moreover, substances added to some aerogels to increase the strength of the product are often not recyclable or biodegradable.

Innovation Details

The aerogel is plant-based, made of a combination of nanofibrils, alginate (a naturally occurring in seaweed), calcium carbonate, and water. It is produced through an air drying process. In this process, different weight ratios of carboxymethylated CNF gel, alginate solution, and calcium carbonate are combined to create the aerogels, which are then frozen at a standard temperature of 18 °C (64 °F), thawed, solvent exchanged, and air dried. This process is simple and scalable compared to the supercritical drying method and produces an aerogel that is ultra-low density (2 kg per cubic meter or 0.12 lb per cubic foot), highly porous (∼99% porosity), and wet-resistant.

Biomimicry Story

Plant matter consists mainly of cellulose, hemicellulose, and lignin. Cellulose comprises up to 90% of a plant, and it’s what gives a plant its structure. It is lightweight but has a high strength-to-weight ratio, making it incredibly durable.

See Related Content

Biological Strategy

Nanocrystals Isolated From Cellulose Have Unique Properties

Plants

Nanocrystals isolated from cellulose are strong, flexible, and lightweight

References

Journal article

Hierarchical build-up of bio-based nanofibrous materials with tunable metal–organic framework biofunctionality

ScienceDirect

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