Empowering communities to improve their water supply by detecting & filtering pollutants in a way that is accessible. Modes of detection & filtration will evolve over time to account for novel pollutants or locally specific concerns.

Using the most abundant polymer in nature: cellulose

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Aim 1: Grow bacterial cellulose from Kombucha SCOBY, explore applications

Biological polymers (biopolymers) are naturally occuring polymers that are produced from cells of living organisms. Three key biopolymer types are polynucleotides, polypeptides, and polysaccharides.

Brilliant hierarchical structures

Most biomaterials that are found in nature are composed of a rather small subset of biopolymers building blocks such as cellulose, chitin, silk, and collagen that are produced from cells of living organisms. These small number of biopolymer building blocks are structurally weak from an engineering point of view but come together in brilliant hierarchical structures to form biomaterials that are very structurally performant at the macroscopic scale. This is in stark contrast to manmade materials that are meticulously engineered for their structural stability. It is common for synthetically engineered materials to be very strong at the atomistic scale but they lose strength considerably by the macroscopic scale. Nature’s way is very desirable, so clearly we have a lot to learn from it.

• A diversity of structures leads to a diversity of functions in tooth, bone, artery wall, tendon, spider web, wool, feather, beak, nail, tree, cotton, beetle carapace, in lobster, snail and mussel shell, glass sponge skeleton.

Biological materials are built with a limited number of building blocks, based on polysaccharides, proteins and mineral. [1]

Cellulose

Cellulose is a polysaccharide and is the most abundant organic polymer on Earth. In nature, it’s commonly known to be found in wood, cotton, bamboo, and more with applications for thousands of years in building materials, paper, furniture, and textiles.

Bacterial Cellulose

While cellulose is found in plant and plays an integral role in the structural stability of the plant cell wall, cellulose is also produced by certain types of bacteria, bacterial cellulose (BC) and can be cultured in homes and laboratories at both small and mass-scale. While cellulose is found in plant and plays an integral role in the structural stability of the plant cell wall, cellulose produced by certain types of bacteria, bacterial cellulose (BC), is notable for enhanced characteristics vs its plant counterpart.

Growing from kombucha tea SCOBY

One way of producing BC is via fermentation of the popular kombucha tea drink. During this process, a pellicle of BC forms at the air-liquid interface at the top of the container used for fermentation. The thickness of this layer of BC can be modulated and then (optionally) processed for the use case at hand.

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(A) Biosynthesis of bacterial cellulose (B) downstream processing [22]

Properties emerge from hierarchical structure across scales

• linear homo-polysaccharide composed of repeating β-D-glucopyranose units linked by β-1,4 glycosidic bonds

• key chemical profile: plentiful hydroxyl groups existed along the polymer chain —> large number of hydrogen bonds are formed

  (between hydroxyl groups & oxygen atoms of anhydroglucose units)

• parallel stacking of cellulose molecules into crystalline nanofibers arise from the hydrogen bonding & van der Waals forces —> assemble into cellulose microfibrils

  • hierarchical order helps reinforce structure and yields cellulose microfibrils excellent mechanical strength
  • BC fibrils (width: 20-100 nm) composed of nanofibrils (width: 2-4 nm)

Bacterial Cellulose (BC) Applications

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