L1: Section 2

Where do materials come from today?

Natural Materials: Plant

Cotton is the most widely used natural fiber globally. It is a soft, fluffy, short staple fiber comprised of ‘cellulose’. It grows around the seeds of the cotton Gossypium plant in a ‘boll’.

Linen comes from Linum usitatissimum or flaxseed. The soft, woody fiber is coarser than cotton and good at cooling. Cellulose fibers come from the plant stem and are removed by 'retting'.

Other plants like hemp, nettle, jute or banana can be used for fibers from the cellulose in their stems. Pineapple leaves are another alternative resource.

Natural Materials: animal

Leather is made from the skin or ‘hide’ of an animal, most commonly from cows. A ‘tanning’ process is used to preserve and condition the skin. Leather is comprised of collagen ‘protein’.

Silk is smooth with a luster, it is considered a luxury fiber. The long filament fibers are mainly comprised of fibroin ‘protein’. Most silk is produced by the caterpillar of the Bombyx Mori moth.

Wool is obtained mainly from sheep when they are sheared. Warm and lightweight, it is a crimped staple fiber comprised of keratin ‘protein’.

Other animal hairs such as mohair and cashmere come from goats. They are rare and considered luxurious. Mohair is native to Turkey. Cashmere goats are grazed in ‘Kashmir’ in the Western Himalayas.

Man-made cellulosics

Viscose is a soft, silky, lustrous material harvested from wood pulp. The pulp is dissolved and regenerated into cellulose using synthetic chemicals.

Lyocell is a softer form of viscose. It also contains regenerated cellulose from wood pulp. Manufacturing lyocell uses less harmful chemicals than viscose. Tencel® is a brand name of lyocell.

Modal is another form of viscose with less environmental impacts. It has better durability and is lightweight. The cellulose comes specifically from wood pulp of beech trees.

Acetate fibers are similar to viscose. They are soft and silky. Technically, acetate is 'cellulose derived' and not regenerated. The fiber name comes from a chemical reaction called acetylation.

Synthetics

Polyester is drawn from plastic pellets made from crude oil. They can be melted into many different fiber shapes and properties. It is cheap, versatile, and the most widely used fiber in the world.

Polyamide (Nylon) is also extracted from crude oil using a chemical reaction. It is more expensive than polyester, but also stronger, stretchier and softer.

Acrylic is obtained from a chemical called acrylonitrile - a chemical from crude oil. It traps heat well and is used as a wool substitute, it is also often used as a replacement for glass too.

Elastane is very stretchy and lightweight. It is mainly blended with other materials to make them elastic and is rarely used alone. Elastane is formed from a reaction of crude oil chemicals.

Biomaterial definitions

‘Biomaterial’ is a general term used for any material that is in some way biologically derived.

A biobased product is made wholly or partly from biomass, such as from plants, animals or microorganisms.

Biosynthetics are synthetic polymer materials comprised, in whole or in part, of bio derived compounds. These can either be made with biomass, and/or, using a biological process such as with a living organism.

Biofabricated (or biomanufactured) materials are produced by living cells (e.g. mammalian) and microorganisms, such as algae, bacteria, yeast, and mycelium.

A bioassembled material is grown directly by living microorganisms such as mycelium or bacteria.

The organism either makes up the material (e.g. mycelium) or may still be present in the material (e.g. bacteria), but the materials are rendered inert so the organisms cannot re-grow.

Meet the organisms

Algae

Algae use photosynthesis like plants but live in water. They are simpler than plants and can be small, single cells called ‘microalgae’. Or, they can make up large organisms like seaweed. ‘Kelp’ is a large type of brown seaweed.

Bacteria & Yeast

Bacteria are tiny single-celled organisms. They can be found everywhere on Earth, including inside the human gut. In our bodies, there are around 10 times more bacterial cells than human ones.

Bacteria divide in two and double in number every 20 minutes. This means in 7 hours a single bacterium can become 2,097,152 bacteria!

Yeast is a type of fungus made from single cells. They are around 3 times bigger than bacteria.

Both yeast and bacteria use a process called fermentation to make carbon dioxide or ethanol from sugar. Ethanol from yeast fermentation is used to make wine and beer.

Mycelium

Mycelium is the root-like system of fungi. Mushrooms are the part of fungi we can see above the ground. Mycelium makes up the networks below the surface.

The largest known organism in the world is a mycelial network. It covers 10 square kilometers - around 1,665 football fields. Mycelium also helps to break down dead plants and recycle them.

Mammalian Cells

Mammalian cells make up tissues and organs in a mammal. A mammal is an animal that feeds their young on milk from the mother’s body.

Mammalian cells can grow into different types of cells in different parts of the body. For example, fibroblasts secrete collagen and are are the most common type of biological cell forming connective tissues. Dermal fibroblasts help the skin to recover from injury.

Fibroblasts can be grown in the lab to repair human skin The living cells are removed from the mammal first and then grown in a controlled environment.

Where’s the ‘bio’ in a biomaterial?

In many instances the ‘bio’ in a biomaterial is some kind of biomass (e.g. from a plant) that is processed directly into a material.

The biomass may be grown specifically for use as a material, or be waste from a different process. An example is fruit waste used to make a leather alternative. A key question to ask is has the biomass been mixed with any other materials e.g. synthetics.

In this example biomass is used as the nutrition (also known as the feedstock) for a microorganism (like a yeast or bacteria). The feedstock (usually a sugar source from a plant) can be grown specifically to feed the organism, or it can be a by-product/waste from growing the crops for another purpose.

The organism then uses this as fuel to produce an ingredient such as a protein or cellulose. This ingredient is extracted and then turned into a yarn or leather alternative. In the same way that silk is produced by a worm but does not contain the insect, the microorganism produces the ingredient but is not present in the final material.

In this example biomass is used as the nutrition (feedstock) for a microorganism like mycelium. The organism then uses this as fuel to grow the material itself, in this case a leather alternative. In the same way that leather is the hide of an animal, here the organism is the material.

During the growth process additional materials may be added, such as a textile substrate for added performance. At the end of the growth process the organism is rendered inert, i.e. is no longer alive.

What materials can organisms produce?

Algae

Algae and seaweed can be dissolved and then wet spun into fibers. It is a similar process to the production of viscose/ modal etc.

Algae can be turned into pigments and dyes. They can be used to print on packaging and textiles, as well as an alternative to (petrochemical-derived) carbon black for dyeing leather.

Algae biomass can be used as an additive to replace a certain percentage of petrochemicals. An example is to create materials like EVA foams for footwear applications.

Microalgae can be used to create algal oils (polyols). Algal oils can replace significant percentages (over 50%) of petrochemical ingredients needed in mixes for materials like cast polyurethane.

Bacteria & yeast

Microorganisms like bacteria and yeast can be designed to produce proteins, cellulose and alternatives to synthetic chemicals. These are extracted, purified and often dried to a powder before wet spinning into a fiber or made into pellets and extruded into a yarn.

Microorganisms like bacteria can also be used to grow whole sheets of materials for use as a leather alternative. For example, bacterial cellulose is where bacteria excrete nano fibers of cellulose that self-assemble into a sheet, which can then be dried, dyed, tanned and finished.

Bacteria can also be engineered to produce biological pigments and dyes. These colors can be used to dye textiles or be used in processes like screen printing.

Bacteria can even be used to grow an alternative to cement. In a process similar to how coral reefs are formed, the organisms produce a limestone material that locks together natural aggregate particles.

Microorganisms can produce alternatives to petrochemically-derived ingredients such as ethanol. They can alsoproduce PHA which is a biological alternative to materials like PET, PVC and polystyrene.

Mammalian cells

‘Lab-grown leather’ can be grown from an initially small number of cells, often fibroblasts . The cells are obtained via a small biopsy directly from an animal, or from a cell bank. They are fed a nutrient and multiply ‘in vitro’ (i.e. outside of a living organism). The cells are rendered inert at the end of growth before tanning.

mycelium

The most common method for producing a leather alternative using mycelium is where the mycelium’s threadlike hyphae (most easily understood as the root-like system of mushrooms) grow and self-assemble into a densely formed sheet, The sheet can then be dyed, ‘tanned’ and finished to look like leather.

Similar to how sheets are formed to create leather alternatives, mycelium can produce structures suitable as alternatives for foams used in footwear.

For alternatives to materials like polystyrene, mycelium is grown throughout its substrate (often waste like hemp hurd). This binds together the substrate making grown-to-shape compostable packaging.

Mycelium composites can be grown in a process similar to mycelium packaging materials. These materials have impressive sound absorption properties making them excellent for use in acoustic panels.

What are biomaterials?

Where will materials come from tomorrow?

Meet the organisms

Algae

Bacteria & Yeast

Mycelium

Mammalian Cells

What materials can organisms produce?

Sources