Alginate¶
Alginates occur both as a structural component in marine brown algae (Phaeophyceae) and as capsular polysaccharides in some bacteria, but all commercial alginates are at present extracted from algal sources only. - Reference
Commercially available alginate is typically extracted from brown algae (Phaeophyceae), including Laminaria hyperborea, Laminaria digitata, Laminaria japonica, Ascophyllum nodosum, and Macrocystis pyrifera by treatment with aqueous alkali solutions, typically with NaOH. The extract is filtered, and either sodium or calcium chloride is added to the filtrate in order to precipitate alginate. This alginate salt can be transformed into alginic acid by treatment with dilute HCl. After further purification and conversion, water-soluble sodium alginate power is produced. On a dry weight basis, the alginate contents are 22–30% for Ascophyllum nodosum and 25–44% for Laminaria digitata.
Bacterial biosynthesis may provide alginate with more defined chemical structures and physical properties than can be obtained from seaweed-derived alginate. Bacterial alginate can be produced from Azotobacter and Pseudomonas. The pathway of alginate biosynthesis is generally divided into synthesis of precursor substrate, polymerization and cytoplasmic membrane transfer, periplasmic transfer and modification, and export through the outer membrane. Recent progress in regulation of alginate biosynthesis in bacteria, and the relative ease of bacteria modification may enable production of alginate with tailor-made features and wide applications in biomedical applications. - Reference
Sodium Alginate¶
The sodium salt form of alginic acid and gum mainly extracted from the cell walls of brown algae. Brown seaweeds are usually large, and range from the giant kelp Macrocystis pyrifera that is often 20 m long, to thick, leather-like seaweeds from 2-4m long, to smaller species 30-60 cm long Alginate is a compound know as a polysaccharide.
Alginate Bioplastic - Calcium Alginate¶
Alginate bioplastic id made by combining two separate mixtures: one containing sodium alginate, water and glycerine (as a base) and a curing agent, calcium chloride. Calcium has the ability to form two bonds which will hold the alginate into a long link forming this gel as a molecule called a polymer. Gels formed from alginates have the amazing ability of withstanding heating to temperatures as high as 150°C without melting.
After coming across such amazing facts about algae, I was very motivated to work with algae based material called alginate. During the Biofabricating materials week at fabricademy, I came across some amazing properties of alginate biomaterials. One of which was, After spraying the curing solution the biomaterial becomes water resistant and can withstand heating to temperatures as high as 150 degree celcius without melting. So I started with fabricating basic alginate material and then explored different raw materials as add ons.
Materials needed :¶
- Pot, spoons and stove.
- Meshes, textiles, nets, moulds.
- Sodium Alginate, Glycerine, Water, Essential oils, Normal oil.
- Food waste or fibres.
- Food colorants or natural dyes extracts (Red cabbage).
Cost sheet for materials:¶
How to make Alginate Biomaterial:¶
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Mix the alginate with water and glycerine. The best way of getting a smooth mixture is to use a hand held mixer or blender. Here I have used half portion Red cabbage dye and half portion of water, so I don't need to add colous/dyes/pigments afterwards.
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Once the mixture is smooth and completely dissolved, let it sit for several hours, this will allow all the bubbles to leave the mixture. We also tried putting the container in a vaccum container but it didn't work out very well.
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Prepare a solution of water and calcium chloride, at 10% and fill a small spray bottle with it.
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Prepare the surfaces and moulds to be filled, by spraying the calcium chloride mixture on the surfaces. You can use 3d textured coated fabrics that are waterproof, to transfer the texture to the bioplastic.
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Cast the alginate mixture onto the surface or mould. Once you start pouring, try to cast slowly, without inglobating air, and by carefully pouring on the liquid itself. Spread the material into a thin film using a very wide spatula or by moving the mould.
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Add any add one that you want to, like I used wool fibres in almost all my samples and final garments.
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After a couple of minutes spray the casted alginate with the calcium chloride mixture, the casted material will shrink both in thickness and width.
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Once the alginate mixture is cured, rinse it thoroughly or dip in it water to eliminate any residue of calcium chloride.
- Here are all the samples that I tried, with recepies and steps.
- The reason for choosing Red cabbage was that the colour is very fugitive i.e. the colour will fade away if put it under the sun. Which could act as a good depiction for the phenomena of coral bleaching, also giving a sense of taking more care of your garments/belongings so that it can last longer.
- I also explored some patterns with biomaterials, you can check the fabrication process under the fabrication section.
- This is a sample of 3D non-commercial weaving, I wanted to give some 3D textures and a sense of inter-connectivity in my collection.
Alginate Extrusion¶
Process of Alginate extrusion :¶
- Make the normal alginate biomaterial mix.
- For increasing strength you can add more alginate, to make it thicker.
- Put the paste into a syringe, Syringe with wider hole will make better extrusion as it shrinks after drying.
- Now Extrude the paste in Calcium Chloride solution, as soon as the paste will get in contact with CaCl2 it will get calcified, water and heat resistant.
Material Properties (Alginate Extrusion with egg shell powder):¶
- Flexibility * *
- Elasticity *
- Water Resistance * * *
- Heat Resistance * * *
- Transparency * * * (Depends on the colour)
- Opacity * * *
- Strength *
This extrusion did not come out very well, maybe it was because of Egg shells powder which made it very brittle.
After sampling, I got some insights on how to add fibres and make it more durable. Once I was satisfied with the samples, I started casting them onto bigger moulds and fabricated the material on a medium scale.
Moulds as canvas - One thing I enjoyed the most about this process was casting biomaterial sheets, It gives the freedom of adding colours and see it flowing.
For this particular sheet of biomaterial, I used red cabbage after extracting dye from it, Dried them in dehydrator, crushed them in a mixer and then added it to the biomaterial mix.
Biomaterial casted onto big moulds.
Material Properties (Alginate biomaterials):¶
- Flexibility * *
- Elasticity *
- Water Resistance * * *
- Heat Resistance * * *
- Transparency * * * (Depends on the colour)
- Opacity * * *
- Strength * * (With wool fibres)
Do's and Dont's¶
- Always wipe off extra calcium chloride, before casting and after casting the biomaterial into the mould. Otherwise it will get calcified.
- Wash off biomaterial once it's dry to remove any deposition of calcium chloride, otherwise it will start sweating (releasing oil on the surface) after a point of time.
- Using essential oils will avoid the smell of alginate, specially when you are using cabbage dye (stinks a lot).
- Using tea tree oil in biomaterial mixed with natural dye will not only avoid smell but also prevents moulds in the mix.
- If you are going to leave your biomaterial for a longer period of time always cover it with a cling film to avoid moulding.
- I would suggest not to leave the biomaterial mix for more than 3-4 days, Here I forgot an extra pot of biomaterial for 2 weeks, and I found a thick layer of mould on it.
Ending it on a fluffy note :) (Can we use this kind of molds, which grows super easily even when we don't want it for something new? Just a thought!)