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Mycelium- Based Composites
Mycelium composites are products that uses mycelium, a vegetative part of a fungi. Fungus depends on mycelium to get nutrients from the environment. There are several uses of mycelium composites in the industry because it is economically and environmentally sustainable. There are several ways to fabricate and synthesize mycelium composites which can alter the properties to produce different types of materials for different types of uses.

Synthesis and Fabrication:
Mycelium- Based Composites are usually synthesized by using different kinds of fungus, especially mushroom. An individual microbe of fungi is introduced to different types of organic substances to form a composite. The selection of fungal species is important for creating a product with specific properties. Some of the fungal species that are used to make composites are ''G. lucidum, Ganoderma sp. P. ostretus, Pleurotus sp., T. versicolor, Trametes sp''., etc. A dense network is formed when the mycelium of the microbe of fungi degrades and colonizes the organic substance. Plant waste is a common organic substrate that is used in mycelium based composites. Fungal mycelium is incubated with a plants waste product to produce sustainable alternatives mostly for petroleum based materials. The mycelium and organic substrate needed to incubate properly and this time is crucial as it is the period that these particles interact together and bind into one to form a dense network and hence form a composite. During this incubation period, mycelium uses the essential nutrients such as carbon, minerals, and water from the waste plant product. Some of the organic substrate components include cotton, wheat grain, rice husk, sorghum fiber, agricultural waste, sawdust, bread particles, banana peel, coffee residue, etc. The composites are synthesized and fabricated using different techniques such as adding carbohydrates, altering fermentation conditions, using different fabrication technology, altering post- processing stages, and modifying genetics or biochemicals to form products with certain properties. Fabrication of most of the mycelium composites are by using plastic molds, so the mycelium can be grown directly into the desired shape. Other fabrication methods include laminate skin mold, vacuum skin mold, glass mold, plywood mold, wooden mold, petri dish mold, tile mold, etc. During fabrication process, it is essential to have sterilized environment, a controlled environment condition of light, temperature (25-35°C) and humidity around 60-65% for the best results. One way to synthesize a mycelium based composite is by mixing different composition ratio of fibers, water and mycelium together and putting in a PVC molds in layers while compressing each layer and letting it incubate for couple of days. Mycelium based composites can be processed in foam, laminate and mycelium sheet by using processing techniques such as laster cutting, cold and heat compression, etc.. Mycelium composites tend to absorb water when they are newly fabricated, therefore this property can be changed by oven drying the product.

Properties:
One of the advantages about using mycelium based composites is that properties can be altered depending on fabrication process and the use of different fungus. Properties depend on type of fungus used and where they are grown. Additionally, fungi has an ability to degrade the cellulose component of the plant to make composites in a preferable manner. Some important mechanical properties such as compressive strength, morphology, tensile strength, hydrophobicity, and flexural strength can be modified as well for different use of the composite. To increase the tensile strength, the composite can go through heat pressing. A mycelium composite made out of 75 wt% rice hulls have density of 193 kg/m3, while 75 wt% wheat grains has 359 kg/m3, which shows how different mycelium substance has effect on its property. One the methods to increase the density of the composite would be by deleting a hydrophobin gene. These composites also have the ability of self fusion which increases their strength. Mycelium based composites are usually compact, porous, lightweight and a good insulator. The main property of these composites is that they are entirely natural, therefore sustainable. Other advantage of mycelium based composites is that this substance acts as an insulator, is fireproof, nontoxic, water resistance, rapidly growing, and has an ability to bond with neighboring mycelium products. Mycelium based foams (MBFs) and sandwich components are two common type of the composites. MBFs are the most efficient type because of their low density property, high quality, and sustainability. The density of MBFs can be decreased by using substrates that are smaller than 2mm in diameter. These composites have higher thermal conductivity as well.

Uses:
One of the most common use of mycelium based composites is for the alternatives for petroleum and polystyrene based materials. These synthetic foams are usually used for sustainable design and architecture products. The use of mycelium based composites are based on their properties. There are several bio-sustainable companies such as Ecovative Design LLC, MycoWorks, MyCoPlast, etc. that use mycelium based composites that make protective packaging for electronics and food, bricks, leather substitutes, alternatives for floors and acoustic tiles, thermal and acoustic insulation, construction panels, etc. The property of being able to bond with neighboring composite helps the mycelium based composite to form strong bonds for a brick which are widely used. There is a 40 foot tall tower in MoMa PS1 at New York City, Hy-Fi made using 1000 bricks made from corn stalks and mycelium. This product won the annual Young Architects Program (YAP) contest in 2014. There are also other several commonly used products such as lamps, kitchen utensils, ceiling panels, decorative items, fashion items, chair, etc made out of mycelium. In architecture, mycelium based composites are widely used because they have better insulation performance and fire resistance than currently used products. Mycelium is being used more in industry to replace common plastic materials that are harming the environment. These products are manufactured using low energy, natural manufacturing process and are biodegradable.