Mycelium Composites
Mold Making:
For the purpose of designers, mycelium is best thought of as a casted composite. This means that it is grown in a mold that shapes the part. The mycelium expands to the limits of the mold and then is de-molded to reveal the final part. Applying what we have learned from farming techniques, this mold is ideally a plastic or other non-porous material. All of the basic concepts of molding is applicable here. There shouldn’t be any overdrafts, and the mold should be split into parts to allow for proper release.
For designer’s this allows for the embedding of other processes to create forms for mycelium. Ecovative Design has mastered the use of vacuumed-formed plastic molds to create mycelium packaging. 3D printing with PLA or PETG is also extremely common for creating these molds. There have also been successes with silicone molds and wooden molds covered with plastic sheets.
When building these molds, air-exchange is a crucial concept. While the molds should hold a form and keep out contaminants, there must be space for CO2 and heat to escape. We recommend that the mold have open spaces or perforations to allow air-exchange. In our lab, we keep our molds with perforations inside of plastic bags to ensure safety from contamination. For larger parts, we often cut slits into these bags and reseal them with micropore tape.
Ecovative’s process for mycelium packaging
As an extension of this technique, our lab experimented with embedded molds, where the material of the mold was accepting of mycelium growth and eventually becomes a part of the colony. Through perforating paper products and PLA with wood impurities, we developed techniques for the mycelium to eat through the mold. By creating edible molds, the mycelium can adopt the characteristics of the mold, such as rigidity and structure. This also eases the process by eliminating de-molding, allow for overdraft and single part molds.
In this example, Woodfill PLA was printed with perforations to allow air exchange and encourage the mycelium to grow outside of the mold walls. This exterior growth mechanically binds the PLA to the mycelium growing inside and creates a single part.
In this case study with Jasper Cohen, laser cut cardboard parts were assembled into a stool and then packed with mycelium. Grown inside a garbage bag, the mycelium eventually “swallowed” the cardboard, creating a much denser and more rigid stool.
Other Techniques:
Molding is not the only way to grow mycelium. With access to higher grade equipment, mycelium can be grown on liquids to create a layer of pure mycelium. This is often used in the development of mycelium textiles. While we have been unable to reverse engineer the technique, mycelium is often grown into a uniform foam which can be compressed into a “leather”.
Another interesting fringe technique is to embed wooden parts into the final object. As we learned earlier, mycelium eats lignin-cellulose which is abundant in wood. This project by Ecovative Design exemplifies how a wooden part could be included in a mycelium structure to allow for screws and other connection methods. Below is an example of embedded wooden frames by Sebastian Cox.
Finally, we would like to call attention to the technique of splicing. Mycelium parts are capable of being cut and then growing together into an assembly. Following the growing of parts, they can be assembled into the final object. These individual parts will interlock mycelium networks, stitching themselves into one assembly.
