Auxetic systems fabricated using mycelia-based composites

Abstract

In an era of increasingly problematic global waste management, innovative materials can hold the key to a circular economy. Within such a context, this work aimed at manufacturing, potentially for the first time, auxetic material (i.e., materials with a negative Poisson鈥檚 ratio) using mycelia-based composites (i.e., materials made by growing fungi on a biodegradable substrate). The fabrication of the auxetic biomaterials was undertaken using both direct growth methods in purposely designed molds and through subtractive manufacturing of commercially available mycelia panels. In the former case, various substrates were employed, differing in sawdust granulation and nutrient content. Furthermore, enhancements in the form of scaffolds and hay were considered with the aim of improving the cohesion and elastic properties of the end product. Mechanical testing of the samples produced showed that both manufacturing methods can produce structures capable of exhibiting a negative Poisson鈥檚 ratio. At the same time, the intrinsic brittle nature of mycelia-based composites limits the compactness and cohesion of the end products. In this context, the different methodologies employed to improve these properties yielded some promising results. Thus, while this work showed that indeed auxetic biomaterials can be fabricated, the manufacturing methods still require further improvement to produce better-performing specimens.