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The ear canal is usually described as an S-shaped funnel. In attempting to classify ear-canal shapes obtained from point clouds digitized from molds of 300 ears, the problem of designing criteria for distinguishing and organizing the canal shapes arose. In this work, we extracted features inspired by the S-shape characteristic (critical point, maximum, minimum, twist, writhe, translation, rotation) and, through them, introduced 14 types of ear-canal shapes. This classification allowed comparison of ears within a type and of ears between different types. It expanded our range of descriptors of canal shapes and unlocked perspectives for applications., (© 2023. The Author(s).)

Bioinspired manufacturing, in the sense of replicating the way nature fabricates, may hold great potential for supporting a socioeconomic transformation towards a sustainable society. Use of unmodified ubiquitous biological components suggests for a fundamentally sustainable manufacturing paradigm where materials are produced, transformed into products and degraded in closed regional systems with limited requirements for transport. However, adoption is currently limited by the fact that despite their ubiquitous nature, these biopolymers are predominantly harvested as industrial and agricultural products. In this study, we overcome this limitation by developing a link between bioinspired manufacturing and urban waste bioconversion. This result is paramount for the development of circular economic models, effectively connecting the organic by-products of civilization to locally decentralized, general-purpose manufacturing.

Cellulose is the most abundant and broadly distributed organic compound and industrial by-product on Earth. However, despite decades of extensive research, the bottom-up use of cellulose to fabricate 3D objects is still plagued with problems that restrict its practical applications: derivatives with vast polluting effects, use in combination with plastics, lack of scalability and high production cost. Here we demonstrate the general use of cellulose to manufacture large 3D objects. Our approach diverges from the common association of cellulose with green plants and it is inspired by the wall of the fungus-like oomycetes, which is reproduced introducing small amounts of chitin between cellulose fibers. The resulting fungal-like adhesive material(s) (FLAM) are strong, lightweight and inexpensive, and can be molded or processed using woodworking techniques. We believe this first large-scale additive manufacture with ubiquitous biological polymers will be the catalyst for the transition to environmentally benign and circular manufacturing models.