Recently a novel type of epithelial cell has been discovered and dubbed the "scutoid". It is induced by curvature of the bounding surfaces. We show by simulations and experiments that such cells are to be found in a dry foam subjected to this boundary condition.

We describe a novel method for the production of lightweight fibrous structures of densities as low as 8.8 kg.m −3. The method is based on the use of liquid foam as a carrier medium for dispersed Kraft fibres. Different to the process of foam forming, where the quick removal of the foam results in the formation of thin fibrous sheets, our samples are allowed to slowly drain and dry until all foam has disappeared. This procedure results in bulk samples whose height (up to 25 mm) and density are controlled by initial fibre concentration and liquid fraction of the foam. Above a minimum density, the compression modulus of elasticity of the samples increases linearly with density. Furthermore, we show compressive strength of the structures being controlled via the initial liquid fraction of the foam, making this an important process parameter for the fabrication of such structures.

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Foam-forming has in the past predominantly been used to create two-dimensional sheet-like fibrous materials. Allowing the foam to drain freely and decay under gravity, rather than applying a vacuum to remove it rapidly, we can produce lightweight three-dimensional fibrous structures from cellulose fibres, of potential use for thermal and acoustic insulation. $$\mu$$ μ CT scanning of the fibrous materials enable us to determine both void size distributions and also distributions of fibre orientations. Through image analysis and uniaxial compression testing, we find that the orientation of the fibres, rather than the size of the voids, determine the compressive strength of the material. The fibrous samples display a layering of the fibres perpendicular to the direction of drainage of the precursor liquid foam. This leads to an anisotropy of the compressive behaviour of the samples. Varying the initial liquid fraction of the foam allows for tuning of the compressive strength. We show an increase in over seven times can be achieved for samples of the same density (13 kg.m-3). Graphic abstract