Marine biofilm formation on flax fibre reinforced biocomposites.

Artificial reefs represent useful tools to revitalize coastal and ocean ecosystems. Their formulation determines the biofilm formation which is the prerequisite for the colonization process by marine micro- and macroorganisms. In comparison with concrete, biobased polymers offer improved characteristics, including architecture, formulation, rugosity and recycling. This article aims to explore a new scale of artificial reef made of biocomposites reinforced with a high flax fibre (Linum utilatissimum) content (30%). Cellular adhesion and resulting biofilm formation were assessed using two marine microorganisms: Pseudoalteromonas sp. 3J6 and Cylindrotheca closterium. The influence of flax fibre leachates and plastic monomers on the growth of those marine microorganisms were also evaluated. Results indicated that the introduction of flax fibres inside the polymer matrix modified its physicochemical properties thus modulating adhesion and biofilm formation depending on the microorganism. This study gives insights for further developments of novel functionalized artificial reefs made of biocomposites.

Biobased and Programmable Electroadhesive Metasurfaces.

Electroadhesion has shown the potential to deliver versatile handling devices because of its simplicity of actuation and rapid response. Current electroadhesion systems have, however, significant difficulties in adapting to external objects with complex shapes. Here, a novel concept of metasurface is proposed by combining the use of natural fibers (flax) and shape memory epoxy polymers in a hygromorphic and thermally actuated composite (HyTemC). The biobased material composite can be used to manipulate adhesive surfaces with high precision and controlled environmental actuation. The HyTemC concept is preprogrammed to store controllable moisture and autonomous desorption when exposed to the operational environment, and can reach predesigned bending curvatures up to 31.9 m-1 for concave and 29.6 m-1 for convex shapes. The actuated adhesive surface shapes are generated via the architected metasurface structure, incorporating an electroadhesive component integrated with the programmable biobased materials. This biobased metasurface stimulated by the external environment provides a large taxonomy of shapes─from flat, circular, single/double concave, and wavy, to piecewise, polynomial, trigonometric, and airfoil configurations. The objects handled by the biobased metasurface can be fragile because of the high conformal matching between contacting surfaces and the absence of compressive adhesion. These natural fiber-based and environmentally friendly electroadhesive metasurfaces can significantly improve the design of programmable object handling technologies, and also provide a sustainable route to lower the carbon and emission footprint of smart structures and robotics.