A robust spider-silk-like calcium alginate fiber with biomineralized rough spindle-knots for water collection

The hydrophilic spindle-knot microfiber serves as a valuable tool for water collection to combat freshwater scarcity. However, balancing microfiber's water collection efficiency and reusability remains a challenge. To address this contradiction, a microfluidic approach utilizing enzyme-mediated, in situ biomineralization is developed to produce biomineralized rough spindle-knot calcium alginate microfibers (BSMs). Specifically, by strategically organizing enzymes within the microfiber, biomineralization occurs mostly at the knot, forming CaCO₃ particles that create a roughness contrast between the knot and joints, thereby increasing water collection efficiency. The CaCO₃ particles, grown from enzyme-mediated reactions, are firmly anchored inside the fiber, ensuring its reusability. As a result, the BSMs exhibit a water collection efficiency rate of 6.1 g·h^-1·cm^-1, which is significantly higher than that of current microfibers. Moreover, the firmly anchored CaCO₃ can also supplement the calcium ions lost during fibers utilization, increasing the BSMs' reusability up to 108 times. Consequently, this strategy offers a novel and scalable platform for highly efficient water collection and the ability of 3D printing biomaterials with elaborate structures.