Water-driven actuation of Ornithoctonus huwena spider silk fibers

Spider silk possesses remarkable mechanical properties and can lift weight effectively. Certain kinds of spider silk have unique response to liquid, especially water, because of their hydrophilic proteins, β-sheet characters, and surface structure. The Ornithoctonus huwena (O. huwena) spider is a unique species because it can be bred artificially and it spins silk whose diameter is in nanometer scale. In this work, we report the “shrink-stretch” behavior of the O. huwena spider silk fibers and show how they can be actuated by water to lift weight over long distance, at a fast speed, and with high efficiency. We further rationalize this behavior by analyzing the mechanical energy of the system. The lifting process is energy-efficient and environmentally friendly, allowing applications in actuators, biomimetic muscles, or hoisting devices.