Remoras of the ray-finned fish family Echeneidae have the remarkable ability to attach to diverse marine animals using a highly modified dorsal fin that forms an adhesive disc, which enables hitchhiking on fast-swimming hosts despite high magnitudes of fluid shear. We present the design of a biologically analogous, multimaterial biomimetic remora disc based on detailed morphological and kinematic investigations of the slender sharksucker (Echeneis naucrates). We used multimaterial three-dimensional printing techniques to fabricate the main disc structure whose stiffness spans three orders of magnitude. To incorporate structures that mimic the functionality of the remora lamellae, we fabricated carbon fiber spinules (270 μm base diameter) using laser machining techniques and attached them to soft actuator–controlled lamellae. Our biomimetic prototype can attach to different surfaces and generate considerable pull-off force—up to 340 times the weight of the disc prototype. The rigid spinules and soft material overlaying the lamellae engage with the surface when rotated, just like the discs of live remoras. The biomimetic kinematics result in significantly enhanced frictional forces across the disc on substrates of different roughness. Using our prototype, we have designed an underwater robot capable of strong adhesion and hitchhiking on a variety of surfaces (including smooth, rough, and compliant surfaces, as well as shark skin). Our results demonstrate that there is promise for the development of high-performance bioinspired robotic systems that may be used in a number of applications based on an understanding of the adhesive mechanisms used by remoras.

Significance: Condensing water droplets can be self-removed from the legs of water striders in a three-step mechanism. First, droplets migrate inside the texture and grow. Then, drops are suddenly expelled out of the hairs, owing to the elastic deformation of the network of setae by growing drops. Ultimately, condensed drops are expelled from the leg. Self-removal of condensing water prevents a major source of risk for the creature, whose hydrophobicity would reverse if setae were impregnated by water. The design of the legs therefore provides a remarkable example where the conjunction of hydrophobicity, geometry, and flexibility yields water repellency both at large and very small scales.