Fin Ray Effect

Year

2006

The idea

The gripping principle is based on the natural capabilities of the fish’s fin; it demonstrates adaptation.

The objective

The Fin Ray effect serves as a technical principle in bionics projects and products.

Technical data

• Configuration: 2 flexible bands form an elongated triangle
• Structure: Lateral struts are connected to the bands at joints

Operating principle

If you press your finger against a fish’s fin, it will bend around it – a reaction that is contrary to our everyday experience. Objects and body parts normally give way as soon as pressure is applied to them: they buckle or move away. This principle of the fish’s fin effect allows fish to move efficiently through water and can be used for tasks involving gripping in industry.

Structure

A fish’s fin consists of individual fin rays, which in turn comprise two narrow bands that converge at their tips. The elastic connective tissue between them ensures the necessary stability. This structure enables the fin rays to be moved against each other.

Active fish’s fin effect

When pressure is applied from the side, the tail fin forms a kind of scoop that encloses a small volume of water. When it moves from side to side, the water is accelerated to the rear – fish use this deformation of their fins for efficient forward motion.

Passive fish’s fin effect

In technology, the passive Fin Ray effect is normally used. The lateral struts located at regular intervals between the bands keep them apart, and the bands’ flexibility allows the struts to move relative to each other. If a lateral force is exerted on the fin ray structure, it automatically bends around the point where the pressure is applied.

Realisation

The so-called FinGripper was created using fin ray structures that act as gripping fingers. The gripper is able to assume the contours of a specific object to be picked up. This adaptive gripping tool is part of the product range of Festo. The Fin Ray effect can also be found in bionics projects such as the NanoForceGripper, the AquaJelly or the AquaPenguin.