Novel concept inspired by campaniform sensilla for the design of strain sensors used in space applications

This paper presents a bio-inspired approach for the design of strain sensors embedded in space structures. Campaniform sensilla, which are natural strain sensors, are used by insects for monitoring deformations of their bodies. The strategy used in nature is to locally amplify, through arrays of elliptical micro-holes, mechanical deformations. The authors focused their research on campaniform sensilla because of their simplicity and straightforward theoretical implementation in engineering systems. In this paper, the biological concept is presented and a structural analysis of an isotropic model, which was performed to understand underlying principles, is presented and discussed. Space applications, in which novel bio-inspired strain sensors could successfully be used, are investigated. 1 UINTRODUCTION Campaniform sensilla, responding to mechanical strain, are found in the external skeleton (cuticle) of insects and are able to sense displacements of the order of 1 nm. The campaniform sensillum is basically a hole extending through the cuticle, arranged such that its shape changes in response to specific loads. The shape change is rotated through 90° by the suspension of a bell-shaped cap whose deflection is detected by a cell attached to the inner layer of the cuticle. When the sensor is strained, a train of impulses is propagated to the central nerve system. Insects such as cockroaches and flies can thus use the sensilla to sense strain deformations and to determine both internal loads such as muscle forces and body weight, and external loads such as aerolastic forces on the wings in flight. Embedded strain sensors are of interest for many space applications, especially when slender structures are used (solar panels, booms, solar sails etc.) or structural frames must be monitored during hazardous mission phases such as during launch and landing. Strain sensors can also be used as force sensors, especially when they are embedded in cantilevers. Therefore, they are suitable for use in several systems and