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Hortense Le Ferrand, Nanyang Technological University, Singapore

Bio-Inspired Bistable Shape-Changing Displacement Sensors

Written by Aashutosh Mistry

Sensing and actuation are at the heart of every modern-day device. In fact, a suitable combination of these two ascribes “smartness” to otherwise conventional systems. Given the diversity in length scales, even for the same measurand, scaling-up of transducers is an ever-present challenge. For example, microelectromechanical systems (MEMS) provide very fine spatial resolution and localized measurement of displacement. But many applications require sensing over much larger dimensions like aircraft wings. Scaling-out is not a viable option given that it generates an enormously large data stream. An associated problem for such large length-scale sensing is a reasonable amount of flexibility in the transducer.

Hortense Le Ferrand and her co-workers have been exploring an unusual bi-inspired approach to addressing this challenge. Their smart material is a bistable shape-changing composite with a fast response (~200 ms). The material is sensitive to both mechanical and magnetic signals, given its composite nature (made up of the multilevel hierarchical structure of ceramic microplatelets, nickel flakes, and epoxy). Appropriate sequencing of the fabrication pre-stresses the composite, leading to curvature and associated bistability. Stable states correlate to specific electrical conductivity, thus providing appropriate sensing principle. They have successfully fabricated these composites for sensing areas of the order of 100 cm2. Future investigations relate to characterizing thermal and environmental stability as well as tuning of transduction function in terms of materials selection and composite structure.

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