Modelling of a Bio-inspired Bistable Structure for Potential Application in Fish Telemetry Tags

Monitoring of aquatic life is important for assessing long-term impacts on activities associated with fish stock and migration. One promising approach for long-term monitoring involves the development of self-powered telemetry devices capable of powering themselves by harnessing energy from the fish body undulations using implanted devices or from fluid motions generated by fish swimming using external devices. One of the latter devices is a broadband low frequency nonlinear bistable energy harvester. This cost-effective harvester has been inspired from the doubly curved leaf blades of a Venus-fly trap. This work ex- amines the static behavior of such a bio-inspired bistable energy harvester by analyzing its force-displacement characteristics. The objective is to identify crucial design parameters to optimize the harvester's performance for potential application in self-powered fish telemetry tags. The unique characteristics of the hysteresis loop and snap-through discontinuity of the bistable structure are investigated using experimentation and finite element analysis. The finite element model is found to qualitatively replicate experimental observations. Addition- ally, geometrical and assembly parameters that affect the force-displacement behavior of the harvester are identified. A sensitivity analysis is performed to determine the effect of the aspect ratio, buckling displacement and thickness of the proposed harvester on the static force-displacement curve. The sensitivity analysis has highlighted that the assembly and geometric parameters of the bistable structure affect multiple aspects of the force-displacement behavior simultaneously. Hence, analytical modeling has been attempted using the theory of lateral torsional buckling to further investigate the complex influence of the said parameters.