Department of Engineering

An explicit finite element scheme is developed for living biological muscular hydrostats such as squid tentacles, octopus arms and elephant trunks. The mechanical stress in each muscle fiber is assumed to be the sum of an active part and a passive part. The active muscle stress is taken as a function of activation state, muscle fiber shortening velocity and fiber strain; while the passive muscle stress depends only on the strain. The detailed three-dimensional musculature of any living organs can be accurately represented through finite element discretization. Numerical calculations show that present finite element scheme can successfully simulate extension and torsion of a squid tentacle, and the bending behavior of octopus arms or elephant trunks. For the extension of a squid tentacle, our numerical results are in excellent agreement with existing experimental results. The technique developed here is suitable for modeling the response of soft robotic systems actuated by compliant, electroactive polymers. The methodology is also extended to the simulation of biological cells, where the active deformations occur due to the effects of actin molecules and biological motors and the passive behavior represents the influence of the cytoskeleton and the cell membrane.

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