Artificial muscles made from simple fishing lines represent great potential for the development of: robotic limbs, prosthetics, simple but reliable thermos-regulators and smart clothing for example. Since polymeric artificial muscles are still relatively poorly understood, their manufacture and use are currently limited to the field of research only.
In this work, we research this topic using theory and experiments. We present a fabrication process of polymeric artificial muscles, manufacture a number samples and experimentally explore them. We examined the influence of the fabricating parameters and heat treatment on their thermo-mechanical response. We have developed simple predictive mathematical models that describe the contraction of polymer muscles in dependence on temperature and constant axial load and describe the muscle generated force in isometric temperature loading. Thus, in contrast to literature, the behavior of axially loaded muscles is also described. The models are mathematically simple, yet accurate. They are based on the mechanics of the helix, the linear theory of elasticity and the linear temperature expansion of the material. We also experimentally investigate the parameters that influence the polymer muscle hysteresis and investigate how the history of loading affects the contraction of the polymer muscle at an elevated temperature. It turned out that the behavior of muscles strongly depends on the history of muscle loading, preparation, and heat treatment.
The presented analysis of the problem enables us to better understand the problem of the artificial muscle response, identify the influential parameters, and moreover, represents a good basis for the development of even more precise mathematical models in the future.
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