Model-based design of a muscle mass for a biohybrid actuator

Abstract

Among soft actuators, biohybrid actuators constructed by the integration of living tissue and flexible materials, show superior properties of intrinsic softness, environmental compatibility, self-repair function over traditional actuators with rigid body. Skeletal muscles, one of the most frequently used biohybrid actuators, are considered ideal options for driving sources. Research on biohybrid actuators has focused on fabricating actuator entities by tissue-culturing or three-dimensional printing and assembling them. These techniques are well-developed. However, they lack the model-based design approach found in existing actuators that achieve specific performances. A muscle contraction model applicable to skeletal muscle actuators has been developed to model the response of skeletal muscle contraction to external electrical stimuli and has been shown to be reproducible. Therefore, we used this model as a basis to establish the design approach of the biohybrid actuator. The performance requirements for the skeletal muscle actuator depend specifically on the target application and size. As the first step in the design process, we set the muscle mass as a design parameter and the contractile force as a design specification, and then used the model to establish a design method that achieves the required contractile force for a muscle mass. The contractile forces of toad gastrocnemius muscles with different masses were used in the experiments to determine the parameters of the model, specifically those related to muscle mass, thus completing the design model. Subsequently, the muscle mass obtained by targeting the actual contractile force was compared with the actual muscle mass in a verification test, and the results confirmed the feasibility of the designed model. This is the first study that attempts to establish a biohybrid actuator design method, which could lead to significant development in this field.

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