Towards Mathematical Modeling of Tissue-Engineered Skeletal Muscle Considering Contraction-Induced Stiffness Changes*

Recently, bio-hybrid devices using muscle tissue or muscle cells as a drive source have been actively studied. Although there have been many reports on the development of bioactuators, most of them are concerned with muscle tissue culture and assembly methods, and very few studies have been conducted from the control engineering perspective of tissue-engineered muscle actuators. It is known that the stiffness of muscle changes between relaxation and excitation, and in particular, empirically, tissue-engineered muscle is immature compared to biological muscle, so the change in stiffness during contraction is relatively very large. Therefore, we will first evaluate the change in stiffness of cultured muscle during relaxation and contraction by a push test and confirm that the stiffness increases significantly with TESM. In addition, it is difficult to represent this large change in stiffness using the conventional Hill’s four-element model. Therefore, this study proposes a model of TESM in which two active elements that are involved only during contraction are added to Hill’s four-element model. The force equations for these isometric tests are derived. As a next step, we plan to experimentally identify the parameters to confirm the validity of this model.