Nature makes extensive use of soft materials characterized by contractility and multi-level structural organization to achieve different functionalities. The mimosa folds its leaves when touched; the jellyfish propels itself by constricting and expanding its bell. Recently, contractile bio-hybrid materials have been built in the Disease Biophysics group led by Prof. Kevin K. Parker by growing a monolayer of spatially aligned cardiac myocytes on synthetic elastomeric thin films. When the hybrid film is released into solution and electrically stimulated it causes the myocytes to contract, forcing the construct into adopting a 3-D conformation. The ability to synthetically produce contractile bio-hybrid structures has created new opportunities to mimic natural configurations and properties.
The development of such muscular thin films for building actuators and powering devices requires exploring several design parameters, which include the alignment of the cardiac myocytes, the thickness and Young's modulus of elastomeric film. Moreover, while the deformation of unconstrained thin films due to the introduction of pre-stretch during myogenesis and tissue development has to be taken into account, very little research has been reported on this issue. To help exploring these design parameters, we propose a 3D constitutive model which accounts both for the pre-stretch induced deformation and the active and the passive behavior of the cardiomyocytes. The proposed 3D constitutive model is implemented within a finite element framework, and can be used to improve the current design of bio-hybrid thin films and help developing bio-hybrid constructs capable of complex conformational changes.
Contractile behavior of muscular thin films with diagonal cell alignment from FE simulations. (A) Snapshots of FE simulation with strongest cell conditions, (B) Snapshots of FE simulation with weakest cell conditions. (C) Comparison of experimental and numerical time-curvature plots. The green shaded region corresponds to the area bounded by simulations with the two extreme cell conditions considered here.
- J. Shim, A. Grosberg, J.C. Nawroth, K.K. Parker and K. Bertoldi. Modeling of cardiac muscle thin films: Pre-stretch, passive and active behavior. Journal of Biomechanics, 45: 832-841, 2012.