An analysis of the complete strain field within FlexercellTM membranes

The purpose of the current investigation was to use finite element analysis to quantify the complete strain field for the membranes of the FlexercellTM apparatus, a device extensively used to study the effects of mechanical loading on cultured cells. Four vacuum pressure simulations were run for the membrane for both the uniaxial and biaxial loading post, yielding the distribution of longitudinal (Exx) and transverse (Eyy) strain for the uniaxial post, and the radial (Err) and the circumferential (Eθθ) strain for the biaxial post. The discrete values of each strain were evaluated at the center of the loading post as well as the region off of the post. Experimental measurements were made for both types of loading posts in order to validate our simulations. The biaxial post simulation was found to provide a central circular region of equal and constant Err and Eθθ in the membrane on the post. Likewise, the uniaxial post simulation provided a definitive region of constant Exx for a central rectangular region on the post. For the uniaxial simulation, the region on the post resulted in small compressive Eyy, while the region off the post resulted in tensile Eyy. The biaxial simulation resulted in large tensile Err and Eθθ on the post, while the region off the post resulted in large Err and smaller Eθθ. Our simulations were reasonably consistent with the experimental measurements made for both types of loading posts. We believe that the results of this study will allow scientists to more accurately describe the response of cells to known strains on all portions of the membrane, thus increasing the range of known strain regions for investigation in the FlexercellTM apparatus.