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Mechanical characterization of the ex vivo tricuspid valve (TV) continues to provide key insights into native valve function and the development of valvular diseases. However, experimental methods to characterize TV biomechanical behavior ex vivo often fail to account for potential changes in the tissue’s mechanical responses that may occur during experiment preparation. Therefore, we assessed the mechanical responses of the anterior tricuspid leaflet (ATL) via biaxial mechanical testing over the course of 5 h to validate the accuracy of our fresh tissue experiments. We hypothesized that ATL mechanical responses would remain consistent for the proposed time scale. We found that ATL stiffness, represented by the upper tangent modulus (UTM), did not significantly change in either the radial or circumferential directions for the 5-h test period. Similarly, no significant change was observed in radial or circumferential strains corresponding to an estimated mean systolic stress value of 85 kPa. Overall mean UTM (±standard error of the mean (SEM)) showed that ATL samples were significantly stiffer in the circumferential direction (11.3 ± 0.98 MPa) compared to the radial direction (2.29 ± 0.20 MPa) across all time points. Thus, our results indicate that the outcomes of ex vivo tricuspid valve studies requiring sample preparation up to 5 h remain reliable. 

Nonsolvent induced phase separation (NIPS) is a widely occuring process used in industrial membrane production, nanotechnology and Nature to produce microstructured polymer materials. A variety of process-dependent morphologies are produced when a polymer solution is exposed to a nonsolvent that, following a period where mass is exchanged, precipitates and solidifies the polymer. Despite years of investigation, both experimental and theoretical, many questions surround the pathways to the microstructures that NIPS can produce. Here, we provide simulation results from a model that simultaneously captures both the processess of solvent/nonsolvent exchange and phase separation. We show that the time it takes the nonsolvent to diffuse to the bottom of the film is an important timescale, and that phase separation is possible at times both much smaller and much larger than this scale. Our results include both one-dimensional simulations of the mass transfer kinetics and two- and three-dimensional simulations of morphologies at both short and long times. We find good qualitative agreement with experimental heuristics, but we conclude that an additional model for the vitrification process will be key for fully explaining experimental observations of microstructure formation.