Date Published: January 15, 2020
Author(s): Mohammad Hadi Esteki, Ali Akbar Alemrajabi, Chloe M. Hall, Graham K. Sheridan, Mojtaba Azadi, Emad Moeendarbary.
Image, graphical abstract
Due to their practical applications in biomedicine and bioengineering, substantial efforts have been made to characterize the unique biophysical properties of soft and hydrated materials such as polymers, colloids, amphiphilics, membranes, micelles, emulsions, dendrimers, liquid crystals and polyelectrolytes . The mechanical responses of a wide range of hydrated materials has been found to be both time- and length- scale dependent and this is best described by poroelastic theory , , , , , , , , , , . The one-dimensional theory of the consolidation of a water-saturated geo-material was first developed by Terzaghi and subsequently extended by Biot to introduce the 3D deformation of the elastic porous medium bathed in fluid , , . Despite significant progress in the development of poroelastic theory and advances in computational modeling, the field still lacks an inclusive framework to estimate the poroelastic properties of soft hydrated materials from experimental measurements. Extracting accurate mechanical behavior of soft materials will accelerate biomedical research in fields such as cell and tissue regeneration, drug delivery, hygiene products, and microfluidic technology [1,16].
Here, we proposed and tested a novel framework to extract poroelastic properties via indentation tests. However, there are some limitations associated with both FEM and experimental aspects of our work. In the FEM, the contact between the indenter and the hydrogel was considered to be frictionless and impermeable. In addition, like many other recent works , , , ,34,35,, , ,54], we considered the solid phase to behave like an ideal linear isotropic elastic material under small strain conditions. While these considerations are quite simplistic for many soft and biological materials, our framework could minimally address the effects of ramp speed and determine the poroelastic parameters solely based on ramp phase of force–indentation experiments. Furthermore, application of our framework to experiments requires optimized instrument settings to minimize the inertia effects, sufficiently stiff systems and a load sensor with good resolution to record the maximum overshoot.
We present here a new generalized indentation framework to extract the poroelastic properties of materials from indentation tests using spherical indenters at different indentation approach velocities. Fig. 7 summaries the fit of all experimental micro (Fig. 5) and macro (Fig. 6) tests to the master curve that we obtained from FEM.Fig. 7All micro and macro experiments on agarose (0.6%, 1%) and PAAm hydrogels match the master curve of our suggested framework obtained by FEM. Poroelastic parameters for these gels at different conditions were estimated by comparing Eqs. (3) and 4. Subsequently FM*(τR)and Fempirical*were estimated using the experimental parameters and plotted against normalized rise time.Fig 7
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.