Heterogeneity and length scale effects in PEG-based hydrogels
Brian G. Bush, Jenna M. Shapiro, Frank W. DelRio, Robert F. Cook, Michelle L. Oyen
Colloidal-probe spherical indentation load-relaxation experiments are conducted on poly(ethylene glycol) (PEG) hydrogel materials to quantify the steady-state mechanical properties and time-dependent transport properties in a single experiment. A probe radius of 3 µm was chosen to ensure experiments were conducted at biologically relevant length scales. PEG-based hydrogels are shown to be heterogeneous in both morphology and mechanical stiffness at this scale; a linear-harmonic interpolation of hyperelastic Mooney-Rivlin and Boussinesq flat-punch indentation models was used to describe the steady state response of the hydrogels and determine upper and lower bounds for indentation moduli. Analysis of the transient load-relaxation response during displacement-controlled hold period provides a means of extracting viscoelastic, τ1, and poroelastic, τ2, time constants. Approximate pore sizes on the order of 1 nm to 5 nm are calculated from τ2. In addition, outliers in the distribution of τ2 values at small indentation loads provide evidence of a near-equilibrium state characterized by a jamming phenomenon that restricts poroelastic fluid flow through the material. These results have important implications in the use of PEG-based hydrogels for bioengineering applications.
, Shapiro, J.
, DelRio, F.
, Cook, R.
and Oyen, M.
Heterogeneity and length scale effects in PEG-based hydrogels, Soft Matter, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917666
(Accessed October 17, 2021)