Heterogeneity and length scale effects in PEG-based hydrogels

Published

August 10, 2015

Author(s)

Brian G. Bush, Jenna M. Shapiro, Frank W. DelRio, Robert F. Cook, Michelle L. Oyen

Abstract

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.

Citation

Soft Matter

Volume

11

Pub Type

Journals

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Keywords

Hydrogels, PEG, Viscoelasticity, Poroelasticity, time-dependent materials, contact mechanics

Citation

Bush, B. , Shapiro, J. , DelRio, F. , Cook, R. and Oyen, M. (2015), 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 11, 2025)