Mechanics of a fiber network within a non-fibrillar matrix: Model and comparison with collagen-agarose co-gels

Spencer P. Lake, Mohammad F. Hadi, Victor K. Lai, Victor H. Barocas

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


While collagen is recognized as the predominant mechanical component of soft connective tissues, the role of the non-fibrillar matrix (NFM) is less well understood. Even model systems, such as the collagen-agarose co-gel, can exhibit complex behavior, making it difficult to identify relative contributions of specific tissue constituents. In the present study, we developed a two-component microscale model of collagen-agarose tissue analogs and used it to elucidate the interaction between collagen and NFM in uniaxial tension. Collagen fibers were represented with Voronoi networks, and the NFM was modeled as a neo-Hookean solid. Model predictions of total normal stress and Poisson's ratio matched experimental observations well (including high Poisson's values of ~3), and the addition of NFM led to composition-dependent decreases in volume change and increases in fiber stretch. Because the NFM was more resistant to volume change than the fiber network, extension of the composite led to pressurization of the NFM. Within a specific range of parameter values (low shear modulus and moderate Poisson's ratio), the magnitude of the reaction force decreased relative to this pressurization component resulting in a negative (compressive) NFM stress in the loading direction, even though the composite tissue was in tension.

Original languageEnglish (US)
Pages (from-to)2111-2121
Number of pages11
JournalAnnals of Biomedical Engineering
Issue number10
StatePublished - Oct 2012

Bibliographical note

Funding Information:
The authors gratefully acknowledge the financial support of the National Institutes of Health (R01-EB005813 and F32-EB012352), the National Science Foundation (GRFP), and the American Heart Association (11PRE5410003).


  • Collagen network
  • Fiber-matrix interactions
  • Microscale model
  • Non-fibrillar matrix
  • Soft tissue


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