title: Microstructural mechanics of collagen gels in confined compression: poroelasticity, viscoelasticity, and collapse.
abstract: BACKGROUND
  Collagen gels are important as platforms for in vitro study of cell behavior and as prototypical bioartificial tissues, but their mechanical behavior, particularly on the microscopic scale, is still poorly understood.
  
  
  METHODS
  Collagen gels were studied in step (10% strain in 0.05 s) and ramp (0.1%/s strain rate for 100 s) confined compression. Real-time birefringence mapping gave the local collagen concentration and orientation along with piston stress. Variations in the retardation allowed material-point tracking and qualitative determination of the strain distribution.
  
  
  RESULTS
  Ramp tests showed classical poroelastic behavior: compression near the piston and relaxation to a uniform state. Step tests, however, showed an irreversibly collapsed region near the piston.
  
  
  CONCLUSIONS
  Our results suggest that interstitial flow and fibril bending at crosslinks are the dominant mechanical processes during compression, and that fibril bending is reversible before collapse.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, 312 Church St SE, Minneapolis, MN 55455, USA.
authors.forename: Preethi L
authors.initials: PL
authors.lastname: Chandran
authors.forename: Victor H
authors.initials: VH
authors.lastname: Barocas
mesh_terms: D000818:Animals; D016880:Anisotropy; D001696:Biomechanical Phenomena / Q000379:methods; D001718:Birefringence; D002417:Cattle; D003094:Collagen / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure*; D019245:Compressive Strength; D004548:Elasticity; D005782:Gels / Q000737:chemistry; D016062:Porosity; D013314:Stress, Mechanical; D014783:Viscosity; D016474:Weight-Bearing
chemical_list: D005782:Gels; D003094:Collagen