@article{afc6583ceb074508a862b78428e2013d,
title = "Cell traction forces on soft biomaterials. I. Microrheology of Type I collagen gels",
abstract = "A laser-trap microrheometry technique was used to determine the local shear moduli of Type I collagen gels. Embedded 2.1 μm polystyrene latex particles were displaced 10-100 nm using a near-infrared laser trap with a trap constant of 0.0001 N/m. The trap was oscillated transversely ±200 nm using a refractive glass plate mounted on a galvanometric scanner. The displacement of the microspheres was in phase with the movement of the laser trap at frequencies less than 1 rad/s, indicating that at least locally, the gels behaved as elastic media. The local shear modulus was measured at various positions throughout the gel, and, for gels at 2.3 mg/mL and 37°C, values ranged from G = 3 to 80 Pa. The average shear modulus G = 55 Pa, which compares well with measurements from parallel plate rheometry.",
author = "Darrell Velegol and Frederick Lanni",
note = "Funding Information: A laser-trap microrheometry technique was used to measure local mechanical properties in Type I collagen gels. The method can measure a frequency range of 0.06 to ∼60 rad/s, and can measure heterogeneity and anisotropy in the mechanical properties. In the experiments reported here, it was shown that collagen gels (0.5–2.3 mg/mL) at 22°C and 37°C have shear moduli that vary from position to position. Although we have not yet determined the length scale of this variation, the variation is large (e.g., for 2.3-mg/mL collagen gels, the local shear modulus varies from 2 to 90 Pa). Future experiments will be more involved, fully enabling the capability to measure anisotropic properties along multiple axes. We thank G. Steven Vanni and Joseph Sukan for the scanning electron micrograph image in Fig. 1 , Lynn Walker for her assistance and advice in doing the parallel-plate rheometry, and David Pane for his help in developing the Automated Interactive Microscope required to synchronize the galvanometric scanner and image acquisition. We also thank the National Science Foundation for funding through grant #MCB-8920118. ",
year = "2001",
doi = "10.1016/S0006-3495(01)75829-8",
language = "English (US)",
volume = "81",
pages = "1786--1792",
journal = "Biophysical journal",
issn = "0006-3495",
publisher = "Elsevier B.V.",
number = "3",
}