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Nat Methods. 2010 Aug;7(8):650-4. doi: 10.1038/nmeth.1474. Epub 2010 Jun 20.

Noncontact microrheology at acoustic frequencies using frequency-modulated atomic force microscopy.

Author information

1
Auditory Mechanics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, USA.

Abstract

We report an atomic force microscopy (AFM) method for assessing elastic and viscous properties of soft samples at acoustic frequencies under non-contact conditions. The method can be used to measure material properties via frequency modulation and is based on hydrodynamics theory of thin gaps we developed here. A cantilever with an attached microsphere is forced to oscillate tens of nanometers above a sample. The elastic modulus and viscosity of the sample are estimated by measuring the frequency-dependence of the phase lag between the oscillating microsphere and the driving piezo at various heights above the sample. This method features an effective area of pyramidal tips used in contact AFM but with only piconewton applied forces. Using this method, we analyzed polyacrylamide gels of different stiffness and assessed graded mechanical properties of guinea pig tectorial membrane. The technique enables the study of microrheology of biological tissues that produce or detect sound.

PMID:
20562866
PMCID:
PMC3508509
DOI:
10.1038/nmeth.1474
[Indexed for MEDLINE]
Free PMC Article

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