Journal of Microelectromechanical Systems
Ping Du; Chen Cheng; Hongbing Lu; Xin Zhang
Volume: 22, Issue: 1, Page(s): 44 - 53
DOI: 10.1109/JMEMS.2012.2213070
Polydimethylsiloxane (PDMS) micropillar-based biotransducers are
extensively used in cellular force measurements. The accuracy of these
devices relies on the appropriate material characterization of PDMS and
modeling to convert the micropillar deformations into the corresponding
forces. Cellular contraction is often accompanied by oscillatory motion,
the frequency of which ranges in several hertz. In this paper, we
developed a methodology to calculate the cellular contraction forces in
the frequency domain with improved accuracy. The contraction data were
first expressed as a Fourier series. Subsequently, we measured the
complex modulus of PDMS using a dynamic nanoindentation technique. An
improved method for the measurement of complex modulus was developed
with the use of a flat punch indenter. The instrument dynamics was
characterized, and the full contact region was identified. By
incorporating both the Fourier series of contraction data and the
complex modulus function, the cellular contraction force was calculated
by finite-element analysis (FEA). The difference between the Euler beam
formula and the viscoelastic FEA was discussed. The methodology
presented in this work is anticipated to benefit the material
characterization of other soft polymers and complex biological behavior
in the frequency domain.