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Noncontact Viscoelastic Measurement of Polymer Thin Films in a Liquid Medium Using Long-Needle Atomic Force Microscopy
journal contribution
posted on 2017-01-17, 00:00 authored by Dongshi Guan, Chloé Barraud, Elisabeth Charlaix, Penger TongWe
report the noncontact measurement of the viscoelastic property
of polymer thin films in a liquid medium using frequency-modulation
atomic force microscopy with a newly developed long-needle probe.
The probe contains a long vertical glass fiber with one end adhered
to a cantilever beam and the other end with a sharp tip placed near
the liquid–film interface. The nanoscale flow generated by
the resonant oscillation of the needle tip provides a precise hydrodynamic
force acting on the soft surface of the thin film. By accurately measuring
the mechanical response of the thin film, we obtain the elastic and
loss moduli of the thin film using the linear response theory of elastohydrodynamics.
The experiment verifies the theory and demonstrates its applications.
The technique can be used to accurately measure the viscoelastic property
of soft surfaces, such as those made of polymers, nanobubbles, live
cells, and tissues.