Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples L. Renbaum-Wolff, J. W. Grayson, and A. K. Bertram Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
Abstract. Herein, a method for the determination of viscosities of small sample volumes
is introduced, with important implications for the viscosity determination of
particle samples from environmental chambers (used to simulate atmospheric
conditions). The amount of sample needed is < 1 μl, and the
technique is capable of determining viscosities (η) ranging between
10−3 and 103 Pascal seconds (Pa s) in samples that cover
a range of chemical properties and with real-time relative humidity and
temperature control; hence, the technique should be well-suited for
determining the viscosities, under atmospherically relevant conditions, of
particles collected from environmental chambers. In this technique,
supermicron particles are first deposited on an inert hydrophobic substrate.
Then, insoluble beads (~1 μm in diameter) are embedded in
the particles. Next, a flow of gas is introduced over the particles, which
generates a shear stress on the particle surfaces. The sample responds to
this shear stress by generating internal circulations, which are quantified
with an optical microscope by monitoring the movement of the beads. The rate
of internal circulation is shown to be a function of particle viscosity but
independent of the particle material for a wide range of organic and
organic-water samples. A calibration curve is constructed from the
experimental data that relates the rate of internal circulation to particle
viscosity, and this calibration curve is successfully used to predict
viscosities in multicomponent organic mixtures.
Citation: Renbaum-Wolff, L., Grayson, J. W., and Bertram, A. K.: Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples, Atmos. Chem. Phys., 13, 791-802, doi:10.5194/acp-13-791-2013, 2013.