New Method for Measuring Water Desorption Rates of In-Vitro Biomaterials

LI Ciortea, EP Berg, P Xiao and RE Imhof.
Poster, 1st Joint ISBS/ISSI Congress, Hamburg, May 2003.


We report a new method for measuring water desorption from soft and non-compact materials, including in vitro bio-materials. It makes use of a new instrument, the AquaFlux™, for measuring water vapour flux density. An important feature of this instrument is the precise control of the microclimate to which the samples are exposed. This ensures that the measured flux densities are repeatable, irrespective of ambient humidity conditions.

The method has two main steps. In the first step, the sample of interest is pre-conditioned by exposing it to an atmosphere of controlled relative humidity (RH) for a sufficient period to reach equilibrium hydration. Various saturated salt solutions can be used for this, but care needs to be taken to avoid condensation at high RH values, and to ensure that the pre-conditioning RH is higher than the RH value to which the sample is subsequently exposed. In the second step, the sample is enclosed in the base of the AquaFlux™ measurement chamber and time-dependent desorption flux density curves are measured as the equilibrium hydration of the sample adjusts to the lower RH conditions that exist within the measurement chamber.

Examples of such measurements on excised stratum corneum, hair and other samples are presented.


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