Observation of Pore Scale Liquid Behavior with NIR-Microscopy and Advanced Laser Techniques Markus Tuller and Dani Or Dept. of Plants, Soils and Biometeorology, Utah State University

Microscopic Observation of Capillary Condensation in Glass Micromodels Dew Point Generator Temperature Controller Video Microscope Microscope Control Units Heat Exchanger Sealed Chamber  A high resolution video microscope (1000x) with black&white CCD camera was used to detect liquid configurations using IR light (880 nm) emitted from a LED light source (capitalizing on water adsorption properties at this wavelength).  A narrow bandpass interference filter with a central wavelength of 880 nm was installed on the CCD camera to increase image contrast for water.  The observations were performed in a temperature and vapor pressure controlled chamber.

Environmentally Controlled Observation Chamber Video Microscope IR Backlight 880 nm Thermistor Glass Model Sample Manipulator Chamber with Water Jacket X-Y Positioning Stage  A temperature controller connected to a thermistor and two thermoelectric Peltier cooling elements are used to maintain a constant temperature within the chamber.  Two heat exchangers connected to two closed water loops are attached to the “hot” and “cool” sides of the Peltier plates.  One loop is guided through the water jacket surrounding the observation chamber, and the second loop is connected to a larger water reservoir.  A LI-COR dew point generator with an accuracy of 0.02 o C was used to control the vapor pressure within the observation chamber.

Observation of Capillary Menisci in Micro Glass Beads  The experimental setup was tested with micro glass beads having an average diameter of 325  m.  Observed capillary menisci for various chemical potentials were compared with calculated menisci obtained from solutions of the Young-Laplace equation for pendular water J/kg J/kg J/kg J/kg J/kg [  m] J/kg aGlass bead radius [m]  Liquid-vapor surface tension [N/m]  Liquid density [kg/m3]  Chemical potential [J/kg]

Observation of Capillary Menisci and Liquid Redistribution in Micro Glass Cells [mm] J/kg J/kg J/kg J/kg J/kg J/kg J/kg J/kg J/kg Quasi equilibrium Non equilibrium J/kg

Advanced Techniques to Measure Thickness and Configuration of Adsorbed Liquid Films  Several micro-scale techniques will be applied to measure the thickness of adsorbed liquid films.  Currently we are testing the following methods to measure the structure of surface water on channeled silica substrates: Laser Interferometer  Ellipsometry For layers from 0.5 nm to 10 nm  Interferometry For layers from 10 nm to 1  m  Phase-Contrast Microscopy Resolution down to 2  m  Diffraction Analysis Conceptual Sketch of the Experimental Setup

Reflectometry for Measurement of Film Thickness Illumination Fibers Read Fiber Reflection Probe Probe Holder Quartz Sample Pulsed Xenon Light Source Reflectance Spectrum EXPERIMENTAL SETUP l A miniature fiber optic spectrometer (Ocean Optics PC2000) with high-performance CCD-array detector and high-speed A/D converter is used to measure the reflectance spectrum of thin films coating solid substrates. l All measurements are conducted with an incidence angle perpendicular to the sample surface and relative to a standard sample with known absolute reflectance.

Reflectometry – Preliminary Results Air Between Quartz Slides (38 mm Spacers) Air Between Quartz Slides (No Spacers) h=12.4  m h=41.6  m

Diffraction Analysis to Determine Liquid Configurations within Periodic Structures l Analysis of the diffraction pattern is used to determine the average interfacial curvature of liquid, filling the periodic structure. Model Prototype 45  m DRY WET Theoretically Derived Diffraction Patterns for Dry and Liquid-Filled Periodical Structures Measured Diffraction Patterns for Dry and Liquid-Filled Periodical Structures