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This page is for showing different apparatus, spaces and capabilities in the Wetting Transitions Lab. To read about the research being done here, click here.

Wetting Transitions Laboratory

Described below are following are the various capabilities in the lab:

Film/Droplet Preparation Area

A small enclosed cleanroom contains a class 1000 laminar flow hood, a Laurel spin processor, Barnstead Easy Pure water purification system for producing Type I water, and an Ocean Optics film reflectometer, for quick film thickness characterization. Immediately adjacent to the cleanroom is a Denton Evaporator used for making thin metallic and carbon films.

M2000X Spectroscopic Ellipsometer

Recently our lab acquired a Wollam M2000X spectroscopic ellipsometer, through an joint MRI grant with Professor Iannacchione, which significantly enhances our capabilities to study surface and wetting phenomena.

Spectroscopic ellipsometry measures polarization-dependent changes that occur to light when it reflects from the surface, which not only gives us information about the dielectric properties of the surface but also the thickness and various dielectric properties of films on that surface. The ellipsometer measures these changes as a function of surface position, wavelength and incident angle, in order to obtain sufficient, very precise information that can be used to fit detailed models of the surface structure, determining film thicknesses, roughness, dielectric anisotropy, from which in turn we may deduce the organization of the material on the surface as a function of temperature and, for example, degree of atmospheric saturation. The particular model M2000X has two sets of focusing probes that allows us to focus the beam to a spot size of only 150 microns, so that measurements of tiny submillimeter features can be individually measured.

Thermostatic Film Reflectometric Microscope

We have two microsocopes. A Mitutoyo inspection microscope, fitted with 10X-400x objectives and capable of both transmittance and reflectance measurements, is used in together with a clamshell thermostatic cell design, has to date primarily been used for studying the coexistence behavior of thin liquid crystal films on silicon. The thermostatic cell uses ir-reflective windows to minimize temperature gradients. These windows also allow us to create large electric fields and/or to make high-resolution measurements of film thickness (see high-res. capacitance bridge below).

A second Leitz polarizing microscope, on loan from Prof. Iannachione's Order-Disorder lab down the hall, is useful for simple characterizations of liquid crystal phases, especially those involving anisotropy. It is typically used with a thermostatically controlled open air cell specifically specialized for use with glass microscope slides.

High Temperature Contact Angle Apparatus

Over the past few years we have developed methods for measuring the contact angle of liquids on solid surfaces over a wide range of temperatures. A central feature is a seamless glass container containing a silicon oil bath. Such a setup substantially reduces temperature gradients in our experimental cells. A second important aspect of our studies is the use of VCO swagelock fittings with metal C-ring seal technology from Thoughventions which allows us to make high-temperature, high-pressure cells with two sapphire windows allowing us to image droplets. For imaging droplets we use telescopic optics and a microprocessor-controlled digital camera. Available also are a variety of pressure gauges ranging from millitorr to 50 atm, together with a pressure generating manifold, suitable for these studies.

Hi-resolution Quartz Microbalance Apparatus

A complete hi-resolution quartz microbalance apparatus is setup using Labview and a high-freqency lock-in amplifier. This apparatus allows us to measure 1/100th of a layer of water on a surface. Such an apparatus has bene used for studying prewetting transitions near room temperature, and we are currently using it to determine basic adsorption potential parameters.

Fume Hood and Convection Oven

A standard fume hood is used for any chemical processes involving the evolution of fumes, such as RCA cleaning procedures. It is also used for experiments studying the wetting of liquid nitrous oxide. Because of the requirements for airflow it is actually located outside the cleanroom area proper, so that we need ultimately to minimize the time that samples spend in this area, if we are concerned with dust contamination. Located next to the fume hood is a convection oven with a range 25-200 C, useful for sample preparation.

High-resolution Capacitance Bridge

Capacitance can be used to make high precision measurement of film thickness, liquid level, etc.. This is of use not only for our work but for the work of Prof. Iannachione and Prof. Koehler for their measurements. To this end, we have all the electronics, Ithaco lock-in, ratio transformer, etc. for high resolution measurement of capacitance in the lab.

Other capabilities

In addition to the above equipment, we have a Mettler balance (200g -0.1mg range), a UV/Vis transmittance spectrometer, several Neslab thermal baths, liquid refractometer, oscilloscopes, voltmeters, and a range of microcomputers with Linux and Windows programs useful for data analysis, report preparation, and calculation.

In Higgins and Washburn labs, we also have available a spectrum of scanning electron microscopes for some of our surface characterizations. In addition, we have made use of the NSLS x-ray facilities at Brookhaven National Lab in collaboration with Masa Fukuto and Ben Ocko at the Condensed Matter Physics and Materials Science Department.