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Apparatus[edit | edit source]

Microfluidics and Interfacial Transport Laboratory in Mechanical Engineering – Engineering Mechanics at MTU is home to a customized sessile drop contact angle measurement system. The setup the comprises of 3 major components: (1) optics and illumination subsystem, (2) sample environment and manipulation stage and (3) a microscope coupled to CCD camera. A Kodak medalist carousel projector is used as the light source. Köhler illumination is implemented using a lens array to produce a collimated beam of light with uniform intensity. The sample environment stage consists of a labjack (Thorlabs L200) mounted on a translation stage (Velmex AXY2509W) enabling X-Y-Z movement of the sample stage. The top of the sample environment stage consists of a copper block with four thermo-electric coolers (Marlow Industries DT12-6-01L). The temperature is controlled by varying the voltage across the coolers. A humidity enclosure is also available to mitigate droplet evaporation. A long distance microscope (Infinity K2/S) is coupled to a CCD camera (PULNIX TM-1325CL) for focusing and image acquisition. Images are captured on an IBM thinkpad T60 laptop using the EPIX XCAP software and the EPIX EL1DB framegrabber.

Droplets of a set volume can be deposited on the sample using a threaded syringe (Hamilton 81242) using a location controlled by the sample environment stage. The setup is capable of acquiring images with a spacial resolution as low as 5 per pixel and a temporal resolution as high as 10000 fps. Image processing and complementary mathematical modeling is necessary to determine the contact angle from the acquired images. A Young-Laplace fit to the edge detected liquid-air interface is extrapolated to the solid substrate and a contact angle is determined. Based on accuracy and time constraints, the values for the contact angle could be measured either using a drop analysis plug-in in the open source ImageJ program or a custom built code. The general technique to determine contact angles and the custom built code for image processing and analysis can be found at [1].

CA setup.png

Basic Tests[edit | edit source]

  1. Room temp CA
  2. near freezing temp (0 to 5 degrees C) CA
  3. movie showing freezing and how CA changes. Might be able to see some frost propagation.

Dynamic tilt clear test? Force to remove ice?

Location[edit | edit source]

MEEM 1001, MTU

Contact[edit | edit source]

Dr. Kishan Bellur