RP13 Sensors for Environmental Monitoring
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall
(MCD-1117-826733) A Novel Method for Observing and Quantifying Surface Wetting Characteristics Employing AutoCAD.
McDaniel, Les1, Romero, Nicholas1, Coimbatore, Gopal1, Cobb, George1, 1 The Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas, USA
ABSTRACT- Our group has developed an inexpensive and novel method for measuring contact angles of liquids on solid surfaces using a computer microscope and AutoCAD© 2005 drafting software. This method was developed to fulfill the needs of our chemical sensors development program for confirming the presence of self assembled monolayers (SAMs) and liquid crystals (LCs) after deposition onto solid surfaces. Photographs (.jpeg) of 1
l droplets of known liquids resting on the surfaces of interest are taken with a Digital Blue™ QX5™ Computer Microscope and are copied and then pasted into the AutoCAD© design window. Droplet images are then manipulated with two dimensional line drawings to determine the angle of contact in order to make inferences about the characteristics of the solid surfaces. Using AutoCAD©, images of droplets on surfaces were overlain with simple geometric shapes matching all profiles. Once these reference lines were applied, 
s were determined via the AutoCAD© software. Multiple surfaces were tested using this method including N-type silicon wafers, 10-20nm thickness gold layer on N-type silicon wafers, a carboxyl-terminated SAM, and an LC layer. For these analyses, three test liquids of varying polarities were enlisted: Milli-Q water, diiodomethane, and ethylene glycol droplets were applied to all surfaces independently. Two replicates of surface groups were tested independently and retested separately to determine repeatability of the procedure. Angles determined as thus were predictable and consistent with literature values. We concluded that expensive software and optical apparatus are not required to perform consistent analyses of surface wetting characteristics. This method of determining the surface energies of solid surfaces has proven reliable in confirming our predictions based on the chemical and physical properties of those surfaces.
Key words: contact angle, Autocad, Sensor, Wetting