Department of Chemistry and Physics Georgia Regents University Determining Surface Tension Using The Pendant Drop Method Camille Miller, Jaleel Bolden, Zane Corder, Charlene Higdon Faculty Advisor: Dr. Guerrero-Millan Applications Surface Tension The energy required to decrease the surface area of a fluid Y. Yuan, T. R. Lee. Surface science techniques. Springer Berlin Heidelberg, 2013. 3‐34. Surface Tension Sessile drops lg cos (θC) = γsg− γsl Experimental Setup Image Processing Original image Edge Detected Edge Plotted A. Egatz‐Gomez, et al. RSC Advances 2(30) (2012) Fitting Literature: 38.6o Our code: 38.5o Concentration VSoap/VWater Contact Angle 5mL/5mL 15.7 5mL/10mL 5mL/20mL 34.7 43.5 Droplet Other Methods of Determination Some instruments to measure surface tension: Du Noüy Ring Wilhelmy plate Pendant drop method Young Laplace Equation Gravity P P0 ( ) gz 1 sin 2 ( )gz x R0 R1 Capillarity 1 1 P R1 R2 Young Laplace Equation In dimensionless parametric form: sin d 2 Z dS X dX cos dS dZ sin dS ( ) gR02 Boundary conditions: X ( 0) Z ( 0) ( 0) 0 ( ) gR02 Shape factor Young Laplace Equation In dimensionless parametric form: sin d 2 Z dS X dX cos dS dZ sin dS ( ) gR02 Boundary conditions: X ( 0) Z ( 0) ( 0) 0 ( ) gR02 Shape factor Young Laplace Equation In dimensionless parametric form: sin d 2 Z dS X dX cos dS dZ sin dS ( ) gR02 Boundary conditions: X ( 0) Z ( 0) ( 0) 0 ( ) gR02 Shape factor Image Enhancement Edge Detection Finding Ro How did we choose the number of points at the bottom of the drop? ( ) gR02 Radius of curvature Ro (pixels) Finding Ro Number of points Finding Ro Needle diameter: 0.9 mm Ro = 1.5 mm Determining the shape factor CC Method 1: Two diameters at different heights ( ) gR02 Method 2: Fitting the profile Method 1: Measuring two diameters within the drop (DE and DS) DE: Largest diameter in the drop DS: Diameter DE to the drop apex CC DS = 56 px DE = 85 px 2 DS DS DS 0.5426 1.7713 0.12836 0.7577 DE DE DE 3 F. K. Hansen and G. Rødsrud, J. Colloid Interface Sci. 141 (1991) Method 2: Fitting the whole profile = 0.05 : 0.01 : 0.5 Method 2: Fitting the profile Surface Tension Values γ (mN/m) From Literature First Method (DS DE) Second Method (fitting the profile) 72.75 73.18 73.47 Water /10 cSt Silicone oil - 40.83 40.87 Glycerol / 10 cSt Silicone oil - 29.19 29.40 Ethylene glycol / 10 cSt Silicone oil - 18.98 15.74 Water / Air Measuring the flow rate in electro-coflow Experimental setup Drop size measurement If the same drop appears in several frames… Monitoring the centroid position Results Thank you!
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