Effect of Surface Treatment on Liquid Adhesion Inside 3-D Structures

This study explores the relationship between chemical surface treatments on the interior of glass tubes and their resistance to fluid flow. By treating the interior of the tubes with functional silanes we can decrease or increase the interaction of the tube walls with the fluid column, which translates to changes in fluid column height for a given pressure differential. Resistance to fluid flow is quantified by using the tubes as integral parts of a barometric pressure column and measuring the changes in column height as the fluid is pulled into the tube by a set pressure differential. The barometric pressure system consisted of a closed end manometer attached to the desired tube samples. About 10 mL of fluid were also initially placed in the manometer. Opening the system to atmosphere causes the pressure to equalize, in this way the system acts like a barometer where the fluid travels up the tube. Fluid adhesion to the tube walls transfers a small amount of force, through friction, to the tube walls, which opposes any force pulling the fluid along the surface. The effect is demonstrated with water and hexadecane. Reduced adhesions were observed due to surface treatment. This work provides insight into reducing backpressure when flowing liquids through small pipes.