Developing Durable, Aerogel-Based, Superhydrophobic Surfaces for the Purpose of Drag Reduction

This project focuses on the development of aerogel-based hydrophobic surfaces for the purposes of studying the effects on drag reduction of water flow in the turbulent regime. Silica aerogel is a lightweight, porous material that has become well-known for its thermally insulative properties. Some silica aerogels possess high concentrations of nonpolar side groups on the surface due to the presence of methyltrimethoxysilane (MTMS), which makes these materials hydrophobic. At Union College, aerogels are made by mixing the precursor chemicals (including MTMS), and then processing the resulting wet get using a rapid supercritical extraction process. The aerogels are then run through a ball mill to make a powder and mixed with Polyvinyl butyral (PVB) to increase the adhesion properties of the materials. When added, PVB enables the aerogel to be formed into thin hydrophobic films. These films can be made into large hydrophobic surfaces which have many research applications. The hydrophobicity of the films is quantified through contact angle analysis which involves placing a water droplet on a surface and quantifying the angle formed between the droplet and the surface. In order to classify a surface as hydrophobic, it must have a contact angle of 150° or greater.  This project has produced several films that meet this 150° threshold and are ready for experimentation. The films will be tested in the Union College water channel, where they will be placed on top of a raised surface that will allow for turbulent flow to pass over them. The resulting boundary layer and separation region will be analyzed using particle image velocimetry (PIV) in order to quantify the drag effects, such as the boundary layer and separation region. By examining the drag effects of these aerogels, as well as their durability in constant fluid flow, their viability in real-world drag reduction scenarios will be evaluated.