Researcher(s)
- Nolan John, Chemistry, University of Delaware
Faculty Mentor(s)
- Rachel Davidson, Chemistry & Biochemistry, University of Delaware
Abstract
Rising global demands for freshwater are straining current resources, forcing a shift towards adoption of more expensive and energy-intensive water purification technologies, such as desalination. A significant and underutilized freshwater reservoir exists as humidity or suspended droplets in fog. Naturally occurring fog, especially in coastal areas, and artificial sources such as power plant cooling towers provide excellent opportunities for freshwater collection.
This project explores the use of electrochemical scanning probe microscopy (E-SPM) to additively manufacture spatially controlled wettability films with micron-scale printing precision for use as fog capture surfaces. Two tetraethyl orthosilicate-based sol-gel precursor solutions were designed and utilized to achieve electrodeposited films exhibiting contrasting wettability. Both the hydrophobic and hydrophilic precursor solutions showed tunability in wettability, producing films with water contact angles ranging from 32° to 120°. In situ manipulation of electrodeposition time at a constant applied potential of -1.4 V vs Ag/AgCl alters film wettability at each deposition point during printing, leading to dynamically adjustable gradients with microscale precision to induce passive fog harvesting and fluid transport.
Laplace gradient patterns were optimized through the development of image-coordinate mapping software, which provides an adaptable platform to alter film deposition patterns and maximize droplet movement. Parameters were tuned in Ansys Fluent, identifying an ideal gradient of 10°/mm for maximum driving force. When both solutions were deposited within the optimized pattern, droplet movement with a 47% efficiency was observed. In addition to scalable fog capture and harvest, the passive microfluidic transport properties of the electrodeposited wettability gradients provide a versatile platform for various applications in biosensing, oil-water separation, and lab-on-chip devices.