Alexander M. Fuller
Biography
Alex graduated with a Master of Science in Mechanical Engineering in 2023. He conducted his graduate research in the Advanced Materials and Technologies Laboratory investigating icing and dew harvesting on nonwetting surfaces.
Research
Long Term Durability of a Lubricant-Infused Surface for Dew Harvesting
Hydrophobic, lubricant-infused surfaces offer enhanced potential for dew harvesting compared to bare metal substrates due to their water repellent nature. Most of the studies to date examine the condensation effectiveness of the nonwetting surfaces over a short duration and have not considered the durability or performance of the surfaces over extended periods. To address this limitation, the present study experimentally investigates the long-term performance of a lubricant-infused surface subject to dew condensation for 96 h. Condensation rates as well as sliding and contact angles are measured periodically to examine the surface properties and water harvesting potential over time. Due to the narrow time window in which dew harvesting can be conducted in application, the additional collection time gained by shedding droplets at lower nucleation times is explored. It is shown that three phases occur in lubricant drainage, which affect performance metrics relevant to dew harvesting. The first 24 h of condensation induces drainage that has little effect on the adhesion of droplets to the surface and on the additional collection time. The next phase, from about 24 to 72 h, showed steady drainage and a steady decrease in performance. The final 24 h, from about 72 to 96 h of operation, was seen to have little added effect on drainage and therefore on the performance metrics. The study bears significance in the design of surfaces for long-term use in practical water harvesters.
Analysis of Freezing of a Sessile Water Droplet on Surfaces over a Range of Wettability
Nonwetting surfaces, by virtue of their water-repelling trait, offer desirable anti-icing characteristics. Surface roughness, type and wettability are important interfacial characteristics that affect the icing dynamics that can be tailored to achieve desired anti-icing designs. The present study systematically explores the effect of surface roughness on the freezing behaviour of water droplets on surfaces ranging in their wettability. Surfaces with tailored textures and wettability were fabricated using chemical etching and electrodeposition by varying the voltage. The surfaces studied include bare copper, five different dry nonwetting copper surfaces, and five different lubricant-infused copper surfaces that ranged in surface texture fractal dimension from nearly 1.0 to 1.92 and wettability measures of average water contact angle from 91° to 162° and sliding angle from less than 3° to greater than 50°. A computational model is developed to simulate the freezing dynamics on the surfaces studied. With increasing roughness features, the freezing time increased due to the dual effects of increased contact angle and poor interfacial conductance caused by trapped air or infused liquid within the asperity textures. In general, the nonwetting surfaces increased the freezing time by a factor of at least 1.33 and up to about 3.2 compared to freezing on bare copper surfaces. The computational model shows close agreement with experimental measurements on the freeze front progression as well as freeze time. Design guidelines on the suitability of the different nonwetting surfaces for anti-icing purposes are derived from the systematic study, with the overall design recommendation favoring lubricant infused surfaces.
Publications
- A. Fuller, K. Kant, and R. Pitchumani, “Analysis of Freezing of a Sessile Water Droplet on Surfaces over a Range of Wettability,” Journal of Colloid and Interface Science, 653, Part A, 960–970, 2024.
- A.M. Fuller and R. Pitchumani, “Long Term Durability of a Lubricant-Infused Surface for Dew Harvesting,” Langmuir, 39(28), 9885–9892, 2023.
