Self-Propelled Droplet Motion on Micro- and Nanoscale Ratchets
Department
Engineering Technologies
Presentation Location
Clark Memorial Library, Room 229 (TLC)
Presentation Start Date and Time
6-3-2024 1:00 PM
Presentation End Date and Time
6-3-2024 2:00 PM
Brief Abstract
We report motion of liquid droplet in the Leidenfrost (film-boiling) regime whose directionality is rectified by topological ratchets. Water droplets dispensed on the asymmetrically ratcheted gratings start to move in a direction perpendicular to the gratings when the surface temperature reaches the Leidenfrost temperature. Topologically ratcheted gratings with the period of 750 μm and the depths of 15 μm and 30 μm were fabricated using micromachining and nickel electroplating processes. The experimental setup with a high speed camera and an automatic injection system was used to investigate the influence of effective length on droplet motion. Geometrical effect between microscale ratchet and millimetric droplet was significant. The droplet even could climb uphill the 1.3° tilted shallow micro-ratchets. We also have demonstrated a simplified, two-dimensional computational fluid dynamics-heat transfer model of Leidenfrost regime on a sub millimeter scale ratchets when the water vapor thickness is less than 100 μm. It is found that the influence of convection and radiation heat transfer to droplet mobility was almost negligible. Finally, the thermal conduction dominant shear viscous model revealed the possible contribution of self-rotating, reversible, and tumbling motion of the droplet to the self-propulsion. Broader applications with micro- and nanoratchets can also be envisioned as a means of increasing efficiencies for film-boiling heat transfer associated with droplets and spray. One critical, but common problem in film-boiling heat transfer systems is that the presence of droplets bounced from the surface hinders a continuous heat transfer between injected droplets and hot surface, which can be avoided by using micro- and nanoratcheted surfaces. Those applications include fuel injection for combustion technology, stream generation for energy conversion in nuclear power energy converters, cooling systems for nuclear reactors, and spray quenching of heat treatable alloys.
Recommended Citation
Ok, Jeong Tae, "Self-Propelled Droplet Motion on Micro- and Nanoscale Ratchets" (2024). Faculty Research and Teaching Expo. 2.
https://digitalcommons.shawnee.edu/ffa/Faculty_Presentations_2024/March_6_2024/2
Self-Propelled Droplet Motion on Micro- and Nanoscale Ratchets
Clark Memorial Library, Room 229 (TLC)
We report motion of liquid droplet in the Leidenfrost (film-boiling) regime whose directionality is rectified by topological ratchets. Water droplets dispensed on the asymmetrically ratcheted gratings start to move in a direction perpendicular to the gratings when the surface temperature reaches the Leidenfrost temperature. Topologically ratcheted gratings with the period of 750 μm and the depths of 15 μm and 30 μm were fabricated using micromachining and nickel electroplating processes. The experimental setup with a high speed camera and an automatic injection system was used to investigate the influence of effective length on droplet motion. Geometrical effect between microscale ratchet and millimetric droplet was significant. The droplet even could climb uphill the 1.3° tilted shallow micro-ratchets. We also have demonstrated a simplified, two-dimensional computational fluid dynamics-heat transfer model of Leidenfrost regime on a sub millimeter scale ratchets when the water vapor thickness is less than 100 μm. It is found that the influence of convection and radiation heat transfer to droplet mobility was almost negligible. Finally, the thermal conduction dominant shear viscous model revealed the possible contribution of self-rotating, reversible, and tumbling motion of the droplet to the self-propulsion. Broader applications with micro- and nanoratchets can also be envisioned as a means of increasing efficiencies for film-boiling heat transfer associated with droplets and spray. One critical, but common problem in film-boiling heat transfer systems is that the presence of droplets bounced from the surface hinders a continuous heat transfer between injected droplets and hot surface, which can be avoided by using micro- and nanoratcheted surfaces. Those applications include fuel injection for combustion technology, stream generation for energy conversion in nuclear power energy converters, cooling systems for nuclear reactors, and spray quenching of heat treatable alloys.