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EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF MICRODROPLET EVAPORATION WITH A FORCED PINNED CONTACT LINE.
Title
EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF MICRODROPLET EVAPORATION WITH A FORCED PINNED CONTACT LINE.
Creator
Gleason, Kevin, Putnam, Shawn, University of Central Florida
Abstract / Description
Experimental and numerical investigations of water microdroplet evaporation on heated, laser patterned polymer substrates are reported. The study is focused on both (1) validating numerical models with experimental data, (2) identifying how changes in the contact line influences evaporative heat transfer and (3) determining methods of controlling contact line dynamics during evaporation. Droplets are formed using a bottom-up methodology, where a computer-controlled syringe pump supplies water...
Show moreExperimental and numerical investigations of water microdroplet evaporation on heated, laser patterned polymer substrates are reported. The study is focused on both (1) validating numerical models with experimental data, (2) identifying how changes in the contact line influences evaporative heat transfer and (3) determining methods of controlling contact line dynamics during evaporation. Droplets are formed using a bottom-up methodology, where a computer-controlled syringe pump supplies water to a ~200 um in diameter fluid channel within the heated substrate. This methodology facilitates precise control of the droplets growth rate, size, and inlet temperature. In addition to this microchannel supply line, the substrate surfaces are laser patterned with a moat-like trench around the fluid-channel outlet, adding additional control of the droplets contact line motion, area, and contact angle. In comparison to evaporation on non-patterned substrate surfaces, this method increases the contact line pinning time by ~60% of the droplets lifetime. The evaporation rates are compared to the predictions of a commonly reported model based on a solution of the Laplace equation, providing the local evaporation flux along the droplets liquid-vapor interface. The model consistently overpredicts the evaporation rate, which is presumable due to the models constant saturated vapor concentration along the droplets liquid-vapor interface. In result, a modified version of the model is implemented to account for variations in temperature along the liquid-vapor interface. A vapor concentration distribution is then imposed using this temperature distribution, increasing the accuracy of predicting the evaporation rate by ~7.7% and ~9.9% for heated polymer substrates at Ts = 50C and 65C, respectively.
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Date Issued
2014
Identifier
CFH0004566, ucf:45212
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004566
Evaporative Vapor Deposition for Depositing 2D Materials
Title
Evaporative Vapor Deposition for Depositing 2D Materials.
Creator
Gleason, Kevin, Putnam, Shawn, Zhai, Lei, Deng, Weiwei, University of Central Florida
Abstract / Description
The development of a new deposition technique called evaporative vapor deposition (EVD) is reported, allowing deposition and formation of atomically-thin, large area materials on arbitrary substrates. This work focuses on the highly popular monolayer material (-) graphene oxide (GO). A droplet of a GO solution is formed on a heated polymer substrate, and maintained at steady-state evaporation (all droplet parameters are held constant over time). The polymer substrate is laser patterned to...
Show moreThe development of a new deposition technique called evaporative vapor deposition (EVD) is reported, allowing deposition and formation of atomically-thin, large area materials on arbitrary substrates. This work focuses on the highly popular monolayer material (-) graphene oxide (GO). A droplet of a GO solution is formed on a heated polymer substrate, and maintained at steady-state evaporation (all droplet parameters are held constant over time). The polymer substrate is laser patterned to control the droplet's contact line dynamics and the droplet's contact angle is maintained using a computer controlled syringe pump. A room temperature silicon wafer is translated through the vapor field of the evaporating GO droplet using a computer controlled translation stage. Dropwise condensation formed on the silicon wafer is monitored using both optical and infrared cameras. The condensation rate is measured to be ~50pL/mm2?s (-) 500 pL/mm2?s and dependent on the substrate translation speed and height difference between the droplet's apex and substrate surface. Nano-sized GO flakes carried through the vapor phase are captured in the condensate, depositing on the translating wafer. Deposition rate is dependent on the stability of the solution and droplet condensate size. Characterization with Raman spectroscopy show expected shifts for graphene/graphite. The presented EVD technique is promising toward formation of large scale 2D materials with applications to developing new technologies.
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Date Issued
2015
Identifier
CFE0006035, ucf:50969
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006035