{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/108249"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/108249","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Condensation driven solid-liquid interfacial phenomenon on functional surfaces","abstract":"Made available in DSpace on 2020-08-27T00:49:55Z (GMT). No. of bitstreams: 3 CHA-DISSERTATION-2020.pdf: 9393430 bytes, checksum: bad2af1456c79eca3ecc06813874b9f7 (MD5) LICENSE.txt: 4210 bytes, checksum: 158c48014e3d7208a4aed33c3343a6cc (MD5) PROQUEST_LICENSE.txt: 4556 bytes, checksum: 7168bb0cd71b4bb86ad9ef20a02d6cf0 (MD5) Previous issue date: 2020-04-15","abstract_html":"Made available in DSpace on 2020-08-27T00:49:55Z (GMT). No. of bitstreams: 3 CHA-DISSERTATION-2020.pdf: 9393430 bytes, checksum: bad2af1456c79eca3ecc06813874b9f7 (MD5) LICENSE.txt: 4210 bytes, checksum: 158c48014e3d7208a4aed33c3343a6cc (MD5) PROQUEST_LICENSE.txt: 4556 bytes, checksum: 7168bb0cd71b4bb86ad9ef20a02d6cf0 (MD5) Previous issue date: 2020-04-15","abstract_has_math":false,"creators":["Cha, Hyeongyun"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Miljkovic, Nenad","Jacobi, Anthony M","King, William","Braun, Paul V","Takata, Yasuyuki"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-08-27T00:49:55Z","date_published":"2020-08-27T00:49:55Z","updated_at":"2026-07-22T22:24:48Z","subjects":["Heat Transfer","Condensation","Hydrophobic","Superhydrophobic","Jumping Droplet","Heterogeneous Nucleation","Volatile Organic Compounds","Durability"],"languages":["en"],"rights":["Copyright 2020 Hyeongyun Cha"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/108249","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Miljkovic, Nenad","Jacobi, Anthony M","King, William","Braun, Paul V","Takata, Yasuyuki"]},{"key":"dc:creator","label":"Author","values":["Cha, Hyeongyun"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-08-27T00:49:55Z","2022-08-27T00:51:40Z","2020-04-15","2020-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Heat Transfer","Condensation","Hydrophobic","Superhydrophobic","Jumping Droplet","Heterogeneous Nucleation","Volatile Organic Compounds","Durability"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2020 Hyeongyun Cha"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/108249"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Made available in DSpace on 2020-08-27T00:49:55Z (GMT). No. of bitstreams: 3 CHA-DISSERTATION-2020.pdf: 9393430 bytes, checksum: bad2af1456c79eca3ecc06813874b9f7 (MD5) LICENSE.txt: 4210 bytes, checksum: 158c48014e3d7208a4aed33c3343a6cc (MD5) PROQUEST_LICENSE.txt: 4556 bytes, checksum: 7168bb0cd71b4bb86ad9ef20a02d6cf0 (MD5) Previous issue date: 2020-04-15","Embargo set by: Seth Robbins for item 115863 Lift date: 2022-08-27T00:50:22Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 115863 Lift date: 2022-08-27T00:51:40Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited","Vapor condensation is routinely observed in nature and has a large influence on the performance of a wide range of industrial systems. This doctoral thesis focuses on the fundamental understanding of solid-liquid interactions on micro/nanoengineered surfaces, as well as the evaluation of long-term durability for such surfaces under industrial condensation conditions. We first studied droplet-surface interactions during condensation on superhydrophobic surfaces to understand jumping droplet dynamics. Droplets are of particular interest due to their large surface-to-volume ratios, and hence enhanced transport properties. For example, coalescence induced droplet jumping on superhydrophobic surfaces has recently received much attention for its potential to enhance heat transfer, anti-icing, and self-cleaning performance by passively shedding microscale water droplets. To study droplet jumping, we developed a single-camera technique capable of providing three-dimensional (3D) information through the use of focal plane manipulation. Termed ‘focal plane shift imaging’ (FPSI), we used FPSI to study the jumping process on superhydrophobic surfaces having a wide range of structure length scales (10 nm < l < 1 µm) and droplet radii (3 µm < R < 160 µm). We benchmarked the FPSI technique and studied the effects of droplet mismatch, multi-droplet coalescence, and multi-hop coalescence on droplet jumping speed. Furthermore, we were able to resolve the full 3D trajectory of multiple jumping events, to show that unlike previously theorized, angular deviation arises due to in-plane motion post-coalescence governed by droplet pinning. The outcomes of this work both elucidate key fundamental aspects governing droplet jumping, and provide a powerful imaging platform for the study of dynamic droplet processes which result in out-of-plane motion such as sliding, coalescence, or impact. Using our understanding of the importance of droplet pinning and defects on coalescence induced droplet jumping, we experimentally investigated the origins of pinning by studying the unexpected nucleation of water droplets on hydrophobic surfaces at low supersaturations (≈ 1), well below the critical supersaturation for low surface energy hydrophobic coatings (≈ 3). We demonstrate the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of aerosol particles inside the droplet and adsorption of volatile organic compounds on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces. In addition to understanding of fundamental mechanisms of droplet pinning and nucleation, a simple but powerful contact angle measurement technique was developed to detect local defect sites. Although powerful, state-of-the-art goniometric techniques have difficulty characterizing microdroplets, can be cumbersome and expensive, and have trouble handling surfaces with local wetting heterogeneity and deformed non-circular contact lines. Furthermore, past methods are incapable of measuring contact angle in situ during experiments (e.g. condensation). Here, we develop simple yet powerful contact angle measurement techniques using conventional optical microscopy that utilizes focal plane shift imaging, ray optics, and wave interference. We used our techniques to study the wetting characteristics for a wide range of water droplet diameters (3 µm < D < 600 µm) and apparent contact angles (0° ≤ θ^app ≤ 180°). The outcomes of this work establish a powerful tool to more easily and rapidly characterize microscale droplet advancing and receding contact angles. Finally, to enable a step forward in the widespread commercial and industrial adoption of functional surfaces, we experimentally investigated coating longevity during steam condensation. We rationally selected various promising hydrophobic promoters on different substrates and evaluated their long-term (~year) durability under industrial condensation conditions in a custom-built experimental chamber. The results offer insights on how to achieve long lasting functional coatings.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01","The student, Hyeongyun Cha, accepted the attached license on 2020-04-13 at 11:57.","The student, Hyeongyun Cha, submitted this Dissertation for approval on 2020-04-13 at 12:15.","This Dissertation was approved for publication on 2020-04-15 at 17:15.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14967 on 2020-08-25 at 17:40:12"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Condensation driven solid-liquid interfacial phenomenon on functional surfaces"]}]}],"canonical_facts":{"dc:contributor":["Miljkovic, Nenad","Jacobi, Anthony M","King, William","Braun, Paul V","Takata, Yasuyuki"],"dc:creator":["Cha, Hyeongyun"],"dc:date":["2020-08-27T00:49:55Z","2022-08-27T00:51:40Z","2020-04-15","2020-05"],"dc:description":["Made available in DSpace on 2020-08-27T00:49:55Z (GMT). No. of bitstreams: 3 CHA-DISSERTATION-2020.pdf: 9393430 bytes, checksum: bad2af1456c79eca3ecc06813874b9f7 (MD5) LICENSE.txt: 4210 bytes, checksum: 158c48014e3d7208a4aed33c3343a6cc (MD5) PROQUEST_LICENSE.txt: 4556 bytes, checksum: 7168bb0cd71b4bb86ad9ef20a02d6cf0 (MD5) Previous issue date: 2020-04-15","Embargo set by: Seth Robbins for item 115863 Lift date: 2022-08-27T00:50:22Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 115863 Lift date: 2022-08-27T00:51:40Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited","Vapor condensation is routinely observed in nature and has a large influence on the performance of a wide range of industrial systems. This doctoral thesis focuses on the fundamental understanding of solid-liquid interactions on micro/nanoengineered surfaces, as well as the evaluation of long-term durability for such surfaces under industrial condensation conditions. We first studied droplet-surface interactions during condensation on superhydrophobic surfaces to understand jumping droplet dynamics. Droplets are of particular interest due to their large surface-to-volume ratios, and hence enhanced transport properties. For example, coalescence induced droplet jumping on superhydrophobic surfaces has recently received much attention for its potential to enhance heat transfer, anti-icing, and self-cleaning performance by passively shedding microscale water droplets. To study droplet jumping, we developed a single-camera technique capable of providing three-dimensional (3D) information through the use of focal plane manipulation. Termed ‘focal plane shift imaging’ (FPSI), we used FPSI to study the jumping process on superhydrophobic surfaces having a wide range of structure length scales (10 nm < l < 1 µm) and droplet radii (3 µm < R < 160 µm). We benchmarked the FPSI technique and studied the effects of droplet mismatch, multi-droplet coalescence, and multi-hop coalescence on droplet jumping speed. Furthermore, we were able to resolve the full 3D trajectory of multiple jumping events, to show that unlike previously theorized, angular deviation arises due to in-plane motion post-coalescence governed by droplet pinning. The outcomes of this work both elucidate key fundamental aspects governing droplet jumping, and provide a powerful imaging platform for the study of dynamic droplet processes which result in out-of-plane motion such as sliding, coalescence, or impact. Using our understanding of the importance of droplet pinning and defects on coalescence induced droplet jumping, we experimentally investigated the origins of pinning by studying the unexpected nucleation of water droplets on hydrophobic surfaces at low supersaturations (≈ 1), well below the critical supersaturation for low surface energy hydrophobic coatings (≈ 3). We demonstrate the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of aerosol particles inside the droplet and adsorption of volatile organic compounds on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces. In addition to understanding of fundamental mechanisms of droplet pinning and nucleation, a simple but powerful contact angle measurement technique was developed to detect local defect sites. Although powerful, state-of-the-art goniometric techniques have difficulty characterizing microdroplets, can be cumbersome and expensive, and have trouble handling surfaces with local wetting heterogeneity and deformed non-circular contact lines. Furthermore, past methods are incapable of measuring contact angle in situ during experiments (e.g. condensation). Here, we develop simple yet powerful contact angle measurement techniques using conventional optical microscopy that utilizes focal plane shift imaging, ray optics, and wave interference. We used our techniques to study the wetting characteristics for a wide range of water droplet diameters (3 µm < D < 600 µm) and apparent contact angles (0° ≤ θ^app ≤ 180°). The outcomes of this work establish a powerful tool to more easily and rapidly characterize microscale droplet advancing and receding contact angles. Finally, to enable a step forward in the widespread commercial and industrial adoption of functional surfaces, we experimentally investigated coating longevity during steam condensation. We rationally selected various promising hydrophobic promoters on different substrates and evaluated their long-term (~year) durability under industrial condensation conditions in a custom-built experimental chamber. The results offer insights on how to achieve long lasting functional coatings.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01","The student, Hyeongyun Cha, accepted the attached license on 2020-04-13 at 11:57.","The student, Hyeongyun Cha, submitted this Dissertation for approval on 2020-04-13 at 12:15.","This Dissertation was approved for publication on 2020-04-15 at 17:15.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14967 on 2020-08-25 at 17:40:12"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/108249"],"dc:language":["en"],"dc:rights":["Copyright 2020 Hyeongyun Cha"],"dc:subject":["Heat Transfer","Condensation","Hydrophobic","Superhydrophobic","Jumping Droplet","Heterogeneous Nucleation","Volatile Organic Compounds","Durability"],"dc:title":["Condensation driven solid-liquid interfacial phenomenon on functional surfaces"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:48Z"}