{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/92867"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/92867","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"A study of shape memory polymers and their usage in the development of directional dry adhesives","abstract":"\"This thesis first introduces shape memory polymers and their unique phase-changing and recoverability properties. The underlying thermodynamic explanations along with their fundamental governing equations is presented. A few possible potential areas of interest for applications of this unique polymer are presented, but the one of particular interest is biomimetic dry adhesives. In this thesis, a shape memory polymer (SMP) surface with geometrically asymmetric micro-wedge array is fabricated as a reversible directional dry adhesive through a double exposure angled lithography technique. The unique shape fixing and recovery properties of SMPs and surface microstructuring enable highly reversible adhesion strength upon thermo-mechanical loading, and the tilted wedge geometry gives rise not only to its capability for varying adhesion strength based on loading direction, but also the reduction of strain energy input necessary to achieve contact area saturation with the opposing surface. To characterize the directional adhesion strength of the fabricated micro-wedge surface, adhesion tests are performed in the forward shear, backward shear, and normal directions based on the tilting direction of the micro-wedges. The adhesion strength is measured as a function of the applied preload for the three directions investigated, and is compared to a computational analysis by modeling the adhesive failure as the initiation of crack growth in linear elastic fracture mechanics. Additionally, reversibility is demonstrated by heating the micro-wedge surface above its T g , allowing the structure to recover its original shape after being deformed, resulting in almost zero adhesion strength. The adhesion tests demonstrate that the forward shear direction is capable of adhesion strengths that are greater than that of the backward shear direction by a factor of over 3, confirming its capability for directional adhesion. Finally, additional novel shapes are introduced, taking advantage of the angled exposure technique and properties of negative photoresist to \"\"cleave\"\" a unique wedge pattern based on the shape of the patterns on the photomask used in fabrication.\"","abstract_html":""This thesis first introduces shape memory polymers and their unique phase-changing and recoverability properties. The underlying thermodynamic explanations along with their fundamental governing equations is presented. A few possible potential areas of interest for applications of this unique polymer are presented, but the one of particular interest is biomimetic dry adhesives. In this thesis, a shape memory polymer (SMP) surface with geometrically asymmetric micro-wedge array is fabricated as a reversible directional dry adhesive through a double exposure angled lithography technique. The unique shape fixing and recovery properties of SMPs and surface microstructuring enable highly reversible adhesion strength upon thermo-mechanical loading, and the tilted wedge geometry gives rise not only to its capability for varying adhesion strength based on loading direction, but also the reduction of strain energy input necessary to achieve contact area saturation with the opposing surface. To characterize the directional adhesion strength of the fabricated micro-wedge surface, adhesion tests are performed in the forward shear, backward shear, and normal directions based on the tilting direction of the micro-wedges. The adhesion strength is measured as a function of the applied preload for the three directions investigated, and is compared to a computational analysis by modeling the adhesive failure as the initiation of crack growth in linear elastic fracture mechanics. Additionally, reversibility is demonstrated by heating the micro-wedge surface above its T g , allowing the structure to recover its original shape after being deformed, resulting in almost zero adhesion strength. The adhesion tests demonstrate that the forward shear direction is capable of adhesion strengths that are greater than that of the backward shear direction by a factor of over 3, confirming its capability for directional adhesion. Finally, additional novel shapes are introduced, taking advantage of the angled exposure technique and properties of negative photoresist to ""cleave"" a unique wedge pattern based on the shape of the patterns on the photomask used in fabrication."","abstract_has_math":false,"creators":["Seo, John"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Kim, Seok"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-11-10T17:55:18Z","date_published":"2016-11-10T17:55:18Z","updated_at":"2026-07-22T22:26:35Z","subjects":["shape memory polymers","dry adhesives","microstructure","reversibility","directionality"],"languages":["en"],"rights":["Copyright 2016 John Seo"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/92867","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Kim, Seok"]},{"key":"dc:creator","label":"Author","values":["Seo, John"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2016-11-10T17:55:18Z","2016-07-19","2016-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"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":["shape memory polymers","dry adhesives","microstructure","reversibility","directionality"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2016 John Seo"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/92867"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["\"This thesis first introduces shape memory polymers and their unique phase-changing and recoverability properties. The underlying thermodynamic explanations along with their fundamental governing equations is presented. A few possible potential areas of interest for applications of this unique polymer are presented, but the one of particular interest is biomimetic dry adhesives. In this thesis, a shape memory polymer (SMP) surface with geometrically asymmetric micro-wedge array is fabricated as a reversible directional dry adhesive through a double exposure angled lithography technique. The unique shape fixing and recovery properties of SMPs and surface microstructuring enable highly reversible adhesion strength upon thermo-mechanical loading, and the tilted wedge geometry gives rise not only to its capability for varying adhesion strength based on loading direction, but also the reduction of strain energy input necessary to achieve contact area saturation with the opposing surface. To characterize the directional adhesion strength of the fabricated micro-wedge surface, adhesion tests are performed in the forward shear, backward shear, and normal directions based on the tilting direction of the micro-wedges. The adhesion strength is measured as a function of the applied preload for the three directions investigated, and is compared to a computational analysis by modeling the adhesive failure as the initiation of crack growth in linear elastic fracture mechanics. Additionally, reversibility is demonstrated by heating the micro-wedge surface above its T g , allowing the structure to recover its original shape after being deformed, resulting in almost zero adhesion strength. The adhesion tests demonstrate that the forward shear direction is capable of adhesion strengths that are greater than that of the backward shear direction by a factor of over 3, confirming its capability for directional adhesion. Finally, additional novel shapes are introduced, taking advantage of the angled exposure technique and properties of negative photoresist to \"\"cleave\"\" a unique wedge pattern based on the shape of the patterns on the photomask used in fabrication.\"","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-11-09 without embargo terms","The student, John Seo, accepted the attached license on 2016-07-18 at 15:11.","The student, John Seo, submitted this Thesis for approval on 2016-07-18 at 15:21.","This Thesis was approved for publication on 2016-07-19 at 11:14.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9993 on 2016-11-09 at 10:25:25","Made available in DSpace on 2016-11-10T17:55:18Z (GMT). No. of bitstreams: 3 SEO-THESIS-2016.pdf: 1696839 bytes, checksum: 7a268671954499a9f1c34bd5acdc95d3 (MD5) MastersThesis.docx: 3441931 bytes, checksum: 3b72a06b1de37fe80e9a15540db81a05 (MD5) LICENSE.txt: 4205 bytes, checksum: 0626929e13a76d9ba52af5f2b9a3f351 (MD5) Previous issue date: 2016-07-19"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["A study of shape memory polymers and their usage in the development of directional dry adhesives"]}]}],"canonical_facts":{"dc:contributor":["Kim, Seok"],"dc:creator":["Seo, John"],"dc:date":["2016-11-10T17:55:18Z","2016-07-19","2016-08"],"dc:description":["\"This thesis first introduces shape memory polymers and their unique phase-changing and recoverability properties. The underlying thermodynamic explanations along with their fundamental governing equations is presented. A few possible potential areas of interest for applications of this unique polymer are presented, but the one of particular interest is biomimetic dry adhesives. In this thesis, a shape memory polymer (SMP) surface with geometrically asymmetric micro-wedge array is fabricated as a reversible directional dry adhesive through a double exposure angled lithography technique. The unique shape fixing and recovery properties of SMPs and surface microstructuring enable highly reversible adhesion strength upon thermo-mechanical loading, and the tilted wedge geometry gives rise not only to its capability for varying adhesion strength based on loading direction, but also the reduction of strain energy input necessary to achieve contact area saturation with the opposing surface. To characterize the directional adhesion strength of the fabricated micro-wedge surface, adhesion tests are performed in the forward shear, backward shear, and normal directions based on the tilting direction of the micro-wedges. The adhesion strength is measured as a function of the applied preload for the three directions investigated, and is compared to a computational analysis by modeling the adhesive failure as the initiation of crack growth in linear elastic fracture mechanics. Additionally, reversibility is demonstrated by heating the micro-wedge surface above its T g , allowing the structure to recover its original shape after being deformed, resulting in almost zero adhesion strength. The adhesion tests demonstrate that the forward shear direction is capable of adhesion strengths that are greater than that of the backward shear direction by a factor of over 3, confirming its capability for directional adhesion. Finally, additional novel shapes are introduced, taking advantage of the angled exposure technique and properties of negative photoresist to \"\"cleave\"\" a unique wedge pattern based on the shape of the patterns on the photomask used in fabrication.\"","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-11-09 without embargo terms","The student, John Seo, accepted the attached license on 2016-07-18 at 15:11.","The student, John Seo, submitted this Thesis for approval on 2016-07-18 at 15:21.","This Thesis was approved for publication on 2016-07-19 at 11:14.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9993 on 2016-11-09 at 10:25:25","Made available in DSpace on 2016-11-10T17:55:18Z (GMT). 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