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Fabrication of polymer microstructures by laser assisted photolithographic methods

Herstellung von Polymer-Mikrostrukturen mittels photolithographischer Methoden
 
: Pérez Hernández, Heidi Rosalia
: Lasagni, Andrés-Fabián

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Dresden, 2013, II, 140 S.
Dresden, TU, Diss., 2013
 
Englisch
Dissertation
Fraunhofer IWS ()
polymer; Laser; Methode; Oberflächentechnik; Wärmebehandlung; Kunststofftechnologie

Abstract
In dieser Arbeit werden zwei, sowohl berührungslose als auch maskenfreie, photolithographische Methoden zur Herstellung zweidimensionaler Strukturen mit Auflösungen im Mikrometerbereich vorgestellt. Nanosekunden-Laserpulse wurden verwendet, um verschiedene Prozesse der chemischen Strukturierung zu induzieren: i) Photovernetzung (Verknüpfung von Oligomeren oder Makromeren in Anwesenheit eines Initiators), ii) Photolytische Spaltung (Zerlegung eines Polymernetzwerkes in kleinere, lösliche Moleküle), iii) Photopolymerisation eines Monomers von einer Oberfläche (Pfropfung von Polymerbürsten) und iv) chemische Pfropfung von Akrylatfunktionalisierten Makromolekülen. Durch Mikrolinsenarray (MLA) Strukturierung wurden proteinabweisende Poly(ethylene glycol)-Mikrostrukturen durch Photovernetzung bzw. photolytische Spaltung auf biofunktionalen Oberflächen erzeugt, um zelladhäsive Mikrodomänen unterschiedlicher Geometrie zu generieren. Die auf diese Weise erzeugten Oberflächen erlauben die räumliche Kontrolle der Zelladhäsion. Abhängig von der Größe der Mikrodomänen konnten einzelne oder multiple Zellenarrays geschaffen werden. Durch die Laserinterferenzlithographie (LIL) Strukturierung wurden "Grafting from"- und "Grafting to"- Polymerbürsten auf verschiedenen Oberflächen erzeugt. Durch LIL konnten Polymerbürsten aus Poly(styrene), Poly(methyl methacrylate) and Poly(N, N dimethylamino ethylmethacrylate) mittels SIPGP auf Aminopropylsilan (APTes) -Monolagen, vernetztem Aminobiphenylthiol (ABPT) sowie auf Graphen- Monolagen erzeugt werden. Zusätzlich wurde mit Hilfe der LIL ein direktes chemisches pfropfen von Akrylat-Poly(ethylenglycol) -Oligomeren und -Makromeren auf APTes Monolagen sowie auf Poly(ethylenterephthalat)- and Poly(etheretherketone)-Filmen durchgeführt.and directly on Polyfethylene terephtalate) and Poly(ether ether ketone) films.

 

This work presents twomask-less photolithographic methods to fabricate polymer structures with micrometer resolution on different surfaces. Pulsed laser irradiation was used to induce different chemical processes for photolithographic patterning: i) photocrosslinking (networking starting from an oligomer or macromersin the presence of an initiator), ii) Photolytic cleavage (break down of a crosslinked polymer network into smaller solublemolecules), iii) photopolymerization of a monomer from a surface ("Grafting From" polymer brushes), and iv) chemical grafting ("Grafting To") of acrylatefunctional macromolecules. Photocrosslinkable or photocleavable (protein repellent) Poly (ethylene glycol) hydrogels were microstructured on biofunctional surfaces by Micro Lens Array Patterning (MLAP) to form cell-adhesive microdomains with different geometries. The patterned surfaces allowed spatial control of cell adhesion and spreading. Depending on the size of these microdomains, single and multiple cell arrays were obtained. Direct patterning of polymer brushes by "Grafting From" or "Grafting To", on different surfaces was performed by Laser Interference Lithography (LIL). By SIPGP (Self-initiatiated photopolymeryzation and photografting) and LIL, patterned polymer brushes of poly(styrene), poly(methyl methacrylate) and poly(N, N dimethylamino ethylmethacrylate) were obtained on aminopropyltriethoxysilane (APTes) monolayer, crosslinked aminobiphenylthiol (ABPT) andgraphene. Direct patterning by chemical grafting and LIL of acrylate functional polyfethylene glycol) oligomer and macromers was performed on APTes.

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I. Introduction 1 // II. Micro and nano patterning techniques for polymers: State of the art 3 // 2.1 Photopolymerization and surface micropatterning 3 // 2.2 Patterning techniques: microstructuring of UV crosslinkable polymers 5 // 2.2.1 Embossing and imprint lithographic methods 6 // 2.2.2 Stamp techniques: soft- lithography and micro contact printing 7 // 2.2.3 Mask- and template- assisted techniques 9 // 2.2.4 Inscribing patterning techniques 11 // 2.3 UV laser assisted micropatterning: // large-area- non-contact mask-less processing 14 // 2.3.1 Micro lens array patterning 15 // 2.3.2 Laser Interference Lithography 16 // 2.4 References 19 // III. Laser assisted MLA patterning: // Physisorbed microstructures by crosslinking of bulk oligomer 22 // 3.1 Micropatterning of hydrogels 22 // 3.2Photocrosslinking of PEG hydrogels 23 // 3.3 Materials and methods: crosslinking bulk PEG oligomer 25 // 3.3.10ligomer and initiators 25 // 3.3.2 Substrate preparation 26 // 3.3.3 Method: crosslinking bulk PEGdma 600 oligomer 27 // 3.3.3.1 Micro Lens Array Patterning of Bulk PEGdma 600 27 // 3.3.3.2 Photoinitiator optimization 28 // 3.3.3.3 Bioassays on patterned surfaces: // protein adsorption and HUVECs 29 // 3.3.3.4 NPCs bioassays on PDL/Laminin // and star PEG hydrogel surfaces 30 // 3.4 Results and discussion 30 // 3.4.1 Photoinitiators: screening and optimization 30 // 3.4.2 Biofunctional layer hydrophobicity-hydrophilicity 37 // 3.4.3 Other processing parameters 40 // 3.4.4 HUVECs on PEMA micropatterned surfaces 49 // 3.4.5 NPCs on PDL/laminin and starPEG // hydrogel micropatterned surfaces 52 // 3.5 References 57 // IV. Micropatterning by MLAP and LIL: // hydrogels, macromers and oligomers 59 // 4.1 Cell microenvironments and their applications 59 // 4.1.1 MLAP and LIL for micropatterning 60 // 4.2 MLAP of macromers and Ormocomp® 62 // 4.2.1 Materials 62 // 4.2.1.1 Support Surfaces 62 // 4.2.1.2 Photocrosslinkable compositions 62 // 4.2.2 Method: MLAP of photocrosslinkable compositions 64 // 4.2.2.1 Patterning macromers 64 // 4.2.2.2 Patterning Ormocomp® 65 // 4.2.2.3 Microstructure characterization 66 // 4.2.2.4 Protein absorption on patterned surfaces 67 // 4.2.2.5 L-929 fibroblasts assays on micropatterned surfaces 67 // 4.2.3 Results and discussion 69 // 4.2.3.1 Patterning of macromers by MLAP 69 // 4.2.3.2 Patterning of Ormocomp® by MLAP 75 // 4.2.3.3 Protein absorption and L-929 cells on patterned surfaces 77 // 4.3 Micro lens array patterning of photocleavable hydrogel 85 // 4.3.1 Materials: Preparation of photocleavable hydrogel films on // RDG functional glass support 85 // 4.3.2 Method: MLAP of thin photocleavable biodegradable hydrogel film 87 // 4.3.2.1 NPCs on patterned hydrogel surfaces 88 // 4.3.3 Results and discussion 89 // 4.4 Laser interference lithography of PEGdma600 and Ormocomp® 97 // 4.4.1 Materials 97 // 4.4.2 Method: micropatterning by LIL 97 // 4.4.2.1 Characterization of microstructures 98 // 4.4.3 Results and Discussion 98 // 4.5 References 101 // V. "Grafting From" and "Grafting To" patterned polymer brushes by LIL 105 // 5.1 Polymer Brushes 105 // 5.1.1 Patterning "Grafting From" brushes by self-initiated polymerization // and Grafting (SIPGP) 107 // 5.1.2 Chemical Adsorption: "Grafting To" technique 108 // 5.2 Patterned polymer brushes by LIL: GF technique 110 // 5.2.1 Materials 110 // 5.2.2 Method: GF polymerization by laser interference lithography 112 // 5.2.2.1 Characterization of patterned surfaces 113 // 5.2.3 Results and discussion: GF patterned brushes by LIL 113 // 5.3 Patterned brushes by LIL: GT technique 120 // 5.3.1 Materials: GT patterned polymer brushes 120 // 5.3.2 Method: GT patterned of polymer brushes by LIL 121 // 5.3.2.1 Characterization of patterned surfaces 121 // 5.3.3 Results and Discussion: GT patterned polymer brushes by LIL 122 // 5.4 Patterned "Grafting To" brushes by two-photon lithography 125 // 5.4.1 Materials: GT by two-photon lithography 125 // 5.4.2 Method: "Grafting to by two-photon lithography 125 // 5.4.3 Results and discussion: // "Grafting to" brushes by two-photon lithography 126 // 5.5 References 127 // VI. Conclusions 131 // 6.1 Microstructuring by micro lens array patterning 131 // 6.1.1 MLAP of PEGdma 600 133 // 6.1.2 MLAP of macromers and Ormocomp® 134 // 6.1.3 Cell responses on patterned surfaces by MLAP 135 // 6.1.4 MLAP of photocleavable hydrogel and NPCs responses on // patterned surfaces 136 // 6.2 Microstructuring by laser interference lithography 137 // 6.2.1 LIL of PEGdma 600 and Ormocomp® with an initiator 137 // 6.2.2 GF brushes by SIPGP and LIL 137 // 6.2.3 GT brushes by LIL 138 // 6.3 Two-photon lithography of PEGdma 600 (without initiator) 139