Micro-Structuring of New Materials Combined with Electronic Polymers for Interfaces with Cells

Materials based on novel Off-Stoichiometry Thiol-Ene polymers, abbreviated OSTE, show promising properties as materials for low cost and scalable manufacturing of microand nanosystems such as lab-on-chip devices. The OSTE materials have tunable mechanical properties, offer possibility for low temperature bonding to many surfaces via tunable surface chemistry, and can be used in soft lithography. Unlike the commonly used elastomer poly(dimethylsiloxane), PDMS, the OSTE materials have low permeability for gasses, are resistant to common solvents and can be more permanently surface modified. In this master’s thesis project, the OSTE materials have been evaluated with focus on compatibility with cells, possibility for nanostructuring using soft lithography and the use of OSTE as a flexible support for conducting polymers. Results from cell seeding studies with HEP G2 cells suggest that cells can proliferate on a low thiol off-stoichiometry OSTE material for at least five days. The biocompatibility for this type of OSTE material may be similar to poly(styrene). However, high levels of free thiol monomers in the material decrease cell viability considerably. By using soft lithography techniques it is possible to fabricate OSTE nanochannels with at least the dimensions of 400 nm x 15 nm. Combined with the advantages of using the OSTE materials, such as low temperature bonding and possibility for stable surface modifications, a candidate construction material for future development of systems for DNA analysis is at hand. OSTE can serve as a flexible support for an adsorbed film of a conducting polymer with the possibility for future applications such as electronic interfaces in microsystems. In this project, a film of PEDOT:PSS with the electrical resistance of ~5 kΩ was created by adsorption to an flexible OSTE material. Furthermore, results suggest that it is possible to further optimize the conductivity and water resistance of PEDOT:PSS films on OSTE. Sammanfattning Material som baseras på de nya icke-stökiometriska tiol-en-polymererna OSTE, uppvisar lovande egenskaper för billig och enkel produktion av mikrooch nanosystem som t.ex. ”labon-chip”-enheter. OSTE-materialen besitter egenskaper som möjliggör finjustering av materialens mekaniska egenskaper och som ger möjlighet till att utnyttja materialets justerbara ytkemi för att kovalent binda materialet till olika ytor vid relativt milda temperaturer. Dessutom kan materialen användas inom mjuk litografi och till skillnad från den vanligen använda elastomeren poly(dimetylsiloxan), PDMS, så är OSTE materialen mer tåliga för vanligt förekommande lösningsmedel, har låg permeabilitet för gaser och kan ytmodifieras mer stabilt. I detta examensarbete så har OSTE materialen undersökts med fokus på kompatibilitet med celler, möjlighet för nanostrukturering via mjuk litografi och användning av OSTE material som böjbara substrat för adsorberade filmer av ledande polymerer. Från cellodlingsstudier med HEP G2 celler på OSTE material med lågt tiolöverskott, antyder resultaten att de cellerna kan fästa och växa på materialen i åtminstone fem dagar. Biokompatibiliteten för denna typ av OSTE material liknar den för poly(styren). Dock så visar resultaten att höga nivåer av fria tiolmonomerer hos materialen tydligt minskar överlevnaden hos cellerna. Genom att använda metoder inom mjuk litografi så har OSTE-nanokanaler med dimensionerna 400 nm x 15 nm skapats. I kombination med OSTE materialens fördelar såsom möjlighet till kovalent bindning till olika ytor vid milda temperaturer och möjlighet till stabila ytmodifikationer, så finns goda möjligheter till att använda OSTE som konstruktionsmaterial för framtida utveckling av system för DNA analys. OSTE material kan användas som ett böjbart substrat för adsorberade filmer av en ledande polymer med möjlighet för applikationer såsom elektroniska gränssnitt i mikrosystem. I detta examensarbete så skapades en film av PEDOT:PSS med resistansen ~5 kΩ på ett flexiblet OSTE material. Resultat antyder att det är möjligt med vidare optimering för ökad vattentålighet och konduktivitet hos adsorberade PEDOT:PSS filmer på OSTE. Acknowledgement First I would like to thank my supervisor PhD Student Anders Elfwing for his enthusiastic and very creative guidance and support during this diploma work. I would also like to thank my examiner Professor Olle Inganäs for his creative ideas and help. Anders and Olle have truly enabled expanding the reality! Secondly, I would like to thank the following inspiring and hard working persons who have helped me during my master’s thesis project: The researchers Dr Tommy Haraldsson and Dr Carl Fredrik Carlborg for their knowledge, for providing key components to my work and for guidance during this diploma work PhD Student Gunnar Bergström for help with the cell seeding experiments PhD Student Abeni Wickham for help with the DSC experiments and practical support during the diploma work Dr Thomas Ederth for letting me have access to several instruments PhD Student Hung-Hsun Lee for help with FTIR, Contact angle measurements and more PhD Student Jonas Bergqvist for help with the ellipsometry experiment Dr Kristofer Tvingstedt for help with conducting polymers Researcher and MSc Katarina Bengtsson for the PDMS workshop, photolithography lab and ideas PhD Student Per Erlandsson for help with master design, help with fluorescence microscopy and ideas PhD Student Michalina Lewicka for initial cell studies Dr Mahiar Hamedi, PhD Student Feng-I Tai, Dr Niclas Solin, Secretary Mikael Amlé, PhD Student Fredrick Bäcklund and Dr Viktor Andersson for ideas, support and inspiration Then I would like to thank the following groups: Biomolecular and Organic Electronics, BIORGEL, group and all its members for letting me perform my diploma work in the group and for other support Microsystem Technology, MST, group and all its members at the Royal Institute of Technology in Stockholm, for support, ideas and for letting me visit them The committee of Micronano System Workshop 2012 for me letting present my poster at the conference and for inspiring insight into the research field of microand nanosystems Finally, I would like to thank my girlfriend, family and friends for their support through life.