Electrochemical and mechanical thin film sensors.

Abstract

This thesis focuses on the study of thin-film sensor technologies, novel microfabrication technologies, and thin-film technology in general. The work discusses electrochemical sensors and mechanical sensor technologies as well as fabrication strategies for them. Also included are mechano-chemical studies of the vancomycin DAla (Bacteria membrane analogue motif ) binding reaction in different chemical environments using thin-film sensor technology. One part of this thesis concentrates on the fabrication of sub-micron systems using electron beam and nanoimprint lithography in combination with UV and DUV lithography. Through these processes we successfully constructed interdigitated electrodes from gold (Au) and carbon that had electrode gaps as small as 100 nanometres. Papers discussed here present several different photo-resist systems, among them bi-layer lift-off compositions and single-layer negative tone photo- and electronbeam patterning. Additionally we demonstrated fabrication schemes using nanoimprint lithography. In addition, a pyrolysis technique for creating half-pitch carbon structures from thin film polymer resins on a sub-micron scale has been established. Carbon electrodes are often used in electroanalytical systems due to their chemical inertness and wide operation potential range There-fore, establishing a feasible scheme to create nano-scale carbon structures could have myriad implication for electroanalytical applications as well as battery and fuel cell research. And finally, aspects of mechano-chemical detection using silicon cantilever technology are presented here. The research used silicon micro-cantilevers as static deflection mode cantilever transducers to study vancomycin surface-binding reactions in a model system for a bacterial cell membrane. Vancomycin is an extremely important drug used to treat Methicillin-resistant Staphylococcus areus (MRSA) infections, which are often acquired in hospital. Electrostatic reactions were found to significantly influence the rate constants. Measuring the in-plane mechanical response induced by the binding process contributed useful information to our current understanding of how the drug behaves. The studies further elucidated aspects of the transduction mechanism for static deflection mode sensing cantilevers. While a complete understanding of transduction principles has not been established yet, we have formed an experimental basis for further theoretical and experimental studies.

Abstract (Swedish)

Popular Abstract in Swedish

Forskningen som presenteras i denna avhandling fokuserar på tillverkning av små strukturella enheter (komponenter) samt tillämpning av ny teknologi för att adressera viktiga medicinska forskningsfrågeställningar. Framtagande av teknologi som använder sig av komponenter som är tusentals gånger mindre än bredden på ett hår är svårt men möjligt. Denna avhandling fokuserar på processen att göra små komponenter av antingen metall eller kol. Sådana strukturer kan användas som elektroder för att kontrollera elektrokemiska processer. På grund av den geometriska utformningen av dessa små komponenter, så kan den elektrokemiska uppmätta signalen förstärkas. Detta uppkommer på grund av att den diffusionsdrivna masstransporten mellan angränsande elektrodstrukturer blir snabbare och effektivare. I avhandlingen så presenteras också den banbrytande möjligheten att använda pyrolysteknik för att bygga supertäta kol-komponenter med en samtidig positioneringskontroll av komponenterna på 100-nanometerskalan. Den andra delen av avhandlingen fokuserar på användning av mekaniska sensorer för att mäta molekylära interaktioner. En molekylär reaktion på en kemiskt modifierad yta kan yttra sig som en förändring av ytspänningen. Denna förändring av ytspänningen kan övervakas genom att mäta deformationen av en tunn balk, en balk vars tjocklek är en miljondel aven meter. Balken böjer sig som en funktion av ytspänningen. En böjning ned till en tiondel av en nanometer kan enkelt detekteras med optisk teknik. Böjningens utslag beror i sin tur på hur effektivt en viss typ av kemiskt ämne binder till ytan. I min avhandling så studeras ett kemiskt ämne som är ett läkemedel - och ett antibiotikum - vankomycin. Vancomycin år ett mycket viktigt läkemedel. Det är ett av de få läkemedel som idag effektivt kan användas vid behandling av antibiotikaresistenta bakterier eller så kallade "super-bugs". Målet med mitt arbete är att i ett modellsystem med bakterier förstå hur detta ämne fungerar. Med sådan kunskap skulle det kunna vara möjligt att formulera nya, mer effektiva syntetiska antibiotika.



Popular Abstract in English

The research presented in this thesis focuses on the fabrication of miniature devices and the application of novel technology to address important medical research challenges. The fabrication of technology that has components thousands of times smaller than the width of a hair is difficult but possible. This thesis focuses on the process of making tiny components from either metal or carbon. Such structures can be used as electrodes to monitor electrochemical processes. In addition, due to the geometric design of these tiny components, the electrochemical measured signal is amplified because of diffusion driven mass transport between adjacent electrode structures. For the first time, the possibility of using pyrolysis to construct super dense carbon components with high control of the positioning down to the one hundred nanometre scale is presented. The second part of thesis focuses on the use of mechanical sensors for measuring molecular interactions. A molecular reaction on a chemically modified surface can manifest itself as a change in surface stress. This change in surface stress can be monitored by the deflection of a thin beam, one millionth of a metre thick. The beam bends effectively, responding in a range of one tenth of a nanometre depending on how efficiently a type of substance binds to the surface. The chemical component studied in this thesis is the antibiotic vancomycin, which is important because it is one of the few drugs that can effectively treat antibiotic-resistant bacteria or so-called “super-bugs”. By understanding how this drug works on model systems for bacteria, it could be possible to formulate new, more effective synthetic antibiotics.

• author: Skjolding, Lars Henrik
• supervisor: Lars Montelius; Jenny Emnéus
• opponent: Professor Nyholm, Leif, Dept of Materials Chemistry, Uppsala Univ, Ångström lab, 751 21 Uppsala
• organization: Solid State Physics; Nanometer structure consortium (nmC)-lup-obsolete (research group)
• publishing date: 2010
• type: Thesis
• publication status: published
• subject: Condensed Matter Physics
• keywords: vancomycin, electrochemistry, transducer, DUV lithography, nanoimprint lithography, thin film, cantilever, sensor, interdigitated electrode, electrostatic interaction, mix-and-match processing, bacteria, Fysicumarkivet A:2010:Skjolding
• pages: 150 pages
• defense location: Fysiska Institutionen, Hörsal B, Sölvegatan 14, Lund, Sweden
• defense date: 2010-05-07 13:15:00
• ISBN: 978-91-628-7920-4
• language: English
• LU publication?: yes
• id: be52af85-9eb9-4a8b-8668-59befce8b46d (old id 1583214)
• date added to LUP: 2016-04-04 10:37:11
• date last changed: 2018-11-21 20:59:49