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The buckling of stiff film on a substrate had been of great interest as this response happen spontaneously and is self-organizing. This provides an unconventional, scalable and easy way to fabrication surfaces with tunable structures from the range of nanometers to micrometers. We optimized a process to fabricate stretchable electrodes by transferring wrinkled gold onto elastomer. We tested their electrochemical sensing functionality through detection of glucose concentration with or without strain. Results showed that the stretchable electrodes provide high sensitivity for the detection of glucose (860 ± 60 µA/mM.cm2), comparable to electrodes before transfer. The current detected was also consistent under strain. Investigation of the resistance indicates that the electrode configuration under strain is important as current running parallel to direction of strain is much more affected under tension. We also developed a fast and facile process to fabricate surfaces that consisted of wrinkles and nanoparticles. Using such surfaces, we tested the omniphobicity effect of hierarchical structures consisting of wrinkles and nanoparticles. Results show that all the fluorinated structured surfaces were hydrophobic, ranging from water contact angle of 125° for wrinkled surfaces to 155° for hierarchical surfaces. The surfaces that were either wrinkled or decorated with nanoparticles were oleophilic with low hexadecane contact angles (~26° and ~55° respectively). The combination of both structures achieved oleophobicity of more than 110°. The effectiveness of nanoparticles for low surface tension liquid were due to its re-entrant like structure. The omniphobic surfaces were also shown to be repellent to blood (>135°), making it a potential material for use medical devices. / Thesis / Master of Applied Science (MASc) / Wrinkling is a phenomenon often seen in real life, such as on the skin of a dried plum or human. It is possible to fabricate such wrinkles through having a stiff thin film adhered to an elastic foundation and compressing the foundation. The wrinkles are useful for fabrication of stretchable electrodes as their structure allows the film to stretch without breaking through unfolding. Here, we fabricated stretchable electrodes by transferring such wrinkled structures onto elastic foundation. These stretchable electrodes are shown to be able to detect the concentration of glucose in solution even when stretched. These electrodes are important for creating wearable devices that can monitor glucose levels or other substance continuously. Wrinkles also work as part of hierarchical structure which are helpful for trapping air beneath droplets of fluids. Here we incorporate wrinkles with nanoparticles which helps to make surfaces repellent to both water and oil. Such a function is important for self-cleaning surfaces and can also be used for patterning of surfaces for selective deposition of fluid.

Chronic nerve recording and stimulation can be performed by means of nerve cuff electrodes in both animals and humans. These extraneural electrodes have been used not only for fundamental research but also for rehabilitation purposes as part of a neuroprosthetic device. They have therefore contributed to our knowledge of the nervous system and also allowed partial motor and sensory rehabilitation. However, the performance of existing nerve cuff electrodes remains limited and their designs must be improved. The main drawbacks of cuff electrodes are their poor selectivity and the morphological modifications they induce to surrounding tissue. Their selectivity is mainly dependant on the number of contacts which is limited by the hand-made manufacturing process. The morphological modifications are determined by the tissue-electrode interactions. A new spiral cuff nerve electrode is proposed to improve the selectivity and lessen the tissue reaction. The manufacture of this new electrode, based on photolithographic metal deposition technology, should allow for an increased number of contacts. Additionally, this electrode has self-sizing properties that potentially lowers the implant-induced tissue reaction. The present work aims to study the interactions between the electrode and implanted tissue in an attempt to better characterise the tissue reaction and to further control it. Firstly, the interactions between connective tissue and the laser-irradiated-platinum-metallised silicone rubber are assessed both with in vitro and in vivo methods. The cytocompatibility and biocompatibility of silicone is not altered by the platinum deposition process, suggesting that this new biomaterial can be used to manufacture cuff electrodes that can safely be implanted for chronic studies. The mechanical biocompatibility of spiral cuff nerve electrodes is then investigated by morphological, immunohistochemical and western-blots analyses. The peri-operative, acute and chronic events that are related to the implantation are studied. The results show that the commonly described fibrotic reaction surrounding the implant is preceded by an important early epineurial inflammation. Additionally, cytokines involved in this tissue reaction are identified and include the pro-inflammatory cytokine TNF-alpha and pro-fibrotic cytokine TGF-beta1. In continuation of the biocompatibility testing, cytokine neutralisation through monoclonal antibodies is proposed as a way to control some of the cuff electrode-induced tissue modifications. Immunohistochemistry and morphometry are used to demonstrate the feasibility of such a control. Results show that a single systemic injection of TNF-alpha neutralising antibodies is sufficient to reduce the early inflammatory reaction occurring in the epineurial compartment but not the subsequent fibrosis. The success of an implanted neuroprosthesis is fully dependant upon the interaction between the electrode and the surrounding tissue. This study suggests that, when trying to improve the design of an electrode, one should also consider the modulation of the tissue reaction as a convenient way to enhance the implanted electrode's long-term performance. / L'enregistrement et la stimulation chroniques de nerfs peuvent être réalisés au moyen d'électrodes neurales à manchon, aussi bien chez l'animal que chez l'homme. Ces électrodes extra-neurales ont été utilisées non seulement dans le cadre de recherches fondamentales mais aussi à des fins de réhabilitation au sein d'un dispositif neuro-prosthétique. Elles ont ainsi contribué à notre connaissance du système nerveux et ont parfois permis une restauration sensorielle et motrice partielle. Les performances des électrodes existantes demeurent cependant limitées et leur design doit être amélioré. Les principales faiblesses de ces électrodes à manchon sont leur sélectivité, insuffisante, et les modifications morphologiques qu'elles induisent au sein des tissus implantés. La sélectivité des électrodes dépend principalement du nombre de contacts que limite un procédé de fabrication manuel. Les modifications morphologiques sont, quant à elles, déterminées par les interactions entre les tissus et l'électrode. Une nouvelle électrode neurale, dite à manchon spiral, est proposée qui devrait accroître la sélectivité et réduire la réaction tissulaire. La fabrication de cette nouvelle électrode, basée sur la technologie de déposition photolithographique de métaux, devrait permettre d'augmenter le nombre de contacts. De plus, en raison de son aptitude à s'adapter au diamètre du nerf, cette électrode devrait potentiellement limiter la réaction tissulaire induite par l'implant. Le but de ce travail est d'étudier les interactions entre l'électrode et les tissus implantés afin de mieux caractériser la réaction tissulaire et, ultérieurement, la contrôler. Dans un premier temps, les interactions entre les tissus conjonctifs et le silicone après son irradiation au laser et sa métallisation sont testées au moyen de méthodes in vitro et in vivo. La cyto-compatibilité et la biocompatibilité du silicone ne sont pas altérées pas le procédé de dépôt du platine. Ceci suggère que ce nouveau biomatériau convient à la manufacture d'électrodes à manchon qui pourront être implantées chroniquement de façon sûre. Dans un second temps, la biocompatibilité mécanique des électrodes à manchon spiral est examinée au moyen d'analyses morphologiques, immunohistochimiques et de western-blots. Les événements péri-opératoires, aigus et chroniques liés à l'implantation sont étudiés. Les résultats montrent qu'une importante réaction inflammatoire précoce précède la réaction fibrotique autour de l'électrode, classiquement décrite après une implantation. De plus, une partie des cytokines impliquée dans la réaction tissulaire est identifiée: la cytokine pro-inflammatoire TNF-alpha et la cytokine pro-fibrotique TGF-beta1. Dans la continuité des études de biocompatibilité, la neutralisation de cytokine au moyen d'anticorps monoclonaux est proposé comme moyen de contrôle de modifications tissulaires induite par l'électrode à manchon. L'immunohistochimie et la morphométrie sont utilisées pour démontrer la possibilité d'un tel contrôle. Le résultats montrent qu'une seule injection systémique d'anticorps anti-TNF-alpha est suffisante pour réduire la réaction inflammatoire précoce dans le compartiment épineurial mais pas la fibrose subséquente. Le succès d'une neuroprothèse implantable dépend entièrement des interactions entre l'électrode et les tissus environnants. Cette étude suggère que, lors des tentatives d'amélioration du design des électrodes, la modulation de la réaction tissulaire devrait être considérée comme un moyen aisé d'augmenter les performances à long terme des électrodes implantées.

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