Loic Ledernez

Ultraviolet light in glow discharges

The use of ultraviolet light has prevailed in investigation of gas breakdown phenomena since Townsend developed the model of gas breakdown discharge carrying his name because ultraviolet light creates the supposedly necessary electrons in the interelectrode space. However, the ultraviolet light influences the gas breakdown characteristics. Therefore, the extent of the influence of the ultraviolet light on the prebreakdown current, the breakdown current, the breakdown voltage, and the Townsend’s coefficients is studied.

Magnetron Enhanced Plasma-Polymerization for Biocompatible Sensor Coatings and Membranes on Polymeric Based Materials

One of the key questions in the application of miniaturized sensors and actuators for acute and/or chronic use in living-body environment is the biocompatibility. In case of gas sensors additionally a very fine balance between the biocompatibility of the device and the gas (e.g. O2, NO, CO) permeability of its coating must be maintained. In many sensor configurations polymeric substrate materials are used. Here, we present the application of a unique deposition technique for nano-films with thickness ranging between 10 and 200 nm on top of flexible polymeric foils used as substrates in the technology of a variety of biosensors and lab-on-chip structures. The method employs a 15 kHz magnetron-enhanced glow discharge plasma-polymerization process using methane as precursor. It is configurable for laboratory scale batch sizes but also for continuous industrial coating lines. Unsurpassed results of this processing technique have been documented with contact lenses already. Hence, we tested depositions with this process on top of PMMA, polyimide and polystyrene foils of different surface morphology. Compatibility of the process and of the coatings with these materials, adherence in dry and aqueous environment were checked. Antibacterial behaviour of the films were tested by immersing the coated samples in a bio-film reactor for 48 hours as well as for 7 days in E-coli bacteria solutions. After the inoculation time samples were rinsed and treated in an ultrasonic bath. Colonies formed on different culture media out of the rinsing water were enumerated. Number of colony forming units, depending on inoculation time and coating conditions, has been investigated. Remarkable reduction of bacterial attachment was proven with film thicknesses as low as about 15 nm, which allows a reasonable gas permeation rate. Hence, the technology provides production of antibacterial and gas permeable membranes for miniaturized sensors and sensor arrays on chip.