Search

Abstract: Soft ultraviolet nanoimprint lithography is a cost-effective and versatile technique for the transfer of nano-scaled patterns to various surfaces. Here, we report on the fabrication of sub-micron square pillar arrays in epitaxial Ba0.7Sr0.3TiO3 ceramic films, using a combination of nanoimprint lithography and inductively coupled plasma etching techniques. Based on a similar approach we have also succeeded in preparing positive (direct) and negative (inverse) replicas of silicon master molds. Such a generic process could find application in various materials. [Copyright &y& Elsevier]

Abstract: Soft UV nanoimprint lithography and reactive ion etch techniques have been used to pattern high density and high aspect ratio nanostructures on the surface of a plastic plate such as Plexiglas. A thin film of photo-curable resist is first spin coated on the plastic plate, with or without deposition of a 10nm thick germanium intermediate layer. Then, a soft stamp made of poly-dimethylsiloxane (PDMS) is used to mold the photo-curable resist, followed by a UV light exposure. Finally, the imprinted pattern is used as mask for a sequential reactive ion etch of the residual resist layer, the intermediate layer if any, and the plastic plate. Such a soft nanoimprint and direct etch technique allowed us to obtain high density nanostructures with an aspect ratio up to 15. To demonstrate the applicability of such systems in biology, wetting behaviours and surface functionalization with fluorescent protein molecules have been studied. We believe that this low cost approach is high throughput and efficient for a number of applications. [Copyright &y& Elsevier]

Abstract: Online impedance monitoring of cell suspensions can be performed with integrated microelectrode array in microfluidic devices. However, its accuracy is affected by the formation of cell aggregates on the surface of the electrode array. To make this technical more reliable, we deposited a thin film of agarose which is highly permeable to soluble ions on the electrodes. The growth behavior of yeast cells in YPD medium was studied for more than 24h and the recorded impedance spectra were used to determinate the cell metabolism induced changes of the medium resistance and the double layer capacitance as a function of time. Our results showed a much more important variation of the double layer capacitance, indicating the importance of online monitoring at low frequencies. [Copyright &y& Elsevier]

Abstract: This paper presents a comparative study of three methods for preparing integrated nanoporous TiO2 films for microfluidic based photocatalytic reactors. These porous films have inherent merit of large surface-to-volume ratio and should significantly improve the device photoreactivity. It is also expected that nanoporous thin films have different performance in microfluidic chambers from that in an open environment. Experimentally, films produced by water-based P25 TiO2 colloids and alcohol-based P25 TiO2 colloids as well as tetrabutyl titanate sol–gel have been implemented into both microfluidic chambers and bulk containers for a close comparison using photocatalytic induced degradation of methylene blue model chemical. The results show that although the water-based P25 method produces TiO2 films with lower performance than the alcohol-based P25 method in the bulk container, it achieves the highest reaction rate in the microreactor (1.4%s−1, 17% higher than the alcohol-based P25 method and seven times higher than the TBT synthesis method). Such comparison suggests that the water-based P25 method may be a good choice for the microreactor. [Copyright &y& Elsevier]