Réalisation et caractérisation de microélectrodes de pH : Application au contrôle qualité du greffon de la cornée

Après le prélèvement d’une cornée pour un greffage éventuel, celle-ci est conservée dans un milieu de culture. Lors de cette conservation il existe un risque de contamination bactériologique. Elle se manifeste par une variation locale de pH de la cornée lorsqu’elle est colonisée par les bactéries. Dans ce contexte nous avons conçu un système de mesures ponctuelles du pH de la cornée. Nous décrirons les étapes qui nous ont permis d’atteindre cet objectif. La miniaturisation de ce capteur de pH potentiométrique tout solide offre la possibilité de mesurer des pH ou un gradient de pH dans plusieurs autres domaines. Son originalité réside dans l’utilisation de polymères transducteurs électro-déposés présentant une sensibilité Nernstienne

A very simple compensation technique for bent V-grooves in KOH etched (100) silicon when thin structures or deep etching are required

International audienceCompensation techniques for producing well-defined bent V-grooves in KOH etched (1 0 0) silicon have been widely proposed. However, many of the methods presented in the literature suffer from two drawbacks: the etching depth is supposed to be equal to the V-groove depth and the V-groove must be wide enough for the compensation structures to fit in the pattern. A few solutions have been proposed in order to get round these disadvantages, but they are generally complicated to implement. In this paper, we propose a very simple compensation technique to obtain well-defined structures with any arbitrary etching depth and/or V-groove width. The only condition for the compensation is that the V-groove must be long enough

Self-centring technique for fibre optic microlens mounting using a concave cone-etched fibre

International audienceSeveral techniques of centring a microlens onto the fibre optic end face are studied. In most of them, microsphere lenses are centred with the aid of high-accuracy micro-positioners. This process is complicated with regard to the difficulty in manipulating microsphere lenses. In this paper, a simple and accurate self-centring method for mounting microsphere lenses using a concave cone etched fibre (Demagh et al 2006 Meas. Sci. Technol. 17 119-22) is described. This technique allows the centring of a wide variety of microlens radii, typically 7 mu m to over 24 mu m. The proposed process, however, is not affected by any spatial positioning control of microspheres. In over 85% of the attempts, the microsphere lenses were centred on the fibre axis to within 0.12 mu m

Optics and Microsystems for in vitro Fertilization

There are various difficulties which reduce the percentage of success in human in vitro fertilization (IVF). One of them concerns the choice of the oocyte to be fertilized. Up to now, the selection of the mature cell to be employed essentially relies on subjective criteria. Most biologists visually estimate the morphological properties of the oocyte. Some of the microsystems we are currently developing in our laboratory propose a solution to the objective determination of some of the oocyte properties, with the ulterior motive of grouping the microsystems in a single Lab-On-Chip (LOC). In this paper, we present these microsystems or techniques (microfluidic platform, microoptics, micromechanics, and image processing) together with the first experimental results that have been achieved. To conclude, we would like to say that the systems we describe are unique and that the results we have obtained up to now cannot be achieved using any other IVF techniques. Also, these studies have been approved by the local ethics committee

Position referencing in optical microscopy thanks to sample holders with out-of-focus encoded patterns.

International audienceThis article introduces smart sample holders for optical microscopy. Their purpose is to allow the absolute determination of the position of the observed zone with respect to the sample holder itself and with a high accuracy. It becomes then straightforward to find a given zone of interest by positioning coarsely the microscope slide to the same position coordinates. Furthermore images recorded during different observation sessions; i.e. for slightly different positions; can be processed numerically in order to superimpose them with a high accuracy. Thus the slight deviations of the microscope slide position and orientation due to the different observations are compensated numerically and a perfect superimposition of the recorded images is performed. Then accurate site-by-site image comparisons become possible even for images recorded during different observation sessions and over a long period of time. The subpixel capability of the proposed method is demonstrated and those smart microscope slides constitute a new tool for live cell experiment. In practise, an encoded geometrical pattern used as position reference is inserted in a plane parallel to the surface receiving the tissue section or sample. Then the transition of the focus position from the tissue section to the position reference requires only a vertical adjustment and does not affect the lateral coordinates of observation. The numeric processing of the image of the position reference pattern allows the retrieval of the lateral coordinates that are also used for the tissue section image. Thus each image is recorded with a set of position coordinates that defines accurately the position of the observed area with respect to the sample holder itself

A full micro-fluidic system for single oocyte manipulation including an optical sensor for cell maturity estimation and fertilisation indication

International audienceIn vitro Fertilisation (IVF) is one of the therapeutic techniques offered to patients suffering from reproduction difficulties. Among the various steps involved in gamete manipulation, especially in intra cytoplasmic sperm injection (ICSI), the determination of the cell to be fertilised is critical. Usually, the choice of the oocyte relies on a visual checking of the maturity of the cell and on its morphological properties. Our current work deals with the fabrication of labs-on-chip (LOC), devoted to the characterisation of the cells before fertilisation. They consist of a platform that includes different analysis tools and a system that allows the accurate displacement between the different analysis bays. The first issue that must be addressed is the capture, the transportation and the trapping of a single oocyte on the LOC surface.We recently proposed a system based on micro-translators used for long distance transportation and micro-fluidics for accurate trapping. In this paper, we demonstrate a full micro-fluidic system which allows both, the long range displacement and the accurate trapping of a single oocyte. This simplifies the LOC because there is no more need for any micro-motor or complex mechanical systems.We also demonstrate the first optical sensor that quantifies the degree of maturity of the cell to be fertilised. This sensor can also be used as a fertilisation indicator