pH-CHEMFET-BASED ANALYSIS DEVICES FOR THE BACTERIAL ACTIVITY MONITORING

International audienceSilicon and polymer microtechnologies have been developed in order to integrate pH-metry techniques in the frame of medical diagnosis. Thus, a fluidic analysis device has been designed and realised in order to monitor pH-related bacterial activities. It includes a SiO2/Si3N4 pH-sensitive chemical field effect transistor (pH-ChemFET), its titanium/gold pseudo-reference gate electrode and a poly-dimethylsiloxane (PDMS) integrated flow-cell (total volume: ≤ 2 mm 3). The whole analysis device has been used to detect the biological activities of the Lactobacillus Crispatus bacteria and to estimate its sensitivity to antibiotics. Results demonstrate the detection of pH-related bacterial metabolisms in microvolumes, enabling to reduce significantly the analysis response time with regards to standard procedures and to think to the development of pH-ChemFET-metry for medical analysis

Very high frequency probes for atomic force microscopy with silicon optomechanics

Atomic force microscopy (AFM) has been constantly supporting nanosciences and nanotechnologies for over 30 years, being present in many fields from condensed matter physics to biology. It enables measuring very weak forces at the nanoscale, thus elucidating interactions at play in fundamental processes. Here we leverage the combined benefits of micro/nanoelectromechanical systems and cavity optomechanics to fabricate a sensor for dynamic mode AFM at a frequency above 100 MHz. This is two decades above the fastest commercial AFM probes, suggesting opportunity for measuring forces at timescales unexplored so far. The fabrication is achieved using very-large scale integration technologies inherited from photonic silicon circuits. The probe’s ring optomechanical cavity is coupled to a 1.55 um laser light and features a 130 MHz mechanical resonance mode with a quality factor of 900 in air. A limit of detection in displacement of 3.10-16 m/sqrt(Hz) is obtained, enabling the detection of the Brownian motion of the probe and paving the way for force sensing experiments in the dynamic mode with a working vibration amplitude in the picometer range. Inserted in a custom AFM instrument embodiment, this optomechanical sensor demonstrates the capacity to perform force-distance measurements and to maintain a constant interaction strength between tip and sample, an essential requirement for AFM applications. Experiments show indeed a stable closed-loop operation with a setpoint of 4 nN/nm for an unprecedented sub-picometer vibration amplitude, where the tip-sample interaction is mediated by a stretched water meniscus

IC compatible MEMS technology

This paper deals with an Integrated Circuits (ICs) compatible MEMS technology, which is used to elaborate an ultra compact RF communication module centered at 24GHz. This technology uses conventional equipments and is in adequation with millimeterwave applications. A compatibility test protocol has consequently been defined in order to check that each technological step does not degrade the SiGe circuits’ performances. Finally, the realized demonstrator present a total surface of only 9mm²

Geometry optimization of uncoated silicon microcantilever-based gas density sensors

International audienceIn the absence of coating, the only way to improve the sensitivity of silicon microcantilever-based density sensors is to optimize the device geometry. Based on this idea, several microcantilevers with different shapes (rectangular-, U-and T-shaped microstructures) and dimensions have been fabricated and tested in the presence of hydrogen/ nitrogen mixtures (H 2 /N 2) of various concentrations ranging from 0.2% to 2%. In fact, it is demonstrated that wide and short rectangular cantilevers are more sensitive to gas density changes than U-and T-shaped devices of the same overall dimensions, and that the thickness doesn't affect the sensitivity despite the fact that it affects the resonant frequency. Moreover, because of the phase linearization method used for the natural frequency estimation, detection of a gas mass density change of 2 mg/l has been achieved with all three microstructures. In addition, noise measurements have been used to estimate a limit of detection of 0.11 mg/l for the gas mass density variation (corresponding to a concentration of 100 ppm of H 2 in N 2), which is much smaller than the current state of the art for uncoated mechanical resonators

Efficient prototyping of large-scale pdms and silicon nanofluidic devices using pdms-based phase-shift lithography

International audienceIn this study, we explore the potential of poly-dimethylsiloxane (PDMS)-based phase-shift lithography (PPSL) for the fabrication of nanofluidic devices. We establish that this technology, which was already shown to allow for the generation of 100 nm linear or punctual features over squared centimeter surfaces with conventional photolithography systems, is readily adequate to produce some of the most popular nanofluidic systems, namely nanochannels and nanoposts arrays. We also demonstrate that PPSL technology enables to generate PDMS and silicon nanofluidic systems. This technological achievement allows us to perform single DNA molecule manipulation experiments in PDMS and silicon nano-channels, and we observe an unexpectedly slow migration of DNA in PDMS devices, which is independent on salt or pH conditions. Our data in fact hint to the existence of an anomalous response of DNA in PDMS nanofluidic devices, which is likely associated to transient nonspecific interactions of DNA with PDMS walls. Overall, our work demonstrates the efficiency and the performances of PPSL for prototyping nanofluidic systems

Development and implementation of eco-genomic tools for aquatic ecosystem biomonitoring: the SYNAQUA French-Swiss program

International audienceThe effectiveness of environmental protection measures is based on the early identification and diagnosis of anthropogenic pressures. Similarly, restoration actions require precise monitoring of changes in the ecological quality of ecosystems, in order to highlight their effectiveness. Monitoring the ecological quality relies on bioindicators, which are organisms revealing the pressures exerted on the environment through the composition of their communities. Their implementation, based on the morphological identification of species, is expensive because it requires time and experts in taxonomy. Recent genomic tools should provide access to reliable and high-throughput environmental monitoring by directly inferring the composition of bioindicators' communities from their DNA (metabarcoding). The French-Swiss program SYNAQUA (INTERREG France-Switzerland 2017-2019) proposes to use and validate the tools of environmental genomic for biomonitoring and aims ultimately at their implementation in the regulatory bio-surveillance. SYNAQUA will test the metabarcoding approach focusing on two bioindicators, diatoms, and aquatic oligochaetes, which are used in freshwater biomonitoring in France and Switzerland. To go towards the renewal of current biomonitoring practices, SYNAQUA will (1) bring together different actors: scientists, environmental managers, consulting firms, and biotechnological companies, (2) apply this approach on a large scale to demonstrate its relevance, (3) propose robust and reliable tools, and (4) raise public awareness and train the various actors likely to use these new tools. Biomonitoring approaches based on such environmental genomic tools should address the European need for reliable, higher-throughput monitoring to improve the protection of aquatic environments under multiple pressures, guide their restoration , and follow their evolution