Design of a cantilever-based system for genomic applications

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A Silicon micromachined alcoholometer

This research work was aimed to find an innovative process based on MEMS technologies to measure the alcoholic strength of hydro-alcoholic solutions. A new Silicon micromachined alcoholometer was developed. A microhotplate based on dielectric thin membrane is used to heat and measure the temperature of droplets of hydro-alcoholic solution dispensed by a tiny capillary during an evaporation cycle. It was found that the alcoholic strength is correlated with the integration of the temperature of the droplet over time during its evaporation. Opposed to the old measurement methods this new procedure takes advantage of many properties of the hydro-alcoholic solutions such as: superficial tension, latent heat of evaporation, boiling point and heat capacity. All these issues contribute together to give a good response in terms of good resolution and accuracy over a wide range of alcoholic degree

An innovative microalcoholometer based on AI2O4 microhotplates

The demand of on-line monitoring of processes in wine and spirit production is growing every year, as it can help to increase the quality of the goods and the efficiency of the production. The measurement of the alcoholic degree plays an important role in this field. This paper reports the development of a new Al2O3 microalcoholometer based on an innovative principle of measurement

Development of a microfabrication technology for microcantilever-based detection modules in Lab-On-a-Chip application

Nowadays, the development of Lab-On-a-Chip (LOC) technologies has opened up new perspectives in the field of personalized diagnosis and treatment, by taking advantage of reduced size, low volume requirement for samples, and rapid analysis. In particular, MEMS, microelectronics and nanobiotechnology are enabling technologies for the realization of biosensors by combining both microsystems for sample handling, signal read-out and functionalization methodologies able to detect specific bioaffinity reactions. In this frame, LOC technologies are a powerful tool to perform a wide range of proteomic and genomic tests starting from fluid biological samples such as blood or saliva. In this work we present the design and realization of the first prototypes for testing a technology for LOC detection module for pre-screenings of autoimmune diseases such as multiple sclerosis and rheumatoid arthritis in point-of-care applications. This module is based on arrays of silicon microcantilevers, which are typically suspended beams realised with MEMS fabrication technologies, suitable for biological and chemical sensing. Sensitivity to specific analytes can be achieved by coating the beam surface with proper films, able to selectively bind a particular target molecule. A self assembled monolayer (SAM) of known ss-DNA probes will represent the functional layer. The following hybridization of the complementary target sequence induces a differential stress between the top and the bottom surfaces of a cantilever, driving the deflection of the beam. The proposed technological approach is based on the fabrication of microcantilevers starting from Silicon-On-Insulator (SOI) substrates, allowing an extreme reduction in the thickness of the beams (380 nm), parameter that is related to the sensitivity of the overall biosensor. Both analytical and finite element analysis have been performed, focused on the general validation of the approach and on the design optimization respectively. Preliminary results on the fabrication and testing will be also highlighted

Influence of masking layer stress on anisotropic silicon etching in TMAH solutions

Nowadays MEMS device fabrication requires an accurate knowledge of the silicon etching parameters. We studied the relation between thin film masking layers residual stress and the orientation dependence of the silicon etching rate using TMAH solutions. In particular we focused on widely used masking films such as SiO2 and Si3N4. Dedicated test structures were designed, fabricated and tested. We found an influence of the masking layer residual stress on the silicon etching rate anisotropy and a lower value of anisotropy for higher stressed structures

Mechanical characterization of thin TiO2 films by means of MEMS-based cantilevers

The measurement of mechanical parameters by means of microcantilever structures offers a reliable and accurate alternative to traditional methods, especially when dealing with thin films, which are extensively used in microfabrication technology and nanotechnology. In this work, MEMS-based piezoresistive cantilevers were realized and used for the determination of Young’s modulus and residual stress of thin titanium dioxide (TiO2) deposited by sputtering from a TiO2 target using an RF plasma discharge. Films were deposited at different thicknesses, ranging from a few to a hundred nanometers. Dedicated silicon microcantilevers were designed through an optimization of geometrical parameters with the development of analytical as well as numerical models. Young’s modulus and residual stress of sputtered TiO2 films were assessed by using both mechanical characterization based on scanning profilometers and piezoresistive sensing elements integrated in the silicon cantilevers. Results of MEMS-based characterization were combined with the tribological and morphological properties measured by micro-scratch test and XRD analysis

Micromachined flow sensor on silicon membrane

Design, realisation and testing results of an integrated air flow sensor based on micromachined technology are reported. The mass airflow sensor architecture is based on a dedicated microlelectronic thermal (hot-wire) anemometer design. Two different layouts for the two different splittings projected one for a polysilicon resistor and the other one for a gold resistor has been implemented. This device has a very small sensor size, with a low power consumption, a good accuracy, a very low signal-to-noise ratio, an excellent frequency response, a simultaneous fluid temperature measurement and a low fabrication cost. We realised a micro air flow sensor prototype, fabricated with MEMS technologies. Electro-mechanical tests have been carried out thus demonstrating the high performance of the device

MOS Junction based Nanostructures by Thermal Oxidation of Silicon Wires for Hydrogen Detection

Heavily p-doped monocrystalline silicon wires have been fabricated by employing wet etch and thermal oxidation steps to achieve a nanometric cross-section; a gate oxide growth and a final palladium evaporation made up the MOS junction able to detect hydrogen concentrations in air