Alina Popescu

The Nanopous Al2O3 Material Used for the Enzyme Entrapping in a Glucose Biosensor

This paper presents the enhanced performances of a glucose biosensor constructed with a dielectric multi-layer Si/SiO2/Si3N4/Al2O3. If the Si/SiO2 system is present in all the silicon integrated sensors, the biosensors processing involves special attention to the intermediate layer responsible for the biological receptors entrapping. A first experience imposes to use the Si3N4 layer over the SiO2 layer mainly to stops the Na + and K + ions diffusion from bio-environment toward the silicon transducer. These results are reflected in the CV traced curve and a minimum leakage current. The nitride besides to a nanometric top Al2O3 layer grown by anodization, helps to a better enzyme entrapping, maintains the GOD active centers and are in agreement with the planar technology require- ments. An original Al2O3 deposition technique is presented. The final multilayer structure was characterized as a capacitor by CV-metry, ellipsometry, impedancemetry.

Some particular aspects of the thin membrane by boron diffusion processes

Abstract Micromachining techniques have an increasing importance in the development of microsensors applications. For free standing 3D structures bulk and surface micromachining are used. This paper presents experimental results concerning thin membranes, realized by p + etch stop techniques. We obtained a concentration of 1×10 20 cm −3 through thermal diffusion from boron + solid source by a performed program (thermal cycles). This value is enough for stop-etch layer in anisotropic etching of silicon (100) in KOH solution at 80°C. Spreading resistance has measured the boron profile. The wafers were processed in two ways. Some of them were boron diffused over the entire area of the wafer and other were diffused only in pattern geometries, defined in silicon after thermal oxidation. In this case, we have used double side alignments. We define square geometries for the membranes, with 1.5 and 2.5 mm 2 areas. The performance result could be noticed from the thickness of the membranes of 10–12 μm with good uniformity on wafers.

A two-terminals biodevice with a neurotransmitter solution

This paper proposes another destination for a biodevice. Frequently, the polarografy and amperometry methods are used to detect the analytes concentrations in biosensors. The purpose of the present device is to characterise the electrical properties of one of the most important neurohormone from the human body: epinephrine. Some experimental curves provide information about the non-linear electrical conduction through this neurotransmitter solution.

Front Surface Texturing Processes for Silicon Solar Cells

This paper presents the results of an experimental study regarding the increase in the efficiency of the silicon solar cells, using various methods for texturing the front surface. Designing, patterning and surface etching processes led to obtain reined structures with very low losses of the incident optical radiation. This paper aims to compare the fabrication method using the proposed textured surfaces with the standard method.

Organic Compounds Integrated on Nanostructured Materials for Biomedical Applications

This paper intends to present review aspects of our recent developments in the area of biodevices, nano-structures, organic compounds and integration techniques. Some simulation techniques accompany the hardware products or depict some virtual tools frequently exploited during the design stage. The main results reefer to TiO2 nanostructures used to improve the enzyme adherence in biosensors, planar Nothing On Insulator nano-devices simulation, nano-particles application in biofabrication, besides to organic semiconductors in conjunction with bio-receptor integration for pesticide or glucose detection.

THE ELECTRODES GEOMETRY DESIGN AND GLOBAL SIMULATIONS FOR AN ENFET GLUCO-DETECTOR

The ENFET biodevice integrates on the same chip a field effect transistor as transducer and an enzymatic receptor within a biosensor. This paper presents the global simulations of a MOSFET transistor working as a glucose detector, besides to the computer aided design for the electrodes geometry definition. The values of the simulated parameters prescribe the fabrication process, doping and sizes. A particular experiment for the reference electrode TiAg/AgCl manufacturing is presenting as an original item. Using dedicated software tools, the layers that constitute the fabrication masks for the final ENFET are established, as another novelty of this paper.

Electrochemical processes and characterisation of doped Tio 2 thin films; Relationship between preparation conditions and nanostructure

In this paper, we report an experimental study on electrochemical anodization using different acidic electrolytes of high purity Ti thin film deposited on silicon substrate by sputtering.

Technological Methods for Low Temperature Microfluidic Devices Microfabrication

The microchannel based microfluidic devices were obtained using techniques assuming thermal treatments up to 1000degC affecting the processes previously realized on the IC chip. This paper aims to realize low temperature technological processes to obtain microfluidic devices used for biological applications, and in thermal transfer as micro-heat sinks, used in IC chip cooling. The both methods use the positive resist as a sacrificial layer, for the first one having thickness 2 mum obtaining semicircular channels with applications in biology, for second one 15-20 mum, obtaining near-rectangular channels having applications in thermal transfer for IC chip cooling.

Two Alternative Low Temperature Technological Methods for Microchannels Microfabrication

Microchannel are very important for microfluidic devices because they carry liquid or fluid quantities, aiming to realize biochemical micro reactions, IC cooling, etc. The most of microfluidic devices used until now bulk micromachining technologies to fabricate microchannels, microchambers, involving high temperature bonding processes. So, the material cost is enough expensive because one extra wafer is needed to encapsulate the microfluidic system. In this paper, two low temperatures. IC compatible technological processes for microchannels based microfluidic devices fabrication are described. Arrays of microchannels and microfluidic devices (comprising also microchambers/microalveoli) have been fabricated on silicon, or other substrates

A model for describing the effect of series resistance in pseudo-MOS transistors

This work presents the modeling of drain and source series resistances (R/sub S/ and R/sub D/) effects in MOS transistors, in the linear and saturation regions of operation. The investigation is focused on the saturation regime, where R/sub S/ and R/sub D/ can be determined independently. There are also presented typical values extracted for MOSFET series resistances.