Oana Nedelcu

Ceramic Micro Heater Technology for Gas Sensors

The paper presents the design and manufacturing steps of micro heaters, built on ceramic suspended membranes for gas sensor applications. The micro heaters are designed and fabricated by combining laser milling techniques, and conductive ceramic technology. Trenches are created in the ceramic substrate in order to define the geometry of the heater using laser processing of the substrate. The heater is completed by filling the trenches with conductive ceramic paste and then baking to remove the solvent from the paste. The final step involves releasing the membrane by laser milling, enabling it to be suspended on four bridges, to minimise the dissipation of the heat in the substrate. The temperature of the heater element was measured with a heat camera from FLIR 40 system comparing the case of the heater positioned on top of a released membrane and that of the non-released membrane. The simulation of the heater build on top of a released membrane was compared with the heater measurements

The modeling of a sensor for the human blood pressure

Blood pressure detection requires both sound detection and pressure measurements. Piezoelectric materials fulfill both aims. Starting from a previous work, a pressure sensor based on a SOI transistor with a piezoelectric layer, was adapted for the blood pressure domain. The ANSYS simulations provide the mechanical stress in the structure. The ATLAS software simulates the electrical behavior. This paper offers a modeling of the sensor and consequently design guidelines.

Modelling and Simulation of a Pneumatically Actuated Micropump

Performances of a pneumatically actuated micropump are described. Simulation results combined to an analytical model are used to optimize the micropump design in order to obtain a working frequency of 10 Hz for pneumatic pressure varying between 0.1-6 bar. A pneumatic chamber is placed between a polymer membrane to be actuated, and microchannels connected to a vacuum system. Time for pressurizing cycle and vacuum cycle as function of design parameters and relative pressure are calculated.

A silicon nanoporous membrane used for drug delivery

In the last years, biomedical applications of micro and nanotechnologies have been focused toward multifunctional devices. This paper describes the technological process controlled by the simulation of mechanical behaviour for microporous silicon membrane. These semipermeable structures belong to a complex biodevice used in vitro for cell-based assays and in vivo for immunoisolation and drug delivery application.

Numerical study of induced electric field in a microfluidic system for cell electroporation

Electroporation represents one of the techniques used for cell research. By membrane permeabilization, biological samples can be introduced into the cells or intercellular content is released for further analysis providing information for diagnosis and treatment. This techniques is achieved in microfluidic systems with microelectrodes that induce a high electric field in the vicinity of cells to generate nanopores in cell membrane. In this paper, a micro-electro-fluidic system with channels and various configurations of electrodes is studied by electrostatic simulation in order to find the electric field distribution that ensures electroporation.

Optimization of a passive micromixer using models based on variable diffusion coefficient

In this work a passive micromixer is designed, simulated and optimized in order to obtain fully mixed liquids at the outlet. The basic configuration is a microchannel with two inlets, three outlets, and obstacles that increase the transversal component of velocity and facilitate the mixing. The simulations are based on an improved model of diffusion coefficient that depends on local concentration and properties of each mixing liquid. The model is applied to two cases of miscible fluids: water with methanol and water with glucose solution. The simulations based on this model are used to optimize design specifications. The results are discussed in terms of velocity and concentration distribution and compared to results obtained by classic approach.

Design and manufacturing of micro heaters for gas sensors

Abstract The paper presents the design and manufacturing steps of micro heaters, built on ceramic suspended membranes for gas sensor applications. The micro heaters are designed and fabricated by combining laser milling techniques, and conductive ceramic technology. Trenches are created in the ceramic substrate in order to define the geometry of the heater using laser processing of the substrate. The heater is completed by filling the trenches with conductive ceramic paste and then baking to remove the solvent from the paste. The final step involves releasing the membrane by laser milling, enabling it to be suspended on four bridges, to minimise the dissipation of the heat in the substrate. The temperature of the heater element was measured with a heat camera from FLIR 40 system comparing the case of the heater positioned on top of a released membrane and that of the non-released membrane. The simulation of the heater build on top of a released membrane was compared with the heater measurements.

Simulation and design of a resonant polysilicon microbridge

Chemical or mechanical microsensors based on resonant microstructures can be produced in microsystems silicon technology. Detection is related to a shift of the resonant frequency of a microbridge by means of a laser beam. The use of conductive polysilicon is appropriate for fabrication of the structure. This paper develops a reliable electromechanical model for design of the device and its technological process. By MemCAD and MathCAD software the dynamic behaviour is numerically simulated. Random deviations for physical and technological parameters were also simulated by the Monte Carlo method.

Design and simulation of a piezoelectric sensor with applications in image stabilization

The piezoelectric materials used in the device industry with a very high market share are piezoceramics. They are used in medicine, robotics, mechanics but not least and the image stabilization. This material is easy to handle and with good properties related to mechanical and electric response. In full development are micro-electro-mechanical systems (MEMS) that bring with them new features, but also as small size, so they can be integrated into almost any device on the market. In this paper a piezoelectric accelerometer has been designed and optimized by simulation studies regarding the material and geometry. Based on electric response as function of mechanical deformation, an optimized geometry has been proposed and investigated by numerical analysis using Comsol Multiphysics software package. The simulation results for this new configuration are discussed and compared to basic accelerometers design.

Numerical design of a 3D microfluidic systems for bioparticle analysis: Electrostatic and dielectrophoretic simulations

Development of in vitro techniques for medical and industrial applications has introduced over the past few years modern devices for detecting and manipulation of biological probes. A major interest is granted for unicellular analysis in order to produce new techniques for cell membrane permeabilization. Microfluidics became an indispensable tool used in cell research and analysis. In this paper, we present a new device for cell manipulation, electroporation and observation. Dielectrophoresis (DEP) is used to transport the cells by dielectroforetic forces (FDEP). The influence of electric field and flow behavior is studied. The simulation results show the influence of flow and dielectrophoretic force on cells migration inside the microfluidics channel.