The development of a low-cost multiparametric platform for enzymatic electrochemical biosensing that can be integrated in a disposable, energy autonomous analytical device is the target of the current work. We propose a technology to fabricate nano-electrodes and ultimately biosensors on flexible polymeric-based substrates (cyclo olefin polymer, and polyimide) using standard microfabrication (step and repeat lithography and lift-off) and rapid prototyping techniques (blade cutting). Our target is towards the fabrication of a miniaturized prototype that can work with small sample volumes in the range of 5-10μL without the need for external pumps for sample loading and handling. This device can be used for the simultaneous detection of metabolites such as glucose, cholesterol and triglycerides for the early diagnosis of diabetes.
A novel design of a fuel-flexible micro-reactor for hydrogen generation from ethanol and methane is proposed in this
work. The micro-reactor is fully fabricated with mainstream MEMS technology and consists of an array of more than
20000 through-silicon vertically aligned micro-channels per cm2 of 50 μm in diameter. Due to this unique configuration,
the micro-reformer presents a total surface per projected area of 16 cm2/cm2 and per volume of 320 cm2/cm3. The active
surface of the micro-reformer, i.e. the walls of the micro-channels, is homogenously coated with a thin film of Rh-
Pd/CeO2 catalyst. Excellent steam reforming of ethanol and dry reforming of methane are presented with hydrogen
production rates above 3 mL/min·cm2 and hydrogen selectivity of ca. 50% on a dry basis at operations conditions
suitable for application in micro-solid oxide fuel cells (micro-SOFCs), i.e. 700-800ºC and fuel flows of 0.02 mLL/min for
ethanol and 36 mLG/min for methane (corresponding to a system able to produce one electrical watt).
Micromachined thermal infrared emitters using heavily boron doped silicon as active material have been developed. The
proposed fabrication process allows the integration of infrared emitters with arrays of thermopile infrared detectors to
achieve integrated non dispersive infrared (NDIR) microspectrometers. A set of emitters with a common radiating silicon
slab size (1100x300x8μm3) has been successfully fabricated and characterized. The working temperature of Joule heated
radiating elements has been controlled by means of DC or pulsed electric signals, up to temperatures exceeding 800°C.
Measured thermal time constants, in the order of 50 ms, enable direct electrical modulation of emitted radiation up to a
frequency of 5Hz with full modulation depth. The temperature distribution in the radiating element has been analyzed
with infrared thermal imaging.
The present study is devoted to analyze the compatibility of yttria-stabilized zirconia thin films prepared by pulsed laser
deposition technique for developing new silicon-based micro devices for micro solid oxide fuel cells applications. Yttriastabilized
zirconia free-standing membranes with thicknesses from 60 to 240 nm and surface areas between 50x50 μm2
and 820x820 μm2 were fabricated on micromachined Si/SiO2/Si3N4 substrates. Deposition process was optimized for
deposition temperatures from 200ºC to 800ºC. A complete mechanical study comprising thermomechanical stability,
residual stress of the membranes and annealing treatment as well as a preliminary electrical characterization of ionic
conductivity was performed in order to evaluate the best processing parameters for the yttria-stabilized zirconia
membranes.
In this paper, a preconcentrator-based sensor &mgr;-system for low level benzene detection is presented. It consists of a
spiral-shaped &mgr;-reconcentrator with dimensions of 10cm × 300&mgr;m × 300&mgr;m, followed by a &mgr;-hotplate sensor matrix. The
&mgr;-preconcentrator was fabricated on a silicon wafer by means of DRIE and anodic bonding techniques. To obtain the
concentration factor of the fabricated devices, a GC/MS: Shimadzu-QP5000 equipment was used. The results obtained
showed excellent repeatability and preconcentration factors up to 286. A considerable improvement (1500%) in the
sensor responses was achieved with Pd doped SnO2 sensors. The small size of the manufactured devices enables their
incorporation in an integrated GC/MS gas sensor system.
The development of an integrated gas chromatographic system using micro and nanotechnologies is presented in this
paper. For this purpose, the different components of the chromatographic system, namely the preconcentrator, the
chromatographic column and the gas sensors are being investigated and developed, and the actual state of this
investigation is presented. The proposed target application comes from the agrofood industry, in particular the
determination of the fish freshness. The structure of the preconcentrator has been fabricated using deep reactive ion
etching (DRIE). The same fabrication technique has been employed for the patterning of the silicon microcolumns,
which have been sealed with Pyrex glass. Inlet and outlets have been connected and initial experiments of
functionalization have been performed. Gas sensors have been obtained by microdeposition of doped WO3 or SnO2
nanomaterials on microhotplates and their responses to the gases of interest have been measured, proving that the target
gas concentrations can be detected.
Fabrication and characterization of a passive silicon microfabricated direct methanol fuel cell (&mgr;DMFC) are reported.
The main characteristics of the device are its capability to work without complex pumping systems, only by capillary
pressure, and the fact that its performance is not affected by the device orientation. A simple fabrication process, based in
DRIE (Deep Reactive Ion Etching), allows obtaining a reliable and low-cost final device. The device consists of two
silicon microfabricated plates mounted together with a commercial membrane electrode assembly (MEA). Current-voltage
(I-V) and current-power (I-P) curves of the device at different methanol concentration, orientation and geometric
variation of silicon plates are presented. Optimal performance was obtained with a methanol concentration of 3M, that
yielded a maximum power density of 10.5 mW/cm2. The results obtained in this work demonstrate the feasibility of the
device and give a guideline for design and conditions optimization.
The paper presents a recently developed method of measuring frozen elastic stresses in micro components and devices.
The approach bases on stress release at the component surface by focused ion beam (FIB) milling. Stresses are deduced
from the experimentally determined deformation field around the FIB milling pattern, applying reasonable stress
hypotheses and appropriate modeling of the stress release field. Because of the local nature of ion milling and the
limited material volume affected by deformation, the method suites to very local stress measurement. Commonly,
spatial resolution is achieved in a range from submicron to some tens of microns. Residual stresses in membrane type
MEMS structures have been measured and results are reported. A broader group of potential applications is expected for
non-membrane structures in micro-/nanosystems or their packaging. Possible approaches for those cases are discussed,
considering comparison of measured deformation fields with either analytical solutions of the mechanical problem or
with finite element simulations.
The paper comprises research results obtained for stress determination on micro and nanotechnology components. It
meets the concern of controlling stresses introduced to sensors, MEMS and electronics devices during different
micromachining processes. The method bases on deformation measurement options made available inside focused ion
beam equipment. Removing locally material by ion beam milling existing stresses / residual stresses lead to deformation
fields around the milled feature. Digital image correlation techniques are used to extract deformation values from
micrographs captured before and after milling. In the paper, two main milling features have been analyzed - through
hole and through slit milling. Analytical solutions for stress release fields of in-plane stresses have been derived and
compared to respective experimental findings. Their good agreement allows to settle a method for determination of
residual stress values, which is demonstrated for thin membranes manufactured by silicon micro technology. Some
emphasis is made on the elimination of main error sources for stress determination, like rigid body object displacements
and rotations due to drifts of experimental conditions under FIB imaging. In order to illustrate potential application
areas of the method residual stress suppression by ion implantation is evaluated by the method and reported here.
KEYWORDS: Sensors, Gas sensors, Reliability, Silicon, Platinum, 3D metrology, Temperature metrology, Digital image correlation, Atomic force microscopy, Scanning probe microscopy
Micromachined microsensors for gas or flow detection based on physical behaviour of a special layer of a membrane have to fulfil high quality and reliability requirements especially in safety or security applications. For the reliability assessment a combination of simulative and experimental methods is usually carried out for the fully understanding of the thermo-mechanical behaviour. Due to the micromachining involved in the production of the sensor components the thermo-mechanical response of the layers are strongly dependent on process parameters. Therefore experimental methods for the 3D deformation detection are essential. In this paper experimental methods such as profilometry and scanning probe microscopy are tested for the evaluation of residual stresses and thermomechanical induced stress/strain fields.
KEYWORDS: Digital image correlation, Ions, Scanning electron microscopy, Microelectromechanical systems, Ion beams, Material characterization, Image resolution, Sensors, Error analysis, Copper
The authors present a new approach, fibDAC, which allows to measure and analyze deformation fields on stressed micro and nano components, which can be utilized for mechanical material characterization. The method bases on digital image correlation (DIC) algorithms applied locally to load state images captured from focused ion beam (FIB) equipment. As a result, deformation fields are determined, which occur due to loading of microsystem structures inside the focused ion beam system. A similar tool, called microDAC/nanoDAC, has been reported earlier and applies DIC techniques to SEM or AFM images. The advantages of the new fibDAC approach occur in the incorporation of specimen preparation like ion milling, ion beam surface polishing and DIC patterning as well as specimen loading by ion milling and DIC deformation measurement in a single equipment. Combining measured fields with finite element simulations or analytical solutions of the corresponding mechanical problem, relevant mechanical material properties can be evaluated. Corresponding object loading is accomplished either externally by testing modules designed for application inside the FIB equipment or by ion milling on the test specimen. As an example ion milling on specimens with residual stresses is demonstrated. Released in this way residual stresses cause object deformations nearby the milling area. Measured deformation fields by fibDAC allow to evaluate very local residual stresses. Some principal experiments illustrate the feasibility of the chosen approach. Features and challenges connected with this new method are discussed in some detail.
The requirements of flow measurement and control in the home-appliances field lead to the need of a measurement system able to monitor the flow and the quality of gas. The integration of a set of sensors with different functionalities on a single chip arises as an advantageous solution. In this paper, the description of the structures and technologies required for the gas, flow and temperature sensor devices is presented prior to the complete description of the process flow for the full on-chip compatibilization. In this sense, semiconductor gas sensors and thermal flow sensors have arisen as the best candidates to address the compatibilization.
A gas flow sensor has been developed for home-appliances applications. The main requirements were to obtain a low cost single device able to work in the range 0-1slm with high linearity, low power, reliability and robustness. A thermal flow sensor has been designed with the help of thermal and flow FEM simulation for the design of the sensor chip as well as its packaging. The process flow is based on a simple silicon micromachined technology. Chip-on-board solution has been selected to simplify the packaging. Electronics for driving the sensor and for compensation offsets and temperature dependence and for linearising the output signal has been implemented. Final device shows good sensitivity and linearity in different zones of the range of interest.
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