This work presents polymeric microsensors for the monitoring of alcohol contents in aqueous solutions. The inexpensive
sensor device is partially built by polymers. The housing consists of (100) Si substrate, whereas the sensitive material is
poly(N-isopropylacrylamide) (PNIPAAm). The acquisition of the sensor data is realized by a non-contact light barrier.
The output answer of this light barrier is strong linear. The continuous sensor signal observed by the light barrier is the
deflection of an elastic membrane, which is caused by the swelling or deswelling of the stimuli-responsive hydrogel. To
achieve an electronic adjustment of the sensor’s measurement range we use a controlled double-sensitivity of hydrogel.
By controlling the temperature of the temperature-responsive hydrogel PNIPAAm the phase transition concentration is
precisely adjustable to the required value. The electrothermic control interface is based on a Peltier element.
The response time of the sensors is in the lower minute range and therefore fast enough for the most of applications. The
average sensor resolution for measurements of ethanol is ca. 23mV/wt.-%. The shift of measurable concentration range
approximately amounts to 5.6 wt.-% ethanol per 5°C. Further improvements are possible.
Due to their small footprint and high sensitivity to biological molecule binding, planar optical microring resonators gained high interest for use as optical biosensors. Typically, microring resonators are made of semiconductor based materials, and are manufactured by time-consuming lithography and etching steps. Semiconductor based waveguides have high refractive indices, and thus, a high refractive index contrast between core and cladding. In this case, due to strong mode confinement, bending loss is a comparably minor issue and becomes relevant only at small bending radii of less than 5 μm. The main loss is determined by surface scattering, and thus, semiconductor based curved waveguides need to be designed and manufactured to have very smooth sidewalls. If polymer materials are used, microring resonators can be cost-efficiently manufactured by nanoimprint lithography. The resulting larger polymer waveguide dimensions facilitate in- and out-coupling, and polymer surfaces allow using established surface biofunctionalization techniques. For polymer waveguides, due to the small refractive index contrast, surface scattering loss is a minor issue, but bending loss becomes dominant for radii of less than 80 μm due to the low mode confinement to the core. In this work, design guidelines for polymer microring resonator waveguides are given and compared to semiconductor based waveguides. Waveguide losses due to bending and surface roughness are determined analytically or numerically by finite element methods. Coupling coefficients are calculated by finite element methods and coupled-mode theory. Resulting conclusions for designing polymer waveguides and semiconductor waveguides are derived.
KEYWORDS: Systems modeling, Chemical elements, Magnetism, Electromechanical design, Finite element methods, Network architectures, Transducers, 3D modeling, Actuators, Computer simulations
The combination of Network Methods and Finite Element Methods on user level is a time-efficient method for the simulation
of dynamic behavior of electromechanical systems. Combined simulation can be structured into five areas of application:
determination of network structures with FE-simulations, determination of network parameters with FEsimulations,
inclusion of network elements in FE-models, inclusion of equivalent network structures in FE-models and
simulation of models incorporating different model levels. The capabilities of the combined simulation are demonstrated
by sample applications. Combined Simulation is suited for a better system insight and fast simulation-based optimization.
KEYWORDS: Ear, Actuators, Sensors, Amplifiers, Finite element methods, Systems modeling, Transducers, Chemical elements, Computer simulations, Voltage controlled voltage source
To achieve an efficient simulation of the dynamic behavior of electromechanical devices it is often necessary to
use more than one simulation method or program. The main reason for this is that electromechanical systems
contain different physical domains and transduction principles. In many cases a smart solution is the combination
of network methods with finite element methods on user level which is referred to as combined simulation. This
paper deals with one area of application of the combined simulation, which is the use of network methods to
improve finite element models. After the description of the method the procedure is illustrated by the example
of the model of a hearing aid.
A magnetostrictive bending sensor with rectangular planar coil is investigated. Its purpose is to measure contactlessly
mechanical quantities of non-vibrating structures using an alternating magnetic field. The coil turns are electrodeposited
by pattern plating on top of a magnetostrictive Galfenol layer and a thin isolation layer. The coil turns investigated in this
paper were manufactured with a constant height of 10 μm and gap of 20 μm but variable width.
The sensor is operated near its electrical self-resonance between 5 and 40 MHz and requires a high quality factor. FEMsimulations
show that the quality factor of circular planar coils is almost independent on the conductor width under the
given design restrictions when skin and proximity effects are included.
Analytical calculations of rectangular coil parameters with three different turn numbers and conductor widths depending
on the turn number predict an almost constant self-resonance quality factor in the DC case. Measured self-resonance
quality factors are up to 59 % lower. The main reason for the disagreement is the current crowding by the proximity
effect since analytical calculation show a significant influence of the skin effect only at higher frequencies with respect
to the investigated self-resonance frequencies. Compared to the results of an FEM analysis obtained for circular coils the
proximity effect is much smaller as well as the achievable low frequency quality factor.
Electromechanical network models are used in this paper to analyze a prototype micro-gyro sensor that employs the
magnetostrictive alloy GalFeNOL for transduction of Coriolis induced forces into an electrical output at a given angular
velocity. The sensor is designed as a tuning fork structure which reacts with vibration of the prongs in tangential
direction due to an excited vibration in radial direction. A GalFeNOL patch attached to the axial-radial-surface changes
its permeability depending on the bending. When it is surrounded by a solenoid coil and a magnet creates a bias
magnetic field in the sensor patch, then this field fluctuates with the prong vibration. The induced voltage in the sensor
coil is used as sensor output. A sinusoidal angular velocity being effective on the tuning fork structure causes an
amplitude modulation of the excitation frequency which is the carrier frequency.
A circuit representation of the electromechanical system is derived where the prongs are modeled as dynamic bending
beams. The network model enables an understanding and explanation of the behavior of this system involving different
physical domains, as well as fast analytical and numerical calculations, e.g. with pSpice. Experiments confirm the
predicted sidebands of the sinusoidal rotation.
A new rotational magnetomechanical transducer network model for a magnetostrictive unimorph is presented.
Often these laminated structures define an operating point about which the mechanical, magnetic and electrical
quantities show only small variations and the behavior can be decribed by a linear model. It is shown how
the magnetomechanical transduction coefficient in actuation direction, which is obtained via classical laminated
plate theory, holds also for the sensing relation. The magnetomechanical model is combined with electromagnetic
coil models. The electromagnetic and the magnetomechanical transducer are connected by a magnetic voltage
divider which takes demagnetization or the planar coil field distribution into account. The presented models can
be used for a fast analysis of existing systems and also for the optimization of new designs. The resulting circuit
description can be simplified, e.g. to a single impedance, by transforming network elements into other domains.
In this paper an electromechanical network model of a magnetostrictive unimorph structure, acting as solenoid
coil core, is developed. For typical applications a non-uniform stress distribution in the magnetostrictive layer
results which is simulated via FEM. This phenomenon leads to a spatial varying electromechanical transduction
coefficient for large deflections and was taken into account by coupled finite electromechanical network elements.
By simplifying the finite network model an easy to use new network model is obtained which enables the fast
analysis of the system and optimization of sensor and actor properties.
Tungsten oxides thin films were obtained by electron beam deposition and annealed in the temperature range 350-800°C for 1-3 h. The structure, morphology and phase composition of the as-deposited and annealed films were characterized by X-ray diffraction and AFM. The electrical response towards NO2 and O3 was studied both experimentally and theoretically. In order to interprete the kinetic characteristics of tungsten oxide thin films upon exposure to different gases a model, based on surface adsorption/desorption processes coupled with bulk diffusion was used. A link between the geometrical and chemical heterogeneities of the tungsten oxide film surfaces and their performance characteristics as gas sensors was established. It was shown that the nature and the amount of the surface adsorption sites of the different non-stoichiometric phases (WnO3n-2 or WnO3n-1) or WO3, and their conductive mechanism are defined from: the phase composition of the film, the crystallographic and electronic structure of the phases, the orientation of the crystallites within the film, and the geometrical form and dimensions of the crystallites. All tungsten oxide thin films investigated in this work are suitable to detect very low concentrations of NO2 (0.05-0.5 ppm in N2 and synthetic air) and ozone (25-90 ppb) at very low working temperatures (80-160°C). The films annealed at 400°C for 1-2 h are very selective to ozone and the films annealed at 400°C for 3 h and at 800°C for 1 h are very selective to NO2.
The sensor processor circuit has been developed for hand-held devices used in industrial and environmental applications, such as on-line process monitoring. Thereby devices with SAW sensors or MEMS resonators will benefit from this processor especially. Up to 8 sensors can be connected to the circuit as multisensors or sensor arrays. Two sensor processors SP1 and SP2 for different applications are presented in this paper. The SP-1 chip has a PCMCIA interface which can be used for the program and data transfer. SAW sensors which are working in the frequency range from 80 MHz to 160 MHz can be connected to the processor directly. It is possible to use the new SP-2 chip fabricated in a 0.5(mu) CMOS process for SAW devices with a maximum frequency of 600 MHz. An on-chip analog-digital-converter (ADC) and 6 PWM modules support the development of high-miniaturized intelligent sensor systems We have developed a multi-SAW sensor system with this ASIC that manages the requirements on control as well as signal generation and storage and provides an interface to the PC and electronic devices on the board. Its low power consumption and its PCMCIA plug fulfil the requirements of small size and mobility. For this application sensors have been developed to detect hazardous gases in ambient air. Sensors with differently modified copper-phthalocyanine films are capable of detecting NO2 and O3, whereas those with a hyperbranched polyester film respond to NH3.
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