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The current effort was done to assess the utility of surface acoustic wave (SAW) detectors for analyzing multicomponent gaseous mixtures in real time. Tasks included surveying currently available SAW detector capability, selecting several candidate SAW coating materials, fabricating vapor monitors, and testing for sensitivity and selectivity. An assessment of possible SAW designs for real- time analysis of multicomponent mixtures is attempted. Surface acoustic wave detector, Real-time multicomponent vapor analysis.

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An amperometric solid electrolyte oxygen (O2) microsensor using a novel and robust structure has been developed with a detection range of 0.025 to 21 percent of O2 concentration. The microsensor has a simple structure with a sensing area of 1.10 0.99 mm(exp 2), and is operated by applying voltage across the electrodes and measuring the resulting current flow at a temperature of 600 C.

This report describes the cermet sensors and system control software recently evaluated in shipboard tests for shipboard damage control. The tests were conducted to evaluate a database of sensor responses to fire and nuisance sources for algorithm development, and to provide a basis for further refinement. In this work, the cermet sensors incorporate four sensors with multivariate analysis methods and classification algorithms for detecting a wide variety of analytes including toxic industrial chemicals, fires, and nuisance sources. The test series successfully demonstrated the functionality and performance of the microsensor system for use in fire detection. The detection system demonstrated the ability to detect flaming and smoldering fires at the same level as the commercial multicriteria detector. It was on average 2 to 3 minutes faster for flaming fires, vs. all detector types evaluated, and 7.5 to 8.3 minutes faster for smoldering fires, vs. all detector types evaluated. The system needs improvement in addressing fire-like nuisances.

Micro fiber optics and combination sensors have been fabricated which can measure light distribution, temperature, and electrical activity in the in vivo ocular fundus. These sensors have been tested in the rabbit and monkey eye. (Author)

An ambient temperature oxygen microsensor, based on a Nafion polymer electrolyte, has been developed and was microfabricated using thin-film technologies. A challenge in the operation of Nafion-based sensor systems is that the conductivity of Nafion film depends on the humidity in the film. Nafion film loses conductivity when the moisture content in the film is too low, which can affect sensor operation. The advancement here is the identification of a method to retain the operation of the Nafion films in lower humidity environments. Certain salts can hold water molecules in the Nafion film structure at room temperature. By mixing salts with the Nafion solution, water molecules can be homogeneously distributed in the Nafion film increasing the film s hydration to prevent Nafion film from being dried out in low-humidity environment. The presence of organics provides extra sites in the Nafion film to promote proton (H+) mobility and thus improving Nafion film conductivity and sensor performance. The fabrication of ambient temperature oxygen microsensors includes depositing basic electrodes using noble metals, and metal oxides layer on one of the electrode as a reference electrode. The use of noble metals for electrodes is due to their strong catalytic properties for oxygen reduction. A conducting polymer Nafion, doped with water-retaining components and extra sites facilitating proton movement, was used as the electrolyte material, making the design adequate for low humidity environment applications. The Nafion solution was coated on the electrodes and air-dried. The sensor operates at room temperature in potentiometric mode, which measures voltage differences between working and reference electrodes in different gases. Repeat able responses to 21-percent oxygen in nitrogen were achieved using nitrogen as a baseline gas. Detection of oxygen from 7 to 21 percent has also been demonstrated. The room-temperature oxygen micro sensor developed has extremely low power consumption (no heating for operation, no voltage applied to the sensor, only a voltmeter is needed to measure the output), is small in size, is simple to batch-fabricate, and is high in sensor yield. It is applicable in a wide humidity range, with improved operation in low humidity after the additives were added to the Nafion film. Through further improvement and development, the sensor can be used for aerospace applications such as fuel leak detection, fire detection, and environmental monitoring.

This report describes the cermet sensors and system control software recently evaluated in shipboard tests for shipboard damage control. The tests were conducted to evaluate a database of sensor responses to fire and nuisance sources for algorithm development, and to provide a basis for further refinement. In this work, the cermet sensors incorporate four sensors with multivariate analysis methods and classification algorithms for detecting a wide variety of analytes including toxic industrial chemicals, fires, and nuisance sources. The test series successfully demonstrated the functionality and performance of the microsensor system for use in fire detection. The detection system demonstrated the ability to detect flaming and smoldering fires at the same level as the commercial multicriteria detector. It was on average 2 to 3 minutes faster for flaming fires, vs. all detector types evaluated, and 7.5 to 8.3 minutes faster for smoldering fires, vs. all detector types evaluated. The system needs improvement in addressing fire-like nuisances.

Health diagnostics is an area where major improvements have been identified for potential implementation into the design of new reusable launch vehicles in order to reduce life cycle costs, to increase safety margins, and to improve mission reliability. NASA Ames is leading the effort to develop inspection and health management technologies for thermal protection systems. This paper summarizes a joint project between NASA Ames and SRI International to develop 'SensorTags,' radio frequency identification devices coupled with event-recording sensors, that can be embedded in the thermal protection system to monitor temperature or other quantities of interest. Two prototype SensorTag designs containing thermal fuses to indicate a temperature overlimit are presented and discussed.

Health diagnostics is an area where major improvements have been identified for potential implementation into the design of new reusable launch vehicles in order to reduce life cycle costs, to increase safety margins, and to improve mission reliability. NASA Ames is leading the effort to develop inspection and health management technologies for thermal protection systems. This paper summarizes a joint project between NASA Ames and SRI International to develop 'SensorTags,' radio frequency identification devices coupled with event-recording sensors, that can be embedded in the thermal protection system to monitor temperature or other quantities of interest. Two prototype SensorTag designs containing thermal fuses to indicate a temperature overlimit are presented and discussed.

Health diagnostics is an area where major improvements have been identified for potential implementation into the design of new reusable launch vehicles in order to reduce life cycle costs, to increase safety margins, and to improve mission reliability. NASA Ames is leading the effort to develop inspection and health management technologies for thermal protection systems. This paper summarizes a joint project between NASA Ames and SRI International to develop 'SensorTags,' radio frequency identification devices coupled with event-recording sensors, that can be embedded in the thermal protection system to monitor temperature or other quantities of interest. Two prototype SensorTag designs containing thermal fuses to indicate a temperature overlimit are presented and discussed.

This paper investigates the localization and classification of ground vehicles using a field of microsensor systems employing acoustic, seismic, and magnetic sensors at each node location. Specific results will focus on the ability of individual nodes to detect ground vehicle targets of varying types and provide information on those vehicles. We also discuss the fusion of information from multiple nodes to further enhance target information over time.

This paper investigates the localization and classification of ground vehicles using a field of microsensor systems employing acoustic, seismic, and magnetic sensors at each node location. Specific results will focus on the ability of individual nodes to detect ground vehicle targets of varying types and provide information on those vehicles. We also discuss the fusion of information from multiple nodes to further enhance target information over time.

This article is from PLoS ONE , volume 9 . Abstract This study aimed to elucidate the effects of periphyton on the microprofiles of oxygen (O2), pH, and oxidation-reduction potential around the stems and leaves of a submerged macrophyte Potamogeton malaianus and on the plant growth in the eutrophic shallow Taihu Lake, China. The microprofiles were measured using a motorized microprofiling system equipped with microsensors. The leaf age of the macrophyte and periphyton exerted significant effects on the microprofiles of O2, pH, and oxidation-reduction potential. O2 concentration and pH increased whereas the oxidation-reduction potential decreased with decreasing distance to the stem/leaf surface. The fluctuation amplitudes of O2, pH, and oxidation-reduction potential were the largest in the microprofiles of mature leaves and the lowest in senescent leaves. The periphyton increased the thickness of the broad diffusive boundary layer and fluctuation amplitudes of O2, pH, and oxidation-reduction potential. When the periphyton was removed, the thickness of the broad diffusive boundary layer in the microprofiles of stems, senescent leaves, and mature leaves reduced by 29.0%, 49.72%, and 70.34%, and the O2, pH, and oxidation-reduction potential fluctuation amplitudes also declined accordingly. Our results suggest that a thick periphyton exerted negative effects on the growth of macrophytes by providing extensive shading and creating a barrier that hindered the transport of dissolved substances such as O2, and led to premature decline in macrophytes in the eutrophic Taihu Lake. The consequent implications can help to elucidate the control mechanism of the broad diffusive boundary layer around macrophytes on nutrient cycling in eutrophic waters and to better understand the role of this layer in the Taihu Lake and other similar eutrophic waters.

The chromogenic detector reagents 1,3-diisonitrosoacetone (DIA) and 4,4'-bis(diethylamino)benzophenone oxime (EMKO) have been studied as solid-state coatings for sensing methane-sulfonyl chloride vapor. The strength of the optical detection signals produced on contact of the coatings with methanesulfonyl chloride vapor are strongly affected by the composition of the solid reaction support; silica gel is the preferred support for coatings made with either reagent. When monitored with a fiber-optic spectrophotometer, coatings made with DIA and EMKO are capable of sensing methanesulfonyl chloride vapor down to the low parts per million level. Keywords: Microsensor coating; 1, 3-Diisonitrosoacetone; Methanesulfonyl chloride; Chromogenic; Solid-state; Silica gel; Vapor detection.

This report describes the cermet sensors and system control software recently evaluated in laboratory tests for shipboard damage control. The tests were conducted to generate a database of sensor responses to fire and nuisance sources for algorithm development, and to develop fire detection alarm algorithms. In this work, the cermet sensors incorporate four sensors with multivariate analysis methods and classification algorithms for detecting a wide variety of analytes, including toxic industrial chemicals, fires, and nuisance sources. The test series successfully demonstrated the functionality and performance of the microsensor system for use in fire detection. The detection system demonstrated the ability to detect flaming and smoldering fires at the same level as the commercial multicriteria detector. It was on average 2.5 to 5.5 minutes faster for smoldering fires versus all detector types evaluated, and 50 to 80 seconds faster for flaming fires versus multicriteria and photoelectric detectors, but 50 seconds slower than the ionization detector. The system needs improvement in addressing fire-like nuisances.

Users desire microsensors that support reconnaissance, surveillance and target acquisition (RSTA) operations. Typically, the communications bandwidth on these microsensors limits the amount of data that can be transmitted. Therefore, much of the signal processing must be performed within the aggressive size, power, and weight constraints of the microsensor. Furthermore, these microsensors need to be inexpensive and have a very small logistics tail. Low-power ASIC technology can address the performance and power issues but may not be reusable over a wide range of applications. Programmable processors (DSPs, and Microprocessors) may provide the flexibility but not necessarily the performance. A new paradigm is sought to provide low-power, high-performance, reprogrammable computing. To ensure low expense, a common and open architecture should be developed. This will allow the cost to be shared among the widest range of applications possible while allowing for technology upgrades. This paper describes the development of a computing architecture which uses a general purpose processor combined with field programmable gate array technology (FPGA) that can be used to accelerate a range of microsensor applications. We have demonstrated two orders of magnitude reduction in size, weight, and power over an existing Army Research Laboratory testbed.

This paper describes some of the operational characteristics and performance limitations of microfabricated sensors for chemical vapors which use surface acoustic wave (SAW) phenomena to probe a vapor sensitive coating. Comparisons are made with bulk wave piezoelectric crystal sensors and key technical challenges for future development of SAW vapor sensors are discussed.

The objectives of our research on the d.c. conductivity of proteins was to investigate and demonstrate that appropriate electrical properties of macromolecular substrates of biological origin can be exploited for analytical purposes using macroscopic techniques. More concretely, we wanted to show that the specificity and selectivity of specific antibodies in molecular (target) recognition and binding, combined with monitoring binding-induced changes in their d.c. electric conductivity may represent such properties. If so, at least these bimolecular systems can be considered as potential sensory elements in designing chemically highly selective and very sensitive chemical microsensors. Such chemically sensitive gate elements of appropriate bimolecules in F(ield) E(ffect) T(ransistor) - type devices could then be ued for the real-time evaluation of vanishingly smal quantities of diverse molecular species present in the vapor (gas) or liquid form. Our investigations demonstrated that the utility of d.c. conductivity measurements on thin immunoprotein films as a probe of antigen/haplen binding by monoclonal move anti-DNP IqE antibody. Upon binding to the antibody, appropriate nitropenyl ligands (2,4-DNP-Lysine, TNP) bring about typical changes in the d.c. conductivity: it decreases by about a factor of two. Model compounds (BSA and its derivatived forms) were used to provide information about the possible mechanism of resistance lowering by DNP-based haptens.

The formalism of molar refraction was extended to cover the wavelength range of 200 nm - 2500 nm, in order to predict the index of refraction and index increment of a wide range of molecules of biochemical interest. Data for the model was obtained using a unique interferometer cell within a standard laboratory spectrophotometer. The resulting models for protein index increment suggest that both the sensitivity and specificity of refractometric sensors may be improved by operating at ultraviolet wavelengths and that measurement at two wavelengths may be used to quantify the total protein present and distinguish between similar proteins, of potential use to reduce false positive responses in affinity assays. The impact of refractive index and particle size on semiconductor-based evanescent field sensors was analyzed, along with the magnitude of optical scattering. The results are particularly important in quantitatively explaining the benefits of using a nanoparticle-enhanced assay, and of using high-index nanoparticles for enhancement. For particles below 100 nm in diameter, optical scattering will be negligible. For particles larger than 100 nm, scattering becomes measurable, and single one-micron diameter particles were detected in a novel monolithic evanescent field sensor.

Ultrasmall glucose sensors have been constructed by using platinum deposited carbon ring microelectrodes with glucose oxidase. Response times as low as 270 ms have been obtained with these sensors. Moreover, there is a linear relationship between sensor tip diameter and response times. The use of these sensors have been demonstrated in the detection of glucose in a single cell cytoplasm of the large dopamine cell of the pond snail, Planorbis corneus. Current responses obtained at these sensors implanted into a cell increase following injection of 2 pL glucose solution (3 M) into the cell. Results obtained from these experiments show that these sensors are suitable for glucose monitoring in ultrasmall environments. In addition, characterization of these sensors have been investigated under different O2 concentrations. At atmospheric oxygen concentrations, glucose levels in the submillimolar range can be measured without oxygen interference; however, oxygen interference can be substantial at low oxygen concentrations.

The behavior of fluid droplets contained within shaped capillaries and voids can be utilized to convert forces acting upon the droplets to observable displacements which accurately quantify these forces. The position of droplets within such micro-sensors is governed by surface tension, wettability, and the geometric configuration of the confining walls. If non-wetting fluids are employed, the micro-sensors can also be made to operate as micro-valves, micro -switches, optical micro-shutters, as well as other devices. Having no mechanical parts to wear out, such micro-sensors are inherently immune to many orders-of-magnitude over-actuation. Both circular and non-circular confining structures can be employed.

Advanced microfabrication processes have been developed for producing a hermetic cover wafer with low resistance dielectrically isolated through-wafer interconnects. The feasibility of manufacturing encapsulated pressure sensors, utilizing the cover-wafer approach, has been demonstrated. Such pressure sensors represent a new generation of environmentally protected, cost effective devices. The accomplishments of Phase I include the following: the study of conversion of single crystal silicon into porous silicon; the study of conversion of porous silicon into oxide; process for producing through-wafer interconnects has been established; the stresses in the cover wafer have been investigated, which enabled the fabrication of flat cover-wafers. The surface and cross-sectional morphology of the cover wafer was investigated; hermeticity and dielectric isolation of the oxidized rings was verified; Sensors compatible with the cover- wafer approach were fabricated and tested. The new generation of sensors was designed

The reliable operation of wide-bandgap HEMT (High Electron Mobility Transistor) devices at elevated temperatures up to 400°C, along with their less vulnerability to thermal or optical excitation, combined with their greater resistance to chemical corrosion by acids and alkalis, has encouraged researchers to make endeavours towards the development of a family of sensors for harsh environments, an area where conventional silicon MOSFET (metal-oxide-semiconductor field-effect transistor) and ISFET (ion-sensitive field-effect transistor) devices are rendered ineffective. Additionally, the close proximity of the conducting 2DEG (two-dimensional electron gas) HEMT channel to the surface provides enhanced sensitivity to adsorption of substances, while the miniaturization and high-frequency operation capability of HEMT-based microsensors enables their seamless integration into wireless sensor networks for remote monitoring of patient’s health through bedside or handheld instrumentation. This paper reviews the recent progress of HEMT-based microsensors for physical, chemical and biological applications, describes the challenges faced, and also points out the future trends and opportunities in this field. The notable HEMT sensing devices include physical sensors for pressure, stress and magnetic field measurements, and for terahertz detection; chemical sensors for pH, ammonium, potassium, mercury and other ions; oxygen, hydrogen, chlorine, HCl vapor, and other gases; biosensors for glucose, lactic acid, uric acid, DNA, prostate and breast cancer markers, kidney injury molecule-1, perkisus marinus, botulinum toxin, and various other analytes.

The following document details the results of efforts to develop a high temperature sensor technology based in Kopin's proprietary ISEtm SOI material. Results are presented from a detailed analysis of the piezoresistive properties, and of the internal stress in the layer. These results show the material to be electrically similar to bulk, with very low internal stress. This makes ISEtm an ideal material choice for this application. A full sensor process sequence, with mask set, and enabling process equipment and techniques, was developed for this program. In parallel with the process development, extensive circuit analysis and modeling was performed to identify the best high temperature sensing circuit for this task. After modeling, test circuits were fabricated in bulk wafers to evaluate the design. The final design, a switching capacitive MOS circuit with proportional output, is expected to produce a sensor with 0.1% accuracy over the temperature range of -60 deg C to 300 deg C. Kopin is currently pursuing industrial financing for Phase III of this work to complete the integration of this work for commercial application. Microsensors, High Temperature, Smart, SOI, Sensors, Capacitive, Pressure.

Within the framework of the project 'Acoustic Microsensors' (A93KL448) the possibilities of a biosensor system based on an immunological reaction on a piezoelectric crystal sensor are investigated at the TNO Prins Maurits Laboratory (TNO-PML). The results described are a continuation of previous reported work in which the toxin Staphylococcal Enterotoxin B (SEB) was detected in a competition assay with a preincubation period of at least 20 minutes and a detection limit of 100 ng/ml. A new biochemical interface based on a flexible carboxylated dextran matrix, to which antibodies are bound, was developed. With this biosensor system SEB could be detected directly without a preincubation step at a lowest concentration of approximately 7 ng/ml. The biosensor can be easily regenerated by a one-minute injection of 0.1 M HCl.

This study introduces a refined current feedback instrumentation amplifier (CFIA) specifically designed for amplifying biopotential signals that originate from resistive-bridge sensors. The proposed architecture uniquely incorporates a multipath chopper-stabilized CFIA which has been developed to minimize the effects of bridge offsets, while maintaining low power usage, high input impedance, and reduced noise characteristics. The engineering blueprint employs a ripple reduction loop (RRL) to mitigate output ripple caused by chopper up-modulation. To speed up offset cancellation and to limit the offset caused by bridge mismatch, an automatic offset cancellation loop (AOCL) circuit is integrated within the analog front end (AFE). Crafted using a conventional 0.18 µm CMOS process, the CFIA in this design provides adjustable gain between 20.35 dB to 55.14 dB, with a power supply rejection ratio (PSRR) and a common mode rejection ratio (CMRR) of 103 dB and 114 dB, respectively. The system demonstrates an input-referred noise (IRN) value of 16 ηV/√Hz at 200 Hz frequency, equivalent to a noise efficiency factor (NEF) of 5.18. Operating from a supply voltage of 1.8V, the AFE shows a power consumption of 291 μW.

An instrument has been built which can generate up to twelve different vapors from bubbler or premeation tube sources. These vapors can be randomly selected, diluted to concentrations typically in the range of 1 to 10,000 mg/cubic meter volume, and delivered at a programmable flow rate to the system output. Mixtures of two vapors can also be easily generated. The system is fully automated using a small personal computer and premits completely unattended operation during elaborate vapor exposure sequences. Parameters describing the vapor test conditions are automatically stored in the computer disk memory along with the sensor responses to the test. This instrument has proved to be extremely valuable for rapidly testing prototype chemical sensors.

An instrument has been built which can generate up to twelve different vapors from bubbler or premeation tube sources. These vapors can be randomly selected, diluted to concentrations typically in the range of 1 to 10,000 mg/cubic meter volume, and delivered at a programmable flow rate to the system output. Mixtures of two vapors can also be easily generated. The system is fully automated using a small personal computer and premits completely unattended operation during elaborate vapor exposure sequences. Parameters describing the vapor test conditions are automatically stored in the computer disk memory along with the sensor responses to the test. This instrument has proved to be extremely valuable for rapidly testing prototype chemical sensors.

This article is from Sensors (Basel, Switzerland) , volume 12 . Abstract MicroRNAs (miRNAs) are small molecules of single strand non-coding RNAs, which are able to regulate gene expression. miRNAs have been involved in multiple cellular processes, such as proliferation, apoptosis and differentiation, thus alterations in miRNA expression have been shown to be directly linked with the pathological origin of multiple diseases, including cancer. In this way, during last few years, an increasing number of exciting advances have contributed to the understanding of miRNA roles in cancer. Moreover, researchers have exploited the special characteristics of miRNAs, such as the tissue and disease specificity or miRNA presence in blood, to explore their use as non-invasive tumour markers. In the present review, we summarize the current data on the potential usefulness of circulating miRNAs as diagnostic and prognostic tools in gastrointestinal tumours.

This paper provides a brief summary of the research being performed under the ODDR&E MURI on the topic of data fusion in large arrays of microsensors, a program that involves researchers from MIT. The University of Illinois, and Princeton University. The overall objective of this program is the investigation and development of innovative concepts and solutions to the challenges presented by the envisioned availability of very large numbers of heterogeneous sensors each of which is limited in sensing capability, power, computation, and communication.

This report documents the findings of Kopin Corporation during the first five months of the program. Significant results include the development of a new process sequence, and a verification of the low stress in ZMR (ISE) material. Current direction is aimed at the fabrication of both accelerometers and pressure sensors using our advanced SOI process. During this reporting period, wafers from Phase I which had been processed were closely examined. The structures being observed were fabricated on a 3 micron oxide layer and had 1 micron of silicon film thickness. Therefore, from the base of the beam or bridge to its free area there exists a step height of 3 micron. If the microscope is focussed on the free region of the bridge, as in the photo, then the bridge bases will be out of focus. This fact is readily apparent in the photograph. If the free region of the beam had collapsed onto the substrate, then it would be out of focus in the photograph. None of the bridge structures are out of focus in the figure 1a indicating that they are all freely supported 3 microns above the substrate.

Microsensors find applications in many important areas of U.S. military hardware. Advances in aircraft and internal combustion engines are placing increasing demands on the electronics which play an increasingly important role in engine control. Complexity of control circuits has demanded increases in the scale of integration and in reliability, and have suggested the placement of high levels of functionality near the point of use. Engine performance must be evaluated with sensors and used intelligently to maintain optimum efficiency. Recent advances in microsensor technology have provided smaller, more economical sensors for these applications. With smaller sensors the need for signal conditioning electronics in close proximity to the sensor has become an increasingly important issue. The proposed three-phase project addresses the development of smart sensors for applications under high temperature ambients (up to 350 C). The approach proposed here is the demonstration of the usefulness of the SOI material obtained by the Isolated Silicon Epitaxy (ISE) process for high temperature sensor applications. This would couple with process development of sensor elements.

This article is from Scientific Reports , volume 4 . Abstract Stochastic microsensors based on diamond paste and three types of electroactive materials (maltodextrin (MD), α-cyclodextrin (α-CD) and 5,10,15,20-tetraphenyl-21H,23H porphyrin (P)) were developed for the assay of estradiol (E2), testosterone (T2) and dihydrotestosterone (DHT) in children's saliva. The main advantage of utilization of such tools is the possibility to identify and quantify all three hormones within minutes in small volumes of childen's saliva. The limits of quantification obtained for DHT, T2, and E2 (1 fmol/L for DHT, 1 pmol/L for T2, and 66 fmol/L for E2) determined using the proposed tools allows the utilization of these new methods with high reliability for the screening of saliva samples from children. This new method proposed for the assay of the three hormones overcomes the limitations (regarding limits of determination) of ELISA method which is the standard method used in clinical laboratories for the assay of DHT, T2, and E2 in saliva samples. The main feature of its utilization for children's saliva is to identify earlier problems related to early puberty and obesity.

There are two tasks in this grant. The first is to develop a micromachined miniature polysilicon hot-wire anemometers with improved spatial resolution and frequency response. The finished device was a micron sized polysilicon wire supported by free-standing gold/silicon-nitride beams. These devices have time constants as small as a few microseconds and, under constant temperature mode, an unprecedented bandwidth of 1.4 N 4Hz was achieved measured in wind tunnel. The second task is to study gaseous microchannel flows as an effort to understand the basic science of fluid mechanics when the mean free path of the gas is about the size of the channel. A micromachined microsystem was developed with a micron-sized flow channel (one micron high) and (4 or 13) distributed pressure sensors. A range of pressure drop up to 20 psi was used and nonlinear pressure distributions were for the first time, successfully obtained. It was found that surface-gas interaction plays an important role in the flow behavior in microflow systems and that new flow models have to be developed to explain the new phenomena.

The displacement of non-wetting fluid droplets contained within capillaries that have axial profiles and are non-uniform can be used to accurately and reproducibility measure the forces acting upon these droplets. The position of droplets within such micro-sensors is dictated by surface tension, wettability, geometric configuration of the confining walls, and the forces acting upon the droplet. These micro-sensors can measure pressure and acceleration, and can also be made to operate as micro-valves, micro-switches, optical shutters, as well as other devices. They have no moving mechanical parts to wear out, and can theoretically endure high amounts of over-actuation and still return to initial levels of accuracy and precision without harm. The axial profiles of these shaped capillaries are easily fabricated using microtube technology developed at the Air Force Research Laboratory at Edwards Air Force Base. However, it is also possible to use non-circular shaped voids and still achieve similar capabilities with some limitations. These non-circular shaped voids can be manufactured using more conventional MEMS technologies such as photo lithography and LIGA.

A sensitive resistor-based NO microsensor, with a wide detection range and a low detection limit, has been developed. Semiconductor microfabrication techniques were used to create a sensor that has a simple, robust structure with a sensing area of 1.10 ~ 0.99 mm. A Pt interdigitated structure was used for the electrodes to maximize the sensor signal output. N-type semiconductor indium tin oxide (ITO) thin film was sputter-deposited as a sensing material on the electrode surface, and between the electrode fingers. Alumina substrate (250 m in thickness) was sequentially used for sensor fabrication. The resulting sensor was tested by applying a voltage across the two electrodes and measuring the resulting current. The sensor was tested at different concentrations of NO-containing gas at a range of temperatures. Preliminary results showed that the sensor had a relatively high sensitivity to NO at 450 C and 1 V. NO concentrations from ppm to ppb ranges were detected with the low limit of near 159 ppb. Lower NO concentrations are being tested. Two sensing mechanisms were involved in the NO gas detection at ppm level: adsorption and oxidation reactions, whereas at ppb level of NO, only one sensing mechanism of adsorption was involved. The NO microsensor has the advantages of high sensitivity, small size, simple batch fabrication, high sensor yield, low cost, and low power consumption due to its microsize. The resistor-based thin-film sensor is meant for detection of low concentrations of NO gas, mainly in the ppb or lower range, and is being developed concurrently with other sensor technology for multispecies detection. This development demonstrates that ITO is a sensitive sensing material for NO detection. It also provides crucial information for future selection of nanostructured and nanosized NO sensing materials, which are expected to be more sensitive and to consume less power.

This article is from Current Neuropharmacology , volume 10 . Abstract In this paper is presented an overview of the technological barriers faced by the in vivo brain analysis with microelectrodes. Numerous microsensors and enzymatic microbiosensors have been developed for the real time monitoring of neurotransmitters, neuromodulators, drugs and diverse other biological relevant substances. A clear understanding of the working principle, advantages and limitations is essential for the acquisition of valid data in neurological investigations. Some of the aspects presented here refer to: microelectrode insertion and positioning related to possibilities to minimize tissue damage, spatial and temporal resolution of the measurements, actual controversies in data interpretation and sensor calibration, simultaneous detection of multiple analytes, interferences and state of the art in the development of wireless devices.

This article is from Current Neuropharmacology , volume 10 . Abstract In this paper is presented an overview of the technological barriers faced by the in vivo brain analysis with microelectrodes. Numerous microsensors and enzymatic microbiosensors have been developed for the real time monitoring of neurotransmitters, neuromodulators, drugs and diverse other biological relevant substances. A clear understanding of the working principle, advantages and limitations is essential for the acquisition of valid data in neurological investigations. Some of the aspects presented here refer to: microelectrode insertion and positioning related to possibilities to minimize tissue damage, spatial and temporal resolution of the measurements, actual controversies in data interpretation and sensor calibration, simultaneous detection of multiple analytes, interferences and state of the art in the development of wireless devices.

This article is from Sensors (Basel, Switzerland) , volume 11 . Abstract Recognition of body posture and motion is an important physiological function that can keep the body in balance. Man-made motion sensors have also been widely applied for a broad array of biomedical applications including diagnosis of balance disorders and evaluation of energy expenditure. This paper reviews the state-of-the-art sensing components utilized for body motion measurement. The anatomy and working principles of a natural body motion sensor, the human vestibular system, are first described. Various man-made inertial sensors are then elaborated based on their distinctive sensing mechanisms. In particular, both the conventional solid-state motion sensors and the emerging non solid-state motion sensors are depicted. With their lower cost and increased intelligence, man-made motion sensors are expected to play an increasingly important role in biomedical systems for basic research as well as clinical diagnostics.

This article is from Sensors (Basel, Switzerland) , volume 11 . Abstract This study presents the fabrication and characterization of a humidity microsensor that consists of interdigitated electrodes and a sensitive film. The area of the humidity microsensor is about 2 mm2. The sensitive film is polyaniline doping polyvinyl alcohol (PVA) that is prepared by the sol-gel method, and the film has nanofiber and porous structures that help increase the sensing reaction. The commercial 0.35 μm Complimentary Metal Oxide Semiconductor (CMOS) process is used to fabricate the humidity microsensor. The sensor needs a post-CMOS process to etch the sacrificial layer and to coat the sensitive film on the interdigitated electrodes. The sensor produces a change in resistance as the polyaniline/PVA film absorbs or desorbs vapor. Experimental results show that the sensitivity of the humidity sensor is about 12.6 kΩ/%RH at 25 °C.

This article is from Sensors (Basel, Switzerland) , volume 11 . Abstract This study presents the fabrication and characterization of a humidity microsensor that consists of interdigitated electrodes and a sensitive film. The area of the humidity microsensor is about 2 mm2. The sensitive film is polyaniline doping polyvinyl alcohol (PVA) that is prepared by the sol-gel method, and the film has nanofiber and porous structures that help increase the sensing reaction. The commercial 0.35 μm Complimentary Metal Oxide Semiconductor (CMOS) process is used to fabricate the humidity microsensor. The sensor needs a post-CMOS process to etch the sacrificial layer and to coat the sensitive film on the interdigitated electrodes. The sensor produces a change in resistance as the polyaniline/PVA film absorbs or desorbs vapor. Experimental results show that the sensitivity of the humidity sensor is about 12.6 kΩ/%RH at 25 °C.

This article is from Sensors (Basel, Switzerland) , volume 14 . Abstract A humidity microsensor integrated with a readout circuit on-a-chip fabricated using the commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process was presented. The integrated sensor chip consists of a humidity sensor and a readout circuit. The humidity sensor is composed of a sensitive film and interdigitated electrodes. The sensitive film is titanium dioxide prepared by the sol-gel method. The titanium dioxide is coated on the interdigitated electrodes. The humidity sensor requires a post-process to remove the sacrificial layer and to coat the titanium dioxide. The resistance of the sensor changes as the sensitive film absorbs or desorbs vapor. The readout circuit is employed to convert the resistance variation of the sensor into the output voltage. The experimental results show that the integrated humidity sensor has a sensitivity of 4.5 mV/RH% (relative humidity) at room temperature.

This article is from Sensors (Basel, Switzerland) , volume 14 . Abstract A humidity microsensor integrated with a readout circuit on-a-chip fabricated using the commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process was presented. The integrated sensor chip consists of a humidity sensor and a readout circuit. The humidity sensor is composed of a sensitive film and interdigitated electrodes. The sensitive film is titanium dioxide prepared by the sol-gel method. The titanium dioxide is coated on the interdigitated electrodes. The humidity sensor requires a post-process to remove the sacrificial layer and to coat the titanium dioxide. The resistance of the sensor changes as the sensitive film absorbs or desorbs vapor. The readout circuit is employed to convert the resistance variation of the sensor into the output voltage. The experimental results show that the integrated humidity sensor has a sensitivity of 4.5 mV/RH% (relative humidity) at room temperature.

This article is from Sensors (Basel, Switzerland) , volume 14 . Abstract A humidity microsensor integrated with a readout circuit on-a-chip fabricated using the commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process was presented. The integrated sensor chip consists of a humidity sensor and a readout circuit. The humidity sensor is composed of a sensitive film and interdigitated electrodes. The sensitive film is titanium dioxide prepared by the sol-gel method. The titanium dioxide is coated on the interdigitated electrodes. The humidity sensor requires a post-process to remove the sacrificial layer and to coat the titanium dioxide. The resistance of the sensor changes as the sensitive film absorbs or desorbs vapor. The readout circuit is employed to convert the resistance variation of the sensor into the output voltage. The experimental results show that the integrated humidity sensor has a sensitivity of 4.5 mV/RH% (relative humidity) at room temperature.

This article is from Sensors (Basel, Switzerland) , volume 9 . Abstract In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems.

This article is from Sensors (Basel, Switzerland) , volume 9 . Abstract In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems.

This article is from Sensors (Basel, Switzerland) , volume 13 . Abstract This study investigates the design and fabrication of magnetic microsensors using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process. The magnetic sensor is composed of springs and interdigitated electrodes, and it is actuated by the Lorentz force. The finite element method (FEM) software CoventorWare is adopted to simulate the displacement and capacitance of the magnetic sensor. A post-CMOS process is utilized to release the suspended structure. The post-process uses an anisotropic dry etching to etch the silicon dioxide layer and an isotropic dry etching to remove the silicon substrate. When a magnetic field is applied to the magnetic sensor, it generates a change in capacitance. A sensing circuit is employed to convert the capacitance variation of the sensor into the output voltage. The experimental results show that the output voltage of the magnetic microsensor varies from 0.05 to 1.94 V in the magnetic field range of 5–200 mT.