Fabrication Process Of Sensor Research Articles

Embedded Capacitive Displacement Sensor for Nanopositioning Applications

The scale of nano-sized objects requires very precise position determination. The state-of-the-art manipulators involve accurate nanometer positioning. This paper presents the design, fabrication process, and testing of a capacitance-based displacement sensor. The nanopositioner application required active sensing area dimensions to be hundreds of micrometers, making it necessary to develop sensor electrodes that are a few micrometers in size. The advantages of the sensor presented are its noninvasive method and very low voltage necessary for signal conditioning. Initial results suggest good linearity and sensitivity of 0.001 pF/μm, permitting a reliable displacement resolution on the order of 100 nm.

Highly selective GaN-nanowire/TiO2-nanocluster hybrid sensors for detection of benzene and related environmentpollutants

Nanowire–nanocluster hybrid chemical sensors were realized by functionalizinggallium nitride (GaN) nanowires (NWs) with titanium dioxide (TiO2) nanoclusters for selectively sensing benzene and other related aromaticcompounds. Hybrid sensor devices were developed by fabricating two-terminaldevices using individual GaN NWs followed by the deposition ofTiO2 nanoclusters using RF magnetron sputtering. The sensor fabrication process employedstandard microfabrication techniques. X-ray diffraction and high-resolutionanalytical transmission electron microscopy using energy-dispersive x-ray andelectron energy-loss spectroscopies confirmed the presence of the anatase phase inTiO2 clusters afterpost-deposition anneal at 700 °C. A change of current was observed for these hybrid sensors when exposed tothe vapors of aromatic compounds (benzene, toluene, ethylbenzene, xylene andchlorobenzene mixed with air) under UV excitation, while they had no response tonon-aromatic organic compounds such as methanol, ethanol, isopropanol,chloroform, acetone and 1,3-hexadiene. The sensitivity range for the noted aromaticcompounds except chlorobenzene were from 1% down to 50 parts per billion (ppb)at room temperature. By combining the enhanced catalytic properties of theTiO2 nanoclusters with the sensitive transduction capability of the nanowires, an ultra-sensitiveand selective chemical sensing architecture is demonstrated. We have proposed amechanism that could qualitatively explain the observed sensing behavior.

A new interdigitated array microelectrode-oxide-silicon sensor with label-free, high sensitivity and specificity for fast bacteria detection

Abstract We introduce a new interdigitated array microelectrode-oxide-silicon (IDAMOS) sensor with label-free, high sensitivity and specificity for fast bacteria detection. The sensor is composed of Al interdigitated array microelectrodes (IDAM) insulated from an active Si substrate by a layer of SiO 2. The Al microelectrodes are protected by a thin layer of Al 2O 3. It is found that charged target molecules deposited on the IDAM surface can modify the space-charge region properties in the active Si substrate through metal-oxide-semiconductor (MOS) capacitor effect, which makes the new sensor more sensitive than the classical IDAM sensor. This opens a new perspective for the future designs of highly sensitive sensors. We investigate the dependence of the IDAMOS sensor sensitivity on its electrode size. The results indicate that for achieving high sensitivity, the IDAMOS sensor should have a suitable ratio of the interspacing width to the electrode width and an interspacing width compatible with the size of the target biomolecule. Staphylococcus aureus is used as a test system to establish the sensitivity and specificity of the IDAMOS sensor. Less than 240 bacteria cells immobilized on the IDAMOS sensing area of 200 μm × 200 μm, leads to significant changes on capacitance and conductance, which can be easily and directly detected in 10 min. Besides featuring rapid, specific, free-label and low-cost bacterial detection, this IDAMOS sensor can be used for more applications and can be easily integrated with complementary metal-oxide-semiconductor circuits. The fabrication process of the IDAMOS sensor is reproducible, reliable and valid for large-scale products.

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors

Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5–9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors.

Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5–9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Control and Optimization of a Sensor Manufacturing Process

This paper presents a feedback control optimization framework for a sensor development and fabrication process. The existing sensor adaptive neuro-fuzzy inference system intelligent model was configured in a closed-loop feedback control framework to optimally automate the sensor manufacturing process. Three main sensor manufacturing components were assumed to be the process inputs while the sensor relative optical density was considered as the output in the sensor intelligent model. The optimization and automation of the phenol sensor development were investigated by designing two controllers in a closed loop control tracking problem. Although the closed loop framework was inherently nonlinear, sensor design parameters with practical significance were successfully achieved for both types of controllers. The fuzzy logic controller receives the closed loop system error and the error rate and generates the incremental changes on the three sensor process inputs. The second controller is a proportional-integral-derivative type that processes each manufacturing process input and that manipulates the closed loop system error to produce the actual sensor process inputs. The numerical results for the proposed frameworks demonstrate that the sensor automation and design optimization can be enormously improved in closed loop control frameworks, eliminating the need of tedious trial-and-error sensor development process.

Fabrication of AC-coupled double-sided silicon strip sensor

The AC-coupled double-sided silicon microstrip sensors are designed and 14 masks are used to produce prototype strip sensors. The biasing resistors are made of p-doped polysilicons and the coupling capacitors are built by separating implanted strips and readout strips by a thin oxide layer. The p-stops in the atoll patterns are introduced to disrupt an electron accumulation layer at the Si–SiO2 interface on the ohmic side. The junction side has a double metal structure using two metal layers separated from each other by a thick insulator layer. The strip sensors are fabricated on a 5-in., high resistivity, 〈100〉-orientation, and 380μm thick n-type double-sided polished silicon wafer. The prototype sensor with an area of 2.8×2.8cm2 consists of 256(512) readout channels with a strip pitch of 100(50)μm. The leakage currents and the bulk capacitances as a function of the reverse bias voltage are measured to understand the fabrication process of the prototype sensors. The signal to noise ratios are measured by using a 90Sr radioactive source in order to evaluate performance of the sensors. The design of the AC-coupled double-sided silicon strip sensor and its various components are described, and measurements of the electric characteristics and the signal to noise ratio are presented.

Pt surface modification of SnO2 nanorod arrays for CO and H2 sensors

Uniform SnO(2) nanorod arrays were deposited on a 4 inch SiO(2)/Si wafer by plasma-enhanced chemical vapor deposition (PEVCD) at low deposition temperature of around 300 degrees C. The SnO(2) nanorods were connected at the roots, thus the nanorod sensors could be fabricated by a feasible way compatible with microelectronic processes. The surface of the sensors was modified by Pt nanoparticles deposited by dip coating and sputtering, respectively. The sensing properties of the Pt-modified SnO(2) nanorod sensors to CO and H(2) gases were comparatively studied. After surface modification of Pt, the sensing response to CO and H(2) gases increased dramatically. The 2 nm Pt-modified SnO(2) nanorod sensors by sputtering showed the best sensing performance. By increasing Pt thickness from 2 nm up to 20 nm, the optimal working temperature decreased by 30 degrees C while the sensing response also decreased by about 4 times. Comparing these two Pt modification approaches by dip coating and sputtering, both could achieve comparable promotion effect if the Pt thickness can be controlled around its optimal value. The deposition technique of SnO(2) nanorod arrays by PECVD has good potential for scale-up and the fabrication process of nanorod sensors possesses simplicity and good compatibility with contemporary microelectronics-based technology.

Triaxial fluxgate sensor with electroplated core

A novel fluxgate sensor with a single ferromagnetic core capable of measurement in three principal axes is presented. The sensor manufacturing process and internal coil structure is explained and its excitation is modelled using FEM. The sensor was implemented utilizing multilayer printed circuit board copper routes and electroplated through holes to create appropriate coils. The sensor magnetic core was electroplated on the printed circuit board surface and through holes using Permalloy (Ni 80Fe 20). The core material properties were identified using a PCB based transformer device showing relative permeability of 2300 at 50 kHz. Sensor excitation effects are investigated with special emphasis on sensor axis orthogonality revealing a significant sensitivity axis tilt due to excitation means. The sensor is characterised in terms of sensitivity, linearity and noise. Measurements show a significant influence of core material anisotropy on sensitivity (90 V/T in x axis vs. 112 V/T in y axis). The z-axis sensitivity (198 V/T) is significantly higher due to the different core geometry in corresponding direction and different number of pick-up coil turns.

Solvent assisted bonding of polymethylmethacrylate: Characterization using the response surface methodology

This work presents the investigation of a novel solvent assisted bonding process developed for the fabrication of closed microchannels made from polymethylmethacrylate (PMMA). The effects of four process parameters on the deformation and the bond strength of the microchannel have been investigated using the response surface methodology (RSM). High bond strengths (3.5 ± 0.8 MPa) at low deformations (1.6 ± 0.3%) have been achieved at the center point of the design of experiment. The limits of the developed bonding process have been investigated by the fabrication of microchannels with low aspect ratios. Microchannels with a width of 130 μm and a depth of 4 μm have been fabricated. This is equivalent to an aspect ratio of 0.03. Further, the integration of the bonding process into the fabrication process of the wireless implantable strain sensor (WIPSS) has been verified and excellent bonding of the microchannel has been confirmed by ultrasound measurements.

An Excellent Platinum Piezoresistive Pressure Sensor Using Adhesive Bonding with SU-8

An excellent pressure sensor based a simple fabrication technology is presented. Differently from the present prevailing fabrication process of silicon piezoresistive pressure sensor: platinum is used as the sensing material, with a smaller but acceptable sensitivity and much simpler processes; adhesive bonding with SU-8 is used as an alternative choice to anodic bonding, and we choose a vacuum hot plate to avoid using a bonding machine. To achieve a successful bonding, it is found that pre-bake time and pumping time are the most important factors. Bonding quality is evaluated by inspection through the glass with 95% of the area successfully bonded and the failed area in the edge of the wafers. The measured bonding strength is 17.34 MPa. The Pressure-Voltage characteristic test results display a good linearity within 0.2% and especially a good precision within 0.035% in square fitting. The temperature drifting is also tested and the TCO is 1250 ppm/(°C FSO). The long-term stability of the sensor at a constant pressure is a fluctuation within 40 Pa (0.098% FSO) in 7 days. Both the simple fabrication process and the excellent performance of the sensor suggest that this sensor is a much good choice in measuring atmospheric pressure.

Clinical Evaluation of Bionime Rightest GM310 Biosensors with a Simplified Electrode Fabrication for Alternative-Site Blood Glucose Tests

Most processes for fabricating biosensors applied to screen-printed carbon electrodes (SPCEs) are complex. This study presents a novel one-step process for manufacturing electrodes for injection-molding biosensors. During the sensor-fabrication process, barrel-plated gold electrodes were inserted into an injection-molded base. The electrode directly touched the electrical contact of a meter. We analyzed technical measurements for this biosensor, including tests of the measurement range, within-run imprecision, and between-meter imprecision. In clinical trials, experienced technicians tested 3 alternative sites (fingertip, palm, and arm). The results were simultaneously compared with plasma values obtained with the hexokinase method on the Olympus AU640 instrument. Analytical results were evaluated according to International Standards Organization 15197 (ISO 15197:2003) criteria and by Clarke error grid analysis (EGA), and CVs were calculated to evaluate within-run imprecision. The glucose measurement range was 0.6- 33.3 mmol/L (y = 0.96x + 0.07 mmol/L; r(2) = 0.9977). The CVs in the within-run imprecision test were 1.7%-3.5%, and the overall CV was 2.1%, indicating good reproducibility of results. The Student t-tests of mean values from 5 meters revealed statistically insignificant differences (P > 0.05). In clinical trials, the agreement of the Rightest GM310 meter results with those of a laboratory method complied with ISO 15197:2003 criteria. In the EGA, 100% of the values were within the acceptable zones (A + B), and the proportion of values within zone A exceeded 95%. The Bionime Rightest GM310 meter applied a simplified process for biosensor fabrication and displayed acceptable performance for monitoring glucose concentrations at alternative test sites.

새 구조의 액정 엑스선 감지기

새 구조의 액정 엑스선 감지기를 만들었다. 이것은 액정판을 만들고 유리판을 얇게 식각한 다음, 그 유리판 위에 반사막과 광전도층을 연속하여 입힌 구조이다. 새 구조의 액정엑스선 감지기는 공정의 안정성, 대면적화, 감도 등에서 이미 상품화된 엑스선 감지기와도 충분히 경쟁할 수 있으며, 따라서 성공적으로 상용화 할 수 있음을 확인했다. We developed a new x-ray image sensor utilizing a reflection-mode liquid crystal panel as its sensitive element, and tested its functionality by using it to obtain an x-ray image of a printed circuit board. In the liquid crystal x-ray image sensors hitherto reported, the liquid crystal layer is in direct contact with the photoconductive film which is deposited on a glass substrate. In the fabrication of the new x-ray image sensor, a liquid crystal panel is fabricated in the first step by using a pair of glass plates of a few centimeters thicknrss. Then one of the glass substrates is ground until its thickness is reduced to about <TEX>$60\;{\mu}m$</TEX>. After polishing the glass plate, dielectric films for high reflectance at 630 nm, a film of amorphous selenium for photoconduction, and a transparent conductive film for electrode are deposited in sequence. The new x-ray image sensor has several merits: primarily, fabrication of a large area sensor is more easily compared with the old fashioned x-ray image sensors. Since the reflection type liquid crystal panel has a very steep response curve, the new x-ray sensor has much more sensitivity to x-rays compared with the conventional x-ray area sensor, and the radiation dosage can be reduced down to less then 20%. By combining the new x-ray sensor with CCD camera technology, real-time x-ray images can be easily captured. We report the structure, fabrication process and characteristics of the new x-ray image sensor.

Ultrathin SnO2 gas sensors fabricated by spray pyrolysis for the detection of humidity and carbon monoxide

Abstract A new gas sensor based on ultrathin SnO 2 -films with high sensitivity for humidity and carbon monoxide has been developed. The SnO 2 -sensing films are fabricated by a spray pyrolysis process with a thickness between 50 and 100 nm on oxidized silicon substrates. The SnO 2 -sensing films are finally processed in arrays of parallel bars to achieve the sensor device. The structure of SnO 2 -layers has been characterized by SEM, AFM and XPS analysis. The sensors are operated at temperatures of 250–400 °C, show high sensitivity to humidity and are able to detect carbon monoxide down to a concentration of less than 5 ppm. The fabrication process of the gas sensor is fully compatible with silicon process technology. The spray pyrolysis technique is a simple and flexible process and thus is suitable for the cost efficient fabrication of a new gas-sensing device. Strategies to improve sensitivity and selectivity of the sensor toward different gas species are discussed.

IR sensors based on silicon–germanium–boron alloys deposited by plasma: Fabrication and characterization

We report the study of a fabrication process and characterization of a thermal IR sensor based on silicon–germanium–boron alloys (a-SixGeyBz:H) deposited by plasma at low temperature. The sensor is an un-cooled micro-bolometer fabricated with surface micro-machining techniques and is fully compatible with the CMOS technology. The temperature dependence of conductivity σ(T) was measured in the sensor in order to calculate the activation energy, Ea, the temperature coefficient of resistance, TCR and the room temperature conductivity, σRT. Current–voltage characteristics, I(U), in darkness and under IR radiation were measured in the device in order to calculate its current responsivity, RI. Spectral noise density was measured and the micro-bolometer detectivity, D∗ was calculated. The thermal time constant of the micro-bolometer was also measured.

Polymer-metal nanocomposites with 2-dimensional Au nanoparticle arrays for sensoric applications

Sensors for volatile organic compounds (VOC) are of increasing interest for various applications ever since. Here we present a novel method to achieve a fast and reversible response by employing a polymer-metal nanocomposite film with 2-dimensional Au nanoparticle arrays. Our sensors are made out of spin-coated polymer substrates on which we deposit gold clusters with a cluster density near the percolation threshold via thermal evaporation. The sensor operates on the principle of swelling of polymers in the presence of VOC. This leads to a change in the interparticle distance and therefore the conductivity of the composites. The method is fast, easy, precisely to control and the sensor fabrication process produces only a minimum amount of waste (like organic solvents). The degree of swelling primarily depends on the type of polymer and the organic solvent, i.e. solubility parameters of the polymer and the vapor. Therefore, the pattern leads to fingerprints of particular polymers towards different vapors. These fingerprints can be employed as a parameter for detecting different VOCs.

Fabrication and Testing of a Medical Surgical Instrument Capable of Detecting Simulated Embedded Lumps

A novel endoscopic grasper is being fabricated and tested. This grasper can be used in detecting lumps or tumors in biological tissues. The detailed fabrication process of the tactile sensor has been discussed. Custom-made sensors were integrated with the jaws of the endoscopic grasper and objects with known tactile features were tested by the designed grasper. Different experiments were performed with the system in order to determine both the position and the size of the lumps or inclusions located in the soft elastomeric media. The average discrepancy between the experimental and theoretical simulations was found to be less than 15%.

A wireless magnetoelastic biosensor for rapid detection of glucose concentrations in urine samples

Abstract A wireless magnetoelastic glucose biosensor is fabricated by co-immobilizing glucose oxidase (GOx) and catalase onto a pH-sensitive-polymer-coated magnetoelastic sensor with chitosan as a supporting substrate. The GOx-catalyzed hydrolyzation of glucose produces gluconic acid, resulting in shrinking and corresponding mass decrease in the pH-responsive polymer, and consequently the resonance frequency of the magnetoelastic sensor increasing. The glucose biosensor is applied to measurement of glucose concentrations within urine samples; the shift in resonance frequency is found proportional to the glucose concentration, with a linear response obtained between 1 mM and 15 mM. The presence of acetaminophen, lactose, saccharose and galactose do not significantly interfere with glucose detection; ascorbic acid does, as expected, however its effect can be eliminated through cross-correlation with a pH-responsive magnetoelastic reference sensor or by pre-adjusting the sample to pH 7.0. A L 9 (3 4 ) orthogonal array based on the Taguchi method is used to optimize the sensor fabrication process and to determine the key factors that affect sensor performance. Assays of 15 clinical urine samples give glucose levels that are in accordance with the results by an urine analyzer, showing the proposed sensor can be applied for glucose assay in urine.

An Experimental Study on the Fabrication of Glass-based Acceleration Sensor Body Using Micro Powder Blasting Method

This study investigated the feasibility of the micro powder blasting technique for the micro fabrication of sensor structures using the Pyrex glass to replace the existing silicon-based acceleration sensor fabrication processes. As the preliminary experiments, the effects of the blasting pressure, the mass flow rate of abrasive and the number of nozzle scanning times on erosion depth of the Pyrex and the soda lime glasses were examined. From the experimental results, optimal blasting conditions were selected for the Pyrex glass machining. The dimensions of the designed glass sensor was 1.7×1.7×0.6mm for the vibrating mass, and 2.9×0.7×0.2mm for the cantilever beam. The machining results showed that the dimensional errors of the machined glass sensor ranged from 3 μm in minimum to 20 μm in maximum. These results imply that the micro powder blasting method can be applied for the micromachining of glass-based acceleration sensors to replace the exiting method.

Polycrystalline Diamond Pressure Sensor using Spin Coat Seeding Method

Pressure sensors using polycrystalline diamond can operate at a high temperature. However, the sensors usually have a very low Gauge Factor (G.F.), less than 100 and the special process is required to improve the sensitivity. In order to obtain a high G.F. without the special fabrication process, the combination of scratch and spin coat seeding methods have been introduced. By using the proposed method, it was possible to grow the diamond film uniformly on a SiO2 substrate and the adhesion force of the film to the substrate increased up to 900 N/cm2 at the maximum value. Boron doped diamond films were deposited on a Si diaphragm using the developed method in a fabrication process of a pressure sensor. Although the sensor demonstrated a good linearity in the pressure response, the G.F. was only 29 because of the poor surface conduction. To improve the surface conduction, the oxygen termination of the surface and relaxation of hydrogen defect by annealing were introduced respectively. As a result, the G.F. was improved up to 168. Oxidization by hot mixed acid also improved the G.F. to 285. The sensor treated by this oxidization showed the better uniformity in the temperature characteristic.