Proposed Sensor Chip Research Articles

Sputtered Deposited Cu Functionalized MoS2 Nanoworm Thin Films for Nitrogen Dioxide (NO2) Gas Sensor

Semiconducting nanostructures thin films are used in state-of-arts applications due to their heightened physical properties. Semiconducting metal sulfides nanostructures are a growing asset in current semiconductor technology due to their extraordinary physical, chemical, and electronic properties and their outstanding applications in different sensing and optoelectronic devices. The gas sensing capability of semiconducting nanostructures is a recent research interest of many researchers. The MoS2 thin films were grown using reactive sputteringand the sensing performance of pure MoS2 and Cu-MoS2 thin films was studied towards nitrogen dioxide (NO2) gas concentrations (2-200 ppm) at the optimum working temperature of 100℃. The Cu-MoS2 sensor provides a high sensing response as compared to the pure MoS2 thin-film sensor towards 20 ppm of NO2 gas with a fast response and recovery time of 54 s and 82 s, respectively. It was observed that the proposed sensor chip displays an almost stable signal up to the 5th cycle. It is observed that the proposed sensor device exhibits the highest response (30%) to NO2 concerning weak response (10%) towards additional potentially interfering gases (NH3, CO, and H2) at 100°C. It reveals that the Cu-MoS2 thin-film sensor chip is highly selective to NO2 gas at 100 °C.

A 27-mW Ka-Band Complex Dielectric Sensor Chip With Readout and Reference Circuits Using 1.2-V Supply in 130-nm SiGe BiCMOS

The capability to sense the dielectric properties of liquids and tissues is valuable in many applications, because accurate assessment of the material composition can be made from the complex permittivity measurements. Laboratory-on-chip systems for continuous dielectric monitoring impose low-voltage and low-power operation on the circuits to enable long-term use without battery replacement. In addition, high level of integration is necessary to facilitate the implementation of 2-D sensor arrays. This letter presents the design and characterization of a SiGe BiCMOS capacitive sensing oscillator-based complex dielectric sensor chip at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band operating with a supply voltage of 1.2 and consuming 27 . The chip is integrated with readout circuits to provide simple dc outputs for easier processing and with reference circuits to serve as a tool to compensate for both the external and internal variations, which affect the sensor output. The experimental results show that different alcohols can be differentiated using the proposed sensor chip.

The Influence of Electrode Design on Detecting the Effects of Ferric Ammonium Citrate (FAC) on Pre-Osteoblast through Electrical Cell-Substrate Impedance Sensing (ECIS)

Detection sensitivity is a crucial factor in the application of ECIS sensors. For these biosensors, the electrode configuration has a direct impact on sensitivity, yet few studies on monopolar electrodes have been reported. In this study, ECIS sensor arrays, which have a series of working electrode configuration with a wide diameter range and different electrode number, were fabricated to monitor living osteoblast-like MC3T3-E1 cells. The experimental results revealed that when the electrode diameter was larger than 25 μm, electrodes with smaller diameter and number yielded higher impedance values and generated more impedance shift to cell status change. The membrane capacitance obtained by equivalent circuit fitting was at the same level. When the electrode diameter was even smaller, the results in detection of cell monolayer were opposite, and there was no distinct relationship between impedance and membrane capacitance shift to cell status change and electrode geometry. The proposed sensor chip, allowing for a sustained and stable detection of cellular impedance, provides the basis for the selection of the electrode configuration of monopolar electrodes. The test results of electrodes with a diameter of 25 μm and lower indicated the possibility of single cell impedance measurement, which can provide unique insight into the heterogeneous electrical behavior of cells, and, in this case, the electrode size should be close to the cell size.

In-situ label-free optical biosensing with plasmonic enhanced ellipsometry using partially-embedded bimetallic Ag-Au alloy nanoparticles

This work presents a label-free optical biosensing platform by integrating the localized surface plasmon resonance (LSPR) and in-situ ellipsometry technique. A sensor chip composed of partially embedded Au-Ag alloy nanoparticles was fabricated on a glass substrate by the thermal dewetting method. The sensor chip was characterized using spectroscopic ellipsometry to determine the optical constant. The bulk RI resolution estimated from the ellipsometry phase (∆) signal was found to be 4.62 × 10−7 RIU for the bare sensor chip. Also, the biosensing experiment toward protein detection gives a detection limit of 23 pM. Further, hexagonal-boron nitride nanosheets (h-BNNS) modified sensor chip shows enhanced sensitivity with the detection limit down to 4.2 pM. The protein adsorption coefficients obtained from the fitting of kinetics data give values of 4.6 × 104 mol−1s−1 and 2.65 × 105 mol−1 s−1 for bare, and h-BNNS modified sensor chips, respectively. A theoretical simulation performed with COMSOL shows good agreement with our experimental outcomes. We believe that our proposed sensor chip enables the features of high stability, surface-sensitive, non-destructive, label-free, easy to fabricate, and cost-effectiveness, which make it feasible for large-scale production and commercialization in biomedical applications.

A Self-Driven Microfluidic Chip for Ricin and Abrin Detection.

Ricin and abrin are phytotoxins that can be easily used as biowarfare and bioterrorism agents. Therefore, developing a rapid detection method for both toxins is of great significance in the field of biosecurity. In this study, a novel nanoforest silicon microstructure was prepared by the micro-electro-mechanical systems (MEMS) technique; particularly, a novel microfluidic sensor chip with a capillary self-driven function and large surface area was designed. Through binding with the double antibodies sandwich immunoassay, the proposed sensor chip is confirmed to be a candidate for sensing the aforementioned toxins. Compared with conventional immunochromatographic test strips, the proposed sensor demonstrates significantly enhanced sensitivity (≤10 pg/mL for both toxins) and high specificity against the interference derived from juice or milk, while maintaining good linearity in the range of 10–6250 pg/mL. Owing to the silicon nanoforest microstructure and improved homogeneity of the color signal, short detection time (within 15 min) is evidenced for the sensor chip, which would be helpful for the rapid tracking of ricin and abrin for the field of biosecurity.

Characterization and analysis of a novel structural SOI piezoresistive pressure sensor with high sensitivity and linearity

A novel structural piezoresistive pressure sensor with four-grooved diaphragm combined with rood beam has been proposed for low pressure measurements of less than 1 psi. The proposed sensor chip is fabricated on a SOI wafer by traditional MEMS micromachining and anodic bonding technology. By localizing more strain energy in the stress concentration region and increasing the constraint of the partial pedestal, the sensor achieved a high sensitivity and linearity of 30.9 mV/V/psi and 0.25% FSS respectively at room temperature, and thereby the contradiction between sensitivity and linearity is alleviated. Besides, a sensitivity of 21.2 mV/V/psi and a linearity of 0.5% FSS were obtained at 150 °C, which illustrates that the proposed sensor has a stable high temperature output characteristic. Additionally, the mechanisms about strain energy transmission and partially stiffened diaphragm are also discussed.

A Low Power and Fast Tracking Light-to-Frequency Converter With Adaptive Power Scaling for Blood SpO 2 Sensing.

This paper presents a monolithic low power and fast tracking light-to-frequency converter for blood SpO 2 sensing. Normally, the tracking speed and the power consumption are two contradictory characteristics. However, different gain-bandwidth specifications for various ambient light intensities allow the dynamic optimization of the power consumption according to the light intensity. In this paper, the amplifier power consumption is adaptively scaled by the generated light-intensity-positively-correlated control voltage. Thus, the chip total power consumption at low light intensity is significantly decreased. Moreover, the proposed adaptive power scaling is achieved with a continuous analog domain, which does not introduce extra switching noise. The proposed light-to-frequency sensor chip is fabricated by using 0.35 μm CMOS technology with a die area of 1 × 0.9mm 2. The measurement results show that the pulse light response for any light intensity is no longer than two new output square-wave cycles. The maximum total current consumption is 1.9mA from a 3.3V supply voltage, which can be adaptively scaled down to only 0.7mA if the output frequency is about 25KHz or lower. The minimum operational supply voltage of the proposed sensor chip is 2.5V in the temperature range of -25 to 80 °C with 4KV ESD level (human-body model).

CMOS Luminescence Imager With Ambient Light Compensation and Lifetime to Frequency Conversion.

This paper presents a novel CMOS image sensor for luminescence imaging with direct lifetime-dependent digital pulse frequency modulated output. Recently reported parasitic insensitive multicycle charge modulation scheme is applied to accumulate photon-generated charges in discrete programmable time windows over multiple exposures. An autoreset pulse serving as the digital output is generated by comparing the multicycle charge integrated output with a reference threshold. The detected luminescence's lifetime is extracted by monitoring the frequency in this digital pulse. To compensate for the background photocurrent generated by ambient light and built-in offset, a charge pump based calibration circuitry is also proposed. Driven by a 10-KHz clock signal with 20-μs pulse width as the integration time window, the proposed circuitry can achieve responsivity and resolution at 575 nm wavelength. It has lifetime resolution of 8 ns. The proposed sensor chip was applied for lifetime measurement of a Ru(dpp)3(PF6)2 fluorescent sample whose lifetime was estimated to be 4.2 μs. A two-dimensional luminescence intensity and lifetime images of a single white LED have also been obtained to further validate its functionality.

Development of graphene oxide/poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) thin film-based electrochemical surface plasmon resonance immunosensor for detection of human immunoglobulin G

An electrochemically synthesized graphene oxide (GO)/poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(styrene sulfonate) (PSS) thin film-based electrochemical surface plasmon resonance (EC-SPR) sensor chip was developed and employed for the detection of human immunoglobulin G (IgG). GO introduced the carboxylic group on the film surface, which also allowed electrochemical control, for the immobilization of the anti-IgG antibody via covalent bonding through amide coupling reaction. The SPR sensitivity of the detection was improved under the control by applying an electrochemical potential, by which the sensitivity was increased by the increment in applied potential. Among the open-circuit and different applied potentials in the range of −1.0 to 0.50 V, the EC-SPR immunosensor at an applied potential of 0.50 V exhibited the highest sensitivity of 6.08 × 10−3 mL µg−1 cm−2 and linearity in the human IgG concentration range of 1.0 to 10 µg mL−1 with a relatively low detection limit of 0.35 µg mL−1. The proposed sensor chip is promising for immunosensing at the physiological level.

COMSOL modeling of an integrated impedance sensor in a hanging-drop platform

Event Abstract Back to Event COMSOL modeling of an integrated impedance sensor in a hanging-drop platform Raziyeh Bounik1*, Massimiliano Gusmaroli1, Vijay Viswam1, Mario M. Modena1 and Andreas Hierlemann1 1 ETH Zürich, Department of Biosystems Science and Engineering, Switzerland Motivation Traditional dish-based, two-dimensional cell cultures have limited prediction capability for drug testing, whereas three-dimensional spherical microtissues (spheroids) and organoids much more accurately replicate physiological conditions of cells in the respective tissue [1,2]. Such spheroids can be formed and cultured in microphysiological multi-tissue formats by using the hanging-drop technology as depicted in Fig. 1 [3]. Like most other microfluidic platforms, the hanging-drop platform still requires a microscope for visual inspection and considerable time for doing off-line measurements, as the spheroids/media have to be harvested from the microfluidic device for labeling and chemical analysis. It would be beneficial to have an integrated on-line multi-functional sensor as an additional readout, located directly at the tissue sites in the hanging-drop platform, so that measurements can be performed in situ and without harvesting medium or the tissue and without interrupting the overall culturing process. Material and Methods The proposed sensor chip includes a configurable microelectrode array (2 mm x 2 mm) with integrated impedance spectroscopy readout on a single CMOS chip, that will be used for microtissue growth profiling. A model has been developed and simulated by COMSOL Multiphysics to investigate the effect of physical parameters, such as hanging-drop dimensions, to find an optimal electrode size. Fig. 2 (a) shows the implemented model, which includes a droplet (filled by medium), a microtissue, reference electrode, and an example working electrode. The medium (electrolyte) was modeled with a conductivity of 1.2 S/m, and the microtissue as an insulator with a conductivity of 0.01 S/m. The electrode-electrolyte interface was modeled by a double-layer capacitance of 0.25 F/m2 [4]. Results Fig. 2 (b) shows the current density in the medium while applying a sinusoidal voltage to the reference electrode and measuring the current through the working electrode. Fig. 2 (c) illustrates the effect of the spheroid size on the measured impedance for three electrode sizes, which shows that larger electrodes provide better-quality data for monitoring spheroid growth. Summary and conclusion A COMSOL model of a hanging-drop platform was developed, and the effects of electrodes and hanging-droplet dimensions were investigated. Results showed that in order to monitor the microtissue growth through impedance measurements, working electrodes should be larger than 100 µm × 100 µm. Figure 1 Figure 2 Acknowledgements Acknowledgements Financial support through MHV Grant 171267 and ERC Advanced Grant 694829 “neuroXscales” are acknowledged.

A Current-Integration-Based CMOS Amperometric Sensor with 1024 × 1024 Bacteria-Sized Microelectrode Array for High-Sensitivity Bacteria Counting

CMOS amperometric sensors with a microelectrode array offer great potential for counting bacteria because of their low cost, compact size, and ease of use. This paper presents a current-integration-based CMOS amperometric sensor for high-sensitivity bacteria counting. It has a current integrator for noise reduction and reportedly the most large-scale microelectrode array (1024 × 1024). This proposed sensor can count the number of bacteria ranging from a single cell to approximately a million cells. A prototype chip was fabricated using two-poly three-metal (2P3M) 0.6-µm standard CMOS technology. A 7.6 × 7.1-mm2 chip operates from a 5V supply at 1.9mA. In addition, by using the prototype chip, we performed electrochemical measurement and partial 2D imaging of silicone through constant potential amperometry. The measurement results indicate that the proposed sensor chip was able to accurately readout redox current from the 1024 × 1024 sensor array.

A bossed diaphragm piezoresistive pressure sensor with a peninsula–island structure for the ultra-low-pressure range with high sensitivity

A sensor chip with a bossed diaphragm combined with a peninsula–island structure was developed for a piezoresistive pressure sensor. By introducing a stiffness mutation above the gap position between the peninsula and island structures, the strain energy of the proposed diaphragm was mainly concentrated upon the gap position, which remarkably increased the sensitivity of the sensor chip. A beam–diaphragm coupled model and an optimization method for the novel sensor chip were also developed, which gave guidelines for optimizing the sensor chip structure. Finally, a sensor chip with the bossed diaphragm combined with peninsula–island structure was fabricated and tested. The experimental results showed that the proposed sensor chip was able to measure ultra-low pressure within 500 Pa with high sensitivity.

A high sensitive pressure sensor with the novel bossed diaphragm combined with peninsula-island structure

A Micro Electromechanical Systems (MEMS) piezoresistive pressure sensor chip with high sensitivity has been developed to measure the ultra-low pressure of several mbar. A novel bossed diaphragm combined with peninsula-island structure is designed. The proposed diaphragm can alleviate the trade-off between sensitivity and non-linearity to realize the measurement of ultra-low pressure with low non-linearity. Especially, the strain energy dissipating outside the stress concentration region (SCR) is reduced remarkably by the proposed diaphragm to achieve high sensitivity. The optimization process for the proposed diaphragm has been presented by finite element method (FEM) to make the sensor chip achieve a higher sensitivity and a lower non-linearity. A fabricated pressure sensor was packaged with the proposed sensor chip and tested to obtain the sensitivity of 0.066mV/V/Pa and non-linearity of 0.33%FS in the working range of 0–500Pa. The proposed sensor chip is potentially a better choice for high sensitive pressure sensor.

Highly Sensitive and Selective Sensor Chips with Graphene-Oxide Linking Layer.

The development of sensing interfaces can significantly improve the performance of biological sensors. Graphene oxide provides a remarkable immobilization platform for surface plasmon resonance (SPR) biosensors due to its excellent optical and biochemical properties. Here, we describe a novel sensor chip for SPR biosensors based on graphene-oxide linking layers. The biosensing assay model was based on a graphene oxide film containing streptavidin. The proposed sensor chip has three times higher sensitivity than the carboxymethylated dextran surface of a commercial sensor chip. Moreover, the demonstrated sensor chips are bioselective with more than 25 times reduced binding for nonspecific interaction and can be used multiple times. We consider the results presented here of importance for any future applications of highly sensitive SPR biosensing.

Microfluidic Chip with Integrated Electrical Cell-Impedance Sensing for Monitoring Single Cancer Cell Migration in Three-Dimensional Matrixes

Cell migration has been recognized as one hallmark of malignant tumor progression. By integrating the method of electrical cell-substrate impedance sensing (ECIS) with the Boyden chamber design, the state-of-the-art techniques provide kinetic information about cell migration and invasion processes in three-dimensional (3D) extracellular matrixes. However, the information related to the initial stage of cell migration with single-cell resolution, which plays a unique role in the metastasis-invasion cascade of cancer, is not yet available. In this paper, we present a microfluidic device integrated with ECIS for investigating single cancer cell migration in 3D matrixes. Using microfluidics techniques without the requirement of physical connections to off-chip pneumatics, the proposed sensor chip can efficiently capture single cells on microelectrode arrays for sequential on-chip 2D or 3D cell culture and impedance measurement. An on-chip single-cell migration assay was successfully demonstrated within several minutes. Migration of single metastatic MDA-MB-231 cells in their initial stage can be monitored in real time; it shows a rapid change in impedance magnitude of approximately 10 Ω/s, whereas no prominent impedance change is observed for less-metastasis MCF-7 cells. The proposed sensor chip, allowing for a rapid and selective detection of the migratory properties of cancer cells at the single-cell level, could be applied as a new tool for cancer research.

Design and Fabrication of Complementary Metal–Oxide–Semiconductor Sensor Chip for Electrochemical Measurement

An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 µm complementary metal–oxide–semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

Charge-Based Capacitive Sensor Array for CMOS-Based Laboratory-on-Chip Applications

In this paper, we present a capacitive sensor array for highly integrated lab-on-chip (LoC) applications using the charge-based capacitance measurement method (CBCM). The core-CBCM sensor chip is designed and implemented in 0.18 micron CMOS process featuring an array of capacitive sensors; an offset cancellation module and a low complexity analog-to-digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. We demonstrate the testing results using chemical solvents with known dielectric constants in order to show the viability of the proposed sensor chip for LoCs.