Calibration-Free CMOS Capacitive Sensor for Life Science Applications

Tabrizi, Hamed Osouli; Forouhi, Saghi; Farhanieh, Omid; Bozkurt, Ayhan; Magierowski, Sebastian; Ghafar-Zadeh, Ebrahim

doi:10.1109/tim.2021.3116294

Cited by 8 publications

(6 citation statements)

References 46 publications

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“…Consequently, the digital output will also follow a decreasing pattern with respect to the increasing C R . Using an array of CR values instead of a single CR makes it possible to measure the capacitance in a wider dynamic range with high accuracy and without the need for calibration, as described in [20]. In this circuit, the difference between the CS and all of the N values of CR in a bank of capacitors is measured for each pixel.…”

Section: Cmos Capacitive Sensor Arraymentioning

confidence: 99%

“…These properties include the time of evaporation (ToE), evaporation rate (ER) [8], dielectric constant [9][10][11] humidity characteristics [12] thermal diffusivity [13], refractive index [14], and adhesion [15]. The field of CMOS biosensors has seen a multitude of techniques proposed for droplet analysis such as a magnetic sensor [16], nuclear magnetic resonance (NMR) sensor [17], optical sensor [14,18], thermal sensor [13], and capacitive sensor [19][20][21]. For instance a CMOS thermal sensor has been proposed by Cheng et al [13] for the direct measurement of the diffusivity of liquid samples dropped onto the device.…”

Section: Introductionmentioning

confidence: 99%

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A Multidisciplinary Approach toward CMOS Capacitive Sensor Array for Droplet Analysis

Osouli Tabrizi,

Forouhi,

Azadmousavi

et al. 2024

Micromachines

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This paper introduces an innovative method for the analysis of alcohol–water droplets on a CMOS capacitive sensor, leveraging the controlled thermal behavior of the droplets. Using this sensing method, the capacitive sensor measures the total time of evaporation (ToE), which can be influenced by the droplet volume, temperature, and chemical composition. We explored this sensing method by introducing binary mixtures of water and ethanol or methanol across a range of concentrations (0–100%, with 10% increments). The experimental results indicate that while the capacitive sensor is effective in measuring both the total ToE and dielectric properties, a higher dynamic range and resolution are observed in the former. Additionally, an array of sensing electrodes successfully monitors the droplet–sensor surface interaction. However practical considerations such as the creation of parasitic capacitance due to mismatch, arise from the large sensing area in the proposed capacitive sensors and other similar devices. In this paper, we discuss this non-ideality and propose a solution. Also, this paper showcases the benefits of utilizing a CMOS capacitive sensing method for accurately measuring ToE.

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Section: Cmos Capacitive Sensor Arraymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Multidisciplinary Approach toward CMOS Capacitive Sensor Array for Droplet Analysis

Osouli Tabrizi,

Forouhi,

Azadmousavi

et al. 2024

Micromachines

Self Cite

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“…The dominant type-A noise charge is depleted in this step, output voltage in this step can achieve lower noise. The residual noise charge on parasitic capacitance is 𝑄 = 𝐾𝑇(𝐶 + 𝐶 + 𝐶 + 𝐶 + 𝐶 ) = 𝐾𝑇𝐶 _ (9) where the 𝑉 is the equivalent input noise of the amplifier and the 𝐵𝑊 is the bandwidth of the amplifier.…”

Section: Principlementioning

confidence: 99%

“…Compared to the closed-loop architecture, the openloop architecture does not need high voltage to drive the MEMS sensor, which consumes less power at the cost of linearity. In the open-loop architecture, the nonlinearity of the mechanical sensing element significantly increases with the increase of the capacitance variation of the sensing element [9,10]. Therefore, the capacitance variation needs to be limited to the femto-farad level to suppress the nonlinearity to an acceptable level [11,12].…”

Section: Introductionmentioning

confidence: 99%

Reset Noise Sampling Feedforward Technique (RNSF) for Low Noise MEMS Capacitive Accelerometer

2022

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The reset noise sampling feedforward (RNSF) technique is proposed in this paper to reduce the noise floor of the readout circuit for micro-electromechanically systems (MEMS) capacitive accelerometer. Because of the technology-imposed size restriction on the sensing element, the sensing capacitance and the capacitance variation are reduced to the femto-farad level. As a result, the reset noise from the parasitic capacitance, which is pico-farad level, becomes significant. In this work, the RNSF technique focuses on the suppression of the parasitic-capacitance-induced noise, thereby improving the noise performance of MEMS capacitive accelerometer. The simulation results show that the RNSF technique effectively suppresses the thermal noise from the parasitic capacitance. Compared with the traditional readout circuit, the noise floor of the readout circuit with the RNSF technique is reduced by 9 dBV. The presented circuit based on the RNSF technique is fabricated by a commercial 0.18-μm BCD process and tested with a femto-farad MEMS capacitive accelerometer. The physical measurement results show that, compared with the readout circuit without the RNSF technique, the RNSF technique reduces the noise floor of the readout circuit for MEMS capacitive accelerometer from −72 dBV to −80 dBV. Compared with other similar works, the proposed readout circuit achieves better FoM (FoM=(power×noise floor)/system bandwidth=490 μW·μg/Hz) among the switched-capacitor readout circuits.

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“…MEMS capacitive accelerometers play an important role in inertial measurement units [1][2][3], platform stabilization systems [4][5][6][7][8][9][10], structural health monitoring [11][12][13][14][15], and tilt sensing [16,17]. In these applications, the MEMS capacitive accelerometers are powered by batteries; thus, high power efficiency is required to extend the battery life.…”

Section: Introductionmentioning

confidence: 99%

High-Power-Efficiency Readout Circuit Employing Average Capacitance-to-Voltage Converter for Micro-Electro-Mechanical System Capacitive Accelerometers

Li,

Lai,

Wang

et al. 2023

Sensors

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A capacitance-to-voltage converter (CVC) is proposed in this paper and applied to a readout circuit for a micro-electro-mechanical system (MEMS) accelerometer to improve the power efficiency. In a traditional readout circuit, the front-end CVC has to operate at a high sampling frequency to resist thermal noise deterioration due to the large parasitic capacitance introduced by the mechanical sensing element. Thus, the back-end analog-to-digital converter (ADC) also has to operate at a high sampling frequency to avoid noise aliasing when sampling the output signal of the CVC, which leads to high power consumption. The average CVC technique is proposed in this paper to reduce the sampling frequency requirement of the back-end ADC and thus reduce the power consumption. Both the traditional readout circuit and the proposed readout circuit are simulated with a commercial 0.18 μm BCD process. The simulation results show that noise aliasing occurs, and the noise power spectral density (PSD) of the traditional readout circuit increases by 12 dB when the sampling frequency of back-end ADC is reduced by 24 dB. However, in the proposed readout circuit, a noise aliasing effect does not occur. Moreover, the proposed readout circuit reduces the power consumption by 53% without thermal noise deterioration. In addition, the proposed CVC circuits are fabricated in an 0.18 μm BCD process, and the test results show that the presented readout circuit based on the average CVC technique can obtain better performance than the traditional CVC-based readout circuit.

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Calibration-Free CMOS Capacitive Sensor for Life Science Applications

Cited by 8 publications

References 46 publications

A Multidisciplinary Approach toward CMOS Capacitive Sensor Array for Droplet Analysis

A Multidisciplinary Approach toward CMOS Capacitive Sensor Array for Droplet Analysis

Reset Noise Sampling Feedforward Technique (RNSF) for Low Noise MEMS Capacitive Accelerometer

High-Power-Efficiency Readout Circuit Employing Average Capacitance-to-Voltage Converter for Micro-Electro-Mechanical System Capacitive Accelerometers

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