Search

In this letter, we report the temperature effect and noise characterization of the Parylene-based capacitive humidity sensor which can be used for integrated CMOS compatible thermal comfort sensing. The sensor is comprised of a pair of interdigitated Pt electrodes deposited on a silicon substrate and a parylene hygroscopic layer coated on the electrodes using room temperature chemical vapor deposition process. The sensor was characterized at different relative humidity (RH) values and working temperatures in a testing setup. The capacitance of the sensor increases with the RH due to the absorption of water molecules on the surface of the sensing film. The capacitance of the sensor also increases with temperature, which is due to the stronger thermal movement of the molecules that helps increase the polarization at increased temperature levels. Besides, a readout circuit was done on a printed circuit board using capacitance to voltage converter for the sensor. The sensor achieved a maximum sensitivity of 76.2 mV/%RH and response and recovery times of about 31.5 and 29.2 s, respectively. Besides, the sensor shows a noise level of 1.399 mV rms within 25 Hz bandwidth in the output voltage response. The experimental results also indicated a resolution of about 0.072–2% within the ASHRAE standard approved RH range (25–95%) for the fabricated sensor.

A two-dimensional (2D) model was developed, for the first time, to describe the characteristics of the micromachined thermal expansion-based angular motion (TEAM) sensor, which has been validated by the experimental results. Scaling analysis on the performance characteristics through the 2D model was conducted to optimize the TEAM sensor’s design in terms of the normalized distances between the microheaters and temperature detectors in $x$ and $y$ directions, the thickness of the thin film, the heater width, the cavity depth, and the heater temperature. Furthermore, the proposed 2D model was normalized by two dimensionless numbers, namely Rayleigh number Ra and Peclet number Pe, with a critical Rayleigh number (Ra $^{\ast }_{\mathrm {c}} =18$ ,000) identified to differentiate linear and nonlinear operation regimes of the TEAM sensor. In particular, our 2D model is much faster than the conventional CFD model by three orders of magnitude (18.91s versus 5.5h), enabling rapid system-level optimization of the critical design parameters. Accordingly, the TEAM sensors with three pairs of platinum thermoresistive temperature sensors were designed and fabricated. The fabricated device demonstrated a normalized sensitivity of $11.8~\mu \text{V}$ /°/s/mW based on the working fluid of air, which was more than three times better than previous thermal angular motion sensors. Thus, with the experimental validation, the proposed 2D model should be a reliable tool to realize the systematical design optimization of TEAM sensors integrated with on-chip microelectronics for future industrial IoT applications. [2020-0355]

We present a one-dimensional (1D) theoretical model for the design analysis of a micro thermal convective accelerometer (MTCA). Systematical design analysis was conducted on the sensor performance covering the sensor output, sensitivity, and power consumption. The sensor output was further normalized as a function of normalized input acceleration in terms of Rayleigh number R $_{\mathrm {a}}$ (the product of Grashof number G $_{\mathrm {r}}$ and Prandtl number P $_{\mathrm {r}}$ ) for different fluids. A critical Rayleigh number ( R ac = 3,000) is founded, for the first time, to determine the boundary between the linear and nonlinear response regime of MTCA. Based on the proposed 1D model, key parameters, including the location of the detectors, sensor length, thin film thickness, cavity height, heater temperature, and fluid types, were optimized to improve sensor performance. Accordingly, a CMOS compatible MTCA was designed and fabricated based on the theoretical analysis, which showed a high sensitivity of 1,289 mV/g. Therefore, this efficient 1D model, one million times faster than CFD simulation, can be a promising tool for the system-level CMOS MEMS design.

In this paper, we present a novel structural design of thermal expansion-based angular motion (TEAM) sensors based on a systematic comparative study to improve the sensitivity. Compared with the traditional TEAM sensor design with the Heaters oriented Pe rpendicular to the temperature detectors (abbreviated to PeH), the novel structural design employs the Heaters Parallel to the detectors (PaH). The dominant superiority of the novel design is the sensitivity enhancement without increasing the chip area and power consumption, which can be attributed to the higher thermal working efficiency of heaters based on the analysis of the proposed 2D model. Experimental tests under the angular rate range of 0 ~ 2520q/s show that the sensitivity of a TEAM sensor can be enhanced by more than 65% to 0.4856 mV/°/s by adopting the novel PaH design instead of the traditional PeH design. Therefore, the proposed PaH TEAM sensor will be a promising device for future industrial IoT applications.

For the first time, we designed and fabricated a Coriolis-force compensated micro thermal convective accelerometer (CMTCA), which could reduce the Cross-axis sensitivity of a double-aixs MTCA within 2% from 15%. In this design, a couple of compensation detectors are implemented for each of the master detectors. The master detectors are used for acceleration input detecting. By means of this novel structure, the angular input signal could be monitored, which could be used to compensate the cross-axis signal by means of the signal processing circuit simultaneously. This novel design is quite meaningful for improving the accuracy of MTCA and decoupling the signal between acceleration and gyroscope.

For the first time, we conduct theoretical and experimental analysis on the z-axis (out-of-plane direction) acceleration detection of the micro thermal convective accelerometer (MTCA). Instead of using the complex assembling method to make an out-of-plane detection structure, an indirect way to measure the z-axis acceleration is proposed. The mechanism is proposed with the evidence that the sum of the upstream and downstream detectors’ temperature keeps the same under in-plane acceleration, while their differential output keeps constant with the out-of-plane (z-axis) acceleration. By means of monitoring the variation of temperature of in-plane detectors under out-of-plane acceleration, the z-axis acceleration could be indirectly sensed. Theoretically, the coupling error on z-axis induced by x-axis is quite small (less than 1%). Through this method, it could be easy to convert a single-axis (X) MTCA to a two-axis (X-Z) MTCA, which is also promising to improve the two-axis (X-Y) MTCA to a tri-axis (X-Y-Z) accelerometer. In addition, an MTCA is fabricated based on a CMOS compatible fabrication method and demonstrate the proposed detection mechanism with high sensitivity for both x-axis (1211μV/g) and z-axis (402μV/g).

We report, for the first time, a novel two-dimensional (2D) model for the micro thermal expansion-based gyroscope (µTEG) to predict the sensor’s performance, which has been validated by the experimental results. Scaling analysis on the sensor’s performance characteristics by this model enables the optimization of µTEG design, including the normalized distances between the heater and temperature detectors in two directions, the thin film thickness, the heater width, the cavity depth and the heater temperature, to achieve extremely high sensitivity (11.78 mV/°/s) and low power consumption (12.8mW). According to the analysis by 2D model, the sensitivity of the optimized µTEGs by using the working gases (SF6 and C4F8) with larger density, better than the best published µTEG (1.287 mV/°/s) by one order of magnitude, can reach the level of the commercial product (>6 mV/°/s). In particular, our new 2D model can significantly save the CPU time in comparison with the conventional CFD model (1.92s versus 5h) to realize the efficient systematical optimization of the key design parameters. Thus, the proposed 2D model can be a useful tool for µTEGs’ system-level designs for industrial IoT applications.

Circulating tumor cell (CTC) isolation has made positive impacts on metastatic detection and therapy analysis for cancer patients. Microfluidic-elasto-filtration (MEF) device based on the critical elasto-capillary number (Ca * ) has been proposed to utilize the optimal multi-parameter conditions, including cell diameter (dc), the diameter of cylindrical filter pores (dp), nonlinear cell elasticity and hydrodynamic drag force, for selectively capturing CTCs and depleting white blood cells (WBCs). In this paper, we propose a novel two-degree-of-freedom nonlinear mass–damper–spring (m–c–k) model to predict the dynamic behaviors of CTCs and WBCs in a generic MEF device. This model enables the optimization of the device design to achieve extremely high CTC capture efficiency and WBC depletion efficiency. In particular, the function of nonlinear cell stiffness specific to different cell types and MEF’s pore diameters is first determined by finite element method with neo-Hookean hyperelastic model, based on which the mechanical behaviors of CTCs and WBCs in MEF devices are systematically studied. Herein, the predicted normalized deformations of a CTC and WBC as a function of Cae are used to determine the optimized Cae of 0.043, consistent with the experimental results from the fabricated MEF devices using MCF-7 cells (0.04 ± 0.006). In addition, the normalized cell diameter versus Cae phase diagram is proposed for the first time as a useful tool for design optimization of MEF devices and other microfiltration devices.

Early cancer diagnosis, critical to the increase survival rate of cancer patients, is still challenging although to date more than 745,000 relevant published research articles (Google Scholar database) and more than 346,000 articles (PubMed database). In recent years, the detection of Circulating Tumor Cells (CTCs) from patients’ blood samples using microfluidics is a popular non-invasive method for diagnosis and therapy monitoring of cancer. However, the translation from the research of microfluidic CTC devices to a practical CTC detection system in clinics is still challenging because of the significant variation of biological properties among different patients. From the viewpoint of nonlinear dynamic system engineering, we propose a novel methodology: new nonlinear Microfluidic Elasto-Filtration (MEF) model for patients using hyperelasticity for prediction of large deformation of CTC and biophysical measurements of blood samples from each patient for the estimation of equivalent energy dissipation parameter. In this approach, we demonstrate the patient-specific Microfluidic Elasto-Filtration (psMEF) CTC technology can overcome the barrier of translation research. The pre-clinical study of psMEF CTC technology has shown the excellent clinical sensitivity and clinical specificity according to US FDA regulation. Increasing number of clinical data can enable the continuous improvement of psMEF methodology for early cancer diagnosis.