This letter presents a three-dimensional (3D) integrated Molybdenum (Mo) Thermoresistive Micro Calorimetric Flow (TMCF) sensor in a 0.18 μm CMOS MEMS technology. The sensor consists of a MEMS structure which is fabricated inside a sealed micro channel and a constant temperature (CT) control circuit implemented on the CMOS wafer. The MEMS structure and CMOS circuit are 3D integrated at the wafer level. For the N2 gas flow, the proposed flow sensor achieves a high sensitivity of 0.71 mV/(m/s) and a wide bidirectional detection ability of -26 ~ 26 m/s. Moreover, an Equivalent Circuit Model (ECM) is proposed in this letter, which depicts the nonlinear output/overheated temperature (Vout/μTh) sensor response to the input gas flow. This model would be an efficient tool for the design and optimization of high-performance System on Chip (SoC) calorimetric flow sensors.

In this paper, we presented a wafer-level encapsulated Thermoresistive Micro Calorimetric Flow (TMCF) sensor with the integrated packaging by using the proprietary InvenSense CMOS MEMS technology. For the nitrogen gas flow from -26m/s to 26m/s, the pulsed operated TMCF sensor (device size = 3.4mm²) under the Constant Temperature Difference (CTD) mode achieved a normalized sensitivity of 112.4μV/(m/s)/mW with respect to the input heating power. Besides, the measured TMCF sensor response time (τ_max<;3.63ms) shows good agreement with a theoretical model. With the pulsed operation, the proposed low-power TMCF sensor will be a promising digital CMOS MEMS flow sensor for the Internet of Things (IoT), especially for smart building/home.

We present an integrated complimentary metal-oxide-semiconductor (CMOS) MEMS flow sensor, which demonstrates a very compact system on chip (SoC) that can sense N ₂ gas flow ranging from 0 to 26 m/s (0-50 sccm). Implemented in the proprietary InvenSense AlN process, our SoC features a very low-power current feedback instrumentation amplifier (CFIA) as a front-end readout circuit for a micro-calorimetric flow sensor configured in a Wheatstone bridge. To maintain a constant temperature difference of 56 K, an on-chip heater with off-chip op-amp feedback circuit is also implemented. The on-chip CFIA is chopped at 50 kHz to reduce its offset and flicker-noise and consumes 250 μA current. The measured sensitivity of our CMOS MEMS flow sensor is 35 mV/sccm.

Both bacterial viability and concentration are significant metrics for bacterial detection. Existing miniaturized and cost-effective single-mode sensor, pH or optical, can only be skilled at detecting single information viability or concentration. This paper presents an inverter-based CMOS ion-sensitive-field-effect-transistor (ISFET) sensor array, featuring bacterial pH detection which is an indicator of viability. The proposed design realizes pH detection using the native passivation layer of CMOS process as a sensing layer and configuring an inverter-based front-end as a capacitive feedback amplifier. This sensor array is assisted by temperature sensing and optical detection which reveals bacterial concentration. The optical detection is enabled using the leakage current of a reset switch as a response to a light source. While in reset mode, the inverter-based amplifier works as a temperature sensor that could help to reduce temperature influences on pH and optical detection. All the functionalities are realized using one single inverter-based amplifier, resulting in a compact pixel structure and largely relaxed design complexity for the sensor system. Fabricated in 0.18 $\mu$ m standard CMOS process, the proposed CMOS sensor array system achieves an amplified pH sensitivity of 221 mV/pH, an improved sensor resolution of 0.03 pH through systematic noise optimization, a linear optical response, and a maximum temperature error of 0.69 $^{\circ }$ C. The sensing capabilities of the proposed design are demonstrated through on-chip Escherichia coli (E. coli) detection. This study may be extended to a rapid and cost-effective platform that renders multiple information of bacterial samples.

In this paper, we present a CMOS hybrid magnetic field sensor for real-time motor speed monitoring for smart energy-efficient autonomous systems. The sensor system consists of a micro Hall effect sensor (μHES) and a micro search coil magnetometer (μSCM) using TSMC 0.18μm 1P6M CMOS process with a die size of 1.5×2mm ² . The hybrid sensor is realized completely by the CMOS process without post-processing. A wide range of rotation speed can be measured by the presented passive μSCM without signal amplification (> 600 rpm) and the combination of the μSCM and μHES on the same chip allows the low rotation speed range measurement (<600 rpm). Furthermore, the μSCM has zero offset and very low-temperature dependency. The magnetic field of a permanent magnet on the rotating shaft of the motor is measured by the μSCM and the μHES to determine the rotation speed. The sensitivity of the μHES (at 5V bias voltage) and the μSCM inside a uniform magnetic field are 113.6 μV/mT and 11.3 μV/mT at 1 Hz without amplification, respectively. The noise equivalent magnetic induction of the μSCM was calculated and verified experimentally by utilizing a zero-drift instrumentation amplifier. Furthermore, a simplified equivalent circuit model for the μSCM is presented and verified experimentally. According to the equivalent circuit model, the linear frequency response region of the μSCM is up to 20 kHz, which suits the controlling motors in smart autonomous systems and other low-frequency applications.

This paper presents a CMOS ion-sensitive-field-effect-transistor (ISFET) array with superior offset distribution tolerance, resolution and linearity for long-term bacterial metabolism monitoring. A floating gate ISFET is adopted as the sensing front end to maximize ion sensitivity and support ultra-long-term measurement. To solve the DC offset issue induced by trapped chargers and drifts in each ISFET sensor, a complementary readout scheme with column offset compensation is proposed. P-type and N-type source followers are combined to cover a wide range of input DC offsets while maintaining small area and high linearity. The DC offset is digitally compensated during signal readout to facilitate global amplification and quantization. Fabricated in 0.18 μm standard CMOS process, the ISFET array can tolerate an offset distribution beyond power supply with a linear pH-to-output response. Due to high ion sensitivity and low circuit noise, the whole system achieves a high resolution of 0.017 pH. The proposed ISFET system has successfully demonstrated an accurate pH monitoring of normal Escherichis coli growth for 11 hours and its response to antibiotics, showing long-term bacterial metabolism monitoring capability.