Achieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr_0.5Pr_0.5Fe_0.4Ti_0.6O_3-δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr_0.5Pr_0.5Fe_0.4-xMg_xTi_0.6O_3-δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr_0.5Pr_0.5Fe_0.2Mg_0.2Ti_0.6O_3-δ (SPFMg_0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm^-1 along with an attractive fuel cell performance of 0.83 W cm^-2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg_0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO_3-δ and Sr_0.5Pr_0.5Fe_0.4-xMg_xTi_0.6O_3-δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg_0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr_0.5Pr_0.5Fe_0.4Ti_0.6O_3-δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.

In this paper, by using 0.35 μm 2P4M CMOS MEMS technology, a Thermoresistive Micro Calorimetric Flow (TMCF) sensor with two packaging designs were systematically investigated: Open-space (O-Type) and Probe-with-channel (P-Type) designs. In comparison with the O-Type design, the P-Type sensor showed an 80% enhanced sensitivity with a relieved tilt angle effect on the mainstream airflow detection. Accordingly, the P-Type packaged flow sensor for HVAC gained a prominent normalized sensitivity (S*) of 228 μV/(m/s)/mW, while also having a low power consumption (P) of less than 4.2 mW. Moreover, within the linear range of -2 to 2 m/s, an accuracy of ±0.05 m/s was achieved, thus enabling this robust flow sensor (repeatability < 0.2%) for indoor airflow measurements even in a variable ambient environment. Furthermore, the proposed P-Type TMCF sensor and its wireless multi-sensor module were applied for the development of personalized ventilation (PV) and the monitoring of predicted mean vote (PMV), both of which confirm the functionality of the developed sensor for indoor airflow measurements in the HVAC system.

This article presents a bidirectional thermoresistive micro calorimetric flow (TMCF) sensor implemented by a 0.18- μ m complementary metal–oxide–semiconductor microelectromechanical systems (CMOS-MEMS) technology, while the sensor thickness is thinned to 2.7 μm through an in-house developed MEMS fabrication process. For the bidirectional airflow of −6 to 6 m/s, the TMCF sensor achieves the highest sensitivity of 453 mV/(m/s), and its highest normalized sensitivity with respect to the signal amplification gain (gain = 250) and the input heating power (1.58–1.72 mW) is 1150 mV/(m/s)/W. By reducing the heating power to the sub-mW of <220 μW, the TMCF sensor can still give a remarkable sensitivity of 87.4 mV/(m/s). In addition, the developed TMCF sensor has an intrinsic minimum detectable flow velocity of 99 μm/s and a response time of 4.8 ms. The performance achieved by this flow sensor enables accurate indoor airflow measurements even when dealing with the extremely low-speed flow (<0.05 m/s). Furthermore, the high-performance TMCF sensor is applied for remote human motion detection, where different walking speeds and moving patterns of the occupants can be captured. Therefore, this developed CMOS-MEMS sensor will not only be a promising flow sensing node in the HVAC system, but also potentially be used for the nonvisible and private occupant counting in buildings/rooms.

In this paper, we propose a new 1D thermoresistive micro calorimetric flow (TMCF) sensor model for moist airflow with the temperature-dependent thermophysical properties. The 1D model and the corresponding proposed equivalent circuit model enable rapid design optimization of an ambient temperature-compensated TMCF (T²MCF) sensor integrated with the interface circuit by using a commercial 0.35-μm 2P4M CMOS MEMS technology. The fabricated sensor shows a prominent sensitivity of 0.543 V/(m/s) and a low power consumption of less than 2.8 mW. Moreover, in comparison with the large drifting of 49% for the uncompensated TMCF sensor, the T²MCF sensor's output has an ultralow drifting of 0.5% with the ambient temperature variation of 22°C~48°C. Therefore, this robust T²MCF sensor can be a promising Internet of Things (IoT) for smart energy-efficient buildings. [2018-0241]

This article presents a complementary metal-oxide semiconductor (CMOS)-microelectromechanical system (MEMS) monolithic integrated thermal flow sensor system, which consists of a MEMS sensor with dual pairs of thermistors, a precise constant temperature difference (CTD) control circuit, and a low-noise readout circuit with a current feedback instrument amplifier (CFIA). The MEMS sensor is fabricated using an in-house developed post-CMOS process, while its sensing structure is thinned to 2.52 $\mu \text{m}$ for power reduction. Meanwhile, the distance between the microheater and thermistors is optimized with a linear range of larger than ±4 m/s by the Peclet number (Pe) < 1 criterion. The designed CTD control circuit can offer a driving current of 1.88 mA with an output swing of up to 2.82 V, which enables the microheater to operate in 50-K CTD mode with a deviation of less than 0.01 K. Additionally, the designed CFIA has a noise floor of 12.4 nV/rtHz with a 1/f corner of less than 400 mHz. The performance of the system-on-chip (SoC) sensor is evaluated with N2 gas flow. The SoC sensor has a high sensitivity of 156 mV/(m/s) with a detectable flow range of up to ±11 m/s, while its system power is less than 5 mW. The SoC sensor also has state-of-the-art linearity in a range of ±6 m/s and a detection limit down to 86 $\mu \text{m}$ /s. Moreover, the tested results of this SoC sensor are in good agreement with the theoretical models, confirming the feasibility of the proposed design strategy.