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Plant microbial fuel cells represent an innovative type of microbial fuel cell technology, utilizing plant rhizodeposition to fuel electrochemically active bacteria on the anode surface, thereby generating bioelectricity. This study delves into some botanical aspects of plant species employed in PMFCs and Constructed Wetland PMFCs, aiming to investigate whether their bioelectrical performance is influenced by Raunkiær life forms and root architecture. Our study involved 40 plant species described in 38 documents. In some cases, nomenclature issues prevented the interpretation of actual species used in the experiments. The bioelectrical performance of PMFCs appeared to be significantly affected by both life forms and root architecture. Therophytes and Hemicriptophytes exhibited higher median values than the other life forms, while the Geophyte group showed very high power density values despite a lower median value. In contrast, CW-PMFCs do not appeared to be significantly affected by the botanical traits considered, likely due to the limited data collected on this experimental configuration. The plant species that performed the best in PMFCs include Carex hirta, Alisma plantago-aquatica, Glyceria maxima and Canna indica, all of which have an adventitious root system. C. hirta, G. maxima and C. indica are geophytes, while A. plantago-aquatica is a hydrophyte. Consequently, epiphytes, chamaephytes and nanophanerophytes, as well as plants with fibrous root systems, appeared to be not recommended for PMFCs. Nevertheless, the results of our study may have certain limitation due to nomenclature issues that prevented the accurate identification of species used in the PMFCs, the absence of a standardized benchmark for electrical measurement, and the lack of clear match between each species and its bioelectrical performance, reducing the data pool.

This paper presents a generalized control architecture for implementing the active balancing of the flying capacitor voltage in any kind of 3-level switching-mode DC-DC converters, independently from the desired conversion ratio or targeted output power level. The proposed strategy is based on the detection of the flying capacitor voltage through the inductor voltage, sensed at the switching node, and acts on the duty cycle of the PWM (Pulse Width Modulation) control signals in order to make the correction, implementing the voltage balancing. The circuit implementation and its operation are described in detail. Extensive simulations were performed in the SIMPLIS environment, taking as examples the cases of a 3-level buck, 3-level boost and 3-level inverting buck-boost DC-DC converter and considering different combinations of input voltage, output voltage and load current. Moreover, the proposed strategy was implemented in the control architecture of a hybrid switched-capacitor 3-level inverting buck-boost converter, fabricated in a 180-nm BCD process. The effectiveness and the versatility of the proposed active voltage balancing strategy and its circuit implementation were, therefore, verified both through simulations and experimentally.

This paper presents additional circuits and characterization methodologies of novel CAN (Controller Area Networks) receivers that implement new features, aiming at improving CAN signal integrity and data-rate. The first receiver shown includes a circuit for ringing removal. The use of a Notch filter is meant to remove the ringing. The pulse-width symmetry is improved to a range just lower than −20 ns and +15 ns. As a result, during arbitration, the transmission data-rate can be increased up to 8 Mbit/s, a higher limit must be evaluated on a network system level. The second receiver shown is conceived for multi-bit communication. The possibility of parallelizing data transmission leads to an efficient use of the bandwidth available. A table compares the achieved results with the specifications of the latest available protocols. The chips of both receivers were designed and fabricated with a 0.18- $\mu $ m BCD technology. After a block level description of the receivers, a Direct Power Injection (DPI) methodology is described. It is used to evaluate the receiver’s immunity to conducted continuous-wave interference. Considerations regarding future technological directions for new applications are provided at the end of the paper.

Piezoelectric Micromachined Ultrasonic Transducers (PMUT) and Capacitive Micromachined Ultrasonic Transducers (CMUT) have seen great developments in recent years, both in terms of performance and scope of applications within the biomedical ultrasound domain. This paper presents a review of the state-of-the-art of PMUT and CMUT technologies, focusing on their principle of operation, microfabrication techniques and use in different biomedical imaging and therapeutic applications. The advantages and drawbacks of PMUT and CMUT technologies in comparison with conventional bulk transducers are highlighted, the trade-offs among PMUTs and CMUTs are discussed, and their relevance in the current landscape of medical diagnostics and therapeutic uses is outlined, thus providing a clear overview of these promising technologies for the present and the next generation biomedical ultrasound applications.

Converting otherwise wasted kinetic energy present in the environment into usable electrical energy to power wireless sensor nodes, is a green strategy to avoid the use of batteries and wires. Most of the energy harvesters presented in the literature are based on the exploitation of a one-degree-of-freedom arrangement, consisting of a tuned spring-mass system oscillating in the main direction of the exciting vibration source. However, if the direction of excitation changes, the efficiency of the harvester decreases. This paper thus proposes the idea of a curved cantilever beam with a two-degree-of-freedom arrangement, where the two bending natural frequencies of the mechanical resonator are designed to be equal. This is thought to lead to a configuration design that can be used in practical circumstances where excitation varies its direction in the plane. This, in turn, may possibly lead to a more effective energy-harvesting solution to power nodes in a wireless sensor network.

In recent years, wireless power transfer (WPT) has become a widespread method for charging and powering devices, including but not limited to consumer electronics, industrial applications, electric vehicles, medical devices, and sensor nodes. This article provides an overview of the available WPT technologies, focusing on the near-field case, and highlights the main architecture and circuit-level challenges encountered in the implementation of magnetic-based near-field WPT systems while reviewing the proposed solutions in the literature, in order to identify the main research interests as well as the trends for the future.

This paper presents a temperature sensor system providing the reference temperature of TMOS-based thermal detectors, in order to enable contactless absolute temperature measurements. The proposed system directly employs a few pixels of the TMOS detector as sensing element, thus detecting the local TMOS temperature, while the readout circuit is integrated on a separate chip. The readout circuit features a two-phase time-domain architecture, which provides biasing to the sensing element by alternatively switching between two different bias current values in subsequent phases. The temperature reading is converted to the digital domain thanks to a switched-capacitor 1-bit second-order sigma-delta ( $\Sigma \Delta $ ) analog-to-digital converter (ADC). The proposed readout system was fabricated in a 130-nm CMOS process and extensively characterized through measurements, together with the TMOS detector, realized in a 130-nm CMOS SOI technology and bonded on the same package. The proposed reference temperature sensor system, burning 10.8- $\mu \text{W}$ power, features 97-mK resolution when considering a 4096-ms conversion time and $0.13^{\circ} \text{C}$ peak-to-peak inaccuracy after three point calibration in the 15– $40^{\circ} \text{C}$ range, thus satisfying the characteristics for contactless human body temperature measurements.

The input capacitance of the SAR ADC is considered a drawback in many applications. In this paper, a 12-bit low-power SAR ADC with low-input capacitance is proposed. The ADC is based on a separated DAC and sample-and-hold blocks (SB) structure. The SB structure suffers from variation in the input common-mode voltage of the comparator, leading to nonlinear input-referred offset and kickback noise. Here, a closed-loop low-power rail-to-rail offset cancellation technique for the comparator, based on body voltage tuning, is proposed. In order to stabilize the closed loop structure, the open loop gain is controlled by adapting the gain of the preamplifier. Using this structure, the rail-to-rail offset is kept lower than 110 $\mu \text{V}$ and the overall power of the comparator is 1 pJ/Conv. Complementary-clocked dynamic branches are exploited at the input of the comparator to decrease the common-mode dependent kickback noise error to less than 1 LSB. The bootstrapped switch’s controlling signal is also modified to achieve less than 1 LSB error and 18.9% lower power consumption. The proposed ADC is designed in standard 180 nm CMOS technology with a 1.8 V supply voltage and the input capacitance is reduced to 2 pF, which leads to power consumption of 41 nW in the input voltage supply. Electrical simulations including PVT, Monte-Carlo, and post-layout parasitic extraction were conducted to ensure the effectiveness of the approach. The ADC features an ENOB of 11.1-bit and a sampling rate of 1 MHz with a power consumption of $117.9~\mu \text{W}$ including the input power supply which are competitive with the state-of-the-art, and demonstrate the virtue of the proposed approach.

In recent years, Micro-Electro-Mechanical Systems (MEMS) technology has had an impressive impact in the field of acoustic transducers, allowing the development of smart, low-cost, and compact audio systems that are employed in a wide variety of highly topical applications (consumer devices, medical equipment, automotive systems, and many more). This review, besides analyzing the main integrated sound transduction principles typically exploited, surveys the current State-of-the-Art scenario, presenting the recent performance advances and trends of MEMS microphones and speakers. In addition, the interface Integrated Circuits (ICs) needed to properly read the sensed signals or, on the other hand, to drive the actuation structures are addressed with the aim of offering a complete overview of the currently adopted solutions.

InfraRed Focal Plane Arrays (IRFPAs) are crucial components in a wide range of applications, including night vision, thermal imaging and gas sensing. Among the various types of IRFPAs, micro-bolometer-based ones have gained significant attention due to their high sensitivity, low noise and low cost. However, their performance is heavily dependent on the readout interface, which converts the analog electrical signals provided by the micro-bolometers into digital signals for further processing and analysis. This paper briefly introduces these kinds of devices and their function, reporting and discussing a list of key parameters used to evaluate their performance; after that, the focus is shifted to the readout interface architecture with particular attention to the different strategies adopted, across the last two decades, in the design and development of the main blocks included in the readout chain.

This paper presents an extensive review of the main highlights in the Temperature-to-Digital Converters (TDCs) field, which has gained importance and research interest throughout the last two decades. The key techniques and approaches that have led to the evolution of this kind of systems are presented and compared; their peculiarities are identified in order to highlight the pros and cons of the different design methods, and the main trade-offs are extracted from this analysis. Finally, the trends that have emerged from the performance evaluation of the large amount of published works in this field are identified with the purpose of providing a directional view of the past, present and future features of these devices.

This paper presents a detailed analysis of a micromachined thermopile detector featuring high responsivity and a versatile mosaic structure, based on 128 60 µm × 60 µm pixels connected in series and/or in parallel. The mosaic structure is based on the one employed for the thermal sensor known as TMOS, which consists of a CMOS-SOI transistor embedded in a suspended and thermally isolated absorbing membrane, released through microelectro mechanical system (MEMS) post-processing. Two versions of the thermopile detector, featuring different series/parallel connections, are presented and were experimentally characterized. The most performant of the two achieved 2.7 × 104 V/W responsivity. The thermopile sensors’ performances are compared to that of the TMOS sensor, adopting different configurations, and their application as proximity detectors was verified through measurements.

The worldwide spread of COVID-19 has forced us to adapt to a new way of life made of social distancing, avoidance of physical contact and temperature checks before entering public places, in order to successfully limit the virus circulation. The role of technology has been fundamental in order to support the required changes to our lives: thermal sensors, in particular, are especially suited to address the needs arisen during the pandemic. They are, in fact, very versatile devices which allow performing contactless human body temperature measurements, presence detection and people counting, and automation of appliances and systems, thus avoiding the need to touch them. This paper reviews the theory behind thermal detectors, considering the different types of sensors proposed during the last ten years, while focusing on their possible employment for COVID-19 related applications.

This paper presents a sensor-readout circuit system suitable for presence detection. The sensor consists of a miniaturized polysilicon thermopile, realized employing MEMS micromachining by STMicroelectronics, featuring a responsivity value equal to 180 V/W, with 13 ms response time. The readout circuit is implemented in a standard 130-nm CMOS process. As the sensor output signal behaves substantially as a DC, the interface circuit employs the chopper technique in order to minimize offset and noise contributions at low frequency, achieving a measured input referred offset standard deviation equal to 1.36 μ V. Measurements show that the presented system allows successfully detecting the presence of a person in a room standing at 5.5 m from the sensor. Furthermore, the correct operation of the system with moving targets, considering people either walking or running, was also demonstrated.

Over the last decade, MEMS microphones have become the leading solution for implementing the audio module in most portable devices. One of the main drivers for the success of the MEMS microphone has been the continuous improvement of the corresponding integrated interface circuit performance in terms of both dynamic range and power consumption, which enabled the introduction in mobile devices of additional functionalities, such as Hi-Fi audio recording or voice commands. As a result, MEMS microphone interface circuits evolved from just simple amplification stages to complex mixed-signal circuits, including A/D converters, with ever improving performance. This paper provides an overview of such evolution based on actual design examples, focusing, finally, on the latest cutting-edge solutions.