Heavy metal pollution remains a major concern for the public today, in line with the growing population and global industrialization. Heavy metal ion (HMI) is a threat to human and environmental safety, even at low concentrations, thus rapid and continuous HMI monitoring is essential. Among the sensors available for HMI detection, the field-effect transistor (FET) sensor demonstrates promising potential for fast and real-time detection. The aim of this review is to provide a condensed overview of the contribution of certain semiconductor substrates in the development of chemical and biosensor FETs for HMI detection in the past decade. A brief introduction of the FET sensor along with its construction and configuration is presented in the first part of this review. Subsequently, the FET sensor deployment issue and FET intrinsic limitation screening effect are also discussed, and the solutions to overcome these shortcomings are summarized. Later, we summarize the strategies for HMIs’ electrical detection, mechanisms, and sensing performance on nanomaterial semiconductor FET transducers, including silicon, carbon nanotubes, graphene, AlGaN/GaN, transition metal dichalcogenides (TMD), black phosphorus, organic and inorganic semiconductor. Finally, concerns and suggestions regarding detection in the real samples using FET sensors are highlighted in the conclusion.

Recently, there has been increasing interest in electrochemical printed sensors for a wide range of applications such as biomedical, pharmaceutical, food safety, and environmental fields. A major challenge is to obtain selective, sensitive, and reliable sensing platforms that can meet the stringent performance requirements of these application areas. Two-dimensional (2D) nanomaterials advances have accelerated the performance of electrochemical sensors towards more practical approaches. This review discusses the recent development of electrochemical printed sensors, with emphasis on the integration of non-carbon 2D materials as sensing platforms. A brief introduction to printed electrochemical sensors and electrochemical technique analysis are presented in the first section of this review. Subsequently, sensor surface functionalization and modification techniques including drop-casting, electrodeposition, and printing of functional ink are discussed. In the next section, we review recent insights into novel fabrication methodologies, electrochemical techniques, and sensors’ performances of the most used transition metal dichalcogenides materials (such as MoS₂, MoSe₂, and WS₂), MXenes, and hexagonal boron-nitride (hBN). Finally, the challenges that are faced by electrochemical printed sensors are highlighted in the conclusion. This review is not only useful to provide insights for researchers that are currently working in the related area, but also instructive to the ones new to this field.

In this present work, we aim to improve the hydrophobicity of a polydimethylsiloxane (PDMS) surface. Various heights of 3D PDMS micropillars were fabricated via grayscale photolithography, and improved wettability was investigated. Two approaches of PDMS replication were demonstrated, both using a single master mold to obtain the micropillar arrays. The different heights of fabricated PDMS micropillars were characterized by scanning electron microscopy (SEM) and a surface profiler. The surface hydrophobicity was characterized by measuring the water contact angles. The fabrication of PDMS micropillar arrays was shown to be effective in modifying the contact angles of pure water droplets with the highest 157.3-degree water contact angle achieved by implementing a single mask grayscale lithography technique.

Background: Brain cooling therapy is one of the subjects of interest, and currently, data on direct brain cooling are lacking. Hence, the objective is to investigate the clinical outcomes and discuss the thermodynamics aspect of direct brain cooling on severely injured brain patients. Methods: This pilot study recruited the severely injured brain patients who were then randomized to either a direct brain cooling therapy group using a constant cooling temperature system or a control group. All studied patients must be subjected to an emergency neurosurgical procedure of decompressive craniectomy and were monitored with intracranial pressure, brain oxygenation, and temperature. Further, comparison was made with our historical group of patients who had direct brain cooling therapy through the old technique. Results: The results disclosed the direct brain cooling treated patients through a newer technique obtained a better Extended Glasgow Outcome Score than a control group (P < 001). In addition, there is a significant outcome difference between the combined cooling treated patients (new and old technique) with the control group (P < 0.001). Focal brain oxygenation and temperature are likely factors that correlate with better outcomes. Conclusion: Direct brain cooling is feasible, safe, and affects the clinical outcomes of the severely traumatized brain, and physics of thermodynamics may play a role in its pathophysiology.

This paper reports on the novel implementation of a tunable solenoid inductor using the fluid-based inductance varying technique. The concept utilized material permeability variation that directly modifies self-induced magnetic flow density inside the coil, which in turn creates a variation of the inductance value. The core is formed by a channel which allows the circulation of a liquid through it. The liquid proposed for this technique has ferromagnetic behavior, called ferrofluid, with a magnetic permeability higher than unity. To evaluate the proposed technique, two different types of solenoid inductor were designed, simulated and measured. The two structures are wire-wound and wire bond solenoid inductors. The structures are simulated in a 3D EM analysis tool followed by fabrication, test and measurement. The wire-bonded-based inductor showed a quality factor of 12.7 at 310 MHz, with 81% tuning ratio, by using ferrofluid EMG 901. The wire-wound-based inductor showed that the maximum tuning ratio is 90.6% with quality factor 31.3 at 300 MHz for ferro fluidic EMG 901. The maximum measured tuning ranges were equal to 83.5% and 56.2% for the wire-wound type and the wire-bonded one, respectively. The measurement results for the proposed technique showed a very high tuning range, as well as high quality factor and continuous tunability.

In acoustic receiver design, the receiving sensitivity and bandwidth are two primary parameters that determine the performance of a device. The trade-off between sensitivity and bandwidth makes the design very challenging, meaning it needs to be fine-tuned to suit specific applications. The ability to design a PMUT with high receiving sensitivity and a wide bandwidth is crucial to allow a wide spectrum of transmitted frequencies to be efficiently received. This paper presents a novel structure involving a double flexural membrane with a fluidic backing layer based on an in-plane polarization mode to optimize both the receiving sensitivity and frequency bandwidth for medium-range underwater acoustic applications. In this structure, the membrane material and electrode configuration are optimized to produce good receiving sensitivity. Simultaneously, a fluidic backing layer is introduced into the double flexural membrane to increase the bandwidth. Several piezoelectric membrane materials and various electrode dimensions were simulated using finite element analysis (FEA) techniques to study the receiving performance of the proposed structure. The final structure was then fabricated based on the findings from the simulation work. The pulse–echo experimental method was used to characterize and verify the performance of the proposed device. The proposed structure was found to have an improved bandwidth of 56.6% with a receiving sensitivity of −1.8864 dB rel 1 V µPa. For the proposed device, the resonance frequency and center frequency were 600 and 662.5 kHz, respectively, indicating its suitability for the targeted frequency range.