Micromachines, Volume 12, Issue 7 (July 2021) – 120 articles

Aluminum optics are widely used in modern optical systems because of their high specific stiffness and high reflectance. With the applied optical frequency band moving to visible, traditional processing technology cannot meet the processing precision. Ion beam sputtering (IBS) provides a highly deterministic technology for high-precision aluminum optics fabrication. However, the surface quality is deteriorated after IBS. The interaction between the bombard atoms and the surface morphology evolution mechanism are not clear, and systematic research is needed. Thus, in this paper, the IBS process for single crystal aluminum with different crystallographic orientations are studied by the molecular dynamics method. The ion beam sputter process is firstly demonstrated. Then, the variation of sputter yield of the three crystal faces is analyzed. The sputter yield difference of different crystal surfaces causes the appearance of the relief structure. Then, the gravel structure generates on the single crystal surfaces and dominates the morphology evolution. The state of the atom diffusion of the specific crystal surfaces will determine the form of the gravel structure. Furthermore, the form and distribution of subsurface damage and stress distribution of three different crystal surfaces are analyzed. Although there are great differences in defect distribution, no stress concentration was found in three workpieces, which verifies that the ion beam sputter is a stress-free machining method. The process of IBS and the mechanism of morphology evolution of aluminum are revealed. The regularity and mechanism will provide a guidance for the application of IBS in aluminum optics manufacture fields. Full article

The natural compound eye system has many outstanding properties, such as a more compact size, wider-angle view, better capacity to detect moving objects, and higher sensitivity to light intensity, compared to that of a single-aperture vision system. Thanks to the development of micro- and nano-fabrication techniques, many artificial compound eye imaging systems have been studied and fabricated to inherit fascinating optical features of the natural compound eye. This paper provides a review of artificial compound eye imaging systems. This review begins by introducing the principle of the natural compound eye, and then, the analysis of two types of artificial compound eye systems. We equally present the applications of the artificial compound eye imaging systems. Finally, we suggest our outlooks about the artificial compound eye imaging system. Full article

The recent development of 3D flash memories has promoted the widespread application of SSDs in modern storage systems by providing large storage capacity and low cost. Garbage collection (GC) as a time-consuming but necessary operation in flash memories largely affects the performance. In this paper, we perform a comprehensive experimental study on how garbage collection impacts the performance of flash-based SSDs, in the view of performance cliff that closely relates to Quality of Service (QoS). According to the study results using real-world workloads, we first observe that GC occasionally causes response time spikes, which we call the performance cliff problem. Then, we find that 3D SSDs exacerbate the situation by inducing a much higher number of page migrations during GC. To relieve the performance cliff problem, we propose PreGC to assist normal GC. The key idea is to distribute the page migrations into the period before normal GC, thus leading to a reduction in page migrations during the GC period. Comprehensive experiments with real-world workloads have been performed on the SSDsim simulator. Experimental results show that PreGC can efficiently relieve the performance cliff by reducing the tail latency from the 90th to 99.99th percentiles while inducing a little extra write amplification. Full article

In this paper, a gas detection system with an environmental compensation algorithm based on nondispersive infrared (NDIR) technology was designed. The prepared infrared pyroelectric detector was a dual-channel type based on the lithium tantalate (LiTaO₃) wafer. The design of the optical gas chamber adopted a combination of two ellipsoids and a spherical top surface, which not only enhanced the coupling efficiency of the light propagation but also facilitated the miniaturization of the sensor module. In addition to this, a temperature and humidity compensation algorithm based on the least square method was proposed to make the measurement accuracy up to ±0.9% full scale (FS). Full article

Intra-operative target pose estimation is fundamental in minimally invasive surgery (MIS) to guiding surgical robots. This task can be fulfilled by the 2-D/3-D rigid registration, which aligns the anatomical structures between intra-operative 2-D fluoroscopy and the pre-operative 3-D computed tomography (CT) with annotated target information. Although this technique has been researched for decades, it is still challenging to achieve accuracy, robustness and efficiency simultaneously. In this paper, a novel orthogonal-view 2-D/3-D rigid registration framework is proposed which combines the dense reconstruction based on deep learning and the GPU-accelerated 3-D/3-D rigid registration. First, we employ the X2CT-GAN to reconstruct a target CT from two orthogonal fluoroscopy images. After that, the generated target CT and pre-operative CT are input into the 3-D/3-D rigid registration part, which potentially needs a few iterations to converge the global optima. For further efficiency improvement, we make the 3-D/3-D registration algorithm parallel and apply a GPU to accelerate this part. For evaluation, a novel tool is employed to preprocess the public head CT dataset CQ500 and a CT-DRR dataset is presented as the benchmark. The proposed method achieves 1.65 ± 1.41 mm in mean target registration error(mTRE), 20% in the gross failure rate(GFR) and 1.8 s in running time. Our method outperforms the state-of-the-art methods in most test cases. It is promising to apply the proposed method in localization and nano manipulation of micro surgical robot for highly precise MIS. Full article

We investigated the performance of single-structured light-emitting electrochemical cell (LEC) devices with Ru(bpy)₃(PF₆)₂ polymer composite as an emission layer by controlling thickness and heat treatment. When the thickness was smaller than 120–150 nm, the device performance decreased because of the low optical properties and non-dense surface properties. On the other hand, when the thickness was over than 150 nm, the device had too high surface roughness, resulting in high-efficiency roll-off and poor device stability. With 150 nm thickness, the absorbance increased, and the surface roughness was low and dense, resulting in increased device characteristics and better stability. The heat treatment effect further improved the surface properties, thus improving the device characteristics. In particular, the external quantum efficiency (EQE) reduction rate was shallow at 100 °C, which indicates that the LEC device has stable operating characteristics. The LEC device exhibited a maximum luminance of 3532 cd/m² and an EQE of 1.14% under 150 nm thickness and 100 °C heat treatment. Full article

The liver is a target organ of life-threatening pathogens and prominently contributes to the variation in drug responses and drug-induced liver injury among patients. Currently available drugs significantly decrease the morbidity and mortality of liver-dwelling pathogens worldwide; however, emerging clinical evidence reveals the importance of host factors in the design of safe and effective therapies for individuals, known as personalized medicine. Given the primary adherence of cells in conventional two-dimensional culture, the use of these one-size-fit-to-all models in preclinical drug development can lead to substantial failures in assessing therapeutic safety and efficacy. Advances in stem cell biology, bioengineering and material sciences allow us to develop a more physiologically relevant model that is capable of recapitulating the human liver. This report reviews the current use of liver-on-a-chip models of hepatotropic infectious diseases in the context of precision medicine including hepatitis virus and malaria parasites, assesses patient-specific responses to antiviral drugs, and designs personalized therapeutic treatments to address the need for a personalized liver-like model. Second, most organs-on-chips lack a monitoring system for cell functions in real time; thus, the review discusses recent advances and challenges in combining liver-on-a-chip technology with biosensors for assessing hepatocyte viability and functions. Prospectively, the biosensor-integrated liver-on-a-chip device would provide novel biological insights that could accelerate the development of novel therapeutic compounds. Full article

An environmentally friendly method was proposed to prepare mesoporous Mobil Composition of Matter No.48 (MCM-48) using fly ash as the silica source. Silver nanoparticles were infiltrated on MCM-48 facilely by an in situ post-reduction method and evaluated as an effective catalyst for CO oxidation. The as-prepared MCM-48 and Ag/MCM-48 nanoparticles were characterized by XRD, N₂ adsorption/desorption, and TEM. Investigations by means of XPS for Ag/MCM-48 were performed in order to illuminate the surface composition of the samples. Studies revealed the strong influence of the loading of Ag nanoparticles on catalysts in the oxidation of CO. CO conversion values for Ag/MCM-48 of 10% and 100% were achieved at temperatures of 220 °C and 270 °C, respectively, indicating that the Ag-decorated MCM-48 catalyst is extremely active for CO oxidation. Full article

In this paper we study the dynamics of single cells encapsulated in water-in-oil emulsions in a microchannel. The flow field of a microfluidic channel is coupled to the internal flow field of a droplet through viscous traction at the interface, resulting in a rotational flow field inside the droplet. An encapsulated single cell being subjected to this flow field responds by undergoing multiple orbits, spins, and deformations that depend on its physical properties. Monitoring the cell dynamics, using a high-speed camera, can lead to the development of new label-free methods for the detection of rare cells, based on their biomechanical properties. A sheath flow microchannel was proposed to strengthen the rotational flow field inside droplets flowing in Poiseuille flow conditions. A numerical model was developed to investigate the effect of various parameters on the rotational flow field inside a droplet. The multi-phase flow model required the tracking of the fluid–fluid interface, which deforms over time due to the applied shear stresses. Experiments confirmed the significant effect of the sheath flow rate on the cell dynamics, where the speed of cell orbiting was doubled. Doubling the cell speed can double the amount of extracted biomechanical information from the encapsulated cell, while it remains within the field of view of the camera used. Full article

Artificial intelligence algorithms need an external computing device such as a graphics processing unit (GPU) due to computational complexity. For running artificial intelligence algorithms in an embedded device, many studies proposed light-weighted artificial intelligence algorithms and artificial intelligence accelerators. In this paper, we propose the ASimOV framework, which optimizes artificial intelligence algorithms and generates Verilog hardware description language (HDL) code for executing intelligence algorithms in field programmable gate array (FPGA). To verify ASimOV, we explore the performance space of k-NN algorithms and generate Verilog HDL code to demonstrate the k-NN accelerator in FPGA. Our contribution is to provide the artificial intelligence algorithm as an end-to-end pipeline and ensure that it is optimized to a specific dataset through simulation, and an artificial intelligence accelerator is generated in the end. Full article

People’s health has been threatened by several common food hazards. Thus, it is very important to establish rapid and accurate methods to detect food hazards. In recent years, biosensors have inspired developments because of their specificity and sensitivity, short reaction time, low cost, small size and easy operation. Owing to their high precision and non-destructive characteristics, cell-based electrochemical detection methods can reflect the damage of food hazards to organisms better. In this review, the characteristics of electrochemical cell-based biosensors and their applications in the detection of common hazards in food are reviewed. The strategies of cell immobilization and 3D culture on electrodes are discussed. The current limitations and further development prospects of cell-based electrochemical biosensors are also evaluated. Full article

Having a basic understanding of non-Newtonian fluid flow through porous media, which usually consist of series of expansions and contractions, is of importance for enhanced oil recovery, groundwater remediation, microfluidic particle manipulation, etc. The flow in contraction and/or expansion microchannel is unbounded in the primary direction and has been widely studied before. In contrast, there has been very little work on the understanding of such flow in an expansion–contraction microchannel with a confined cavity. We investigate the flow of five types of non-Newtonian fluids with distinct rheological properties and water through a planar single-cavity microchannel. All fluids are tested in a similarly wide range of flow rates, from which the observed flow regimes and vortex development are summarized in the same dimensionless parameter spaces for a unified understanding of the effects of fluid inertia, shear thinning, and elasticity as well as confinement. Our results indicate that fluid inertia is responsible for developing vortices in the expansion flow, which is trivially affected by the confinement. Fluid shear thinning causes flow separations on the contraction walls, and the interplay between the effects of shear thinning and inertia is dictated by the confinement. Fluid elasticity introduces instability and asymmetry to the contraction flow of polymers with long chains while suppressing the fluid inertia-induced expansion flow vortices. However, the formation and fluctuation of such elasto-inertial fluid vortices exhibit strong digressions from the unconfined flow pattern in a contraction–expansion microchannel of similar dimensions. Full article

Using molecular beam epitaxy, we prepared seven p-type AlGaN samples of ~25% in Al content, including six samples with Mg-doped/un-doped AlGaN alternating-layer structures of different layer-thickness combinations, for comparing their p-type performances. Lower sheet resistance and higher effective hole mobility are obtained in a layer-structured sample, when compared with the reference sample of uniform Mg doping. The improved p-type performance in a layer-structured sample is attributed to the diffusion of holes generated in an Mg-doped layer into the neighboring un-doped layers, in which hole mobility is significantly higher because of weak ionized impurity scattering. Among the layer-structured samples, that of 6/4 nm in Mg-doped/un-doped thickness results in the lowest sheet resistance (the highest effective hole mobility), which is 4.83 times lower (4.57 times higher) when compared with the sample of uniform doping. The effects of the Mg-doped/un-doped layer structure on p-type performance in AlGaN and GaN are compared. Full article

This paper focuses on the power dissipation of a plasma torch used for an optical surface fabrication process. The process utilizes an inductively coupled plasma (ICP) torch that is equipped with a De-Laval nozzle for the delivery of a highly collimated plasma jet. The plasma torch makes use of a self-igniting coil and an intermediate co-axial tube made of alumina. The torch has a distinctive thermal and electrical response compared to regular ICP torches. In this study, the results of the power dissipation investigation reveal the true efficiency of the torch and discern its electrical response. By systematically measuring the coolant parameters (temperature change and flow rate), the power dissipation is extrapolated. The radio frequency power supply is set to 800 W, E mode, throughout the research presented in this study. The analytical results of power dissipation, derived from the experiments, show that 15.4% and 33.3% are dissipated by the nozzle and coil coolant channels, respectively. The experiments also enable the determination of the thermal time constant of the plasma torch for the entire range of RF power. Full article

Shape memory polymers (SMPs) have been applied in aerospace engineering as deployable space structures. In this work, the coupled finite element method (FEM) was established based on the generalized Maxwell model and the time–temperature equivalence principle (TTEP). The thermodynamic behavior and shape memory effects of a single-arm deployment structure (F-DS) and four-arm deployment structure (F-DS) based on SMPs were analyzed using the coupled FEM. Good consistency was obtained between the experimental data and simulation data for the tensile and S-DS recovery forces, verifying that the coupled FEM can accurately and reliably describe the thermodynamic behavior and shape memory effects of the SMP structure. The step-by-step driving structure is suitable for use as a large-scale deployment structure in space. This coupled FEM provides a new direction for future research on epoxy SMPs. Full article

Caenorhabditiselegans (C. elegans) has gained importance as a model for studying host-microbiota interactions and bacterial infections related to human pathogens. Assessing the fate of ingested bacteria in the worm’s intestine is therefore of great interest, in particular with respect to normal bacterial digestion or intestinal colonization by pathogens. Here, we report an in vivo study of bacteria in the gut of C. elegans. We take advantage of a polydimethylsiloxane (PDMS) microfluidic device enabling passive immobilization of adult worms under physiological conditions. Non-pathogenic Escherichia coli (E. coli) bacteria expressing either pH-sensitive or pH-insensitive fluorescence reporters as well as fluorescently marked indigestible microbeads were used for the different assays. Dynamic fluorescence patterns of the bacterial load in the worm gut were conveniently monitored by time-lapse imaging. Cyclic motion of the bacterial load due to peristaltic activity of the gut was observed and biochemical digestion of E. coli was characterized by high-resolution fluorescence imaging of the worm’s intestine. We could discriminate between individual intact bacteria and diffuse signals related to disrupted bacteria that can be digested. From the decay of the diffuse fluorescent signal, we determined a digestion time constant of 14 ± 4 s. In order to evaluate the possibility to perform infection assays with our platform, immobilized C. elegans worms were fed pathogenic Mycobacterium marinum (M. marinum) bacteria. We analyzed bacterial fate and accumulation in the gut of N2 worms and mitochondrial stress response in a hsp-6::gfp mutant. Full article

With the increasing application field, a higher requirement is put forward for the mass spectrometer. The reduction in size will inevitably cause a loss of precision; therefore, it is necessary to develop a high-performance miniature mass spectrometer. Based on the researches of rectangular ion trap, the relationship between mass resolution and structural parameters of the ion trap array was analyzed by further simulation. The results indicate that, considering the balance of mass resolution and extraction efficiency, the preferable values for the field radius of exit direction y₀ and ion exit slot width s₀ are 1.61 mm and 200 μm, respectively. Afterwards, a miniature four-channel ion trap array (MFITA) was fabricated, by using MEMS and laser etching technology, and mass spectrometry experiments were carried out to demonstrate its performance. The mass resolution of butyl diacetate with m/z = 230 can reach 324. In addition, the consistency of four channels is verified within the error tolerance, by analyzing air samples. Our work can prove the correctness of the structural design and the feasibility of MEMS preparation for MFITA, which will bring meaningful guidance for its future development and optimization. Full article

Durability is a critical issue concerning energy-harvesting devices. Despite the energy-harvesting device’s excellent performance, moving components, such as the metal spring, can be damaged during operation. To solve the durability problem of the metal spring in a vibration-energy-harvesting (VEH) device, this study applied a non-contact magnetic spring to a VEH device using the repulsive force of permanent magnets. A laboratory experiment was conducted to determine the potential energy-harvesting power using the magnetic spring VEH device. In addition, the characteristics of the generated power were studied using the magnetic spring VEH device in a high-speed train traveling at 300 km/h. Through the high-speed train experiment, the power generated by both the metal spring VEH device and magnetic spring VEH device was measured, and the performance characteristics required for a power source for wireless sensor nodes in high-speed trains are discussed. Full article

The ZnO/Ni₂S₃ composite has been designed and in situ synthesized on Ni foam substrate by two steps of electrodeposition. ZnO was achieved on Ni foam by a traditional potentiostatic deposition, followed by cyclic voltammetric (CV) electrodeposition, to generate Ni₂S₃, where the introduction of ZnO provides abundant active sites for the subsequent Ni₂S₃ electrodeposition. The amount of deposit during CV electrodeposition can be adjusted by setting the number of sweep segment and scan rate, and the electrochemical characteristics of the products can be readily optimized. The synergistic effect between the ZnO as backbones and the deposited Ni₂S₃ as the shell enhances the electrochemical properties of the sample significantly, including a highly specific capacitance of 2.19 F cm⁻² at 2 mA cm⁻², good coulombic efficiency of 98%, and long-term cyclic stability at 82.35% (4000 cycles). Full article

This paper presents a simulation and experimental study of the structure of small holes in GH4169 alloy electrolytic ally processed by tube electrodes with different characteristic power sources. It analyzes the multi-physical field coupling relationship of flow, temperature, and electric fields within the interstitial space. The results indicate that the tube electrode electrolytic processing of the GH4169 alloy small hole structure with a pulsed power supply has more uniform temperature and current density distribution within the gap, which is beneficial to the processing accuracy and smoothness of the small hole structure. Meanwhile, SEM was used to analyze the microscopic morphology of the electrode end surface during short-circuiting, and it was concluded that as the processing continued, the electrode end surface gradually produced a non-metallic oxide layer, which destroyed the electric field of the gap and affected the processing stability. The use of high-frequency positive and negative pulse power can effectively avoid the generation of a non-metallic oxide layer. Through the combination of simulation analysis and experimental verification, it is concluded that increasing electrolyte pressure in stages can effectively improve machining accuracy and stability. The interstitial current increases as the feed rate of the tool electrode increases, and the diameter of the machined small hole decreases as it increases. Full article

Based on the clustering effect of shear-thickening fluids (STFs), a high-shear low-pressure flexible grinding wheel has been developed. In order to explore the material removal mechanism, the coupled Eulerian—Lagrangian (CEL) method is adopted to simulate the novel grinding process. The simulation results show that particle clustering effects do occur at the tangential and bottom positions of the micro-convex peak when it instantaneously strikes the workpiece surface. The particle clusters drive the harder abrasive particles to resist the strong interactions of micro-convex peaks. The micro-convex peaks are removed due to the cutting effect of the harder abrasive particles. Compared with traditional grinding, the ratio of tangential force to normal force for the high-shear low-pressure flexible grinding wheel is improved. The various trends in force ratio are consistent with the experimental results, which verifies the effectiveness of high-shear low-pressure grinding. Full article

This review aims to summarize the recent advances and progress of plasmonic biosensors based on patterned plasmonic nanostructure arrays that are integrated with microfluidic chips for various biomedical detection applications. The plasmonic biosensors have made rapid progress in miniaturization sensors with greatly enhanced performance through the continuous advances in plasmon resonance techniques such as surface plasmon resonance (SPR) and localized SPR (LSPR)-based refractive index sensing, SPR imaging (SPRi), and surface-enhanced Raman scattering (SERS). Meanwhile, microfluidic integration promotes multiplexing opportunities for the plasmonic biosensors in the simultaneous detection of multiple analytes. Particularly, different types of microfluidic-integrated plasmonic biosensor systems based on versatile patterned plasmonic nanostructured arrays were reviewed comprehensively, including their methods and relevant typical works. The microfluidics-based plasmonic biosensors provide a high-throughput platform for the biochemical molecular analysis with the advantages such as ultra-high sensitivity, label-free, and real time performance; thus, they continue to benefit the existing and emerging applications of biomedical studies, chemical analyses, and point-of-care diagnostics. Full article

Airborne metal particles (MPs; particle size > 10 μm) in workplaces result in a loss in production yield if not detected in time. The demand for compact and cost-efficient MP sensors to monitor airborne MP generation is increasing. However, contemporary instruments and laboratory-grade sensors exhibit certain limitations in real-time and on-site monitoring of airborne MPs. This paper presents a microfluidic MP detection chip to address these limitations. By combining the proposed system with microcirculation-based particle-to-liquid collection and a capacitive sensing method, the continuous detection of airborne MPs can be achieved. A few microfabrication processes were realized, resulting in a compact system, which can be easily replaced after contamination with a low-priced microfluidic chip. In our experiments, the frequency-dependent capacitive changes were characterized using MP (aluminum) samples (sizes ranging from 10 μm to 40 μm). Performance evaluation of the proposed system under test-bed conditions indicated that it is capable of real-time and continuous monitoring of airborne MPs (minimum size 10 μm) under an optimal frequency, with superior sensitivity and responsivity. Therefore, the proposed system can be used as an on-site MP sensor for unexpected airborne MP generation in precise manufacturing facilities where metal sources are used. Full article

Based on the conventional structure of traveling wave ultrasonic motor, a rotary ultrasonic motor with double-sided staggered teeth was proposed. Both sides of the stator could be used to actuate the rotors to rotate and output torque. Moreover, the staggered teeth in the stator could be dedicated to accommodating the piezoelectric ceramic chips. Under the excitation of two alternating voltages with a 90° phase difference, a traveling wave could be generated in the ring-like stator. Then, a rotary motion could be realized by means of the friction between the rotors and the driving teeth of the stator. The finite element method was adopted to analyze the motion trajectories of the driving tips. Moreover, the experimental results showed that the load-free maximum speed and maximum output torque of the prototype were 99 rpm and 0.19 N·m at a voltage of 150 V_p with a frequency of 28.25 kHz. Full article

Optical modulators were, are, and will continue to be the underpinning devices for optical transceivers at all levels of the optical networks. Recently, heterogeneously integrated silicon and lithium niobate (Si/LN) optical modulators have demonstrated attractive overall performance in terms of optical loss, drive voltage, and modulation bandwidth. However, due to the moderate Pockels coefficient of lithium niobate, the device length of the Si/LN modulator is still relatively long for low-drive-voltage operation. Here, we report a folded Si/LN Mach–Zehnder modulator consisting of meandering optical waveguides and meandering microwave transmission lines, whose device length is approximately two-fifths of the unfolded counterpart while maintaining the overall performance. The present devices feature a low half-wave voltage of 1.24 V, support data rates up to 128 gigabits per second, and show a device length of less than 9 mm. Full article

Bone defects of orthopedic trauma remain a challenge in clinical practice. Regarding bone void fillers, besides the well-known osteoconductivity of most bone substitutes, osteoinductivity has also been gaining attention in recent years. It is known that stromal cell-derived factor-1 (SDF-1) can recruit mesenchymal stem cells (MSCs) in certain circumstances, which may also play an important role in bone regeneration. In this study, we fabricated a gelatin/hyaluronate (Gel/HA) copolymer mixed with hydroxyapatite (HAP) and SDF-1 to try and enhance bone regeneration in a bone defect model. After material characterization, these Gel/HA–HAP and Gel/HA–HAP–SDF-1 composites were tested for their biocompatibility and ability to recruit MSCs in vitro. A femoral condyle bone defect model of rats was used for in vivo studies. For the assessment of bone healing, micro-CT analysis, second harmonic generation (SHG) imaging, and histology studies were performed. As a result, the Gel/HA–HAP composites showed no systemic toxicity to rats. Gel/HA–HAP composite groups both showed better bone generation compared with the control group in an animal study, and the composite with the SDF-1 group even showed a trend of faster bone growth compared with the composite without SDF-1 group. In conclusion, in the management of traumatic bone defects, Gel/HA–HAP–SDF-1 composites can be a feasible material for use as bone void fillers. Full article

Carbon containing materials, such as graphene, carbon-nanotubes (CNT), and graphene oxide, have gained prominence as possible electrodes in implantable neural interfaces due to their excellent conductive properties. While carbon is a promising electrochemical interface, many fabrication processes are difficult to perform, leading to issues with large scale device production and overall repeatability. Here we demonstrate that carbon electrodes and traces constructed from pyrolyzed-photoresist-film (PPF) when combined with amorphous silicon carbide (a-SiC) insulation could be fabricated with repeatable processes which use tools easily available in most semiconductor facilities. Directly forming PPF on a-SiC simplified the fabrication process which eliminates noble metal evaporation/sputtering and lift-off processes on small features. PPF electrodes in oxygenated phosphate buffered solution at pH 7.4 demonstrated excellent electrochemical charge storage capacity (CSC) of 14.16 C/cm², an impedance of 24.8 ± 0.4 kΩ, and phase angle of −35.9 ± 0.6° at 1 kHz with a 1.9 kµm² recording site area. Full article

The almost ubiquitous, though undesired, deposition and accumulation of suspended/dissolved matter on solid surfaces, known as fouling, represents a crucial issue strongly affecting the efficiency and sustainability of micro-scale reactors. Fouling becomes even more detrimental for all the applications that require the use of membrane separation units. As a matter of fact, membrane technology is a key route towards process intensification, having the potential to replace conventional separation procedures, with significant energy savings and reduced environmental impact, in a broad range of applications, from water purification to food and pharmaceutical industries. Despite all the research efforts so far, fouling still represents an unsolved problem. The complex interplay of physical and chemical mechanisms governing its evolution is indeed yet to be fully unraveled and the role played by foulants’ properties or operating conditions is an area of active research where microfluidics can play a fundamental role. The aim of this review is to explore fouling through microfluidic systems, assessing the fundamental interactions involved and how microfluidics enables the comprehension of the mechanisms characterizing the process. The main mathematical models describing the fouling stages will also be reviewed and their limitations discussed. Finally, the principal dynamic investigation techniques in which microfluidics represents a key tool will be discussed, analyzing their employment to study fouling. Full article

We present a survey on battery-less Radio Frequency Identification (RFID-based wireless sensors that have emerged in the past several years. We discuss the evolution of RFID turning into wireless sensors. Moreover, we talk about different components of these battery-less RFID-based wireless sensors, five main topologies that transform a simple RFID chip into a battery-less wireless sensor, and state-of-the-art implementations of these topologies. In battery-less wireless sensors, the read range is of key importance. Hence, we discuss how each component of the sensor plays its role in determining the read range and how each topology exploits these components to optimize read range, complexity, and/or cost. Additionally, we discuss potential future directions that can help provide improvements in RFID-based wireless sensor technology. Full article