Micro and Nanosystems - Volume 15, Issue 3, 2023

The basic objective of this review is to furnish extensive confirmation on the bioactive chemical compounds and pharmacological aspects of Nagarmotha, i.e., Cyperus scariosus of the family Cyperaceae and some others plants used to treat various diseases of eyes as mentioned in Ayurveda, Charaka Samhita, and Sushrut Samhita. Nagarmotha showed an extensive ethnomedicinal record and constituted a phytonutrient pool of heuristic medicinal value. Various observations on pharmacological affirmation have illustrated the potential of plants as antioxidant, hypotensive, stimulant of the central nervous system, hepatoprotective, antidiabetic, analgesic, ophthalmic, anti-inflammatory, astringent, and antimicrobial actions which aid its conventional benefits. Nagarmotha remained to be an important part of various prescriptions used in nearly all indigenous systems of medicines to cure a variety of ailments. Various investigations on bioactive chemical compounds revealed that Cyperus scariosus has countless essential components like essential oils, terpenoids, sesquiterpenes, hydrocarbons, steroidal saponins, ketones, cyperene, cyperol, cyprotene, flavonoids, and various polyphenolic compounds. In the present work, more emphasis is on the bioactive chemical compounds, enlistment of bioactive chemical compounds responsible for therapeutic values, conventional benefits, and their detailed reported pharmacological properties. Some of the available marketed ayurvedic preparations were also mentioned in this review. Overall, researchers may get assisted and synchronized for impending potency, profitability, and effectiveness of Nagarmotha especially, and other medicinal plants generally. The demand for herbal products is expanding immensely all around the world and several biopharmaceutical regions are nowadays managing substantial research on herbal materials for their promising medicative value. Further curative usefulness of various phytochemicals obtained from Cyperus scariosus may be validated and corroborated.

The present time has witnessed a never-before-heard interest in and applications of microfluidic devices and systems. In microfluidic systems, fluid flows and is manipulated in microchannels. Mixing is one of the most important criteria for a majority of microfluidic systems, whose laminar nature hinders the efficiency of micromixing. The interface between the flowing fluid and the inner wall surface of the microchannel greatly influences the behaviour of fluidic flow in microfluidics. Many researchers have tried to pattern the surface, introduce obstacles to flow, and include micro- or nanoprotruded structures to enhance the mixing efficiency by manipulating the microchannel flow. New and rapid advances in MEMS and micro/nanofabrication technologies have enabled researchers to experiment with increasingly complex designs, enabling rapid transformation and dissemination of new knowledge in the field of microfluidics. Here, we report the fluid flow characteristics, mixing, and associated phenomena about microfluidic systems. Microfluidic systems and components such as microreactors, micromixers, and microchannels are reviewed in this work. We review active and passive micromixers, with a primary focus on widely used passive micromixers. Various microchannel geometries and their features, mixing efficiencies, numerical analysis, and fabrication methods are reviewed. Applications as well as possible future trends and advancements in this field, are included too. It is expected to make the reader curious and more familiar with the interesting field of microfluidics.

Background: Tunnel Field-effect transistor (TFETs) has appeared as a promising candidate due to its steep slope (SS<60 mV/dec), which can be used for low-power applications.Objectives: Authors investigated AlxGa1-xAs as the channel material in Silicon-on-Insulator (SOI) TFETs and compared it to other existing channel materials, SiGe, Ge, Si, Ge, Strained Si, and GaAs.Methods: For the entire device study, the mole fraction x = 0.2 has been used in AlxGa1-xAs channel material. The direct energy bandgap for Al0.2Ga0.8As has been used because the mole fraction is less than 0.4. The Al0.2Ga0.8As-based device has been analyzed in terms of Direct Current (DC) and Alternating Current (AC) characteristics using the Synopsys TCAD tool.Results: The proposed device offers enhanced switching speed with a high on/off ratio of ∼10¹² and a steep subthreshold swing of 30 mv/dec As a channel material, Al0.2Ga0.8As also enhances the miller capacitance of the device, which is one of the essential requirements of the device performance.Conclusion: In next-generation devices, Al0.2Ga0.8As as channel material and TFET device based on this channel material act as a promising contender for low-power applications.

Introduction: A new method of modelling surface roughness of the resultant structure from various parameters in the microforming of CNT forests has been developed. One of the top-down microforming methods of CNT forests is called micromechanical bending (M2B). The method uses a high-speed rotating spindle to compact and flatten the surface of CNT forests. It results in the surface structure becoming smoother and increased reflectance of the surface. The reason for this phenomenon is the porosity that decreases by bending CNTs, hence preventing light from passing through. Moreover, the surface roughness is also significantly reduced. However, a study has yet to be conducted to estimate the theoretical value of surface roughness from the identified parameters.Aim: This research aims to develop an approach to model the surface roughness of resultant surface from a set of parameters in a micropatterning method.Methods: Experiments were conducted using a CNC machine to pattern onto CNT Forests using specific parameters, such as 1000, 1500, and 2000 rpm (spindle speed) with feed rates of 1, 5 and 10 mm/min. The step size was kept fixed at 1 μm for each level of the patterning pass. It was found that the periodic pattern of trochoidal mark was engraved on the surface, contributing to the value of measured surface roughness.Results: The results were compared with the theoretical value from the calculation of surface roughness using trochoidal motion with the assumption of the grain sizes of 0.2 µm, 0.3 µm, and 0.4 µm. The actual value of surface roughness was measured using the XE-AFM machine. The grain of 0.2 μm produced the same experimental trend with the theoretical value at rotational speeds of 1000, 1500, and 2000 rpm. However, the theoretical result was shifted downward because the surface could return to the original position due to the elastic properties of the CNTs, hence reducing the surface roughness. The best-fit result was reported for the grain of 0.4 µm, rotational speed of 2000 rpm, and speed rate of 1 mm/min, showing less than 1% difference.Conclusion: Experimentally and theoretically, a good agreement and comparable results proved the effectiveness of the proposed estimating method.

Introduction: Micro-Electrical Discharge Machining (μEDM) is a technique for non-contact machining of conductive or semiconductor materials. It is mainly adapted to machining hard materials. Its principle is based on the creation of electrical discharges between the micro tool and the workpiece, which are immersed in a dielectric. Methods: It is a complementary process to mechanical or laser micromachining techniques or microelectronics (RIE, DRIE, LIGA). These methods can reach a resolution of 50 nm, but their main drawback is that they are mainly dedicated to silicon. The μEDM process depends on several physical, geometrical, and/or electrical parameters that need to be optimized in order to achieve a resolution lower than 5 μm in a reproducible way. The objective of this paper is to study the effect of the applied voltage VEE and the micro-tool diameter on the machining performances (removed volume, lateral gap, machining depth, and crater shape). Result: The optimal parameters were used during drilling holes. An applied voltage of VEE = 50V was used as an optimal parameter. Conclusion: Concerning the diameter of the micro tool, we propose to use large diameter wires (Φ=250 μm; Φ=125 μm) during the roughing phase for machining complex structures and small diameter micro tools (Φ=80 μm; Φ=40 μm; Φ=20 μm) during the finishing phase.

Introduction: Thermal drifts of MEMS sensors are one of their biggest shortcomings. However, experimental studies may offer a solution while striving for the reduction of related errors.Objective: The aim was to determine the thermal drifts of MEMS accelerometers associated with the offset voltage and the scale factor and then to propose a way of reducing the resultant errors.Methods: Four commercial dual-axis MEMS accelerometers (two pieces of ADXL 202E and two pieces of ADXL 203 by Analog Devices Inc.) with analog outputs were experimentally tested with respect to their thermal instability, employing two computer-controlled test rigs that provided a stable orientation of the accelerometers.Results: It was found that the thermal drifts of the offset voltage generated by the tested accelerometers were considerable, resulting in respective errors of about 14 mg (ADXL 202E) or 7 mg (ADXL 203), whereas catalog values of drifts of the scale factor were much lower.Conclusion: The determined values are smaller than their counterparts specified in the relevant manufacturer datasheets; significant differences exist between the tested pieces of the two accelerometers (40% or 78%) as well as between the two sensitive axes of a single accelerometer (84% or 80%), this can be taken into consideration while striving for a higher accuracy of an acceleration measurement.

Introduction: This paper aims to fabricate the high aspect ratio tungsten micro-tools with diameters up to 80 μm by electrochemical etching. This process is simple and easy to develop, but it requires a deep study to achieve the fabrication of micro-tools with a diameter of 5 μm.Methods: In this work, we studied the effect of the pulsed signal parameters used during the electrochemical etching. The parameters studied are VON and TOFF (The applied voltage and the rest phase, respectively).Results: The experiments show that VON = 0.5 V leads to satisfactory results (validation of the reproducibility, homogeneous etching, and fabrication of micro-tools with a diameter of 80 μm with an initial tungsten wire diameter of 250 μm) by applying an etching charge of 13 C. Voltages VON = 0.1 V and VON = 1 V does not ensure homogeneous etching. A rest phase TOFF = 3 s allows obtaining micro- tools with a diameter of 80 μm in 7 min. For a rest phase of TOFF = 9 s, the etching takes 20 min and the micro-tool diameter is almost the same.Conclusion: The results of this study will be used in the manufacture of cylindrical micro-tools with a high aspect ratio Fc > 100.

Background: The technique of approximation allows for a trade-off between accuracy, speed, area use, and power usage. It is essential in applications that can withstand errors because even a modest accuracy loss can have a significant impact on the result.Methods: In this research, a novel approximate adder and exact 3:2 and 4:2 compressors are used to create a power-efficient approximation multiplier. In order to reduce the partial product while keeping a fair level of accuracy, approximate compressors are used.Results: The proposed approximate multiplier performs better in terms of LUTs, area, memory usage, and power consumption when compared to state-of-the-art work.Conclusion: The proposed approximate multiplier is applied to two sets of images for image blending to validate the results. PSNR values of 25.49 dB and 24.7 dB were attained for set 1 and set 2, respectively.