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(Volume: 2, Issue: 10)
Microheaters not required for temperature control in Digital Microfluidic Systems
Can various laboratory tasks such as, a controlled chemical analysis or synthesis, the sample preparation for clinical diagnostics or biological assays, the screening or discovery of drugs and the environmental monitoring for pollutants can be achieved without massive laboratory set-ups? Yes, the Lab-on-a-Chip (LoC) makes them possible. They do so by manipulating fluids, cells, chemical reagents or proteins, which are being injected into its micro-scaled channels, ending up in greater research findings from a single chip!!! Traditionally, external pipes and valves facilitated the control of fluids within the chip. But, this tedious manual control of fluid flow diminished with the advent of digital microfluidic technology. As the name indicates, the digital microfluidic systems use electric fields to control the movement of the fluid droplets being placed on a dielectric substrate, powered by voltages from microelectrodes. Hence, heat generation and temperature control via chip-mounted microheaters or materials with resistance heating effect, laser or infra- red sources have a vital role in reducing the fluid viscosity, maintaining a perfect temperature for the laboratory task and mixing or splitting of droplets. However, the mounting of microheaters or similar other heat-controlling units on LoC always require few considerations. For instance, the associated heat losses and dissipation, their number on the chip and their size constraints to manipulate droplets of varying microscales. So, numerous researchers have worked upon optimizing the parameters for microheater placement and controlling the fluid flow in the LoCs. There are also existing researches in search of generating or controlling temperatures of the microdroplets, without using microheaters. Krishnadas Narayanan Nampoothiri, Mahadevan Subramanya Seshasayee, Vinod Srinivasan, M.S. Bobji and Prosenjit Sen, three Indian and one USA-based researchers, have investigated whether the aqueous droplets be heated directly by the high frequency AC voltage signals from the microelectrodes on the same LoC, without employing a microheater. The researchers state that the droplet temperature tends to rise due to Joule heating from the ohmic currents inside the drop, at high actuation frequencies. In their research in Sensors and Actuators B: Chemical (vol. 273), the researchers also conclude that they were able to achieve temperatures of 93–94 °C, which can aid in exploring several biochemical or biological processes. Providing a biggest advantage of avoiding microheaters on the LoC, the researchers have also paved way for adaptive temperature control of droplets in future systems. Naturally, the future LoC devices are aimed at concurrent achievement of more than one complex clinical or biochemical tasks. This simply implies that the number of functional components integrated on to a single chip grows largely. Hence, the temperature control without microheaters for liquid manipulation in the digital microfluidics- based LoCs have a great scope in future. Image courtesy: www.vecteezy.com
Type-II Superlattice (T2SL) heterostructures for improved IR detectors
Want an object to be seen across visible light spectrum? Then, go for Infrared Detectors (IRDs). Since IRDs have the ability to sense and measure infrared radiation of longer wavelengths than visible light, they have found amazing applications in: (i) industrial thermal imaging, (ii) intruder-detection or motion sensing in security or surveillance applications, (iii) object detection in night vision, (iv) physiological change detection in medical imaging, (v) weather and vegetation health monitoring in remote sensing applications, (vi) spectroscopy, (vii) anomaly detections like, gas leakage or accidental fires, (viii) missile or navigation guidance and (ix) optical or telecommunication applications. Usually, the core of an IRD is a semiconductor material with narrow bandgap, which absorbs the incident IR radiation and creates an associated electrical signal. Indium antimonide (InSb), Mercury Cadmium Telluride (MCT) and lead selenide (PbSe) are a few commonly used semiconducting materials, detecting IR of distinct wavelengths. Of these, the MCT (MCT: Hg1–xCdxTe) is highly-utilized because of its high absorption coefficient, bandgap tunability, thermal generation rates, low leakage current density and high wavelength tunability. Though MCT holds better for IRD, its need for cryogenic cooling and the high dark current density constrained by Auger recombination processes allow to seek for a low cost, narrow bandgap semiconductor alternative with enhanced sensitivity and longer wavelength operation. It is at this instant, the Type-II superlattice (T2SL) materials/ structure have gained attention. The T2SL structure is formed of alternating layers of different semiconducting materials, wherein the physics of quantum wells and heterostructures are used to engineer the bandgap for attaining improved performance in the infrared wavelength range. Since these structures offer reduced dark current and improved quantum efficiency, they can be beneficial in producing high-performance IRDs with low noise. Previous researches have reported several heterostructures like, InAs/ GaSb, InAs/ InAsSb and graphene/ Hg1–xCdxTe to work in different IR wavelengths. Shonak Bansal from Chandigarh university of India has also suggested a T2SL heterostructure, formed of Bilayer Graphene (BLG) and Hg1–xCdxTe, to create a self-powered T2SL detector in the Long-Wave IR spectral regime (8–12 μm). He has named the detector as the GBp LWIR detector and examined its optoelectronic properties. As per Results in Optics, Elsevier (vol. 12), the unipolar GBp barrier detector attained high efficiency and detectivity by blocking the dark current density and the surface leakage current density, but failed to suppress the photocurrent density. Furthermore, the detector was viable to be used as a temperature-controlled variable-gain IR detector because of its hot carrier multiplication effect. However, there are also Very Long-Wave IR (VLWIR: 12–30 μm) and Far IR (FIR: 30–1000 μm) ranges for the IRD to operate. So, further research can also center around finding T2SL heterostructures that aid detection in almost all IR spectral regimes. Image courtesy: www.freepik.com
Approach for constricting the construction-site accidents!
We find massive buildings under construction almost everywhere. However, these gorgeous buildings might not look good to all because of the deadliest as well as the non-fatal injuries caused by the construction-site accidents!!! These accidents might be a fall, electrocution, caught-in-between and struck-by type. Whatever its kind might be, it just creates hardships or loss of life, in addition to the disruption of lean construction management. The major offender here is the human error, being produced by negligence, the lack of awareness and the lack of training to handle the construction-site equipment. The researchers of the past have made several investigations to identify and cut down the human errors, based on the analysis of age, education, ability, competence, experience and the awareness on past accidents or their associated safety measures. However, the construction-site accidents will be totally nullified, only if the risks and the human error probability associated with the tasks are thoroughly analysed and a right person is recruited for a right job. This is not easy as stated, because a construction site will be flooded up with umpteen number of labors, supervisors, technicians, equipment and so on. So, obviously artificial intelligence approaches can be of greater support, while handling and choosing the right person for a right job in an optimal sense. Three researchers, C. Sivapragasam, S. Ajith and V. Arumugaprabu, have taken efforts to minimize the construction-site accidents using the Task-Personnel Nexus Matrix (TPM). Their ideology in their research published in the International Journal of Construction Management involved the following: (i) Evaluate the worker’s level of performance, (ii) Evaluate the Risk Cum Human Error (RHE) probability for a given task and (iii) Evaluate the number of workers fit for a particular RHE. The RHE was actually framed using the techniques like, the Hazard Identification and Risk Assessment (HIRA) as well as the Human Error Assessment and Reduction Technique (HEART). The researchers have affirmed that their approach improves the construction-site safety, since the approach allows only a high-performer to perform a high-risk task. However, as the researchers have also alerted their approach to be recursive, trial and error-based and ineffective to handle smaller-sized construction sites, the future researchers have a large arena to put up their contributions. Image courtesy: www.freepik.com
Achieve efficient power control with 4-quadrant SiC MOSFETs
Attaining high power efficiency is the foremost objective of any research on power systems, be it electrical, renewable or their hybrid. The switching devices have a vital role in achieving this objective. These basic power system components can do several tasks like, control the current flow, voltage levels or frequency and ensure power system safety with improved fault detection, system integration and operation. Silicon MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and Insulated Gate Bipolar Transistors (IGBTs) were the most-predominantly used switching devices in the past, but until one time- ‘The time at which the Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistors (SiC MOSFETs) emerged’. This is because the SiC MOSFETs with Silicon Carbide as the semiconductor material imparted the following benefits: (i) High temperature-withstanding ability, (ii) High voltage and frequency operation, (iii) low conduction losses because of low-on-resistance, (iv) higher switching speeds, (v) reduced electromagnetic interference and (vi) attainability of compact, reliable and denser power system designs. So, SiC MOSFETs are currently found to master almost all the power electronics and renewable energy systems like, Electric Vehicle charging systems, industrial motor drives, power supplies, inverters, aircraft power distribution/control and many other power system applications. However, only 2-quadrant SiC MOSFETs are widely used, wherein the power flow control between the source and the load (or vice versa) is unidirectional. But, the recent power systems such as, the single-stage solid-state transformers or the matrix converters achieve simultaneous power delivery and recovery to attain improved power efficiency. So, bidirectional power flow control becomes a need and it is achievable only with 4-quadrant switches or two 2-quadrant switches. Since the 4-quadrant SiC MOSFETs are not much commercially available, research on designing such switching devices is mandated. Nishant Anurag from IIT Guwahati and Shabari Nath, a member of the IEEE, in support from the Science and Engineering Research Board, Government of India, have investigated the characteristics of the 4-quadrant SiC MOSFET switch in a 21 matrix converter. Their research in IEEE Access (vol.11) included the following aspects: (i) The finding of dominating devices, which were responsible for the turn ON/ OFF time, (ii) The observation on the switching trends, with respect to the switch current on each quadrant and (iii) the study on the influence that the gate resistances have on the turn ON/OFF time. However, the researchers have witnessed a drop in the switching frequency for the 4-quadrant SiC MOSFET, in comparison with its 2-quadrant counterpart. Hence, the upcoming researchers can concentrate on designing and commercializing 4-quadrant SiC MOSFETs or their better-performing variants with different semiconducting materials, enabling the smooth functioning of the power systems or grids.
Digital image tampering needs research attention
Is it not a shocking experience to see your image in a photo that is portraying an unethical act, when you are not actually involved in it? This deceptive manipulation of a digital image to add, remove or falsify the image contents is known as digital image tampering. Though the digital image tampering might be legally used to create an artistic effect, image enhancement in terms of color or brightness and digital recreation of a demolished historical monument, it is more often used to reduce a person’s fame or to deceive the public about a theft or crime by tampering the images obtained at the site of the crime or the criminal itself. So, what are the ways to perform digital image tampering? The first way is an active approach, while the second way is a passive one. By the active approach, the image can be dynamically-manipulated in real-time. In contrast, the passive approach involves altering the contents of stored, non-real-time images. Indeed, the passive approach is even more threatening, since the active approach is hard to be unethically achieved because of real-time image manipulation. There are so many uncontrollable passive approaches a deceiver employs and few frequently- applied approaches are: (i) Cloning the regions in an image and pasting it seamlessly at different locations on the same image to hide a scene, (ii) Cutting an image portion and pasting it to another image for falsifying the original identity in an image and (iii) Splicing to create an image from fragments of different images. Three researchers from Iraq, named Mohammed Fakhrulddin Abdulqader, Adnan Yousif Dawod and Ann Zeki Ablahd, have reviewed the present literature on image tampering forgery detection and they have found most works to handle splicing, cut/ paste and copy-move image tampering techniques. Suggesting a strategy for further improvement in their article in Measurement: Sensors (vol. 27), the researchers state that “future studies must investigate the basic issues, and detecting methods that provide a dependable solution with flexibility and high accuracy”. Though the analysis of shadows, lighting or the pixel patterns in the images and secure digital imaging like, the blockchain technology exists, the tampered images look extremely real that proving oneself against a crime act or falsified image is hardly impossible!!! Moreover, since this is a digital era, the image forgeries will certainly remain uncontrolled and flourish largely. So, the researchers should provide highly accurate means for eradicating this unethical image manipulations. Image courtesy: www.freepik.com
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