Narrow Results

Chiral metamaterial-based sensor is designed for sensing the change in substance ratio of chemical substances when combined with distilled water. These samples have been prepared with 10%, 50% and 90% volume fraction of methanol, ethanol, acetone, ammonia and isopropyl alcohol. The complex permittivity of the prepared samples has been measured by Agilent 85070E dielectric probe kit and compared with the simulations. In the proposed design, linear shifts with the frequency bands of more than 100 MHz are observed in different measurements. For different material sensing, pure samples have been used and their reflection coefficient measurement results have been presented. Unique side of this study is that the structure provides very clear and sensitive results and presents a new approach to the microfluidic sensor applications by using the sample holder.

The microfluidic device with sharp-edge structures excited with acoustic wave has the characteristics of simple structure, easy manufacture, good bio-compatibility and fast response and has a good application prospect. In order to make full use of its driving characteristics, a scheme of microfluidic driving device with sharp-edge structures is designed in this paper, and the effect of structural parameters on its driving performance is analyzed with the finite element software COMSOL5.6. The model of sharp-edge structure in micro channel is established, and the relationship between the vibration mode and the resonant frequency and the inclined angle of sharp-edge structure is simulated. With the increase of the inclined angle of the sharp-edge structure, its resonant frequency with optimal vibration mode increases. The effects of the micro channel width, the inclined angle between the sharp-edge structure and the micro channel, and the distance between the two sharp-edge structures on the driving velocity are analyzed with the optimal vibration mode. The results show that the parameters of the sharp-edge structure and the micro channel can significantly affect the micro flow field and the driving effect of the micro fluid. As the width of the micro channel, the inclined angle between the sharp-edge structure and the micro channel, and the distance between the two sharp-edge structures decrease, the flow field in the micro channel increases. When the micro channel width is 500$\mu$m, the inclined angle between the sharp-edge structure and the micro channel is 45^∘, and the distance between the two pairs of sharp-edge structures is 150$\mu$m, the microfluidic driving effect is the best, the maximum flow rate is 458.24$\mu$m/s and the velocity fluctuation transverse along the micro channel is the smallest.

Silicon has been widely used to fabricate microfluidic devices due to the dominance of silicon microfabrication technologies available. In this paper, theoretical analyses are carried out to suggest suitable laser machining parameters to achieve required channel geometries. Based on the analyses, a low-power CO₂ laser was employed to create microchannels in Acrylic substrate for the use of manufacturing an optical bubble switch. The developed equations are found useful for selecting appropriate machining parameters. The ability to use a low-cost CO₂ laser to fabricate microchannels provides an alternative and cost-effective method for prototyping fluid flow channels, chambers and cavities in microfluidic lab chips.

The following topics are under this section:

• ASIA-PACIFIC — Identification of Therapeutic Points for Genetically Diverse and Fatal Leukaemia
• ASIA-PACIFIC — Novel Microfluidic Processes for Drug Development
• ASIA-PACIFIC — Development of Anti-Microbial Coating against COVID-19
• ASIA-PACIFIC — Partnership between Arcturus Therapeutics and Duke-NUS Medical School to develop COVID-19 Vaccine
• ASIA-PACIFIC — Nanoscopic Insights to Proteins against Huntington’s Disease
• ASIA-PACIFIC — Unravelling the Impact of Marine Heatwave on Coral Reef Fishes
• ASIA-PACIFIC — Regulation of Plant Pores by MicroRNAs
• ASIA-PACIFIC — Discovering Clues to Longevity in Our Genome
• ASIA-PACIFIC — Repurposing Nature’s Products to Viable Materials
• ASIA-PACIFIC — Reverse Conversion of Oestrogens to Androgens
• REST OF THE WORLD — HER2-targeted Antibody Drug Conjugate Shows Promise in Patients with Non-Breast-Gastric Cancers
• REST OF THE WORLD — New Research finds Teeth as a Biological Archive
• REST OF THE WORLD — Finding Treatment for Muscular Dystrophy using CRISPR

Microreactor technology is a new concept of chemical synthesis for nanoparticle production. The "state of the art" in microreactor fabrication and its application to the synthesis of nanoparticles is reviewed. The microfluidic concepts, the materials and technologies for microreactor manufacture, with particular emphasis on polymers and microreplication techniques, and their application to the synthesis of various nanomaterials in microreactors are presented. The unique synthesis properties of various nanoparticles using a microfluidic process as well as broader impact in term of nanomaterials engineering, i.e., selectivity and monodispersity, reduced amount of chemicals, fast reaction, minimum cost, a better control of the process, minimum waste and reduced amounts of reaction byproducts and improved safety, are discussed in comparison with the traditional wet-chemical batch synthesis approach.

A geometrically confined dripping was employed to enable precise control over the dimension and structure of millimeters-sized double-emulsion precursors of poly(divinylbenzene) foam shells in a new kind of double Y-shaped compound channels. Due to the 3D axial-symmetric microfluidic device, a more stable and robust flow field was maintained to obtain a continuous and regular emulsification. Various factors were systematically investigated for the precise size control of dripping in confined channel geometry, such as outlet channel size, fluid properties and flow rates. It was seen that phase properties and synergistic effects of main factors played key roles in determining droplet size. Thus, we used the optimized microfluidic approach to fabricate predetermined size foams to satisfy inertial fusion energy experiments, ranging from 4 to 4.6mm in diameter with a 50–300$\mu$m wall thickness and a coefficient of variation $<0.5$%. The results presented in this work provided a practical guideline for creating size-desired polymersome from comparable double emulsions.

Along with the rapid growth of research of microfluidics, monitoring and understanding micro flow behavior is a challenge for researchers. Particle Image Velocimetry (PIV), a powerful tool that makes flow visible, was extended to microscale by Santiago et al. 1998. In this paper, we presented the micro Particle Image Velocimetry (μPIV) system at Nanyang Technological University (NTU), its calibration and characterizations of microfluidic devices using μPIV. Since the fully developed microchannel flow has been well investigated, it is suitable to calibrate the measurements of μPIV. In our experiment, an in-channel microdispenser fabricated on printed circuit board is used to form a microchannel. A syringe pump forces water that contains fluorescent particles. The flow field is obtained by μPIV. At the same time, a three-dimensional model with ANSYS/FLOTRAN was used. The comparison between the two results demonstrates that our μPIV system works well. Furthermore we use this system to characterize a Tesla valve - a non-moving part valve. The valve consists of a fluid channel structure that has rectification property, which favors forward flow while hampers reverse flow. The velocity fields are also validated by ANSYS/FLOTRAN.

So far the verification of specific bacteria is time consuming and costly. The reason is the neccessity for highly specialised laboratory equipment and the requirements regarding clean-room facilities ensuring environments free of any germs. Additionally growing bacteria in equivalent petri dishes may require quite some time until a reasonable number is grown sufficient for further evaluation. For many bacteria and even viruses alternative processes for multiplication have been developed, basically relying on the so called Polymerase Chain Reaction (PCR). We developed the Goeppingen GeneReactor, a microsized system (MEMS) for PCR as a low cost device, that can be used without any clean-room facilities, while additionally a device for electrophoresis is added as a tool for analysis. Thus this system can be used as a throw analysis tool, i.e. specimen containig the required bacteria or viruses could be preparated and investigated in every physician's pratice. It should be noted, that even tiny amounts of starting materials are sufficient, since the whole system is no large than a human finger-nail and the PCR allows to multiply the number of desired genes by a factor of 10³ to 10⁶ within 10 to 20 heating cycles.

About 50% of all candidate drugs that make it past Phase-I clinical trials ultimately fail to receive U.S. Food and Drug Administration (FDA) marketing approval due to human toxicity or bioavailability problems that the drug develops. To remedy this state of affairs, in recent years, researchers have attempted to develop improved in vitro assays which can be applied pre-clinically to produce data with a higher degree of correlation to in vivo responses, and which circumvent the allometric limitations inherent in animal models. Such in vitro assays are intended to enable preclinical research and development groups to better predict the pharmacokinetic and pharmacodynamic action of candidate molecules prior to clinical trials, thereby reducing high late-stage failure rates. While most such in vitro systems comprise a static cell culture environment, microfluidic systems have been shown to provide better results. For example, experiments performed with the HμREL^® microfluidics system demonstrated increased clearance rates and better in vitro–in vivo correlation (IVIVC) than that observed with static culture systems. Several hypotheses were suggested to account for these improvements: (1) enhanced mass transport resulting in better functional efficiency; (2) a flow-induced transduction of gene and protein expression and function; and (3) a flow-induced effect resulting in increased cellular uptake. In this paper, we describe a framework, utilizing computational fluid dynamics (CFD), that can be used to study culture systems with a level of scrutiny and spatial precision not offered using standard in vitro assays. Using this approach, we were able to successfully model experimental observations of increases in the clearance rates of high and medium clearance compounds in the microfluidics system. Based on these results we posit that the increase in clearance is most likely due to the addition of convective transport, and a thinning of the boundary layer present in static and mixed plate cultures systems.

Drug delivery as a strategy to improve the effect of therapeutic treatment is gaining tremendous interest in biomedical research. The recent advancement in microfluidic technique designed to precisely control the liquid at micro or nano liter level has shed some new lights on reshaping the ongoing drug delivery research. In this aspect, this present mini-review gives an overview on the potential applications of microfluidic technique in the area of drug delivery, which basically covers the fabrication of drug delivery carriers and the design of microfluidic-based smart systems for localized in vivo drug delivery.

Complete blood cell counts (CBCs) are one of the most commonly ordered and informative blood tests in hospitals. The results from a CBC, which typically include white blood cell (WBC) counts with differentials, red blood cell (RBC) counts, platelet counts and hemoglobin measurements, can have implications for the diagnosis and screening of hundreds of diseases and treatments. Bulky and expensive hematology analyzers are currently used as a gold standard for acquiring CBCs. For nearly all CBCs performed today, the patient must travel to either a hospital with a large laboratory or to a centralized lab testing facility. There is a tremendous need for an automated, portable point-of-care blood cell counter that could yield results in a matter of minutes from a drop of blood without any trained professionals to operate the instrument. We have developed microfluidic biochips capable of a partial CBC using only a drop of whole blood. Total leukocyte and their 3-part differential count are obtained from 10 mL of blood after on-chip lysing of the RBCs and counting of the leukocytes electrically using microfabricated platinum electrodes. For RBCs and platelets, 1 mL of whole blood is diluted with PBS on-chip and the cells are counted electrically. The total time for measurement is under 20 minutes. We demonstrate a high correlation of blood cell counts compared to results acquired with a commercial hematology analyzer. This technology could potentially have tremendous applications in hospitals at the bedside, private clinics, retail clinics and the developing world.

Simple fluid pumps have been developed to improve microfluidic device portability, but they cannot be easily programmed, produce repeatable pumping performance, or generate complex flow profiles — key requirements for increasing the functionality of portable microdevices. We present a detachable, paper-based, “hydraulic battery” that can be connected to the outlet of a microfluidic channel to pump fluid at varying flow rates over time, including step changes, ramping flows, and oscillating flows.

The phenomenal success and worldwide acceptance of mRNA vaccines against COVID-19 has highlighted one remarkable aspect of these vaccines — the ease of scale-up and the fast manufacturing of the vaccines. The timeline from starting the development (by making the plasmid DNA construct for the spike protein) to FDA Emergency Use authorization was accomplished in less than two years. The reasons for this “Warp Speed” accomplishment are varied, and we will go through each step to highlight where translation was rapid.

A microelectrode array-based cell electrofusion chip was fabricated by using the MEMS technique. Because of the short distance between two counter microelectrodes, the working voltage on this chip was only 1/100–1/20 as that in the traditional cell electrofusion method. Simulation method was used to analyze the on-chip electric field distribution and optimize the structure of the microelectrodes. The results showed the length and width of the microelectrode, and the distance between two microelectrodes in the horizontal and vertical direction would impact the strength and distribution of the electric field. Thus, optimized chip architecture was obtained, on which six individual chambers were integrated. At least 1680 microelectrodes were patterned within any one chamber. Alternating current signals have been used to manipulate and align cells, and most cells were aligned as cell–cell twins. High-intensity (~10³ V/cm) electric pulses were used to fuse the aligned cell–cell twins. The fusion efficiency was about 40%, which was much higher than that in traditional chemical method (less than 1‰) and electrofusion methods (less than 5%).

Advances in the packaging approaches and semiconductor materials used for high-power electronic devices will usher in a paradigm shift in the thermal management strategies employed to dissipate extremely high heat fluxes at reasonable operating temperatures. Traditional “remote cooling” systems that have been commonly used to manage thermal loads generated by these devices suffer from parasitic interfacial, conduction, and spreading resistances, which lead to large temperature gradients. The next generation of “embedded cooling” systems will bring coolant very close to the heat source, eliminating these thermal resistances but requiring a solution that can directly manage high local heat fluxes without an intermediate heat spreader. This work highlights recent advances in the experimental characterization and modeling of two-phase embedded-cooling systems. Specifically, it summarizes the development of two-phase hierarchical manifold microchannel heat sinks, a promising high-performance embedded-cooling solution, as well as experimental and numerical studies investigating the underlying microchannel flow boiling phenomena. Static and dynamic flow boiling instabilities among parallel channels, along with the potential for coupling between transient heating conditions and these two-phase flow dynamics, offer unique implementation challenges that may arise in embedded-cooling systems. With continued progress in the understanding of these phenomena and predictive high-fidelity numerical modeling of microchannel flow boiling, embedded cooling systems will alleviate the thermal challenges that currently limit the power and performance of many electronic devices, enabling technological advancements across many industries.

Microfluidic chips coupled to electrospray ionization mass spectrometer (ESI-MS) have been comprehensively studied by researchers. The performance of joint electroosmotic and pneumatic driving force was investigated, based on our recently proposed poly(dimethylsiloxane) microfluidic chip with a corner-integrated emitter. The experiment and simulation flow rates, and the MS-coupling results of signal intensity and RSD indicated an optimal region showed excellent performance of this driving method. But externally imposed pressure driving force also brought problems. Electroosmotic driving played a significant role and using it as major driving was of great potential in the application of coupling to ESI-MS. As for portable MS for on-site analysis, highly integrated tiny microchip using electroosmotic driving solely would make a big difference.