Real-time detection of isoprene marker gas based on micro-integrated chromatography system with GOQDs-modifiedµGC column and metal oxide gas detector.

Isoprene is a typical physiological marker that can be used to screen for chronic liver disease. This work developed a portable micro-integrated chromatography analysis system based on micro-electromechanical system technology, nanomaterials technology and embedded microcontroller technology. The system integrated components such as graphene oxide quantum dots modified semi-packed microcolumn, In2O3nanoflower (NF) gas-sensitive detector and 3D printed miniature solenoid valve group. The effectiveness of the separation effect of the micro-integrated system was verified by gas mixture test; the laws of the influence of carrier gas pressure and column temperature on the chromatographic separation performance, respectively, were investigated, and the working conditions (column temperature 90 °C and carrier gas pressure 7.5 kPa) for system testing were determined. The percentages of relative standard deviation of the peak areas and retention times obtained for the separated gases were in the range of 0.95%-6.06%, indicating the good reproducibility of the system. Meanwhile, the microintegrated system could detect isoprene down to 50 ppb at small injection volume (1 ml). The system response increased with increasing isoprene concentration and was linearly correlated with isoprene concentration (R2= 0.986), indicating that the system was expected to be used for trace detection of isoprene, a marker gas for liver disease, in the future.

Fabrication of solid-state nanopores.

Nanopores are valuable single-molecule sensing tools that have been widely applied to the detection of DNA, RNA, proteins, viruses, glycans, etc. The prominent sensing platform is helping to improve our health-related quality of life and accelerate the rapid realization of precision medicine. Solid-state nanopores have made rapid progress in the past decades due to their flexible size, structure and compatibility with semiconductor fabrication processes. With the development of semiconductor fabrication techniques, materials science and surface chemistry, nanopore preparation and modification technologies have made great breakthroughs. To date, various solid-state nanopore materials, processing technologies, and modification methods are available to us. In the review, we outline the recent advances in nanopores fabrication and analyze the virtues and limitations of various membrane materials and nanopores drilling techniques.

A Novel Swept-Back Fishnet-Embedded Microchannel Topology.

High in reliability, multi in function, and strong in tracking and detecting, active phased array antennas have been widely applied in radar systems. Heat dissipation is a major technological barrier preventing the realization of next-generation high-performance phased array antennas. As a result of the advancement of miniaturization and the integration of microelectronics technology, the study and development of embedded direct cooling or heat dissipation has significantly enhanced the heat dissipation effect. In this paper, a novel swept-back fishnet-embedded microchannel topology (SBFEMCT) is designed, and various microchannel models with different fishnet runner mesh density ratios and different fishnet runner layers are established to characterize the chip Tmax, runner Pmax, and Vmax and analyze the thermal effect of SBFEMCT under these two operating conditions. The Pmax is reduced to 72.37% and 57.12% of the original at mesh density ratios of 0.5, 0.25, and 0.125, respectively. The maximum temperature reduction figures are average with little change in maximum velocity and a small increase in maximum pressure drop across the number of fishnet runner layers from 0 to 4. This paper provides a study of the latest embedded thermal dissipation from the dimension of a single chip to provide a certain degree of new ideas and references for solving the thermal technology bottleneck of next-generation high-performance phased array antennas.

Thermal Induced Interface Mechanical Response Analysis of SMT Lead-Free Solder Joint and Its Adaptive Optimization.

Surface mount technology (SMT) plays an important role in integrated circuits, but due to thermal stress alternation caused by temperature cycling, it tends to have thermo-mechanical reliability problems. At the same time, considering the environmental and health problems of lead (Pb)-based solders, the electronics industry has turned to lead-free solders, such as ternary alloy Sn-3Ag-0.5Cu (SAC305). As lead-free solders exhibit visco-plastic mechanical properties significantly affected by temperature, their thermo-mechanical reliability has received considerable attention. In this study, the interface delamination of an SMT solder joint using a SAC305 alloy under temperature cycling has been analyzed by the nonlinear finite element method. The results indicate that the highest contact pressure at the four corners of the termination/solder horizontal interface means that delamination is most likely to occur, followed by the y-direction side region of the solder/land interface and the top arc region of the termination/solder vertical interface. It should be noted that in order to keep the shape of the solder joint in the finite element model consistent with the actual situation after the reflow process, a minimum energy-based morphology evolution method has been incorporated into the established finite element model. Eventually, an Improved Efficient Global Optimization (IEGO) method was used to optimize the geometry of the SMT solder joint in order to reduce the contact pressure at critical points and critical regions. The optimization result shows that the contact pressure at the critical points and at the critical regions decreases significantly, which also means that the probability of thermal-induced delamination decreases.

A Fast Evaluation Method for Electrical Performance of Frequency and Pattern Reconfigurable Microstrip Antenna Based on Electromechanical Coupling.

With the constant increase in communication requirements in modern society, the number and type of antennas on communication platforms have been increasing at an accelerating rate. This has led to a continuous increase in platform volume and weight, and the electromagnetic environment of antenna operating has increasingly worsened, seriously restricting the further development of communication systems. As a new communication system antenna type, a reconfigurable microstrip antenna can reconstruct operating frequencies, beam directions, etc., by changing the antenna structure to provide the good multifunction characteristics of a single antenna, avoiding the electromagnetic compatibility issues caused by numerous system antennas. At present, most of the research on reconfigurable antennas judges the influence of structural characteristics on electromagnetic characteristics by simulation, which has imposed restrictions on their development and application. Therefore, a reconfigurable antenna with a resonant frequency of 8.66 GHz and 15.26 GHz and a reconfigurable antenna with maximum radiation directions of 36.2° and -36.5° are designed in this paper, and the electromechanical coupling theory of the reconfigurable antennas is studied. The resonance frequency coupling model and the pattern function coupling model considering the structural deformation of a reconfigurable microstrip antenna are established. Within the applicable range of antenna structural parameters, the relative error between the resonance frequency coupling model and the pattern function coupling model is less than 5%, which meets practical engineering application requirements. Finally, the method is shown by experimentation to verify the accuracy and validity of the proposed electromechanical coupling model.

A Novel Manifold Dual-Microchannel Flow Field Structure with High-Performance Heat Dissipation.

With the development of miniaturization and integration of electronic devices, the conventional manifold microchannels (MMCs) structure has been unable to meet the heat dissipation requirements caused by the rapid growth of internal heat flux. There is an urgent need to design a new heat dissipation structure with higher heat dissipation capacity to ensure the working stability and life of electronic devices. In this paper, we designed a novel manifold dual-microchannel (MDMC) cooling system that embedded the microchannel structure into the manifold microchannel structure. The MDMC not only has good heat dissipation performance that can meet the development needs of electronic equipment to miniaturization and integration, but also has a compact structure that does not increase the overall thickness and volume compared with MMC. The high temperature uniformity and heat transfer performance of MDMC are significantly improved compared to MMC. The Tmax is reduced by 13.6% and 17.5% at the heat flux density of 300 W/cm2 and 700 W/cm2, respectively. In addition, the influence of the inlet-2 velocity and the total microchannels number on the heat transfer performance of the MDMC structure are numerically investigated. The results show that the decrease rate of Tmax and ΔT is about 6.69% and 16% with the increase of inlet-2 velocity from 1.2 m/s to 2.4 m/s and microchannels number from 10 to 48, respectively. At the same time, the best temperature uniformity is obtained when the number of microchannels is 16.