Showing papers by "Xinxin Li published in 2019"

Schadenfreude: A Counternormative Observer Response to Workplace Mistreatment

Abstract: Although almost all employees have heard of or witnessed colleagues being mistreated, we have an incomplete understanding of how employees perceive and respond to such events. In previous research ...

Detection of Phenylketonuria Markers Using a ZIF-67 Encapsulated PtPd Alloy Nanoparticle (PtPd@ZIF-67)-Based Disposable Electrochemical Microsensor

Abstract: Phenylketonuria (PKU) is a common disease in congenital disorder of amino acid metabolism, which can lead to intellectual disability, seizures, behavioral problems, and mental disorders. We report herein a facile method to screen for PKU by the measurements of its metabolites (markers). In this work, a disposable electrochemical microsensor modified with a ZIF (zeolitic imidazolate framework)-based nanocomposite is constructed, in which ZIF-67 crystals are encapsulated with PtPd alloy nanoparticles (NPs) forming the nanocomposite (PtPd@ZIF-67). According to electrochemical measurements, the PtPd@ZIF-67-modified microsensor shows good responses and selectivity to phenylpyruvic acid and phenylacetic acid, while almost no response toward other amino acid analogues is observed. Here, a new sensing mechanism based on the acylation reaction between the imidazole linker in ZIF-67 and carboxyl in PKU markers has been proposed and verified through the Fourier-transform infrared spectroscopy study. Moreover, the encapsulated PtPd NPs elevate the electron transfer capability of the PtPd@ZIF-67-modified microsensor and further improve the electrochemical sensing performance. Finally, we demonstrate that the developed PtPd@ZIF-67-modified microsensor has the possibility to sensing of PKU markers with high response and good specificity and may be extended to exploit the point-of-care rapid PKU screening.

In situ construction of metal-organic framework (MOF) UiO-66 film on Parylene-patterned resonant microcantilever for trace organophosphorus molecules detection.

Abstract: The detection of organophosphorus (OP) compounds, which are extremely toxic, is a requirement in many application fields such as food security. Mass-type chemical sensors based on ultra-sensitive resonant microcantilevers exhibit high comparative advantages in OP compound detection. However, it is still a big challenge to construct a sensing film in situ from corrosive precursors on resonant cantilevers for batch fabrication. In this work, Parylene-C is patterned and a sample reservoir is formed on the free-end of resonant microcantilever for constructing the sensing material directly. Not only utilized for corrosive precursor loading and in situ sensing material construction, the Parylene-C film can also be used to effectively protect the integrated elements from damage by corrosive substances. For extremely toxic OP molecule detection, a typical metal-organic framework (MOF) of UiO-66 film has been regioselectively constructed in situ on the Parylene-C patterned microcantilevers. A limit of detection (LOD) of 5 ppb for the OP simulant dimethyl methylphosphonate (DMMP) is achieved. The in situ MOF construction method manifests satisfactory consistency for sensor batch fabrication. The DMMP sensing mechanism is identified as the specific host-guest interaction between the UiO-66 and OP molecule.

Smart Amphiphilic Random Copolymer-Coated Sponge with pH-Switchable Wettability for On-Demand Oil/Water Separation.

Abstract: To prepare intelligent controllable oil/water separation materials with high mechanical stability and good recyclability, we fabricated a novel pH-controlled wettability melamine sponge by using a facile dip-coating method. The coated sponge exhibits reversibly switchable wettability between superhydrophilicity-superoleophobicity through acidic surrounding and superhydrophobicity-superoleophilicity under neutral or alkaline conditions. The as-prepared sponge possesses excellent absorption capacity (46.06-122.81 g/g) and oil/water separation efficiency (above 98%). The coated sponge also has good mechanical stability and recyclability which means it can be reused for absorption and oil/water separation. This smart porous material, which can flexibly transform wettability on demand, has great application prospects in oil/water separation.

A Front-Side Microfabricated Tiny-Size Thermopile Infrared Detector With High Sensitivity and Fast Response

Abstract: This paper reports a novel tiny-sized ( $116\,\,\mu \text {m} \times 134\,\,\mu \text{m}$ ) single-crystalline silicon/aluminum infrared (IR) thermopile detector, which is micromachined only from the front side of (111) wafer for IC-foundry compatible low-cost manufacturing. The tiny-sized detector consists of six serially connected p-silicon/aluminum thermocouples that show significantly higher Seebeck coefficient and lower noise compared with the traditional poly-silicon/aluminum counterparts. With the proposed symmetric helical structure, the length of thermocouple leg length as well as the thermal resistance of the detector can be enlarged within the tiny sensing area. Specific detectivity ( $D^{\ast }$ ) is improved by optimizing the cross-sectional area of the two thermoelectric-material layers, which is more practically effective than traditional mathematic analysis methods. The device is fabricated in a (111) wafer [instead of normal (100) wafer] by using a novel single-side micromachining technique. The testing results show that the detector achieves an ultrahigh responsivity of 342 V/W and ultrashort response time of 0.56 ms. Featuring tiny-size, low-cost, and high-performance single-point detection, many thermopile detecting units can be integrated into an IR focal-plane array (IRFPA) for high-resolution imaging.

Controllable TiO2 coating on the nickel-rich layered cathode through TiCl4 hydrolysis via fluidized bed chemical vapor deposition

Abstract: Surface coating of metal oxides is an effective approach for enhancing the capacity retention of a nickel-rich layered cathode. Current conventional coating techniques including wet chemistry methods and atomic layer deposition are restricted by the difficulty in perfectly balancing the coating quality and scale-up production. Herein, a highly efficient TiO2 coating route through fluidized bed chemical vapor deposition (FBCVD) was proposed to enable scalable and high yield synthesis of a TiO2 coated nickel-rich cathode. The technological parameters including coating time and TiCl4 supply rate were systematically studied, and thus a utility TiO2 deposition rate model was deduced, promoting the controllable TiO2 coating. The FBCVD TiO2 deposition mechanism was fundamentally analyzed based on the TiCl4 hydrolysis principle. The amorphous and uniform TiO2 coating layer is compactly attached on the particle surface, forming a classical core–shell structure. Electrochemical evaluations reveal that the TiO2 coating by FBCVD route indeed improves the capacity retention from 89.08% to 95.89% after 50 cycles.

Single-Side Fabricated p + Si/Al Thermopile-Based Gas Flow Sensor for IC-Foundry-Compatible, High-Yield, and Low-Cost Volume Manufacturing

Abstract: In this brief, a low-cost and high-yield bulk under thin-film (BUT) MEMS technique for the volume production of flow sensors is proposed and developed. The IC-foundry-compatible process is conducted only from the front side of (111) silicon wafers, without double-sided alignment exposure, wafer bonding, cavity silicon on insulator, and double-sided polished wafers needed. With the single-wafer-based BUT structure, the thermopile consisting of 21 pairs of single-crystalline Si/Al thermocouples that show significantly higher Seebeck coefficient and lower noise compared to the traditional poly-Si/Al thermocouples is employed to construct the gas flow sensor, and the fabricated sensor chip size is as small as ${0.65}\,\,\text {mm} \times {0.65}$ mm that facilitates low-cost high-throughput IC-foundry batch fabrication. The fabricated sensor shows a high normalized sensitivity of $199~\mu \text{V}$ /(SLM)/mW for nitrogen gas flow, which is 1 order of magnitude higher than that of the reported thermopile-based gas flow sensor, and a short response time of 3.5 ms could be achieved. With the new technique, the proposed sensors are promising in automotive and process control system applications.

Schiff-base reaction induced selective sensing of trace dopamine based on a Pt41Rh59 alloy/ZIF-90 nanocomposite.

Abstract: Zeolitic imidazole frameworks (ZIFs) are a new class of functional porous materials with attractive characters, such as gas storage, selective separation, catalysis, and drug delivery. We report herein using nanoscale ZIF-90 crystals with free aldehyde group of imidazole-2-carboxaldehyde (ICA) ligand for the selective electrochemical detection of dopamine. The averaged adsorption enthalpy ΔH (i.e., isosteric heat) of ZIF-90 to dopamine is estimated as 72 kJ mol-1 according to grand canonical Monte Carlo (GCMC) simulation. With further modification of a Pt41Rh59 alloy nanocatalyst, the electrochemical sensing performances towards dopamine are improved. The synergetic effect generated by a Pt41Rh59/ZIF-90 nanocomposite endows it a low detection limit of 1 nM and good specificity. The different anti-interference mechanisms to coexisting redox active species and amino analogues are also included in this work. The strategy demonstrated here may be extended to tune metal nodes as well as ligands of ZIFs crystals and further regulating their functionalities for different target molecules identification.

A Multidrug Resistance Plasmid pIMP26, Carrying blaIMP-26, fosA5, blaDHA-1, and qnrB4 in Enterobacter cloacae

Abstract: IMP-26 was a rare IMP variant with more carbapenem-hydrolyzing activities, which was increasingly reported now in China. This study characterized a transferable multidrug resistance plasmid harboring blaIMP-26 from one Enterobacter cloacae bloodstream isolate in Shanghai and investigated the genetic environment of resistance genes. The isolate was subjected to antimicrobial susceptibility testing and multilocus sequence typing using broth microdilution method, Etest and PCR. The plasmid was analyzed through conjugation experiments, S1-nuclease pulsed-field gel electrophoresis and hybridization. Whole genome sequencing and sequence analysis was conducted for further investigation of the plasmid. E. cloacae RJ702, belonging to ST528 and carrying blaIMP-26, blaDHA-1, qnrB4 and fosA5, was resistant to almost all β-lactams, but susceptible to quinolones and tigecycline. The transconjugant inherited the multidrug resistance. The resistance genes were located on a 329,420-bp IncHI2 conjugative plasmid pIMP26 (ST1 subtype), which contained trhK/trhV, tra, parA and stbA family operon. The blaIMP-26 was arranged following intI1. The blaDHA-1 and qnrB4 cluster was the downstream of ISCR1, same as that in p505108-MDR. The fosA5 cassette was mediated by IS4. This was the first report on complete nucleotide of a blaIMP-26-carrying plasmid in E. cloacae in China. Plasmid pIMP26 hosted high phylogenetic mosaicism, transferability and plasticity.

Integrated Resonant Dual-Microcantilevers Combined Sensor with Accurate Identification and Highly-Sensitive Detection to H 2 S Gas

Abstract: This paper shows a novel integrated resonant dual-microcantilevers combined gas sensor which can identify and detect trace-level H 2 S. With two kinds of specially designed sensing materials loaded respectively, one cantilever can identify H 2 S by outputting positive frequency shift signals, while the other cantilever will detect H 2 S as a normally used cantilever sensor with negative frequency shifts. Experiments show that the sensor can distinguish H 2 S from a variety of common gases, and the detection limit to H 2 S is as sensitive as a few ppb.

A Front-Side Micro-Fabricated Tiny-Size Thermoresistive Gas Flow Sensor with Low Cost, High Sensitivity, and Quick Response

Abstract: A novel thermoresistive micro gas flow sensor is proposed and fabricated only from the front-side of (111) silicon wafer for high-yield and low-cost volume production. In order to minimize heat loss from the heater to the silicon substrate through the insulation membrane, micro air-trench between the heater and the thermistor is opened to furthest increase the thermal resistance. With the single-wafer-based single-side fabrication process and the optimal thermal-insulation configuration, the fabricated MEMS-based thermoresistive flow sensors achieve a tiny size of 0.7mm × 0.7mm, ultra-high normalized sensitivity of 3.9mV/(SLM)/mW for nitrogen gas flow, which is 17-fold higher than that of the reported MEMS-based thermoresistive gas flow sensor, and short response time of 1.5ms.

Design, Fabrication, and Testing of a Monolithically Integrated Tri-Axis High-Shock Accelerometer in Single (111)-Silicon Wafer.

Abstract: In this paper, a monolithic tri-axis piezoresistive high-shock accelerometer has been proposed that has been single-sided fabricated in a single (111)-silicon wafer. A single-cantilever structure and two dual-cantilever structures are designed and micromachined in one (111)-silicon chip to detect Z-axis and X-/Y-axis high-shock accelerations, respectively. Unlike the previous tri-axis sensors where the X-/Y-axis structure was different from the Z-axis one, the herein used similar cantilever sensing structures for tri-axis sensing facilitates design of uniform performance among the three elements for different sensing axes and simplifies micro-fabrication for the multi-axis sensing structure. Attributed to the tri-axis sensors formed by using the single-wafer single-sided fabrication process, the sensor is mechanically robust enough to endure the harsh high-g shocking environment and can be compatibly batch-fabricated in standard semiconductor foundries. After the single-sided process to form the sensor, the untouched chip backside facilitates simple and reliable die-bond packaging. The high-shock testing results of the fabricated sensor show linear sensing outputs along X-/Y-axis and Z-axis, with the sensitivities (under DC 5 V supply) as about 0.80⁻0.88 μV/g and 1.36 μV/g, respectively. Being advantageous in single-chip compact integration of the tri-axis accelerometers, the proposed monolithic tri-axis sensors are promising to be embedded into detection micro-systems for high-shock measurement applications.

Self-powered wireless sensor network using event-triggered energy harvesters for monitoring and identifying intrusion activities

Abstract: Monitoring concerned activities and identifying activity types usually require sensors and corresponding data processing circuits, which are often restricted by the limited power supply in wireless sensor networks (WSNs). This study presents a self-powered smart WSN for passively monitoring and distinguishing different vibration events. In the proposed WSN, the sensing function is performed by vibration-threshold-triggered energy harvesters (VTT-EHs). The output power of the VTT-EH dramatically increases when an input vibration exceeds the pre-set vibration-threshold of the harvester, indicating the occurrence of specific concerned events. On the basis of this principle, two VTT-EHs with different thresholds were designed to detect and distinguish vibration events with different vibration characteristics. Meanwhile, electromagnetic EHs were applied to generate sufficient power for wirelessly transmitting the alarm signals within several seconds. The prototype of the proposed WSN was developed and evaluated. The sensor node was able to identify two types of intrusive activities: weak shake and strong knock. The alarming signals were first sent to a router node and then transmitted to a mobile phone through the global system of mobile communication network. The mobile phone received the alarming text messages with correct event type within 2 s after the excitation occurred.

Self-Clocking Electro-Mechanical Sigma-Delta Modulator Quadrature Error Cancellation for MEMS Gyroscope

Abstract: This paper presents a novel electromechanical sigma-delta modulator ( $\text{EM}-\Sigma\Delta\mathrm{M}$ ) closed-loop quadrature error cancellation technique for the sense mode of a MEMS vibratory gyroscope. The interface circuit system adopts a quadrature sigma-delta modulator structure, which allows in-phase and quadrature decomposition to efficiently realize noise shaping and quadrature error cancellation. Experimental results demonstrate that the proposed quadrature sigma-delta modulator ( $Q-\Sigma\Delta\mathrm{M}$ ) control loop results in better noise and bias drift performance when compared with an $\text{EM}-\Sigma\Delta\mathrm{M}$ single-loop architecture. Measurement results showed that the proposed quadrature $\text{EM}-\Sigma\Delta\mathrm{M}$ gyroscope achieved −80dB quadrature error cancellation within a bandwidth of 64Hz, and an approximately 5.5-fold improvement in bias instability (decreasing the bias instability from 5°/h to 0.9°/h), compared to the same gyroscope operating in a single-loop $\text{EM}-\Sigma\Delta\mathrm{M}$ .

System and method for preparation of metal fluoride-coated lithium-ion battery anode material based on chemical vapor deposition method of fluidized bed

Abstract: The invention relates to a system and method for the preparation of metal fluoride-coated lithium-ion battery anode material based on a chemical vapor deposition method of a fluidized bed. The systemmainly comprises a silo, a spiral feeder, a feeding valve, a fluidized bed reactor, a discharging valve, a product cooler, a product collector, a burner, a reaction gas-carrier preheater, a metal reaction raw material generator, a reaction raw material nozzle, a fluidized gas-carrier preheater, a fluorine reaction raw material generator, a first-stage cyclone separator, a primary cyclone separator, a cloth bag dust collector and a hydrochloric acid and exhaust absorber formed in accordance with the established combination. The method comprises the steps that based on a metal fluoride-coated modification method, the metal fluoride-coated anode composite powder is obtained through fluidized chemical vapor deposition. The system has the advantages of being high in coating efficiency, simple and controllable in process, low in cost and the like, is suitable for the large-scale industrial production of the lithium-ion battery metal fluoride coating modification anode material, and has higheconomic and social benefits.

A Novel Thermopile-Based Gas Flow Sensor Fabricated with a Single-Wafer-Based Front-Sided Bulk-Micromachining Technique

Abstract: This paper presents a novel p+Si/Au thermopile-based micro flow sensor, which is fabricated only from the front- side of (111) silicon wafer for high-yield and low-cost volume production. Benefited from the MIS (Micro-openings Interetch & Sealing) micromachining process and the developed patterned technique of single-crystalline silicon (SC-Si) layer under thin-film, the p+Si/Au thermocouple with significantly high Seebeck-coefficient can be employed to construct the thermopile-based gas flow sensor, and the $0.65\text{mm}\times 0.65\text{mm}$ tiny-sized MEMS gas flow sensor is achieved. The testing results show that the sensor has an ultra-high normalized sensitivity of 0.158mV/(SLM)/mW (Output without any amplification) for nitrogen gas flow and the short response time of 3.0ms. Besides, the minimum detectable flow rate is estimated at about 9.0 sccm.

Tranforming Lateral Limbs Movement to Vertical Frequency-up-Conversion (FUC) Resonance for Wearable Energy Harvesters

Abstract: This paper reports a novel wearable energy-harvester to generate electric-power from human-joint rotation induced lateral stretch/rebound of the flexible substrate. The energy harvester integrates micro-plated nickel cantilever with the piezoelectric film and fixes them to the flexible substrate. By using the magnetic coupled frequency-up-conversion (FUC) between the ferromagnetic nickel cantilever and the magnet on the substrate, the low-frequency lateral human limbs movement is converted into high-frequency vertical (perpendicular to the substrate) resonant power generation of the piezoelectric cantilever, thereby effectively generating stable electric energy. Within the whole elbow/knee movement in the frequency-range of 0.5Hz∼5.0Hz, the electric-energy generated in one movement cycle always stably keeps within $0.56\mu\mathrm{J}-0.69\mu\mathrm{J}$ . Body kinetic energy-harvesting experiments under limbs movements like squat, walking, jogging and fast running have verified the device to be promising in various wearable applications.

Enhancing the closed-loop stability of a high-Q polysilicon micro-hemispherical resonating gyroscope

Abstract: This paper presents an enhanced stability strategy for the sense mode of a force-rebalanced closed-loop polysilicon micro-hemispherical resonating gyroscope (μHRG) with a high-Q quality-factor value (15.2k). The sense mode closed-loop control including the Coriolis force and quadrature error force rebalanced loop, respectively. Specific demodulation theoretical deductions with mode-split are performed to identify a precise linear model of the sense mode open loop. The frequency responses obtained by experimental tests show good agreement with the theoretical model. The experimental results demonstrate that a bandwidth of 10 Hz and a 0.51 Hz frequency-splitting closed loop gyroscope can be extended to 86 Hz and 3.3 Hz, from 6 Hz and 0.13 Hz in the open loop. The mode-matching (0.51 Hz frequency-splitting) gyroscope with closed loop control can achieve a scale factor of 2.25 mV/°/s with a nonlinearity of 0.087%, and a bias instability of 21.8°/hr with an angle random walk of 3.1°/√hr.

System and method for coating lithium ion battery cathode material with fast ion conductor

Abstract: The present invention provides a system and a method for coating a lithium ion battery cathode material with a fast ion conductor. The system mainly comprises a stock bin, a screw feeder, a feed valve, a fluidized bed reactor, a discharge valve, a product cooler , a product collector, a burner, an No.1 reaction carrier gas preheater, a metal reaction raw material generator, a reaction raw materialnozzle, an No.2 reaction carrier gas preheater, a lithium reaction raw material generator, a fluidized carrier gas preheater, a primary cyclone separator, a secondary cyclone separator, a baghouse dust collector and a hydrochloric acid tail gas absorber according to predetermined combination; the method is a fast ion modification method based on the system. The fast ion conductor coating the cathode composite powder is obtained through fluidization chemical vapor deposition. The system and the method for coating a lithium ion battery cathode material with a fast ion conductor are high in coating efficiency, simple and controllable in the process and low in cost, are suitable for large-scale industrial production of lithium ion battery fast ion conductor coating the modified cathode material, and have good economic and social benefits.

System and method for composite cladding of lithium ion battery positive electrode material with carbon and metal oxides

Abstract: The invention relates to a system and method for the composite cladding of a lithium ion battery positive electrode material with carbon and metal oxides. The system is mainly composed of a material chamber, a spiral feeding device, a feeding valve, a fluid-bed reactor, a discharging valve, a product cooling device, a product collecting device, a combustion device, a reactor gas carrying preheating device, a precursor generator, a reactor raw material nozzle, a fluidifying gas carrying preheating device, a first-stage cyclone separator, a second-stage cyclone separator, a cloth bag dust collecting device and a hydrochloric tail gas device according to a set combination. The method is characterized in that a positive electrode composite powder body cladded by the carbon and the metal oxidesis obtained through fluidized chemical vapor deposition based on a carbon and metal oxide composite cladding modified method of the system. The system and the method have the advantages that the cladding efficiency is high, the technology is simple and controllable, the cost is low, the system and the method are suitable for the scaled industrial production of the carbon and metal oxide compositecladding modified positive electrode material of a lithium ion battery, and better economic benefits and social benefits are achieved.

System and method for coating modification of lithium ion battery positive electrode material with metal oxide

Abstract: The invention relates to a system and a method for coating modification of a lithium ion battery positive electrode material with metal oxide. The system mainly comprises a bunker, a spiral feeder, afeed valve, a fluidized bed reactor, a discharge valve, a product cooler, a product collector, a combustor, a reaction carrying gas preheater, a reaction raw material generator, a reaction raw material nozzle, a fluidized carrying gas preheater, a primary cyclone, a secondary cyclone, a bag collector and a hydrochloric acid tail gas absorber in a preset combination form; and the method is a metaloxide coating modification method based on the system, and allows a metal oxide coated positive electrode composite powder to be obtained through fluidized chemical vapor deposition. The system and the method have the advantages of high coating efficiency, simple and controllable process, low cost, suitableness for the large-scale industrial production of metal oxide coated positive electrode materials of lithium ion batteries, and good economic and social benefits.

The Exploration of Silicon Nanowires as a Stationary Phase Support for Micro Gas Chromatographic Columns

Abstract: In this paper, silicon nanowires were innovatively used as a stationary phase support for micro-fabricated gas chromatographic column ( $\mu \mathrm{GC}$ colunm). The silicon nanowires were grown in-situ in the high aspect ratio microchannels of the $\mu \mathrm{GC}$ colunm, and polydimethylsiloxane (OV-101) was used as the stationary phase. It was demonstrated that the alkane mixture of C6-C10 was well separated by using the $2\ \mathrm{m}\ \mu \mathrm{GC}$ colunm. The separation efficiency of the $\mu \mathrm{GC}$ colunm was as high as 23647 plates/m, which could be attributed to the large surface area of the silicon nanowires.

Improved Peformance of Micro-Preconcentrator Using Silicon Nanowires as a Surface Template

Abstract: In this paper, silicon nanowires (SiNWs) with high specific surface area were used as a surface template to improve the enrichment ability of micro-preconcentrator (μPC). The μPC was fabricated based on MEMS technology. The SiNWs were grown in-situ on the surface of the cavity of the μPC, and then the Tenax-TA was coated. The enrichment abilities of VOCs of the μPC with Tenax-TA and Tenax-TA using SiNWs as a surface template (SiNWs + Tenax-TA) were respectively measured. The enrichment ratio of butyl acetate of the μPC with Tenax-TA was 67.4, and the μPC with SiNWs + Tenax-TA was 193.8, which had an enhancement as high as 188%, suggesting that SiNWs as the surface template of Tenax-TA effectively enhanced the enrichment ability.

Synergistic Enhancement Effect of Palladium-Silver Alloy Nanoparticle Catalysts Towards High-Sensitive Hydrogen Detection

Abstract: For high performance H 2 sensing, PdAg alloy nanoparticle (NP) catalyst with synergistic effect is utilized to enhance the sensitivity of ZnO-based sensors. Compared with single Pd or Ag NPs, PdAg NPs show much higher catalytic activity to H 2 . To form a PdAg enhanced ZnO chemiresistive sensor, ZnO nanowires array is firstly grown onto an integrated MEMS chip and then, PdAg NPs are homogeneously self-assembled onto the surface of ZnO nanowires via an ultrasonic method. Our sensor exhibits highly sensitive to ppm-level H 2 .

Magneto-Elastic μ-Vibrator for Smashing Thrombus

Abstract: A miniaturized thrombus dredger is proposed and developed in this study. The flexural resonance of the µ-resonator dredger is driven by a bulk-extensional magneto-elastic vibrator that is externally excited by alternating magnetic-field. With the fabricated prototype of the resonant dredger, a mice thrombus blocked in a simulated vessel is broken into micro-pieces, and the previously blocked vessel can recover to an unobstructed state within 1 h. A flow-rate ratio detection method is used to evaluate the thrombus-cleaning effectiveness. The comparison between the finite-element simulation and the experimental results validates the flow-rate ratio detection method. By optimally exciting the resonant dredger in its third resonant mode, the flow-rate ratio in the cleaned vessel increases by about 2.7 times compared with that in the partly blocked vessel, and the thrombus is smashed into micro-pieces.

Solenoid Fluxgate Current Sensor Micromachined by Wafer-Level Melt-Metal Casting Technique

Abstract: This paper for the first time reports a practical solenoid-structure fluxgate sensor chip made by MEMS-Casting technology. The size of the sensor is only 1/3 of traditional wire-wound structure. The main progress is that wire break as a main and fatal problem of MEMS-Casting is solved. Wire break which can cause open circuit of the solenoid coils, is result of volume shrinkage during alloy solidification. Compared to previously reported SnBi alloy casted solenoid coils, the employed SnPb alloy can reduce the total resist of solenoid coil by 30%. Such a reduction on resist makes it can meet the thermal budget during practical application. MEMS-Casting method provides an alternative way to make solenoid MEMS fluxgates in addition to electroplating and wire-bonding.

In-Situ Transmission Electron Microscopy Coupled with Resonant Microcantilever for Comprehensive Evaluating Sulfurization Performance of Zinc Oxide Nanowires

Abstract: This paper reports a new technique with in-situ transmission electron microscopy (in-situ TEM) and resonant microcantilever to comprehensively evaluate sulfurization performance of ZnO nanowires. Herein, in-situ TEM is used to real-time observe the sulfurization process of ZnO nanowires under SO 2 -contained atmosphere. Based on temperature-varying micro-gravimetric method, thermodynamic interaction between ZnO nanowires and SO 2 molecules is quantitatively evaluated by resonant microcantilever. By exposing the ZnO nanowires sample to SO 2 -contained atmosphere, a thick shell layer of ZnSO 3 can be formed onto the surface of ZnO nanowires and a novel core-shell nanowire structure of ZnO@ZnSO 3 is obtained finally. According to our comprehensive evaluation results, the ZnO nanowires sample with 100 nm diameter exhibits high reactive to SO 2 molecules and is suitable for SO 2 capture and storage.

Analytical Model and Experiments of Phase Noise in Oven-Controlled Mems Resonators

Abstract: We develop an analytical model of phase noise in an oven-controlled MEMS resonator, which behaves like 1/f. The model reveals that the 1/f like phase noise is up-converted of the self-heating noise of the spring constant. Though the self-heating voltage is white noise, the temperature fluctuation of the spring constant is 1/f like due to the thermal diffusion. When the supporting beam is infinite long, the power of the temperature fluctuation of the resonator are inversely proportional to f. The temperature fluctuation of the real resonator can be simulated by an equivalent circuit model. The temperature fluctuation is further modulated by the relaxation process of resonator damping. The power of the 1/f like phase noise in mechanical resonators is approximately proportional to Q2 when f approaches 0, Q being the quality factor of the resonator. The model matches the experiments qualitatively.

Micro-Reactor Chip for Real-Time Observing Metal-Organic Framework (MOF) nanocrystals grown under in-situ transmission Electron microscopy

Abstract: This work reports a new method for real-time observing the growth process of metal-organic framework (MOF) nanocrystals under in-situ TEM (transmission electron microscopy). For MOF grown via gas-solid reaction, the ligands should be firstly vaporized and then introduced to the surface of metal-contained building-blocks for further gas-solid reaction. One challenge for in-situ TEM observing MOF growth process lies in that it is difficult to directly introduce the solid-state ligand molecules into micro-reactor. Herein, a micro-reactor integrated with SiN x observing windows, gas channel and micro-heater is fabricated for gas-solid growing MOF nanocrystals. The ligand molecules are previously encapsulated in mesoporous silica particles (MSNs) and then sustained released to avoid blocking the tiny capillary channel of the micro-reactor. By using the new method, dynamic process of vaporized H 3 BTC (trimesic acid) ligands reacting with ZnO nanowires for Zn 3 (BTC) 2 nanocrystal growing is successfully observed.

Micro Gas Chromatographic Column Embedded Elliptic Cylindrical Pillars with Low Inlet Pressure and Short Separation Time

Abstract: In this paper, a serpentine micro gas chromatographic (μGC) semi-packed column embedded elliptic cylindrical pillars (ECPs-column) with mesoporous silica as stationary phase was fabricated. Compared with μGC column with cylindrical posts (CPs-column), effective width of ECPs-column was increased by 30%, which could achieve lower pressure drop and shorter separation time. Both μGC columns had been used in experiments of separating alkanes (hexane, heptane, octane, nonane, decane). When the two kinds of μGC columns yielded a minimum height equivalent to a theoretical plate (HETP) of octane, the inlet pressure of the ECPs-column was reduced by 22.7% compared with the CPs-column. Besides, this ECPs-column had shortened the separation time under the same inlet pressure compared with the CPs-column in the separation of alkanes.