TBAB hydrate formation and growth in a microdevice under static and dynamic conditions

The natural gas hydrate has become one of the most promising future green energy sources on the earth.The natural gas hydrates mostly exist in the sediments with porous structure, so a solid understanding of the hydrate formation and growth processes in the porous medium is of significance for the exploitation of natural gas hydrate. The micro-packed bed device is one of the efficient microfluidic devices in the engineering field, but it has been rarely used for the hydrate-based research. In this study, a transparent micro-packed bed device filled with glass beads was developed to mimic the porous condition of sediments, and used to in-situ visualize the hydrate formation and growth habits in the pore spaces under both static and dynamic conditions. For the static experiment, two types of hydrate growth patterns in porous medium were observed and identified in the micro-packed bed device, which were the graincoating growth and pore-filling growth. For the dynamic condition, the hydrate formation, growth,distribution habits and hydrate blockage phenomena in the pore spaces were in-situ visually captured.The impacts of flowrate and subcooling on the pressure variation of the micro-packed bed and the duration of the hydrate growth under dynamic flow condition in pores were in-situ monitored and analyzed. The higher flowrate could result in the faster hydrate growth and more severe blockage in pores, but the effect of subcooling condition might be less significant at the high flowrate.

Ultra-Short Pulsed Laser Manufacturing and Surface Processing of Microdevices

Ultra-short laser pulses possess many advantages for materials processing.Ultrafast laser has a significantly low thermal effect on the areas surrounding the focal point;therefore,it is a promising tool for micro-and submicro-sized precision processing.In addition,the nonlinear multiphoton absorption phenomenon of focused ultra-short pulses provides a promising method for the fabrication of various structures on transparent material,such as glass and transparent polymers.A laser direct writing process was applied in the fabrication of high-performance three-dimensional(3D)structured multilayer microsupercapacitors(MSCs)on polymer substrates exhibiting a peak specific capacitance of 42.6 mF·cm^-2 at a current density of 0.1 mA·cm^-12.Furthermore,a flexible smart sensor array on a polymer substrate was fabricated for multi-flavor detection.Different surface treatments such as gold plating,reducedgraphene oxide(rGO)coating,and polyaniline(PANI)coating were accomplished for different measurement units.By applying principal component analysis(PCA),this sensing system showed a promising result for flavor detection.In addition,two-dimensional(2D)periodic metal nanostructures inside 3D glass microfluidic channels were developed by all-femtosecond-laser processing for real-time surfaceenhanced Raman spectroscopy(SERS).The processing mechanisms included laser ablation,laser reduction,and laser-induced surface nano-engineering.These works demonstrate the attractive potential of ultra-short pulsed laser for surface precision manufacturing.

ADI收购宽带GaAs和GaN放大器专业公司OneTree Microdevices打造完整的电缆基础设施解决方案

Analog Devices,Inc.近日宣布收购位于美国加利福尼亚州Santa Rosa的One Tree Microdevices公司。ADI公司是业界领先的混合信号解决方案供应商,提供从数据转换器、时钟到控制/电源调节等电缆接入解决方案。One Tree Microdevices的GaAs和GaN放大器具有业内最佳的线性度、输出功率和效率,收购该公司及产品组合后,使ADI公司能够支持下一代电缆接入网络的整个信号链。该笔交易的财务条款未予披露。

Droplet morphology analysis of drop-on-demand inkjet printing

As an accurate 2D/3D fabrication tool,inkjet printing technology has great potential in preparation of micro electronic devices.The morphology of droplets produced by the inkjet printer has a great impact on the accuracy of deposition.In this study,the drop-on-demand(DoD)inkjet simulation model was established,and the accuracy of the simulation model was verified by corresponding experiments.The simulation result shows that the velocity of the droplet front and tail,as well as the time to disconnect from the nozzle is mainly affected by density(ρ),viscosity(μ)and surface tension(σ)of droplets.When the liquid filament is about to disconnect from the nozzle,the filament length and filament front velocity are found to have a linear correlation withσ/ρμand ln(ρ/(μσ1/2)).

Modeling the Physical Parameters of Solenoids for MEMS Applications

The paper is devoted to study of the electrical parameters of the motion parts of the MEMS such as solenoids. The analytical background is given in order to describe the influence of the electrical field components on the forces, which are result of interaction of the electromagnetic (EM) field components with the parts of motion devices of MEMS. The given analytical formulas open the ability to calculate the self-inductance of the microsolenoids of the different kind, as well as the stored energy of such motion devices, that could be used for the modeling and optimization of parameters of running devices of MEMS such as actuators, sensors etc.

Single MoTe_(2) sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies engineering

Activating basal plane inert sites will endow MoTe_(2) with prominent hydrogen evolution reaction(HER)catalytic capability and arouse a new family of HER catalysts.Herein,we fabricated single MoTe_(2) sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies introducing.Through the extraction of electrical parameters of single MoTe_(2) sheet,the in-plane and interlayer conductivities were optimized effectively by Te vacancies due to the defect levels.More deeply,Te vacancies can induce the delocalization of electrons around Mo atoms and shift the d-band center,as a consequence,facilitate the adsorption of H from the catalyst surface for HER catalysis.Benefiting by the coordinated regulation of band structure and local charge density,the overpotential at−10 mA·cm^(−2)was reduced to 0.32 V after Te vacancies compared to 0.41 V for the basal plane sites of same MoTe_(2) nanosheet.Meanwhile,the insights gained from single nanosheet electrocatalytic microdevice can be applied to the improved HER of the commercial MoTe_(2) power.That the in situ testing of the atomic structure-electrical behavior-electrochemical properties of a single nanosheet before/after vacancies introducing provides reliable insight to structure-activity relationships.

Hybrid femtosecond laser three-dimensional micro-and nanoprocessing:a review

The extremely high peak intensity associated with ultrashort pulse width of femtosecond(fs)lasers enabled inducing nonlinear multiphoton absorption in materials that are transparent to the laser wavelength.More importantly,focusing the fs laser beam inside the transparent materials confined the nonlinear interaction to within the focal volume only,realizing three-dimensional(3D)micro/nanofabrication.This 3D capability offers three different processing schemes for use in fabrication:undeformative,subtractive,and additive.Furthermore,a hybrid approach of different schemes can create much more complex 3D structures and thereby promises to enhance the functionality of the structures created.Thus,hybrid fs laser 3D microprocessing opens a new door for material processing.This paper comprehensively reviews different types of hybrid fs laser 3D micro/nanoprocessing for diverse applications including fabrication of functional micro/nanodevices.

3D printed millireactors for process intensification

The scope of the present research aims at demonstrating the 3D printing use in the manufacturing of microchannels for chemical process applications. A comparison among digital model processing applications for 3D print(slicers) and a print layer thickness analysis were performed. The 3D print fidelity was verified in several devices, including the microchannels’ printing with and without micromixer zones. In order to highlight the 3D print potential in Chemical Engineering, the biodiesel synthesis was also carried out in a millireactor manufactured by 3D printing. The millireactor operated under laminar flow regime with a total flow rate of 75.25 ml·min^-1(increment of about 130 times over traditional microdevices used for biodiesel production).The printed millireactor provided a maximum yield of Ethyl Esters of 73.51% at 40 ℃, ethanol:oil molar ratio of7 and catalyst concentration of 1.25 wt% and residence time about 10 s. As a result of flow rate increment attained in the millireactor, the number of required units for scaling-up the chemical processes is reduced. Using the approach described in the present research, anyone could produce their own millireactor for chemical process in a simple way with the aid of a 3D printer.

Micro thermoelectric devices:From principles to innovative applications

Thermoelectric devices(TEDs),including thermoelectric generators(TEGs) and thermoelectric coolers(TECs) based on the Seebeck and Peltier effects,respectively,are capable of converting heat directly into electricity and vice versa.Tough suffering from low energy conversion efficiency and relatively high capital cost,TEDs have found niche applications,such as the remote power source for spacecraft,solid-state refrigerators,waste heat recycling,and so on.In particular,onchip integrable micro thermoelectric devices(μ-TEDs),which can realize local thermal management,on-site temperature sensing,and energy harvesting under minor temperature gradient,could play an important role in biological sensing and cell cultivation,self-powered Internet of Things(IoT),and wearable electronics.In this review,starting from the basic principles of thermoelectric devices,we summarize the most critical parameters for μ-TEDs,design guidelines,and most recent advances in the fabrication process.In addition,some innovative applications of μ-TEDs,such as in combination with microfluidics and photonics,are demonstrated in detail.

Casimir Effect in Optoelectronic Devices Using Ferrofluids

Some of the modern electronic and optoelectronic devices exploit ferrofluids contained in narrow gaps between two material plates. When the width of the gap becomes below a micrometer, the boundary plates are subjected to the Casimir force arising from the zero-point and thermal fluctuations of the electromagnetic field. These forces should be taken into account in microdevices with the dimensions decreased to below a micrometer. In this paper, we review recently performed calculations of the attractive Casimir pressure in three-layer systems containing a ferrofluid. We also find the ferrofluidic system where the Casimir pressure is repulsive. This result is obtained in the framework of the fundamental Lifshitz theory of van der Waals and Casimir forces. The conclusion is made that enhanced repulsion due to the presence of a ferrofluid may prevent from sticking of closely spaced elements of a microdevice.

Ultrafast laser processing of materials: from science to industry

Processing of materials by ultrashort laser pulses has evolved significantly over the last decade and is starting to reveal its scientific,technological and industrial potential.In ultrafast laser manufacturing,optical energy of tightly focused femtosecond or picosecond laser pulses can be delivered to precisely defined positions in the bulk of materials via two-/multi-photon excitation on a timescale much faster than thermal energy exchange between photoexcited electrons and lattice ions.Control of photoionization and thermal processes with the highest precision,inducing local photomodification in sub-100-nm-sized regions has been achieved.State-of-the-art ultrashort laser processing techniques exploit high 0.1–1μm spatial resolution and almost unrestricted three-dimensional structuring capability.Adjustable pulse duration,spatiotemporal chirp,phase front tilt and polarization allow control of photomodification via uniquely wide parameter space.Mature opto-electrical/mechanical technologies have enabled laser processing speeds approaching meters-per-second,leading to a fast lab-to-fab transfer.The key aspects and latest achievements are reviewed with an emphasis on the fundamental relation between spatial resolution and total fabrication throughput.Emerging biomedical applications implementing micrometer feature precision over centimeter-scale scaffolds and photonic wire bonding in telecommunications are highlighted.

Microstructuring of carbon/tin quantum dots via a novel photolithography and pyrolysis-reduction process

A novel microfabrication process based on optimized photolithography combined with pyrolysis-reduction is proposed to fabricate interdigital porous carbon/tin quantum dots （C/Sn QDs） microelectrodes.C/Sn QDs active microelectrodes are also employed as current collectors of a micro-supercapacitor （MSC）.A uniform dispersion of Sn QDs （diameter of ～3 nm） in the carbon matrix is achieved using our facile and controllable microfabrication process.The as-fabricated C/Sn QDs MSC obtained by carbonization at 900 ℃ exhibits a higher areal specific capacitance （5.79 mF＆#183;cm-2） than that of the pyrolyzed carbonbased MSC （1.67 mF＆#183;cm-2） and desirable cycling stability （93.3% capacitance retention after 5,000 cyclic voltammetry cycles）.This novel microfabrication process is fully compatible with micromachining technologies,showing great potential for large-scale fine micropatterning of carbon-based composites for applications in micro/nano devices.

Chemical-sensitive graphene modulator with a memory effect for internet-of-things applications

Modern internet of things(IoTs)and ubiquitous sensor networks could potentially take advantage of chemically sensitive nanomaterials and nanostructures.However,their heterogeneous integration with other electronic modules on a networked sensor node,such as silicon-based modulators and memories,is inherently challenging because of compatibility and integration issues.Here we report a novel paradigm for sensing modulators:a graphene field-effect transistor device that directly modulates a radio frequency(RF)electrical carrier signal when exposed to chemical agents,with a memory effect in its electrochemical history.We demonstrated the concept and implementation of this graphene-based sensing modulator through a frequency-modulation(FM)experiment conducted in a modulation cycle consisting of alternating phases of air exposure and ethanol or water treatment.In addition,we observed an analog memory effect in terms of the charge neutrality point of the graphene,Vcnp,which strongly influences the FM results,and developed a calibration method using electrochemical gate-voltage pulse sequences.This graphenebased multifunctional device shows great potential for use in a simple,low-cost,and ultracompact nanomaterial-based nodal architecture to enable continuous,real-time event-based monitoring in pervasive healthcare IoTs,ubiquitous security systems,and other chemical/molecular/gas monitoring applications.

Hybrid microsystem with functionalized silicon substrate and PDMS sample operating microchannel: A reconfigurable microfluidics scheme

A hybrid microsystem with separately functioned temperature controlling substrate and sample operating fluidic microchannel was developed to demonstrate a reconfigurable microfluidics scheme.The temperature controlling substrate integrated a micro heater and a temperature sensor by using traditional silicon-based micromechanical system(MEMS)technique,which guaranteed high performance and robust reliability for repeatable usage.The sample operating fluidic microchannel was prepared by poly-(dimethylsiloxane) (PDMS)based soft lithography technique,which made it cheap enough for disposable applications.The PDMS microchannel chip was attached to the temperature controlling substrate for reconfigurable thermal applications.A thin PDMS film was used to seal the microchannel and bridge the functionalized substrate and the sample inside the channel,which facilitated heat transferring and prevented sample contaminating the temperature controlling substrate.Demonstrated by a one dimensional thermal resistance model,the thin PDMS film was important for the present reconfiguration applications.Thermal performance of this hybrid microsystem was examined,and the experimental results demonstrated that the chip system could work stably over hours with temperature variation less than 0.1oC.Multiple PDMS microchannel chips were tested on one heating substrate sequentially with a maximum intra-chip temperature difference of 1.0oC.DNA extracted from serum of a chronic hepatitis B virus(HBV)patient was amplified by this hybrid microsystem and the gel electrophoresis result indicated that the present reconfigurable microfluidic scheme worked successfully.

Spatially-separated and photo-enhanced semiconductor corrosion processes for high-efficient and contamination-free electrochemical nanoimprint lithography

Free of any thermoplastic or photocuring resists, electrochemical nanoimprint lithography(ECNL) has emerged as an alternative nanoimprint way to fabricate three-dimensional micro/nano-structures(3D-MNSs) directly on a semiconductor wafer by a spatially-confined corrosion reaction induced by the metal/semiconductor contact potential. However, the consumption of electron acceptors in the ultrathin electrolyte between imprint mold and semiconductor wafer will slow down or even cease the corrosion rate. To solve this problem, we change the short-circuited corrosion cell into a spatially-separated primary cell: the imprint mold compacted gallium arsenide(GaAs) wafer in the anodic chamber while the platinum(Pt) plate connected to the imprint mold in the cathodic chamber. Thus, the GaAs corrosion rate will be stabilized in its limiting steady-state current density because of the abundant source of electron acceptors in the catholic chamber. The corrosion processes can be photo-enhanced by white-light illumination. Consequently, both the accuracy and the efficiency are promoted dramatically, which are demonstrated by the excellent performance of the fabricated binary optical elements. Moreover, the contamination problem caused by the electron acceptors is totally avoided. All the results prove that this novel ECNL mode is competitive and prospective in imprinting 3D-MNSs directly on semiconductor wafer.

Microfabricated platforms to investigate cell mechanical properties

Mechanical stimulation has been imposed on living cells using several approaches.Most early investigations were conducted on groups of cells,utilizing techniques such as substrate deformation and flow-induced shear.To investigate the properties of cells individually,many conventional techniques were utilized,such as AFM,optical traps/optical tweezers,magnetic beads,and micropipette aspiration.In specific mechanical interrogations,microelectro-mechanical systems(MEMS)have been designed to probe single cells in different interrogation modes.To exert loads on the cells,these devices often comprise piezo-electric driven actuators that attach directly to the cell or move a structure on which cells are attached.Uniaxial and biaxial pullers,micropillars,and cantilever beams are examples of MEMS devices.In this review,the methodologies to analyze single cell activity under external loads using microfabricated devices will be examined.We will focus on the mechanical interrogation in three different regimes:compression,traction,and tension,and discuss different microfabricated platforms designed for these purposes.