We present an experimental set-up for the production of a beam source of cold 87Rb atoms, which is formed from a
trapped cold atomic cloud in a three-dimensional (3D) magneto-optical trap (MOT). Via a radiation pressure difference
generated by a specially designed leak tunnel along one trapping laser beam, the atoms are pushed out continuously with
low velocity and high flux. The beam was measured to have a mean velocity of 12m/s and a longitudinal velocity spread
of about 3m/s under nominal experimental conditions, based on the fluorescence and the time of flight (TOF)
technologies. And its flux can be tuned by adjusting the MOT parameters from 108 to 109 atoms/s. Especially the beam
performance dependence on trapping laser detuning and power is experimentally studied.
Two longitudinally multimode Febry-Perot diode lasers have been sideband injection-locked to the +1 and -1
sidebands of a 3.4GHz electro-optical modulator (EOM). Optical heterodyne measurement showed that powers of 99.5%
of the slave laser could be injection-locked to the +1 or -1 sidebands, and the unselected master laser carrier was
suppressed down to -24dB. Generally, the long-term stability and efficiency of the injection-locking to the +1 sideband
was worse than the -1 due to the asymmetry of the injection-locking bandwidth. The microwave signal at 6.8GHz had a
measured 3dB linewidth of less than 200Hz, without considering the noise contribution by the driving signal of the
additional acousto-optical modulator. The proposed method will be used for driving the stimulated Raman transitions in a
Rubidium based atom gyroscope.
The researches of single cell's control and operation are the hotspots in whole world. Among the various technologies,
the transmission of ectogenic genetic materials between cell membrane is very significant. Imitating the Chinese
traditional acupuncture therapy, a new ultrasonic resonance driving method, is imported to drive a cell's penetration
probe. A set of the single cell penetration system was established to perform this function. This system includes four
subsystems: driving part, micromanipulation part, observation and measurement part, and actuation part. Some fish egg
experiments indicate that this system is workable and effective.
Piezoelectric micro nebulizer is a typical piezoelectric-solid-liquid coupling problem. A 2D FEM model was presented
for this system. Numerical results show that when the piezoelectric actuator is vibrated, nozzle film also is generated
vibration, and the phase relationship occurs to them, and the operation at the second resonance frequency is more
desirable than others. A good agreement between experimental results and theoretical results confirmed the validity of
the theoretical model we developed. Therefore, the design of micro nebulizer to consider only the amplitude of
piezoelectric vibration is not comprehensive, we must also consider the nozzle film vibration, as well as the phase
between the back film and the nozzle film, and this can provide guidance for the optimal design of micro nebulizer.
In recent years, many kinds of 1-dimension nano-materials (Carbon nanotube, ZnO nanobelt and nanowire
etc.) continue to emerge which exhibit distinct and unique electromechanical, piezoelectric, photoelectrical
properties. In this paper, a 1-dimension nano-materials-based device was proposed. The bottom-up and
top-down combined process were used for constructing CNT-array-based device and ZnO nanowire device.
The electrical characteristics of the 1D nano-materials-based devices were also investigated. The
measurement results of electrical characteristics demonstrate that it is ohm electrical contact behavior between
the nano-material and micro-electrodes in the proposed device which also have the field effect. The proposed
1D nano-material-based device shows the application potential in the sensing fields.
Planar Microtoroid cavities with ultrahigh quality factor have very strong confined function to the electromagnetic wave
coupled into them due to their novel ring-like structures. Therefore, they have very good applications in high sensitivity
sensors and other micro optics components. In this paper, the Planar Microtoroid cavity and its coupling system
constructed together with the tapered fiber are introduced. Then, micro sensors based on the above coupling system are
designed. These sensors measure environmental parameters by means of monitoring the changes in the transmission
spectrum of the high finesse Planar Microtoroid cavities, obtaining fine resolution and high accuracy due to their
ultrahigh quality factor (Q) performance. The sensitive mechanism and the feasibility are demonstrated through optical
and mechanical software simulation. With software BeamPROP, the evident resonance and strengthened phenomenon to
the electromagnetic wave coupled into the micro-cavity are shown, which have a big relation with the light frequency.
The results indicate that, Planar Microtoroid cavity is very promising in designing new micro sensors.
We present simulation and experimental studies of a piezoelectrically actuated microdiaphragm air pump, which is characterized by thin structure, large flow, and low power consumption. A novel large-displacement actuation structure is designed for the air pump. A prototype of the micro air pump is fabricated by precise fabrication. Furthermore, studies of modeling, simulation, and experiments are carried out. The experimental and simulation results demonstrate that both the pump's flow and the amplitude of the actuation structure's motion depend on the frequency of the input voltage. The maximal values of the flow and the amplitude will be obtained when the frequency of the input voltage is equal to the actuation structure's first-order natural frequency. The diaphragm air pump has the best performance when it works in resonance mode. With 20-V input, the flow and the amplitude of the air pump are 4.5 ml/s and 0.00041 m, respectively, and the power consumption of the pump can be as low as 3.18 mW. With the advantages of large flow, thin structure, and low power consumption, the diaphragm air pump has great potential applications for air supply for microfuel cells or the cooling of electronic devices.
Micro machine vision system is an important part of a micromanipulating system which has been used widely in many fields. As the research activities on the micromanipulating system go deeper, micro machine vision system catches more attention. In this paper, micro machine vision system is treated as a kind of machine vision system with constrains and characteristics introduced by specific application environment. Unlike the traditional machine vision system, a micro machine vision system usually does not aim at the reconstruction of the scene. It is introduced to obtain expected position information so that the manipulation can be accomplished accurately. The architecture of the micro machine vision system is proposed. The key issues related to a micro machine vision system such as system layout, optical imaging device and vision system calibration are discussed to explain the proposed architecture further. A task-oriented micro machine vision system for biological micromanipulating system is shown as an example, which is in compliance with the proposed architecture.
A preparation method of cold atomic beam with fine optical characteristics is presented and discussed in this paper. The method is described as followings: cold atoms in three-dimension magneto-optical trap (3MOT) are pushed out because of the imbalanceable resonance-radiation pressure and form a cold atomic beam, whose propagation is limited in a magnetic guide. And then the atomic beam is further transversely compressed by use of two-dimension magneto-optical trap (2MOT). Finally, a state preparation laser processes the atomic beam. Consequently, the continuous cold atomic beam with lower longitudinal velocity, higher flux, much less transverse velocity and homogenous state is obtained. The simulation results show that the preparation method is feasible, which can be used in the establishment of the high-property atom interferometer.
A 3D model of a piezoelectrically actuated microjet was built to characterize acoustic wave propagation in liquid produced by the vibration of a piezoelectric transducer. The model considered the coupling between the piezoelectric transducer, the liquid and the nozzle film. Modal analysis was carried out based on numerical simulation to study the field of pressure wave. The contours of amplitude of pressure wave on the liquid-solid interface at the nozzles inlet were obtained under different resonant frequency. The results demonstrated that the transducer dominated vibration mode with an axis-symmetric distribution is more efficient for the device operation than others. The results also indicated that pressure distribution in the liquid chamber is related to driven frequencies in a different way from that of displacement of structure. The impedance analyzer was used to measure the resonant frequencies of the microjet system and validate the simulation results experimentally. The experimental results agreed well with the predicted. The microjet we developed has the optimum frequency of about 36.5KHz, which corresponds to the first axis-symmetric vibration mode dominated by the transducer, as is predicted well by the simulation result. According to comparison of pressure wave field with nozzle layout of present design under different resonant frequencies, the phenomena that the microjet behaves differently under different orders of resonant vibration are explained, and a frequency design for nozzles layout are presented according to the simulation result.
Micro gas pump is one of the important micro fluidic components, which can be used for gas analysis in chemical, air supply of micro fuel cell and micro fluid cooling systems. Pumping gases requires a strong compression ratio inside the pump chamber for gas could be compressed. This paper presents a micro diaphragm air pump actuated by PZT bimorphs, which characterizes thin structure, large air flow and low power consumption. The diaphragm air pump is made up of a cavity and an actuating structure. The actuating structure consists of two PZT bimorphs and a diaphragm with check valves, which could produce large volumetric change ratio. Then, a prototype of the pump whose cavity's dimension is 60×16×2mm was fabricated by precise manufacture. The mathematical models were established and simulation had been carried out, in which the parameters, such as flow rate, diaphragm's vibrating amplitude and resonant frequency are calculated and analyzed. Furthermore, experiments on the pump were carried out. The experimental data are basically agreement with the simulation results. With a voltage of 20V, the air pump's flow is 85.3ml/min in resonance and its power consumption is only 3.18mW. Simulations and experiments show that the diaphragm air pump has high efficiency and good performance. It also shows good application prospects in air supply for micro fuel cell and micro electronic devices' cooling.
As micro electro-mechanical system (MIEMS) technology matures as an industry, the integration of standard integrated circuit and multi-MEMS-sensors will continue to increase. When assembling multi-sensors into a micro electro-mechanical system, usually exists axis-misalignment problem, which will inevitably induce large measurement error. This paper proposes an error compensation scheme based on optical alignment for solving this problem. A functional explanation is followed by a brief description of the optical layout. The computation including investigation and compensation to the axis-misalignment is covered later. Finally tests are conducted with a micro electro-mechanical azimuth-level detector to prove the validity of the method.
The tunneling effect is a kind of quantum effect used extensively. The sensor based on tunneling effect has some advantages, such as high sensitivity, rapid response, low power consumption, low driving voltage and so on. In particular, combined with the MEMS technology, tunneling effect has shown a good application foreground in micro sensor fields. According to the quantum mechanics, such as Schordinger's equation, the theory models of tunneling effect are presented in this paper. Also the expressions of the transmission coefficient and tunneling current about the tunneling barriers are obtained. On the basis of these, a kind of MEMS micro magnetometer based on tunneling effect is presented. The mechanics model of the membrane, which is the key component and is subjected to the axial residual stress at both ends, is founded. The membrane's parameters are optimized and simulated. Some key fabrication processes of the micro magnetometer, such as silicon wafer, glass, combined plate process are developed. Further more, the prototype ofthe MEMS micro magnetometer based on tunneling effect is fabricated.
A MEMS based micro colloid thruster (including an source emitter array and an extractor) is designed, fabricated and tested. Source emitter array of the thruster is silicon column etched by ICP. The negative electrode on the extractor can be controlled separately. After bonding together, a single emitter and extractor works on an electrical colloid propulsion principle, and produce µN order thrust. Such a small and controllable thrust is the urgent requirement for a micro-satellite. Thrust test for the micro colloid thruster is made in high vacuum box. Thrust is acted on a cantilever beam, and the displacement of cantilever beam is detected by a current vortex sensor. Analysis to the recording data shows that the maxim thrust produced by a single emitter is about 2 µN, which is agreement with theory estimate.
Microfluidics is an important technology for applications including those for chemistry/biology! medicine and those as tools for fundamental researches. Some microfluidic devices developed seemed to function as sheer miniaturized copies ofthose macro devices and most ofthem lacked sufficient cares ofthose dominant forces in micro scale, e.g. fluid-solid interactions, or only tried to avoid their influences. In fact, the active utilizes of micro scale significant forces tend naturally to be more suitable to manipulate and control flows in micro channels. In addition, the lack of the sufficient fundamental studies on micro flow phenomena and a robust and cost-effective integrating technology, making various functional devices together into a system of specific application, has been always a bottleneck problem in the development of microfluidics. In this review, we discussed some selected topics, which are of certain basic importance and concern what have been developed or are being undergone in our group. Some phenomena, which are incapable of been explained by classical Navier-Stokes theory, has been discussed and the characteristics of flows in micro systems have been described. Some examples of devices developed by our group were provided to further the discussion.
Precision positioning and fine motion are needed in many fields, such as micro electromechanical system, ultra-precision machine, optical alignment and integrated circuit manufacture, so it is indispensable to develop precision planar stage. A precision stage driven by one piezoactuator is made to achieve three degrees of freedom motion in plane. To realize precision positioning, movement of the stage should be detected and corresponding control scheme should be designed. A displacement detection system based on image processing is developed to measure three degrees of freedom displacement of the planar stage. The core parts of the system are CCD camera, microscope, image collection and image processing. Large rotation of the planar stage has no influence on displacement detection of the system. The system could obtain high resolution together with relatively large detection range. Performance of the planar stage is tested by the displacement detection system. Interference movements of the stage are less than the main movements. Movements of the planar stage in any direction are obtained by logical open-loop control. Micro motions detected by laser interferometer indicate the stage has very high resolution.
As a non-invasive drug delivery method, atomizing drug delivery method has become an investigating hotspot in the fields ofpharmacy and medical instruments, and has widely potential applications in the future. It is used for delivery of antibiotic, antiviral drug, anti hypertension drug, angina drug, and other drugs including peptide or protein ingredients, even bacterin and biologic synthetic. This paper proposes a piezoelectric array microjet based on MEMS, which is formed by piezoelectric transducer bonded to a silicon chip with nozzles. Droplet diameter is one of the key parameters of the microj et, and has an important effect on detailed deposit position. The processing drag, surface tension and inertia force must be overcome through continuous pressing wave produced by the piezoelectric transducer, and droplet can be squeezed out of the cavity. The theoretical problems on the characteristics of the microjet have been discussed. Conclusions are useful for the design of the microjet.
In this paper, a novel surface micromachined optical switch with a micro vertical SU-8 mirror is reported. Using stress-induced bending of a polysilicon/silicon nitride bimorph beam, a vertical mirror is raised above the substrate. The beam with the mirror is attracted to the substrate by applying a voltage to switch the transmission state to the reflection state of the optical switch. The mirror displacement is about 250 micrometers . The roughness of the sidewall of the gold-coated SU-8 mirror is measured to be 53.5 A for the average roughness (Ra) and 71.3 A for the root mean square (rms). The verticality of the SU-8 mirror is 89.1 degree(s). The insertion loss is measured to be 2.9 dB in the transmission state and 4.1dB in the reflection state for multi-mode fibers. The structure of the switch provides us a possibility of expanding to a large matrix of optical switches.
KEYWORDS: Fermium, Frequency modulation, Neural networks, Manufacturing, Artificial intelligence, Computer simulations, Evolutionary algorithms, Control systems, Decision support systems, Computing systems
In this paper, scheduling problems, including description, solving, and rescheduling, are presented in detail. The scheduling flexibility is an important factor to affect the system flexibility.
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