Simulation and fabrication of magnetic rotary microgenerator with multipolar Nd/Fe/B magnet

This study presents a high power rotary-type electromagnetic microgenerator with multilayer planar copper (Cu) microcoil and multipolar hard magnet of Nd/Fe/B. The size of this microgenerator is smaller than 1 cm³ in volume. It can achieve the goal of compact integrated system. The induced voltage is simulated by FEMLAB and MATLAB software to solve the coupling problem, which involves in kinetic and electric issues. The multilayer microcoil is fabricated by MEMS process (micro-electro mechanical system), and the multipolar magnet is fabricated using sintering process. The sintered Nd/Fe/B exhibits an excellent hard magnet with B_r of 1.44 T and H_c of 975 kA/m. Next, the multipolar magnet rotates relative to planar microcoil to induce electric current. The preliminary result shows that maximum induced voltage of 111.2 mV and maximum power of 386.42 μW can be achieved. Besides, the experimental result is compared with simulated one.     

柔性膜式微型电磁驱动器的设计与仿真分析

硅橡胶具有生物兼容性好且制作技术与微细加工工艺兼容的优点,采用硅橡胶作为MEMS驱动器中的振动膜具有较好的应用前景。研究了一种微型电磁驱动器,由内嵌永磁体阵列的柔性硅橡胶(PDMS)振动膜和线圈两层构成,采用电镀工艺制作线圈层;采用电镀方法制作磁体阵列,由甩胶机旋涂硅橡胶并进行固化,制作内嵌磁体阵列的硅橡胶膜,对磁体磁化后可作为双向驱动器。对该驱动器进行了理论分析与数值模拟,采用有限元分析工具ANSYS对微驱动器的电磁驱动力及其挠度进行分析,二者结果基本一致,振动膜中心最大挠度的分析误差为7.96%,其一阶固有频率的分析误差为16.1%。     

Theoretical analysis and optimization of electromagnetic actuation in a valveless microimpedance pump

The construction of a novel valveless microimpedance pump is proposed and the utilized electromagnetic actuator is designed and optimized in this study. The actuating mechanism comprises an electroplated permanent magnet mounted on a flexible PDMS diaphragm and electroplated Cu coils located on a glass substrate. The electromagnetic force between the magnet and the Cu coils causes the diaphragm to deflect and then creates the accumulative effects of wave propagation and reflection at the junction of the compressible and rigid sections. The resulting pressure gradient in the fluid drives the flow from the inlet to the outlet of the micropump. The constituent parts of the electromagnetic actuator, namely the diaphragm, the microcoils, and the magnet are modeled and analyzed in order to optimize the actuator design. The design models are verified both theoretically and numerically and the relationships between the magnetic force, diaphragm displacement, and diaphragm strength are established. The magnitude of the magnetic force acting on the flexible diaphragm are calculated using Ansoft/Maxwell3D FEA software and the resulting diaphragm deflection simulated by ANSYS FEA software are found to agree with the theoretical predictions. Different diaphragm shapes are investigated and their relative strength and flexibility are compared. It is found that a circular PDMS diaphragm represents the most appropriate choice for the actuating mechanism in the micropump. The desired diaphragm deflection of 15 μm is obtained using a compression force of 16 μN, generated by a coil input current of 0.9 A. The diaphragm deflection can be regulated by varying the current passed through the microcoil and hence the flow rate can be controlled. The valveless microimpedance pump proposed in this study is easily fabricated and can be readily integrated with existing biomedical chips due to its plane structure. The results of the present study provide a valuable contribution to the ongoing development of Lab-on-a Chip systems.     

一种使用平面线圈结构的微型电磁继电器

本文介绍一种采用平面线圈结构的微型电磁继电器的制造工艺和理论分析。这种继电器的大小大约是 4mm× 4mm× 0 .5mm ,工艺比较简单 ,主要采用光刻、蒸镀、电镀和腐蚀牺牲层等普通的微加工技术来完成全部制作工艺。因此可以大大地降低继电器的生产成本、物理尺寸和制造的复杂性。另外 ,还进行了一些有关线圈通过激励电流后对活动电极产生电磁力的理论计算和仿真 ,利用这些结果可以对这种电磁继电器的结构和参数进行优化设计     

高能量密度微电磁驱动器的制作方法

提出了一种非闭合磁路型高能量密度微电磁驱动器的制作方法,即利用MEMS工艺在单位面积硅基体上制作多匝、高深宽比的平面线圈和高厚度的磁芯.通过先面电铸再线电铸的方式,以及动态控制电铸电流密度的方法进行平面线圈的制作;通过改变衬底表面粗糙度和种子层厚度的方法,改善合金镀层与衬底的粘附性能,可以在单位面积的硅片上,制作出厚度更大的磁性合金镀层.初步实验结果表明：该微型电磁驱动器在相同的输入功率下,比同类其他微电磁驱动器,能产生更大的电磁驱动力,具有更高的能量密度.     

高能量密度微电磁驱动器的制作方法

提出了一种非闭合磁路型高能量密度微电磁驱动器的制作方法,即利用MEMS工艺在单位面积硅基体上制作多匝、高深宽比.的平面线圈和高厚度的磁芯.通过先面电铸再线电铸的方式,以及动态控制电铸电流密度的方法进行平面线圈的制作;通过改变衬底表面粗糙度和种子层厚度的方法,改善合金镀层与衬底的粘附性能.可以在单位面积的硅片上,制作出厚度更大的磁性合金镀层.初步实验结果表明:该微型电磁驱动器在相同的输入功率下,比同类其他微电磁驱动器,能产生更大的电磁驱动力,具有更高的能量密度.     

Superconducting magnet system containing Bi-2212/Ag Coil Generates 21.8 T at 1.8K

We fabricated a Bi-2212/Ag double stacked pancake coil of 13 mmØ) in inner bore and of 46.5 mmØ in outer diameter, by using Bi-2212/Ag tapes prepared by the combination of continuous dip-coating process and melt-solidification technique. This small superconducting magnet was used as an insert magnet of a conventional superconducting magnet system and tested at saturated superfluid helium temperature (～ 1.8K) in various bias fields. The generated field of Bi2212/Ag coil was 0.9 T, with I_c of 310 A(criterion 10^-13Ω·m), in the bias field of 20.9 T. Thus, this superconducting magnet system achieved generation of magnetic field of 21.8 T in the full superconducting state.     

A Planar CMOS Field-Emission Vacuum Magnetic Sensor

We have fabricated a CMOS vacuum magnetic sensor that exploits the deflection of an electron beam produced by field emission by a perpendicular magnetic field. The device is planar and fabricated by conventional lithography and etching processes. An extremely high magnetic field sensitivity of $hbox{4} times hbox{10}^{3}%/hbox{T}$ is reported.      

Design,simulation, fabrication and characterization of a micro electromagnetic vibration energy harvester with sandwiched structure and air channel

This paper presents the design, simulation, fabrication and characterization of a novel electromagnetic vibration energy harvester with sandwiched structure and air channel. It mainly consists of a top coil, a bottom coil, an NdFeB permanent magnet and a nickel planar spring integrated with silicon frame. The prototype is fabricated mainly using silicon micromachining and microelectroplating techniques. The tested natural frequency of the magnet–spring system is 228.2 Hz. The comparison between the simulation and the tested results of the natural frequency shows that the Young's modulus of microelectroplated Ni film is about 163 GPa rather than 210 GPa of bulk Ni material. Experimental results indicate that the sandwiched structure and the air channel in the silicon frame of the prototype can make the induced voltage increase to 42%. The resonant frequency of the prototype at 8 m/s² acceleration is 280.1 Hz, which results from the nonlinear behavior of the magnet–spring system. The load voltage generated by the prototype is 162.5 mV when the prototype is at resonance and the input vibration acceleration is 8 m/s² and the maximal load power obtained is about 21.2 μW when the load resistance is 81 Ω.     

Synthesis and electromagnetic absorption properties of polypyrrole/BaFe12O19–Ni0.8Zn0.2Fe2O4/multi-walled carbon nanotube composites

The nanocomposite of hard ferrite (BaFe₁₂O₁₉)/soft ferrite (Ni_0.8Zn_0.2 Fe₂O₄) was prepared by using a sol–gel method, and then the polypyrrole/nanocomposite ferrite/multi-walled carbon nanotube composites were fabricated by an in situ polymerization process. Experimental results, such as X-ray diffraction (XRD), transmission electron microscope (TEM), fourier transform infrared (FTIR) and Raman spectra analyses indicated the formation of PPy and BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄ on the surface of carbon nanotubes. The conductivities of the composites were enhanced with the increasing of MWCNTs׳ content and the value reached 19.514 S/cm in the presence of 30% MWCNTs. However, the magnetic properties did not show any obvious changes. The electromagnetic properties of MWCNTs (5%) composites exceeding −10 dB ranged from 8.5 to 10.3 GHz and the maximum loss value was −25.46 dB at 8.9 GHz. The introduction of MWCNTs had an important influence on the electrical and microwave absorbing properties of the nanocomposite.     

New design concept of the magnet system generating the high pulsed field in combination with the bias field of the superconducting magnet

A new design concept of the axisymmetric magnet system generating the very high pulsed magnetic field which is superimposed on the bias magnetic field of the superconducting magnet is presented. The pulsed magnet consists of two coaxial coils which are wound in opposite directions. The geometry of both pulsed coils, i.e. the working (inner) one and the compensating (outer) one is designed in such a way that the mutual coupling between the small pulsed magnet and the outer superconducting magnet is practically zero. This configuration prevents the rise of the high induced voltage on the current leads of the superconducting magnet when the pulsed magnet is being energised, hence resulting naturally in protection of the system (superconducting magnet and the current source) against possible damage. Further, it is predicted that the stray field of the pulsed magnet, which gives rise e.g. to the eddy currents in the winding of the superconducting magnet, is considerably decreased. The simple theory enabling the design of the geometry of the compensating pulsed coil is derived. The advantages of this new concept are demonstrated on the results of the theoretical analysis using, as an example, one of the pulsed coils that were designed and fabricated in the Clarendon Laboratory, in connection with the Oxford Instrument superconducting magnet (Clarendon hybrid outer) which can generate a steady magnetic field up to 10 T in a room temperature working space with a diameter of 240 mm.     

Magnetic levitation with unlimited omnidirectional rotation range

We have realized a magnetic levitation device in which the motion of a levitated body can be stably controlled in any orientation, with no limits on its spatial rotation range. The system consists of a planar array of cylindrical coils on a fixed base, a levitated frame containing disc magnets and LED position markers, and an optical motion tracking sensor for feedback control of levitation. This system combines the capabilities of fine positioning, vibration isolation, and a spherical motor, with potential applications in omnidirectional antenna and camera pointing, user interaction, manipulation, and simulated spaceflight dynamics and control. The device design is presented including the magnet and coil configuration, analysis and control methods, and position and rotation trajectory control results.The system development process consisted of numerical analysis of electromagnetic forces and torques between coils and magnets, to find the maximum required coil currents for levitation and the condition numbers of the transformation matrices between coil currents and forces and torques generated on the levitated body, for various configurations of coils and magnets, over their full 3D translation and rotation ranges. As a result, a magnetic levitation setup consisting of an array of 27 coils and a levitated object with six disk-shaped permanent magnets was selected. The setup achieved levitation in six degrees of freedom and unlimited rotation about any axis at a fixed height of 40 mm (a 4 mm minimum height above the coil array). The performance was verified with levitated trajectory following rotation command experiments in roll, pitch, yaw, and including 360° rotations about non-principal axes.     

MWECR CVD系统中磁场梯度对a-Si∶H薄膜沉积速率的影响

为了定量地得到磁场梯度对a-Si∶H薄膜沉积速率的影响,对单磁场线圈分散场MWECR CVD系统等离子体室和沉积室中用三种方法得到的磁场形貌进行了研究.通过洛伦兹拟合的方法定量地得到了这些磁场形貌的磁场梯度.结果表明,样品台下面放置钐钴永磁体并使磁场线圈电流为137.7A时其衬底附近磁场梯度值最大,样品台下面无钐钴永磁时,磁场线圈电流分别为137.7A和115.2A的磁场梯度值依次为次之和最小.制备a-Si∶H薄膜时,在衬底附近具有高的磁场梯度值可以得到高的沉积速率.通过红外吸收谱技术分析,虽然样品台下面放置钐钴永磁体并使磁场线圈电流为137.7A下能得到最大的沉积速率,但是沿样品台半径方向沉积速率呈现很明显的不均匀分布.     

Design of multilevel pyramidically wound symmetric inductor for CMOS RFIC’s

This paper presents the design of a multilevel pyramidically wound symmetric (MPS) inductor structure. Being multilevel, the MPS inductor achieves high inductance to area ratio and hence occupies smaller silicon area. The symmetric inductor is realized by winding the metal trace of the spiral coil down and up in a pyramidal manner exploiting the multilevel VLSI interconnects technology. Closed form expressions are also developed to estimate the self resonating frequency (f _res ) of the MPS inductor and results are compared to two layer conventional symmetric and asymmetric stack. The estimation is also validated with full wave electromagnetic simulation. The performance of various MPS inductors of different metal width, metal offsets and outer diameter is demonstrated. For an inductance of 8 nH, the MPS inductor reduces the area by 65–95% over conventional planar symmetric inductors and 71–94% over its equivalent pair of asymmetric planar inductors. The performance is also compared to other symmetric inductors reported in literature. With MPS inductor, the cost and size of RF IC’s will be reduced significantly.     

基于SH0导波的电磁超声换能器设计与实验研究

传统基于周期性永磁体的电磁超声换能器结构较复杂,为此该文提出了一种由单一永磁体和导线阵列线圈构成的电磁超声换能器(EMAT)用于激发板中的SH0导波。首先叙述了设计的原理,并采用有限元软件进行三维数值仿真分析,利用水平极化永磁体垂直于板面的磁场在铝板中成功激发出SH0导波。为使EMAT换能效率达到最优,研究长和宽为10 mm×25 mm的永磁体,其高度及线圈匝数不同时EMAT激励的效率。仿真结果表明,选用永磁体高度为25 mm及线圈匝数为37时EMAT换能效率和声场指向性较好。在此基础上,通过实验研究了不同线圈匝数对换能器换能效率的影响,实验结果与仿真结果一致,充分验证了该文设计EMAT的方法具有可行性。     

3D Helmholtz coil system setup for thermal conductivity measurements of magnetic nanofluids

This study aims to design a mechatronic system that involves a 3D Helmholtz coil system implemented with the 3ω method to measure the thermal conductivity of magnetic nanofluids under uniform and rotating magnetic fields. For this purpose, a 3D Helmholtz coil system was designed and manufactured to generate a uniform and rotating magnetic field up to 400 G. First, the uniformity and rotation abilities of the magnetic field generated by the system were investigated numerically and experimentally. The investigations pointed out that the 3D Helmholtz coil system can generate a uniform magnetic field in 1D, 2D, and 3D with a maximum non-uniformity factor of 0.0016. After that, the thermal conductivity of Fe₃O₄ – water magnetic nanofluid samples with 1, 2, 3, 4, and 4.8 vol.% were measured under 1D, 2D, and 3D uniform magnetic field application. The magnetic field was applied at different direction angles between X, Y, and Z axes in the Cartesian coordinate system. The results pointed out that the thermal conductivity of the samples increases as the magnetic field and particle concentration increase. The maximum thermal conductivity enhancement was observed as ∼9.1% and the minimum thermal conductivity was observed as ∼1.9% when the magnetic field is applied in parallel and perpendicular directions, respectively. The measurement results also pointed out that under the external uniform magnetic field application at 2D and 3D, thermal conductivity enhancement is less affected by the particle concentration increment.     

Fabrication and enhanced field emission properties of novel silicon nanostructures

We reported the fabrication and the field emission properties of two-tier novel silicon nanostructures. First, silicon nanopillars with ordered high aspect ratio were achieved by using conventional lithographic techniques to act as the field emission sources. Second, sharp-edged well-aligned silicon nanograss was fabricated on top of the nanopillars by means of hydrogen plasma dry etching to induce the field emission characteristics. The turn-on fields were obtained as 10.5 and 14.4 V/μm under current density of 0.01 mA/cm² for two-tier patterns separated by respective 5 μm and 2 μm spaces. The excellent field emission property from these novel nanostructures exhibited a great potential as high-performance field emitter arrays towards future nanoelectronic devices.     

Fabrication of suspended thin film resonator for application of RF bandpass filter

Characteristics of AlN thin film and thin film resonator for RF bandpass filter have been studied. AlN thin films were deposited by RF magnetron sputter system. Deposition parameters such as N₂ contents, Ar and N₂ partial pressures, and the distance between metal target and substrate were found to affect the piezoelectric response. To fabricate the suspended thin film resonator (STFR) using the piezoelectric AlN thin film, the etching of AlN and the surface micromachining process were conducted. The thickness of AlN film and membrane for the STFR are 2 and 15 μm, respectively. This membrane was fabricated by SOI technology. The device with the dimension of 160 × 160 μm² has a resonant frequency of 1.653 GHz, a K_eff² of 2.4%, a bandwidth of 17 MHz, and a quality factor of 91.7. The device with the dimension of 200 × 200 μm² has a resonant frequency of 1.641 GHz, a K_eff² of 1.2%, and a bandwidth of 9 MHz, and a quality factor of 50.2.     

Dielectric properties of Fe-doped BaxSr1−xTiO3 thin films on polycrystalline substrates at temperatures between −35 and +85 °C

Large-area Ba_xSr_1−xTiO₃ (BSTO-x) thin films, partially Fe-doped, have been grown by pulsed laser deposition (PLD) on technically relevant polycrystalline alumina based ceramics. The capacity (dielectric constant _r) and Q-factor of planar Pt/BTO:Fe/Pt capacitors were investigated within a temperature range from −35 to +85 °C. The applied DC-bias voltages were up to 10 V and the measurement frequency was 1 kHz.Although operating in the ferroelectric state below the Curie temperature, pure BaTiO₃ (BTO) thin films showed the smallest variation of _r within the temperature range from −35 to +85 °C compared to BSTO-0.6 and BSTO-0.8. The temperature dependence of _r below the Curie temperature (ferroelectric state) seems to be smaller than above the Curie temperature (paraelectric state) for the BSTO-x system. A homogeneous tunability of the capacity of about 60% was achieved for applied electrical DC voltages resulting in electrical field strengths between 0 and 5 V/μm within the whole temperature range. The Q-factor of 2 μm thick BTO films increases with increasing DC bias voltage. Furthermore, by Fe-doping of BTO films Q-factors could be increased by a factor of three up to about 70 compared to the not doped films. In addition, the temperature dependence of capacity is considerably influenced by Fe-doping.At a microwave frequency of 30 GHz high _r values of about 1500 were measured for large-area BSTO-0.45 films at room temperature deposited directly on microwave ceramic substrates. Low values of tanδ of about 0.003 were measured for the PLD-BSTO-0.45 films which corresponds to a Q-factor of more than 300. The results show the potential of ferroelectric BTO thin films for applications as tunable electronic devices in a wide temperature range.     

槽楔材料对PMLSM电磁特性的影响

为提高PMLSM的电磁性能并降低齿槽力和推力波动,文中提出一种在直线电机槽口安装槽楔的解决方案。槽楔材料对电机性能影响较大,为了使电磁性能最佳,文中以分数槽永磁直线同步电机为研究对象,分析了槽楔材料为硬磁、软磁和非磁时对电机气隙系数的影响。利用有限元法对比分析了3种槽楔材料下电机的气隙磁场、反电动势、齿槽力和推力波动等电磁性能,并对不同负载下削弱推力波动的程度进行对比。分析结果表明,硬磁性材料可以有效降低齿槽力和推力波动。最后研究了不同相对磁导率下硬磁性材料对电机性能的影响,并得到电机性能最佳时的相对磁导率值,为进一步提高电机性能提供了理论基础。