Low-field NMR micro coils based on printed circuit board technology

Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.

Electromagnetism and Absorptivity of the Modified Micro-coiled Chiral Carbon Fibers

Micro-coiled chiral carbon fibers are modified by nano-Ni. X-ray diffraction （XRD） and scanning electron microscopy （SEM） are used to compare the composition and morphology of the unmodified and the modified fibers. The results show that electromagnetism parameters of the modified are different from those of the unmodified. After modification by nano-Ni, the micro-coiled chiral carbon fibers have decreased permittivity and electrical loss. The permeability and magnetic loss of the modified carbon fibers become larger than those of the unmodified ones. Moreover, the modification of unmodified chiral carbon fibers into the modified is much like changing hollow electric windings into those with magnetic cores inside. The modifier intensifies the cross polarization of the chiral carbon fibers and makes the permittivity and the permeability get closer to each other which improves the matching performance and enhances absorbability of coatings. In the range of 6-18 GHz, the reflectivity of the coating is 6-8dB and the bandwidth is 12 GHz. The area density of the coating is below 3 kg/m^2.

Modeling and Configuration Design of Electromagnetic Actuation Coil for a Magnetically Controlled Microrobot

Non-contact actuated microbeads have attracted a lot of attention in recent years because of its enormous potential in medical, biological, and industrial applications. Researchers have proposed a multitude of electromagnetic actuation(EMA) systems consisting of a variety of coil pairs. However, a unified method to design and optimize a coil pair according to technical specifications still does not exist. Initially, this paper presented the modeling of an untethered ferromagnetic particle actuated by externally applied magnetic field. Based on the models, a simple method of designing and optimizing the EMA coil pair according to technical specifications, was proposed. A loop-shaped coil pair generating uniform magnetic and gradient fields was chosen to demonstrate this method clearly and practically. The results of the optimization showed that the best distance to radius ratio of a loop-shaped coil pair is 1.02 for a uniform magnetic field and 1.75 for a uniform gradient field. The applicability of the method to other shapes of coil configuration was also illustrated. The best width to distance ratio for a square-shaped coil pair is 0.558 and 0.958 for uniform magnetic and gradient fields, respectively. The best height to width ratio and distance to width ratio for a rectangle-shaped coil pair is h/w =[0.9,1.1], d/w =[0.5,0.6] for uniform magnetic field and h/w =[1.0,1.2], d/w =[0.9,1.1] for uniform gradient field. Furthermore, simulations of a microparticle tracking the targeted trajectory were conducted to analyze the performance of the newly designed coils. The simulations suggested the ability of manipulating microparticles via the coils designed by our proposed method. The research mainly proposed a unified design and optimization method for a coil pair, which can support researchers while designing a specific coil pair according to the technical requirements. This study is aimed at researchers who are interested in EMA system and microrobots.

Development of Wearable Micro-actuator Array for 3-D Virtual Tactile Displays

A novel 4 by 4 array of electromagnetic micro-actuators operating on the principle of voice-coil actuators is presented. The intended application of the array is dynamic tactile stimulation, where multiple actuators generate an illusion of touching a moving pattern. In comparison to earlier designs [1-3], the device has smaller dimensions of 2.28 mm in diameter and 7 mm in length, which allowed its use in an array capable of hosting up to a 5 by 5 set of actuators with a rectangular shape covering an area of 18 mm by 21 mm. Using finite element analysis of several conceptual designs of actuators [1,4,5], it was established that the voice-coil type device (where the coil is the moving part) has most beneficial characteristics for the envisioned application. These include sufficient force over a relatively large distance, allowing tactile stimulation of surfaces with irregular shape, fast response, and small foot-print that matches the density of the tactile sensory neurons in the human finger. Eexperimental evaluation of the operation of neighboring actuators spaced at 3.3 mm apart, indicates that there is no crosstalk between the actuators. The resulting density exceeds that of previously reported alternative designs based on moveable permanent magnets [4,6]. Static force measurement indicate that each micro-actuator can produce at least 26 mN of repulsive force over a stroke of 2100 μm with a peak force of 34 mN. The driving circuit operates at 13.5V and generates a vibration frequency of up to 265 Hz without significant change of the force-displacement characteristics. In the higher frequency range (above 100 Hz) the actuator provides at least 15 mN of force over a slightly reduced stroke of 2300 μm, and a peak force of 21 mN. All of the above parameters meet the required threshold values of tactile human perception known from [2] and [3].

基于准零刚度支撑结构的低频主动隔振平台研究

针对量子科学试验、精密制造等先进应用对亚赫兹微振动的抑制需求,研究基于准零刚度支撑结构和分离式音圈作动器的低频主动隔振技术。首先,给出一种低频主动隔振平台设计方法,考虑准零刚度结构的等效动力学特性,采用牛顿-欧拉方法建立平台的动力学模型;然后,基于所建立动力学模型分析多自由度耦合下平台的扰动传递特性并设计主动隔振算法;最后,研制低频主动隔振平台进行试验验证。试验结果表明,所开发主动隔振平台能够在三个线自由度上实现优于98.3%的微振动抑制效果,在0.1~10.0 Hz内载荷z方向微振动小于1.3×10^(-8) g。

双线圈与单线圈磁脉冲辅助微冲裁对比与分析

为进一步研究磁脉冲辅助微冲裁工艺,提出使用双线圈替代单线圈的磁脉冲辅助微冲裁方法,采用对比试验的方式进行了成形孔宏观效果及冲裁断面质量分析,从而对双线圈与单线圈成形率与冲裁断面质量优劣进行了对比。结果表明,在成形孔的宏观效果方面,双线圈的孔成形率远高于单线圈,双线圈的应用提高了磁脉冲辅助微冲裁的能量利用率。单线圈磁脉冲辅助微冲裁的冲裁断面光亮带占比最高仅有15.3%,而双线圈的冲裁断面光亮带占比最高高达59.6%,双线圈冲裁质量远优于单线圈。

基于Zigzag柔性簧片的大行程XY精密运动平台

通过采用Zigzag柔性簧片作为导向机构,提出了一种具有大行程、高精度、高频响、低应力的并联式XY二自由度精密定位平台,满足精密运动的需求。提出了以Zigzag柔性簧片单元为核心导向梁的柔顺精密运动平台结构,并采用音圈电机进行驱动,实现3 mm×3 mm的运动范围和60 Hz以上的固有频率。对Zigzag柔性簧片和传统直梁柔性簧片进行有限元仿真分析对比,验证Zigzag柔性簧片运动性能的优越性。接着,对XY两自由度运动进行解耦设计,减小运动带来的寄生(耦合)误差。运用有限元分析对平台进行优化,针对高频运动引发的疲劳损伤问题,改进定位平台的构型,降低最大应力,延长平台工作寿命。分析结果表明:该平台满足运动和解耦性能的设计要求,其寄生误差为0.012%,能够实现大行程以及较高频率的运动,并且响应快速,动态特性良好。实验结果表明,定位平台的固有频率达到60 Hz,开环分辨率达1.3μm,可实现XY方向±1.5 mm行程的运动。

大行程推拉电磁驱动微定位平台的内环阻尼与迭代学习控制

为了解决音圈电机驱动柔性微定位平台驱动力小和低阻尼谐振等问题,本文采用两侧音圈电机的推拉模式来提升驱动力的大小,并且利用内环阻尼控制器结合迭代学习控制方法来实现平台的精准控制。首先,搭建了互补配置的双音圈电机驱动双平行四边形柔性机构的微定位平台。其次,设计了内环阻尼速度反馈控制器。然后,采用逆模型迭代学习控制方法来进一步消除周期性的干扰和误差。最后进行了跟踪实验。结果表明:在跟踪1 Hz和2.5 Hz的正弦波时,相比于PI控制,最大误差分别减少74.6%和68.6%,满足微定位平台精准控制的要求。

胃肠道胶囊机器人无线能量传输系统中发射线圈优化设计

基于无线能量传输的模型与原理,仿真分析了几种不同类型发射线圈的磁场分布。结果表明,线圈磁芯开口大小、磁芯与空气界面的形状、线圈放置的位置都会对发射线圈附近磁场分布产生影响。进而优化出扇环型发射线圈,当线圈中通以频率218 kHz、幅值1.125 A的电流时,可在一定的空间区域形成3.0~4.7 G、比较均匀的磁场,满足胃肠道胶囊机器人的供能需求。相较于已有同用途的发射线圈,优化设计的发射线圈结构简单、整体尺寸显著缩小,同时采用较小的电流就能满足供能需求。研究工作可为优化设计无线能量传输系统中的发射线圈提供新的思路和可行途径。

基于旋涡传感的镁合金压铸件表面微观缺陷检测

针对镁合金铸件表面微观形态变化较小,砂眼和毛刺等缺陷视觉特征表现不明显,导致人工检测难度较高的问题,提出基于旋涡传感的镁合金压铸件表面微观缺陷检测方法。将长时间磨损和外力加持两种情况下引起镁金属能量强度变化作为下一步检测的参照,利用旋涡传感技术在被测铸件周围设置带有交流电的线圈磁场,根据铸件表面金属参数调节旋涡传感密度,识别到铸件表面出现与线圈磁场相反方向磁场力时,即完成精准检测。结果表明,所提方法不同提离距离下,砂眼铸件缺陷最大镁金属能量强度为363 MJ和360 MJ,毛刺铸件缺陷最大镁金属能量强度为270 MJ和300 MJ。验证了所提方法可以准确检测镁合金压铸件表面裂纹和凹陷缺陷。

音圈电机驱动微定位平台线性自抗扰滑模控制

针对音圈电机驱动柔性微定位平台控制速度和精度低以及抗干扰能力弱等问题,设计了一种将滑模控制和线性自抗扰控制相结合的复合控制器来提高平台系统的控制性能。首先,搭建了音圈电机驱动复合双平行四杆柔性机构的微定位平台和实验系统,并进行了系统辨识;其次,设计了线性自抗扰控制器,利用线性扩张状态观测器估计系统的内外扰动并在线进行扰动补偿,针对线性自抗扰控制器性能优化上的局限性,提出滑模控制器解决相位滞后问题来进一步提升轨迹跟踪精度;最后,利用所搭建的实验平台对控制方法进行了实验验证。结果表明,滑模和线性自抗扰复合控制器能够很好地克服内外干扰,与经典PID控制和单独的线性自抗扰控制相比,跟踪正弦波信号的最大误差分别减小了52.98%和21.26%,满足了微定位平台高精高速的控制要求。

退火对电流体喷印线圈磁敏特性的影响

研究了热退火对不同电流体喷印方式制备的微纳金属线圈磁感应特性的影响。首先,仿真分析了不同线圈参数对线圈电感性能的影响,设计了磁敏线圈结构;然后,使用电流体喷印设备进行线圈制备,并利用磁场发生及检测系统对喷印线圈进行性能表征;最后,对比了相同条件下(真空,300℃)退火前后不同电流体喷印方式制备的微纳金属线圈在均匀交变磁场下的感应电动势随激励电压/电流的变化规律。实验结果表明,退火后的线圈表现出更为优秀的导电性,并分析了其变化机制。为基于电流体喷印技术的微纳磁敏线圈制备提供了有益思路。

基于分数阶PID的宏微复合驱动器宏动控制策略

针对宏微复合驱动器控制系统中存在定位误差大和调节时间长的问题,提出了一种基于次最优分数阶PID的控制策略。简述了宏微复合驱动器结构及工作原理,并基于电磁驱动原理建立了宏动部分数学模型;设计了分数阶PID控制器,并采用遗传算法和次最优的方法对控制器进行参数整定;通过数值仿真和实验验证了分数阶PID控制器的有效性。结果显示,采用分数阶PID控制器相较于传统PID控制器在5 mm以及更大定位行程中位移超调量下降超过57%,调节时间减少超过24%,且行程越大驱动器采用分数阶PID控制器控制效果越明显。研究结果表明,分数阶PID控制器在宏微复合驱动器宏动系统中的控制效果明显优于传统PID控制器。

CVD法生长弹性微螺旋状碳纤维的研究

We have obtained regularly micro coiled carbon fibers with high reproducibility by the catalytic pyrolysis of acetylene (with impurities) containing a small am ount of sulfur and phosphorus impurities.(S/P).The carbon coils with very small and reg ular coil di ameters (several μm)and coil pitches (>0.7μm )could be obtained with the ma ximum c oil yield of about 20mg/cm 2 substrate and the maximum thickness of coil layer s o f about 8 mm.Carbon coils have generally double helical/spiral structure and may be the ideal candidate for novel subtle energy absorbers,tunable micro devices, bi o activators,Li battery electrodes,absorbers of hydrogen or other gases,etc.In thi s study,we prepared the carbon coils and examined the growth patterns and morpho logies of the carbon coils prepared by different cnditions in detail. It was observed that the coil diameters of the carbon coils and the diameter of the carbon fibers that built up the carbon coils were significantly affected by the reaction temperatures,S/P impurities,and the acetylene flow rate.

急性破裂性颅内动脉瘤早期血管内栓塞治疗

目的探讨急性破裂性颅内动脉瘤早期血管内栓塞治疗的效果.方法对100例急性破裂性颅内动脉瘤患者,早期采用经股或经颈动脉穿刺行全脑选择性血管造影术,应用电解可脱微弹簧圈进行动脉瘤囊内栓塞.结果 100%动脉瘤腔闭塞的45个,95%闭塞的39个,90%闭塞的18个.G1asgow预后评分:I级86例,Ⅱ级5例,Ⅲ～Ⅳ级4例,V级5例.1例椎动脉瘤栓塞后8 h,动脉瘤再次破裂出血死亡.1例栓塞术后36 h再出血,再次行开颅动脉瘤夹闭术.随访0.5～2年无再出血.结论早期动脉瘤囊内栓塞,是治疗急性破裂性颅内动脉瘤较理想的方法,栓塞后早期再出血可能与瘤颈破裂性动脉瘤及夹层囊性动脉瘤有关.

螺旋炭纤维的微观结构与储能特性

采用扫描电镜、激光Raman光谱、X射线衍射(XRD)、热失重分析(TG)、低温氮吸附等研究手段,以平直炭纤维为参照,对比研究了碳氢化合物催化分解法制备的螺旋型炭纤维的微观结构特征。实验结果表明:整体上,螺旋炭纤维的微观结构要比平直炭纤维的结构更加无序;但螺旋炭纤维的外层结构较为有序。与中孔分布广、孔容低的平直炭纤维不同,螺旋炭纤维的中孔主要分布在3nm～4nm范围内,且有着较高的孔容,其比表面积几乎是平直炭纤维的10倍。这些结构特性使得螺旋炭纤维在抗氧化性、储氢、电化学电容等方面都体现出超越平直炭纤维的优势和应用潜力。

微弹簧圈栓塞难治性外伤性颈动脉海绵窦瘘的疗效观察

目的探讨和研究微弹簧圈血管内栓塞难治性外伤性颈动脉海绵窦瘘的疗效。方法回顾13例用微弹簧圈栓塞治疗的难治性外伤性颈动脉海绵窦瘘患者。所有患者均有持续性颅内血管杂音、搏动性突眼及球结膜充血水肿。均采用微弹簧圈栓塞治疗,其中经动脉入路9例,经眼上静脉入路4例。结果 12例术后造影瘘口消失且颈内动脉通畅。1例填入5枚微弹簧圈后,微导管脱离瘘口,反复尝试不能再次进入,术中造影瘘口仍显影,1周后球囊阻断试验阴性后闭塞颈内动脉主干。术中1例微弹簧圈解旋,将解旋部分置于患侧颈外动脉固定。术后3～12个月(平均7.5个月)对10例患者随访了脑血管造影复查。1例复发,原因多与弹簧圈解旋后长期服用抗血小板药物均有关。结论对于球囊闭塞困难的难治性外伤性颈动脉海绵窦瘘,微弹簧圈栓塞安全、有效。

网孔支架辅助微弹簧圈治疗已破裂颅内动脉瘤的临床疗效分析

目的探讨网孔支架辅助微弹簧圈在已破裂颅内动脉瘤栓塞治疗过程中的操控性、相关并发症及临床疗效。方法回顾性分析应用网孔支架辅助微弹簧圈栓塞治疗60例已破裂颅内动脉瘤患者资料。结果所有60枚支架顺利释放到位。术后即刻造影,动脉瘤获100%栓塞34个,95.0%栓塞11个,90.0%栓塞14个,80.0%栓塞1个。术中出现血管痉挛4例,动脉瘤破例3例,血栓形成1例。术后随访3～18个月,死亡2例,患者术后生存质量与术前(Hunt-Hess分级)有统计学差异(P<0.05)。患者术后获影像学随访23例,其中DSA随访19例,1例出现支架内血管狭窄,均无动脉瘤复发。结论使用网孔支架辅助微弹簧圈栓塞治疗已破裂颅内动脉瘤具有操作性良好、安全性高等优点;术者娴熟的技术、对手术时机的准确把握和对介入材料的正确选择有助于减少并发症。

石墨化对微螺旋炭纤维形貌和微观结构的影响

采用化学气相沉积法制备微螺旋炭纤维,在氩气气氛,2500℃下对其进行石墨化处理.通过扫描电镜,激光拉曼光谱和X射线晶体衍射对石墨化前后微螺旋炭纤维的形貌与微观结构进行了研究,并初步探讨了石墨化机理.结果表明:石墨化处理对微螺旋炭纤维具有显著的纯化作用,其螺旋形貌基本保持不变.微观结构更加规整,微螺旋炭纤维的晶面层间距d_(002)(0.3626～0.3378nm)减小,晶粒尺寸L_c(1.6404～3.8590nm)和L_a(2.04～7.21nm)增大,石墨化程度增强.

可脱性微弹簧圈血管内栓塞治疗颅内动脉瘤(附106例分析)

目的总结可脱性微弹簧圈血管内栓塞治疗颅内动脉瘤的经验。方法回顾性分析106例颅内动脉瘤行可脱性微弹簧圈囊内栓塞的经验。结果动脉瘤腔100%闭塞87例,95%闭塞11例,90%闭塞8例。95例破裂性动脉瘤病人术后GOS评分5分68例,4分10例,3分7例,2分4例,1分6例;11例未破裂性动脉瘤均达到临床治愈。本组病死率为5.7%。结论正确处理术中、术后并发症及提高栓塞技术是提高颅内动脉瘤治愈率的重要方法。