微通道导引下数字微流体快速混合

微流体混合是微流控芯片急需完善的重要操作单元,提出了在声表面波驱动下实现微通道内数字微流体快速混合方法.在1280YX-LiNbO3基片上设计相互垂直排列的两叉指换能器和反射栅,并在其声传播路径上制作微通道且进行疏水处理以防止微流体偏离运动方向,待混合的数字微流体移液于微通道中,分别在两叉指换能器上分时加RF电信号激发相互垂直声表面波,以驱动微通道中微流体输运、合并及快速混合.输运实验结果表明微流体在没有微通道时运动发生严重偏离声传播方向;混合实验表明:相比于自由扩散混合,声表面波作用极大地提高微通道中微流体混合速度且混合程度更高.     

一种新的纸基微流开关及其活跃方法

提出了一种新的、基于声表面波的纸基微流开关。通过软光刻技术制作内含两个微孔的聚二甲基硅氧烷(PDMS)微架,其上固定经折叠、长度可变的纸通道。PDMS微架贴附于压电基片之上,并在待连接的两微通道之下方,折叠纸通道最低端离压电基片间距为2 mm。压电基片上采用微电子工艺光刻一对叉指换能器和反射栅。当足够强度的电信号加到叉指换能器对时,激发两相向声表面波,使得压电基片上微流体输运到折叠纸通道,改变其长度,连接其上待连通的两纸基微通道,完成开关功能。对可编程微流器件提供了一种新的编程和开关控制方法。     

基于声表面波实现数字微流体的产生

数字微流体的产生是压电材料为基片的微流控芯片进行微流分析的前提,报道了在压电基片上应用声表面波技术产生数字微流体的方法.在128°旋转Y切割X传播方向的LiNbO3基片上集成PDMS微通道,在微通道出口一侧为经疏水处理的铝薄片,注射泵产生恒定流量的微流体经PDMS微通道到达铝薄片并聚集,当聚集的微流体体积足够大时,微流体克服表面张力作用下滑到达压电基片,并在中心频率为27.7 MHz叉指换能器激发的声表面波作用下输运,实现微流体的数字化.同时,理论分析了微流体在铝薄片表面上受力状况,并以水为实验对象,进行微流体数字化实验.结果表明,声表面波作用下能精确产生微升量级数字微流体,为压电微流控芯片提供了一种新的微流体引入方法.     

基于声表面波微液滴并行加热研究

提出了一种并行加热微液滴的方法。在128°旋转Y切割X传播方向的LiNbO3压电基片上采用微电子工艺制作叉指换能器和反射栅,在其声路径上贴合环形聚二甲基硅氧烷(PDMS)微槽,其内充满石蜡油微流体。设计有多个受热区的图案,经过激光切割转移到导热性良好的、厚度为0.3 mm的铜金属传热片上,并放置于PDMS微槽上。射频电信号加到叉指换能器上激发声表面波,辐射入微槽中的石蜡油微流体,并将能量通过传热片传递到受热区,进而加热受热区上的微液滴。以纯净水微液滴为实验对象,进行了多个微液滴并行加热实验。结果表明,在单个叉指换能器上加电信号激发的声表面波可同时加热多个微液滴,且其温度变化值随射频电信号功率增加而增加,同时,微液滴体积和受热区中并行加热的微液滴数影响其温度变化。     

声表面波辅助实现纸基微流分析

纸基微流器件往往难以实现样品前处理操作.提出了一种简单的纸基微通道制作方法及兼具有前处理操作功能的纸基微流分析方法.采用Protel设计微通道图案,采用印刷电路技术制作铜模板,并涂覆石蜡、覆盖滤纸,而后用电烙铁加热铜模板另一侧,熔融石蜡渗透入滤纸形成纸基微通道.制作的纸基器件放置于128°YX-LiNbO3压电基片上,...     

低功率电信号激发的不连续声表面波破裂压电基片上液滴

提出了一种新的微流器件上液滴破裂的方法。采用微电子工艺在128°yx-LiNbO3 基片上制作一对中心频率为27.5MHz叉指换能器和反射栅。瞬间下降电信号激发不连续声表面波辐射入待破裂液滴,在其内产生不连续声流。当电信号突然消失,部分微流体由于惯性力从液滴中飞逸。采用红色染料溶液进行液滴破裂实验,结果表明：当电信号功率从12.3dBm突然降低到-3.98dBm,压电基片上液滴能产生破裂,并且其均匀性受液滴体积影响。所提出的液滴破裂方法为微流系统进行微流分析提供了一种新的样品前处理技术,具有一定的学术价值。     

基于声表面波技术实现纸基微流开关研究

提出了采用声表面波技术实现纸基微流开关的方法。它由127.68°旋转Y切割X传播方向的LiNbO3压电基片和两个有一定间隙的纸微通道组成。压电基片上采用微电子工艺制作1个中心频率为27.5MHz的叉指换能器和1个反射栅,纸微流通道采用PDMS薄膜贴附于压电基片的声传播路径上,微流通道一侧微流体在没有声表面波作用时,微流...     

基于两相向声表面波快速富集悬液中微粒

为提高生化分析灵敏度,提出了一种快速富集悬液中微粒的新方法.它在127.68°旋转Y切割X传播方向的LiNbO3基片上采用微电子工艺制作了2×2叉指换能器阵列,在该叉指换能器阵列的一对对角叉指换能器上同时加经功率放大器放大后的RF信号,以激发两相向声表面波,采用微量进样器将待富集的微流体(微液滴)进样到两相向传播的声路径上,微液滴中的微粒在该两相向的声表面波作用下快速向心富集.淀粉溶液微液滴富集实验结果表明,两相向声表面波作用下,10秒内实现微液滴中淀粉微粒的快速富集.     

基于SAW器件的微间隙压力监测传感器

声表面波SAW(Surface Acoustic Wave)器件能进行无源无线通信,为微间隙等特殊环境下物理量的测量提供了新的解决思路.研究设计了一种基于声表面波延迟线的接触应力传感器.围绕微间隙环境,研究了声表面波器件的结构类型,并确定压力监测的技术方案;根据设计原理,设计一种新型声表面波传感器,并利用有限元分析法对压电基片进行应力仿真;将设计出的传感器进行实验测试并提出温度补偿.通过对声表面波传感器设计的探究,验证了利用声表面波传感器实现微间隙压力监测的可行性.     

声表面波驱动微流体研究

报道了在128°旋转Y切割X传播方向的LiNbO3基片上研制了微流体驱动器件。RF信号经功率放大器放大后馈入叉指换能器,由它激发的声表面波驱动微流体。为减少由于声波辐射引起微流体温度上升,提出了间接微流体驱动方法,即通过声表面波驱动中间微粒,再由此驱动目标微流体。实验表明:声表面波驱动微流体所需的RF信号功率决定于微流体体积和粘性;采用间接方法驱动1μL50%甘油水液滴,在10V的RF信号持续5min下其温度变化仅0.5℃,而相同条件下直接驱动该液滴,其温度上升12.6℃。     

A Latchable Phase-Change Microvalve With Integrated Heaters

This paper presents a latchable phase-change microvalve with integrated microheaters, which is suitable for lab-on-a-chip systems where minimal energy consumption is desired. The microvalve exploits low-melting-point paraffin wax, whose solid–liquid phase changes allow switching of fluid flow through deformable microchannel ceiling. Switching is initiated by melting of paraffin through an integrated microheater, with an additional pneumatic pressure used for the open-to-close switching. The valve consumes energy only during initiation of valve switching. When paraffin solidifies, the switched state is maintained passively. The microvalve was fabricated from polydimethylsiloxane through multilayer soft lithography techniques. Experiments show that the valve can switch flow within 4–8 s due to the small thermal mass and localized melting of paraffin wax; when closed, the valve can passively withstand an inlet pressure over 50 kPa without leakage. Time response of the valve can be further improved with improved heater and wax chamber designs, while the latching ability can be improved by optimizing the wax chamber/membrane design. Compared to existing latchable phase-change valves, the microvalve has no risk of cross-contamination. In addition, the improved sealing offered by the compliant membrane makes the valve robust and flexible in operation, allowing large ranges of initiation pressure from various actuation schemes. $hfill$[2008-0303]      

Micromachined low-loss microwave switches

The design and fabrication of a micromechanical capacitive membrane microwave switching device is described. The switching element consists of a thin metallic membrane, which has two states, actuated or unactuated, depending on the applied bias. A microwave signal is switched on and off when the membrane is switched between the two states. These switches have a switching on speed of less than 6 μs and a switching off speed of less than 4 μs. The switching voltage is about 50 V. The switches have a bowtie shape and showed low insertion loss of 0.14 dB at 20 GHz and 0.25 dB at 35 GHz, and isolation of 24 dB at 20 GHz and 35 dB at 35 GHz. These devices offer the potential for building a new generation of low-loss high-linearity microwave circuits for a variety of phased antenna arrays for radar and communications applications     

基于电路仿真技术异型声表面波器件特性分析

为了能够采用EDA工具设计含声表面波器件的电子系统,本文研究了应用EDA工具仿真声表面波器件特性的方法.它以叉指换能器一个周期段的Mason等效电路模型为基础,根据电网络理论将Mason等效电路模型中的复阻抗采用LC串并联网络来等效,LC网络中的各L、C值采用进化方法确定,使得串并联网络的等效阻抗和Mason等效电路中的阻抗特性误差最小,并以子电路的形式由自行研制的异型声表面波器件各叉指换能器的等效电路调用,异型声表面波器件幅度特性仿真结果与实测结果在中心频率处插入损耗基本相符.     

Ten switched‐beams with 2 × 2 series‐fed 2.4 GHz array antenna and a simple beam‐switching network

This article presents a 2 × 2 series fed 2.4 GHz patch antenna array having multiple beam switching capabilities by using two simple 3 dB/90° couplers to achieve required amplitude and phase excitations for array elements with reduced complexity, cost and size. The beam switching performance with consistent gain and low side lobe levels (SLL) is achieved by exciting the array elements from orthogonally placed thin quarter‐wave (λ_g/4) feeds. The implemented array is capable to generate ten (10) switched‐beams in 2‐D space when series fed elements are excited from respective ports through 3 dB quadrature couplers. The dual polarized characteristics of presented array provide intrinsic interport isolation between perpendicularly placed ports through polarization diversity to achieve independent beam switching capabilities for intended directions. The implemented antenna array on 1.575 mm thick low loss (tan δ = 0.003) NH9450 substrate with ε_r = 4.5 ± 0.10 provides 10 dB return loss impedance bandwidth of more than 50 MHz. The measured beam switching loss is around 0.8 dB for beams switched at θ = ±20°, Ф = 0°, 90°, and 45° with average peak gain of 9.5 dBi and SLL ≤ ?10 dB in all cases. The novelty of this work is the capability of generating ten dual polarized switched‐beams by using only two 3 dB/90° couplers as beam controllers.     

微流体装置中超声流的研究

应用流体动力学的基本理论,建立起声流场的一维解析模型,对声波在管道内部传播时产生的声场和声流运动进行探讨。然后提出并设计了一种利用PZT激励微管道振动产生超声场的新型微流体装置。该装置为由微管道相连接的两个微腔体,并利用有限元法对超声波激励的微管道和腔体进行瞬态的流场数值分析,得到一阶声压和流场的速度分布结果,最后对数值结果进行处理并讨论了超声波在管道内传播时产生的声流速度以及驱动力的分布情况。     

弹性层中的SH板波传播特性及电磁超声激励方法的研究

研究水平剪切波(Shear Horizontal,简称SH波)的传播特性及激励接收方法对该波在无损检测和声弹性技术范围内的工程应用有着重要的价值.首先,SH波在弹性层中传播的多模态、频散特性在文中作了详细的分析,同时重点研究了电磁超声技术在非铁磁性材料波导中产生SH波的探头结构和基础理论,并以试验的方法验证了其部分电声特性,结果表明,SH板波具有其他类型波所没有的独特特性,而电磁超声技术在SH波的激励接收方面有着很大的优势.     

Size-dependent microparticles separation through standing surface acoustic waves

This study presents a method that uses a standing surface acoustic wave (SSAW) to continuously separate particles in a size-gradient manner in a microchannel flow. The proposed method was applied to a colloidal suspension containing poly dispersed particles with three different sizes (1, 5, and 10 μm) but the same density and compressibility. Particle suspension was focused hydrodynamically at an entrance region, and particles were forced actively toward the side wall where SSAW-pressure nodes were generated by two interdigital transducers (IDTs) across the channel. The particles placed in the middle stream, in which the shear rate was minimized, were separated successfully in a size-gradient manner by acoustic force. In addition, this study further developed an analytical model to predict the displacement of particles in microchannel flow by considering viscous, acoustic, and diffusive forces. The predicted values of particle displacement showed excellent agreement with the experimental results, and diffusion was found to be important and not negligible. The advantage of this method is to minimize the shear rate on particles, which would be useful for potential applications of shear-dependent cells such as platelets.     

Robust switching signal estimation for a class of uncertain nonlinear switched systems

In this paper, a robust switching signal estimation approach is presented for a class of uncertain nonlinear switched systems using a sliding mode robust observer on the continuous state vector of system. In this approach, the estimation of switching signal is achieved at a bounded and arbitrary small time in spite of un-modelled uncertainties. The developed estimation technique can also be employed on mode-dependent control methods to reach a practical controller for nonlinear switched systems with the inaccessible switching signal. The simulation results illustrate the capability of proposed method.     

基于牵制控制的切换布尔网络的分布式集合镇定

切换布尔网络是一种典型的网络化控制系统, 在基因调控、信息安全、人工智能、电路设计等领域具有重 要应用. 本文基于牵制控制方法, 研究切换布尔网络在任意切换下的分布式集合镇定问题. 首先, 利用矩阵半张量积 方法,得到切换布尔网络的代数形式. 其次, 基于代数形式, 提出构造性的算法来实现切换布尔网络在牵制控制的 作用下任意切换集合镇定, 并设计出状态反馈牵制控制器. 再次, 利用逻辑矩阵分解技术和分布式控制方法, 设计任 意切换下切换布尔网络的分布式集合镇定控制器, 并提出分布式控制器存在的充分条件. 文中给出3个例子来说明 所获得结果的有效性.