Name: design and characterization methodology for efficient wide range tunable mems filters
Uploaded: 2018-02-04T13:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters at JoVE.com

这项工作得到了美国陆军研究实验室的支持, 阿德尔菲, 马里兰州, 美国, 根据赠款 W91ZLK-12-P-0447。共振测量是在迈克尔. 斯通和安东尼. 布洛克的帮助下进行的。热摄相机的测量是在科诺菲尔的帮助下进行的乔治华盛顿大学。

1. 优选结构的选择与设计
<ol><li>选择用于宽范围频率调谐的固定固定光束 (与其他候选者相比, 它在加热时可以进行宽范围调谐, 因为其温度系数大 (TCF) 和可忽略的热膨胀常数)。</li>
	<li>设计一个更长的光束, 如果目的是调整效率的改善。设计一个较短的光束, 如果目的是跳频或信号跟踪应用。</li>
</ol>2. 互补金属氧化物半导体 (CMOS) 的建模和制造
<ol><li>设计并制作了基于有限元程序的 MEMS 滤波器的3维模型。</li>
	<li>在集成电路 (IC) 设计工具中重建相同的布局, 按层层创建 gds 文件。</li>
	<li>将此 gds 文件提交到 cmos 铸造厂进行制造 (我们使用了 cmos 0.6 µm 技术)。</li>
	<li>在 CMOS 过程完成后继续进行后处理 (请注意, 芯片应该有多晶硅、铝和氧化物层)。<ol>
<li>通过电感耦合等离子体 (ICP) 蚀刻系统进行 CHF3/O2的干式蚀刻过程。在铝层之间蚀刻2 , 并在5.7 的纵横比下形成光束。对于此过程, 请使用以下参数: CHF3 at 40 sccm, O2在 5 sccm, 压力在 0.5 Pa, ICP 电源在 500 w, 采样功率在 100 w 与56分钟总蚀刻时间。</li>
		<li>在硅衬底上应用 XeF2蚀刻工艺, 在梁下创建9µm 深腔。对于此过程, 请使用 XeF2蚀刻系统进行3次周期为 3T, 为六十年代/周期。</li>
	</ol>
</li>
	<li>用扫描电子显微镜 (SEM) 表征设备, 以确保它们是正确的制造。对于这一步, 改变光束加速电压到 2.58 kV 和工作距离为9.5 毫米。</li>
</ol>3. 设备测试
注: 设备测试包括焦耳加热测试和频率响应测试等多个步骤。
<ol><li>
嵌入式加热器热成像试验
	<ol>
<li>将热成像摄像机放在芯片的顶部, 并测试嵌入式加热器以确保它们加热光束。</li>
		<li>将电源连接到芯片封装, 并将直流电压从0伏到5.7 伏的嵌入式加热器上应用, 以增加整个光束的温度。</li>
		<li>在加热过程中, 通过热敏相机记录整个芯片封装的温度分布。将结果保存在数值计算程序中, 并绘制发热剖面图。</li>
	</ol>
</li>
	<li>
校准 LDV 和测试设置
	<ol>
<li>将激光放置在120µm 长光束的顶端。</li>
		<li>连接两个120µm 长光束之间的电源, 以应用 7 v DC 和 3 v 交流电压进行共振操作。将额外的直流偏置电压与嵌入加热器连接, 最大值为5.7 伏特, 以便在共振操作期间将焦耳加热应用于光束。</li>
		<li>将激光器移到光束的不同位置, 以获得低噪声激光反射。确保增加蓝色棒的强度, 以减少噪音。</li>
		<li>将屏幕分成多个视图以校准和启动测量设置。</li>
		<li>转到采集设置, 将测量模式设置为 FFT, 不使用任何过滤器, 并将带宽设置为 2 MHz。</li>
		<li>更改速度, 使其能够支持 2.5 MHz 的最大频率。</li>
		<li>使用周期性啁啾波形。 注: 在这里, 振幅代表交流电压和直流电压抵消立场。</li>
		<li>使用此新设置开始测量。</li>
		<li>通过将直流电压更改为 1 v 来更新采集设置</li>
		<li>当 Ref1 显示红色警报 (这意味着信号是嘈杂的) 时, 减少在购置设置窗口中应用的偏置电压。</li>
		<li>将激光器移到光束的不同位置, 以进一步增加信噪比。有时, 横梁上可能有坏的斑点, 导致振动条上出现红色警报;在这种情况下, 继续搜索最佳位置。</li>
	</ol>
</li>
	<li>
通过 LDV 测试68µm 长 MEMS 滤波器
	<ol>
<li>选择68µm 长 MEMS 过滤器进行测试。</li>
		<li>在两68µm 长相邻光束之间应用25伏直流电压和5伏交流电压。在这里, 直流电压提供弯曲和交流电压, 使共振操作。</li>
		<li>对放置在68µm 长光束中的嵌入式加热器施加额外的直流电压, 并将电压从0伏增加到5.7 伏。这将提供基于焦耳加热的频率调谐。</li>
		<li>观察并记录每个步骤中应用偏置电压的谐振频率和相位响应, 并在表中总结结果。在这里, 这个样品的总频率调整是大约874赫, 当 5.7 V 直流电压适用于嵌入式加热器。 注意: 模拟 (在右侧) 和实际测量 (在左端) 是同步的。</li>
	</ol>
</li>
	<li>
高模量测量
	<ol>
<li>按下 "a/d" 按钮转到3.2 节中演示的 "购置设置" 窗口, 并更改速度以使其能够支持非常高的频率。</li>
		<li>测量第一个和第二个模式与他们的阶段。 注: 主共振位移为 Y 方向为 mode-1, 它是在 Z 方向 (即朝向显微镜) 为 mode-2。</li>
	</ol>
</li>
</ol>4. 避免设备故障
<ol><li>
低频方波信号在解决迟滞中的应用
	<ol>
<li>应用 1 Hz 方波信号来解决两相邻光束之间的静电充电引起的迟滞问题。</li>
		<li>转到 "偏移" 框并将直流电压设置为 1 V, 同时将交流电压保持在1五</li>
		<li>转到频率框, 并设置频率为1赫兹。</li>
		<li>在横梁上激活并应用这个新的设置。</li>
		<li>观察光束的分离。</li>
	</ol>
</li>
	<li>
高热应力和燃烧
	<ol>
<li>使用额外的样品进行热应力测试。</li>
		<li>增加在嵌入式加热器上施加的偏置电压, 以小的增量, 以找到最大的允许电压之前, 设备失效, 由于高热应力。</li>
	</ol>
</li>
</ol>5. 提高调谐能力
<ol><li>在两个68µm 相邻的光束之间应用一个25伏直流电压和 5 v 交流电压, 同时在嵌入式加热器上增加应用的偏置电压从 0 v 到 5.7 v, 共661赫频移。</li>
	<li>将施加的偏置电压从25伏增加到35伏, 在两68µm 长相邻光束之间添加额外的弹簧软化效果, 同时应用 1 V 交流电压, 并在嵌入式加热器上保持相同的偏置电压设置。</li>
	<li>记录全频移的32% 的改善, 因为它应该增加从661赫到875赫来自这个额外的春季软化效果。 注意: 据我们所知, 改变 MEMS 谐振器的调谐能力是第一次在这项工作中实现的。</li>
</ol>

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我们没有什么要透露的。

建立 MEMS 滤波器的关键步骤之一是设计基于应用领域的设备。为了更好的调谐效率 (ppm/兆瓦), 光束应该更长或更薄, 但对于跳频或信号跟踪应用来说, 更短或更薄。同样地, 通过 LDV 的清晰信号检测是设备测试的关键, 这就是为什么最好设计至少3-4 µm 厚度的光束。否则, 信号将是嘈杂的, 即使是100X 镜头, 它需要多点测试与噪声消除 (嵌入在 LDV 软件), 以达到最佳的检测。由于其大型 TCF, 固定固定梁, ?...

由于其可靠性高、功耗低、设计紧凑、质量因数高、成本低等特点, 对 MEMS 滤波器的需求越来越大。它们在无线通信中被广泛用作传感器和核心部件。温度传感器1、生物传感器2、3、气体传感器4、过滤器5、6、7和振荡器是最受欢迎的应用领域。最流行的静电 MEMS 滤波器有固定固定光束5,8, 悬臂式2, 音叉6, 自由光束6,7, 弯曲磁盘设计7,方形形状设计9。
在实现 MEMS 滤波器时, 有许多关键步骤, 如设计方法 (基于应用的结构优化、宽范围频率调谐范围、避免故障) 和特性 (快速原型, 避免寄生电容, 并检测更高的模式)。由于制造公差或环境温度变化引起的频率变化, 需要频率调谐能力来补偿。在文献中报告了不同的技术10、11、12 , 以满足此要求;但是, 它们有一些缺点, 如频率调谐能力有限、中心频率低、附加的后处理要求和外置加热器10、11。
在本研究中, 我们提出的宽范围频率调谐的焦耳加热法5,13在有限的频率调谐范围内通过弹性模数变化12 (增加直流偏置电压之间的两个相邻的光束) 和材料相变方法10,11。并在 Göktaş和 Zaghloul13中总结了优化结构选择和基于应用的设计。在这里, 我们展示了如何调整固定固定梁的谐振频率, 增加直流电压应用于嵌入式加热器的帮助下, LDV。为了使调谐机构可视化, 有限元分析 (FEM) 模拟与同一帧中的 LDV 测量同步。这包括在整个光束的焦耳加热和弯曲剖面。
我们还介绍了可能的故障 (烧毁设备和迟滞) 及其建议的解决方案。焦耳加热法与固定固定梁的高热应力相结合, 提供了宽范围的频率调谐, 但同时也能在一定的温度水平上产生烧损装置。这归因于不同材料之间的高热应力14。解决办法是增加两个相邻光束之间的直流电压, 从而增加调谐范围 (32%), 并消除对高温的需求。此 "调优范围" 方法首先在 Göktaş和 Zaghloul5中演示, 在 Göktaş和 Zaghloul13中进行了更详细的说明, 并在这里重新介绍。迟滞, 另一方面, 可以发生在制造过程或共振操作。有许多技术提出解决这个问题, 如应用表面涂层, 以减少附着力的能量15,16, 增加表面粗糙度17, 以及激光修复过程18。相比之下, 我们提出了一个简单的技术, 在两个连接光束之间应用了低频方波信号, 并成功地用 LDV 记录了分离。这种方法可以消除额外的成本, 降低设计的复杂性。
另一个关键的步骤, 在建设一个国家的艺术 MEMS 过滤器的特性和验证。用网络分析仪进行表征是最常用和最广泛的方法之一;然而, 它有一些缺点。即使是小的寄生电容也会杀死信号, 所以这通常需要放大电路3,6,8以消除噪声, 并且它只能检测到第一模共振。另一方面, 与 LDV 的表征是无寄生电容问题, 并能检测到更小的位移。这使得快速原型, 同时消除了对放大器设计的需要。此外, LDV 可以检测 MEMS 滤波器的高模态共振。这一特性非常有前景, 特别是在高度敏感的生物传感器领域。较高的悬臂模式可以提供更高的灵敏度19。给出了 LDV 固定梁的高模态测量方法, 并将其应用于有限元模拟测量。有限元模拟的过早结果与固定固定梁的第一模式相比, 灵敏度提高了46倍。

<table><tbody><tr><td>Laser Doppler Vibrometer</td><td>Polytec</td><td>Polytec MSA-500</td><td></td></tr><tr><td>Scanning Electron Microscope</td><td>Zeiss</td><td></td><td></td></tr><tr><td>Thermal Camera</td><td>X</td><td></td><td></td></tr><tr><td>Power Supply&amp;nbsp;</td><td>Egilent</td><td>(E3631A)</td><td></td></tr><tr><td>Microscope</td><td>X</td><td></td><td></td></tr><tr><td>Coventor</td><td>Coventor</td><td></td><td>Simulation Tool</td></tr><tr><td>Cadence Virtuoso</td><td>Cadence</td><td></td><td>Simulation Tool</td></tr><tr><td>Multisim</td><td>Multisim</td><td></td><td>Simulation Tool</td></tr></tbody></table>

design and characterization methodology for efficient wide range tunable mems filters

在这里, 我们展示了激光多普勒测 (LDV) 优于传统技术 (网络分析仪) 的优势, 以及创建基于应用的机械系统 (MEMS) 过滤器的技术, 以及如何有效地使用它 (即, 调优功能并避免故障和迟滞。LDV 使网络分析仪无法进行关键的测量, 如高模式检测 (高度灵敏的生物传感器应用) 和非常小设备 (快速原型) 的共振测量。因此, LDV 被用来表征的频率调谐范围和谐振频率在不同模式的 MEMS 滤波器为本研究所建立。这种宽范围频率调谐机构是基于从嵌入式加热器的焦耳加热和相对较高的热应力就固定固定梁的温度。然而, 我们证明, 这种方法的另一个限制是产生高的热应力, 它可以燃烧的设备。在这项研究中首次取得了进一步的改进, 并显示了在两个相邻光束之间增加了外加直流偏置电压 (25 伏至35伏), 从而使调谐能力增加了32%。这个重要的发现消除了额外的焦耳加热在更广泛的频率调谐范围的需要。另一个可能的失败是通过迟滞和结构优化的要求: 我们提出了一种简单易行的低频方波信号应用技术, 它能够成功地分离光束, 消除了需要在文献中给出的复杂的方法。上述发现需要设计方法, 因此我们也提供了基于应用程序的设计。

采用低频方波信号, 避免了迟滞, 使用 LDV (图 1) 验证了这一点。在显微镜下 (图 2) 验证了在将相对较高的偏置直流电压应用于嵌入式加热器时, 由于高热应力14可能导致的故障。该有限元程序用于推导光束的更高模式 (图 3)。通过改变两个相邻光束之间的直流偏置电压 (25 v 到 35 v) 来改变调...

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Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

高效宽量程可调谐 MEMS 滤波器的设计与表征方法

本文提出了一种利用激光多普勒测 (LDV) 进行固定波束设计的协议, 包括频率调谐的测量、调谐能力的修正以及设备故障和迟滞的避免。LDV 方法在网络分析仪上的优越性是由于其较高的模态能力而表现出来的。

Here, we demonstrate the advantages of the laser Doppler vibrometer (LDV) over conventional techniques (the network analyzer), as well as the techniques ...

design-characterization-methodology-for-efficient-wide-range-tunable

Universidad San Sebastian

Research

JoVE Journal

Engineering

6.1K 次观看.  Harran University. 本文提出了一种利用激光多普勒测 (LDV) 进行固定波束设计的协议, 包括频率调谐的测量、调谐能力的修正以及设备故障和迟滞的避免。LDV 方法在网络分析仪上的优越性是由于其较高的模态能力而表现出来的。

视频: Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

硅胶超高品质因子微谐振器的制造

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

科研

工程学

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

模拟，太赫兹超材料吸收器的制备与表征

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

实时直流偏置的动态法切换时间改善严重欠阻尼边缘化场静电MEMS致动器

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

制造和微流控光机振荡器测试

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Using Micro-Electro-Mechanical Systems (MEMS) to Develop Diagnostic Tools

Using Micro-Electro-Mechanical Systems MEMS to Develop Diagnostic Tools

I'm U De Mercy, I'm the principal investigator of Bio Stick MAMs in Medicine Labs. I did my PhD at Stanford University in electrical engineering. I did a postdoc at Harvard Medical School at MGH working on bio acoustic MAMs or mostly bio MAs.And now I'm continuing as a faculty at Harvard Medical School at Harvard MIT Health Sciences and Technology. And continuing with my research that I enjoy very much. The work that I did during my PhD was very much related to droplets and using acoustics to generate precise size droplets and control their location and position to deposit very sensitive polymers.Now we apply similar technologies to encapsulate cells in droplets and then position them on the surfaces for various applications in tissue engineering to print cells on the surfaces to pattern cells. Also, there are applications where you want to see that you can encapsulate few cells or a single cell or from the same population and to see the differences between the same population from one cell to another there being able to encapsulate cells in droplets at high throughput rates like 10, 000 cells per second kind of rates becomes very important and very useful to understand biological problems. So my research currently has two legs, I would say.One is this cell encapsulation work that I just talked about. How do we pack a cell in a droplet that's, and how can we do this repeatedly and reliably and without harming the cells? So after the cell is ejected or encapsulated in the droplet, we should be able to precisely located on a surface the cell should be functional and alive and viable.It shouldn't be harmed by the effects of ejection and so forth. So currently we have a system where we use acoustic drop focused waves to generate these droplets from open pools where we can encapsulate down to single cells in these really small droplets that are comparable to the cell size. That's very exciting in terms of applying this to cell printing and tissue engineering.The other side of my research is again using these MAMs micro electromechanical system technologies to develop low cost diagnostic tools. Mostly this research uses microfluidic approaches where we can introduce whole blood, very small volumes such as blood from a prick finger prick, less than 10 microliters that you can introduce to a chip. And from that blood we can encapsulate or you can capture certain sub-cellular populations from whole blood.Why is this important? Why should this be cheap for global health applications On top of the mountain in Africa, you want to be able to tell for a HIV patient, for instance, how many CD four T lymphocytes this patient has. Because World Health Organization says that below 200 CD four cells per microliter, you have to start treating the patients In the developed world, you use hundreds of thousands dollars of vert flow cytometers to be able to get this data.And it takes of course time to use and skill of course to be able to use these like huge table size machines. Our small chip can be introduced this small finger brick 10 microliters of whole blood and it'll capture the CD four cells using the surface protein affinities. And then you can rapidly count these cells that are captured because you know that there are CD four cells which are attached to CD four proteins antibodies on the surface of the chip.By controlling the flow rates and shear, you can make sure that the specificity and efficiency for these cell types are optimized. And there's of course always non specific binding, but by our sheer approaches we minimize these effects and make sure that between plus minus 10%errors, which is sufficient to make a diagnostic or prognostic decision on top mountain in Africa. So this has interesting applications for global health as well as these low cost techniques that are disposable can impact the developed world because now these fast blood tests which are really low cost can impact the tests that we use in the developed world.If they're optimized to higher levels of efficiency and specificity, which our initial data shows that they can be, then it'll definitely impact our lives. When I first finished my PhD, I knew more about microfluidics and that in MAMs more than anything else I could see, especially with the droplet application, I could see that if I could print cells and encapsulate cells or manipulate the few cells, single cells, that it'll have great applications in biotechnology area. And I was very interested in working on things that will actually impact people's lives.I used to apply these technologies to semiconductor industry, but then I wanted to to be useful directly to people. So I, that's what directed me towards problems in healthcare. And then that's why I made a big shift and came to a hospital, mass general hospital to the postdoc.And there, you know, I got exposed more and more to problems and it seems, and it's all clear that one of the biggest problems of the world today is global health and there comes illnesses like tuberculosis, HIV that kills thousands of people per day. And these people die not because the drugs are not there, but because there aren't enough diagnostic tools which is much more expensive than the existing drugs. So I know the technology side of the things very well.I get, I got exposed to the biological problems and the more I learned about them, the more I could see that I could make an impact. And that's how it all grew from there. And it's still continuing now.Like I seen biotechnology and in medicine there are like so many problems that actually directly cause our result into loss of people's lives and the technologies, the technology aspect of it and being able to apply it to real world medical problems is a great, I think path to follow. This is like how this whole biotechnology area I think is kind of growing and it's becoming very impactful. If you think about it, HIV cancer, those are big killers in the world.And current micro technologies, current approaches could maybe benefit from early detection of cancer by capturing these cells from blood or making it really cheap, which will make it available to masses. So all these things coming together, I think this whole microtechnology applications in healthcare in medicine could impact the future of human beings. So that's how all these things kind of come together I guess.And being in the Harvard MIT health sciences and technology where on one end you have the technology and on the other end you direct aspect, direct access to patients, direct access to doctors in Brigham and Women's Hospital where I work is a great environment. cause every person that you talk to have their problems and you could maybe it's coming from a different background, provide interesting solutions to those existing real world problems. So this is, I think how I see the whole perspective of how these medical problems meet the technology side.And we try to impact people's lives in a positive way. In single cell cap encapsulation or in cell encapsulation, the major challenge is to be able to encapsulate reliably and repeatably single cells. So you're ejecting 10, 000 hundred thousand cells per second.And how do you make sure that each droplet that you eject has a single cell? This statistics where you are changing the droplet size and minimizing the, optimizing the cell size over the droplet size, which goes into the old problem of packing spheres in a volume and what is the most efficient way to do it. So that's the biggest challenge in the cell printing area for from the technological side.The other aspect of it is now you can say print and precisely locate these cells. How can you generate these three dimensional tissues and how can you keep them alive and how can you transplant them? There comes in the biological end of the problems where you want to now exactly mimic the tissue.We have current approaches to be able to print an eyelet, a pancreas eyelet, and to be able to print using smooth muscle cells, a bladder tissue, directly mimicking what is in human or red bladder so that then we can make this tissue and test how well it performs compared to the real world existing native tissues. So that's the major challenge I guess by taking these novel technologies, how can you make this the ideal tissue that can be replaced, that can be transplanted, that's the, you know, biggest problem from the beginning because the control on single cell gives you the capability to precisely locate them. And then how do you kind of grow it from there?So it's something transplantable there where the impact of human life comes. So that's on that end, what the challenges are in the tissue engineering side of the things in southern encapsulation and in diagnostics using microfluidics, the challenge is to be able to capture a cell out of billions of cells. It's like you have a sugar particle in a salt can and you're trying to pull out that sugar particle and that's like one in a billion.So you, you're processing microliters to milliliters of whole blood and you want to be able to specifically and efficiently without any technological problems like clogging or any biological problems like non-specific binding, you want to be able to isolate at one cell out of billion cells in one microliter of whole blood, you have a few millions of cells. And for the CD four T lymphocyte case in that one microliter, we are after about thousand cells per microliter. So it's like one cell in a thousand kind of a problem where we have shown that it's doable.But when you want to go after circulating tumor cells for cancer, then the challenge becomes one in a billion. So to some summarize it, the challenge is how do we capture this one cell out of billions of other cells around it? And what is the technological aspects?What are the flow rates? What is the device design? What, what are the flow rates?What, what are the volumes of blood that has to be processed and how do you make sure that the cells you capture are the ones that you actually wanted to capture? All these aspects kind formed the whole challenge that can be summarized in one sentence, which is how do you capture this one rare cell out of billion others? So it's really a needle in a haystack kind of problem, which is exciting.And I think this is moving the technologies forward to address these problems is the current technological challenge. Being able to bring them to a level where they do the job that they're supposed to do is one thing. And then taking it to the clinic and making it a product has all different expertise such as being able to start a company, being able to patent these things and all those other aspects come into the picture.And I think we as scientists primarily don't have all of those skills that takes the products from desktop to products. So there comes in again, the importance of collaborations with people who have different backgrounds. And there are many technologies out there that I think could be very impactful and useful.They sometimes don't make it to the clinic or to the use of humankind either because it just didn't happen, wasn't the right time or other effects came into the picture that I just talked about. Or sometimes there isn't a direct link that you couldn't see that the technology could actually solve that problem. And the person who deals with the problem, or let's say the biologists or people in medicine are used to doing it one way for many years.And the people on the technology side mostly if you're not having a biotechnology focus, are not aware of the problems in medicine. So bringing these two sides together is a serious interdisciplinary research. And I think in the past years, the whole emphasis both at NIH level and that we see in research labs and universities is to generate interdisciplinary research.So people end up getting PhDs where they have to know multiple fields. For instance, for my PhD, I had to know acoustics, I had to know mems, I had to know microfluidics and I had to apply this for polymers. So now you see kinda very depth of knowledge in one field where you had to know actually three other fields quite well to be able to solve that problem.So I think the answer is in interdisciplinary research combined with people with business skills to make it available to use of the people, it's a whole big process and some inefficiencies that come in at certain locations. Cause that low percent of tech transfer.

使用微机电系统（MEMS）开发诊断工具

生物学

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

紧凑的镜头少数字全息显微镜的MEMS检测与表征

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...

Microfluidic Pneumatic Cages: A Novel Approach for In-chip Crystal Trapping, Manipulation and Controlled Chemical Treatment

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. Herein, we introduce a microfluidic-based technology, employing a double-layer microfluidic device, which can trap and localize in situ and ex situ synthesized structures on microfluidic channel surfaces. Crucially, we show how such a device can be used to conduct controlled chemical reactions onto on-chip trapped structures and we demonstrate how the synthetic pathway of a crystalline molecular material and its positioning inside a microfluidic channel can be precisely modified with this technology. This approach provides new opportunities for the controlled assembly of structures on surface and for their subsequent treatment.

Herein, we describe the fabrication and operation of a double-layer microfluidic system made of polydimethylsiloxane (PDMS). We demonstrate the potential of this device for trapping, directing the coordination pathway of a crystalline molecular material and controlling chemical reactions onto on-chip trapped structures.

微流控气动笼:在芯片水晶捕获，处理的新方法和控制化学处理

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. ...

化学

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

制备与表征超导谐振器的

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Fabrication of 3D Carbon Microelectromechanical Systems (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long and hollow glassy carbon microfibers derived from human hairs is introduced. The long and hollow carbon structures were made by the pyrolysis of human hair at 900 &#176;C in a N2 atmosphere. The morphology and chemical composition of natural and pyrolyzed human hairs were investigated using scanning electron microscopy (SEM) and electron-dispersive X-ray spectroscopy (EDX), respectively, to estimate the physical and chemical changes due to pyrolysis. Raman spectroscopy was used to confirm the glassy nature of the carbon microstructures. Pyrolyzed hair carbon was introduced to modify screen-printed carbon electrodes ; the modified electrodes were then applied to the electrochemical sensing of dopamine and ascorbic acid. Sensing performance of the modified sensors was improved as compared to the unmodified sensors. To obtain the desired carbon structure design, carbon micro-/nanoelectromechanical system (C-MEMS/C-NEMS) technology was developed. The most common C-MEMS/C-NEMS fabrication process consists of two steps: (i) the patterning of a carbon-rich base material, such as a photosensitive polymer, using photolithography; and (ii) carbonization through the pyrolysis of the patterned polymer in an oxygen-free environment. The C-MEMS/NEMS process has been widely used to develop microelectronic devices for various applications, including in micro-batteries, supercapacitors, glucose sensors, gas sensors, fuel cells, and triboelectric nanogenerators. Here, recent developments of a high-aspect ratio solid and hollow carbon microstructures with SU8 photoresists are discussed. The structural shrinkage during pyrolysis was investigated using confocal microscopy and SEM. Raman spectroscopy was used to confirm the crystallinity of the structure, and the atomic percentage of the elements present in the material before and after pyrolysis was measured using EDX.

Fabrication of 3D Carbon Microelectromechanical Systems C-MEMS

Long and hollow glassy carbon microfibers were fabricated based on the pyrolysis of a natural product, human hair. The two fabrication steps of carbon microelectromechanical and carbon nanoelectromechanical systems, or C-MEMS and C-NEMS, are: (i) photolithography of a carbon-rich polymer precursor and (ii) pyrolysis of the patterned polymer precursor.

3D碳微机电系统（C-MEMS）的制造

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long ...

Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator

Temporal solitons have attracted great interest in the past decades for their behavior in a steady state, where the dispersion is balanced by the nonlinearity in a propagation Kerr medium. The development of dissipative Kerr solitons (DKSs) in high-Q microcavities drives a novel, compact, chip-scale soliton source. When DKSs serve as femtosecond pulses, the repetition rate fluctuation can be applied to ultrahigh precision metrology, high-speed optical sampling, and optical clocks, etc. In this paper, the rapid repetition rate fluctuation of soliton crystals (SCs), a special state of DKSs where particle-like solitons are tightly packed and fully occupy a resonator, is measured based on the well-known delayed self-heterodyne method. The SCs are generated using a thermal-controlled method. The pump is a frequency fixed laser with a linewidth of 100 Hz. The integral time in frequency fluctuation measurements is controlled by the length of the delay fiber. For a SC with a single vacancy, the repetition rate fluctuations are ~53.24 Hz within 10 &#181;s and ~509.32 Hz within 125 &#181;s, respectively.

Here, we present a protocol to generate soliton crystals in a butterfly-packaged micro-ring resonator using a thermal tuned method. Further, the repetition rate fluctuations of a soliton crystal with a single vacancy are measured using a delayed self-heterodyne method.