Name: measuring local tissue strains in tendons via open-source digital image correlation
Uploaded: 2023-01-27T14:30:00
Description: Watch this Scientific Journal Video about Measuring Local Tissue Strains in Tendons via Open-Source Digital Image Correlation at JoVE.com

这项工作由美国国立卫生研究院（R21 AR079095）和美国国家科学基金会（2142627）资助。

这项研究得到了宾夕法尼亚州立大学机构动物护理和使用委员会的批准。
1. 组织准备
<ol><li>对于该协议，从2-4个月大的雄性C57BL / 6小鼠中收获跟腱。 注意：也可以使用来自小鼠或其他小动物的不同肌腱或韧带。<ol><li>在跟腱表面的皮肤上切开一个切口，露出足底肌腱和周围的结缔组织。然后，使用手术刀片将其取出。</li>
		<li>将暴露的比目鱼肌和腓肠肌与后?...

<ol>
	<li>Devkota, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distributing+a+fixed+amount+of+cyclic+loading+to+tendon+explants+over+longer+periods+induces+greater+cellular+and+mechanical+responses.">Distributing a fixed amount of cyclic loading to tendon explants over longer periods induces greater cellular and mechanical responses.</a> Journal of Orthopaedic Research. 11 (4), 1609-1612 (2007).</li><li>Sun, H. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cycle-dependent+matrix+remodeling+gene+expression+response+in+fatigue-loaded+rat+patellar+tendons.">Cycle-dependent matrix remodeling gene expression response in fatigue-loaded rat patellar tendons.</a> Journal of Orthopaedic Research. 28 (10), 1380-1386 (2010).</li><li>Shepherd, J. H., Screen, H. R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fatigue+loading+of+tendon.">Fatigue loading of tendon.</a> International Journal of Experimental Pathology. 94 (4), 260-270 (2013).</li><li>Paschall, L., Pedaprolu, K., Carrozzi, S., Dhawan, A., Szczesny, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+stimulation+as+both+the+cause+and+the+cure+of+tendon+and+ligament+injuries.">Mechanical stimulation as both the cause and the cure of tendon and ligament injuries.</a> Regenerative Rehabilitation: From Basic Science to the Clinic. , 359-386 (2022).</li><li>Andarawis-Puri, N., Ricchetti, E. T., Soslowsky, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rotator+cuff+tendon+strain+correlates+with+tear+propagation.">Rotator cuff tendon strain correlates with tear propagation.</a> Journal of Biomechanics. 42 (2), 158-163 (2009).</li><li>Cheng, V. W. T., Screen, H. R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+micro-structural+strain+response+of+tendon.">The micro-structural strain response of tendon.</a> Journal of Materials Science. 42 (21), 8957-8965 (2007).</li><li>Luyckx, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digital+image+correlation+as+a+tool+for+three-dimensional+strain+analysis+in+human+tendon+tissue.">Digital image correlation as a tool for three-dimensional strain analysis in human tendon tissue.</a> Journal of Experimental Orthopaedics. 1 (1), 7 (2014).</li><li>Duncan, N. A., Bruehlmann, S. B., Hunter, C. J., Shao, X., Kelly, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+cell-matrix+mechanics+in+tendon+fascicles+and+seeded+collagen+gels:+Implications+for+the+multiscale+design+of+biomaterials.">In situ cell-matrix mechanics in tendon fascicles and seeded collagen gels: Implications for the multiscale design of biomaterials.</a> Computer Methods in Biomechanics and Biomedical Engineering. 17 (1), 39-47 (2014).</li><li>Arnoczky, S. P., Lavagnino, M., Whallon, J. H., Hoonjan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+cell+nucleus+deformation+in+tendons+under+tensile+load;+A+morphological+analysis+using+confocal+laser+microscopy.">In situ cell nucleus deformation in tendons under tensile load; A morphological analysis using confocal laser microscopy.</a> Journal of Orthopaedic Research. 20 (1), 29-35 (2002).</li><li>Screen, H. R. C., Bader, D. L., Lee, D. A., Shelton, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+strain+measurement+within+tendon.">Local strain measurement within tendon.</a> Strain. 40 (4), 157-163 (2004).</li><li>Fung, A. K., Paredes, J. J., Andarawis-Puri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+image+analysis+methods+for+quantification+of+in+situ+3-D+tendon+cell+and+matrix+strain.">Novel image analysis methods for quantification of in situ 3-D tendon cell and matrix strain.</a> Journal of Biomechanics. 67, 184-189 (2018).</li><li>Yang, J., Bhattacharya, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Augmented+Lagrangian+digital+image+correlation.">Augmented Lagrangian digital image correlation.</a> Experimental Mechanics. 59 (2), 187-205 (2019).</li><li>Peterson, B. E., Szczesny, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dependence+of+tendon+multiscale+mechanics+on+sample+gauge+length+is+consistent+with+discontinuous+collagen+fibrils.">Dependence of tendon multiscale mechanics on sample gauge length is consistent with discontinuous collagen fibrils.</a> Acta Biomaterialia. 117, 302-309 (2020).</li><li>Humphrey, J. D., O'Rourke, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> An Introduction to Biomechanics. , (2015).</li><li>Reese, S. P., Weiss, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tendon+fascicles+exhibit+a+linear+correlation+between+Poisson's+ratio+and+force+during+uniaxial+stress+relaxation.">Tendon fascicles exhibit a linear correlation between Poisson's ratio and force during uniaxial stress relaxation.</a> Journal of Biomechanical Engineering. 135 (3), 34501 (2013).</li><li>Ahmadzadeh, H., Freedman, B. R., Connizzo, B. K., Soslowsky, L. J., Shenoy, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromechanical+poroelastic+finite+element+and+shear-lag+models+of+tendon+predict+large+strain+dependent+Poisson's+ratios+and+fluid+expulsion+under+tensile+loading.">Micromechanical poroelastic finite element and shear-lag models of tendon predict large strain dependent Poisson's ratios and fluid expulsion under tensile loading.</a> Acta Biomaterialia. 22, 83-91 (2015).</li><li>Szczesny, S. E., Elliott, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interfibrillar+shear+stress+is+the+loading+mechanism+of+collagen+fibrils+in+tendon.">Interfibrillar shear stress is the loading mechanism of collagen fibrils in tendon.</a> Acta Biomaterialia. 10 (6), 2582-2590 (2014).</li><li>Han, W. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macro-+to+microscale+strain+transfer+in+fibrous+tissues+is+heterogeneous+and+tissue-specific.">Macro- to microscale strain transfer in fibrous tissues is heterogeneous and tissue-specific.</a> Biophysical Journal. 105 (3), 807-817 (2013).</li><li>Pedaprolu, K., Szczesny, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel,+open-source,+low-cost+bioreactor+for+load-controlled+cyclic+loading+of+tendon+explants.">A novel, open-source, low-cost bioreactor for load-controlled cyclic loading of tendon explants.</a> Journal of Biomechanical Engineering. 144 (8), 084505 (2022).</li><li>Gatt, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Negative+Poisson's+ratios+in+tendons:+An+unexpected+mechanical+response.">Negative Poisson's ratios in tendons: An unexpected mechanical response.</a> Acta Biomaterialia. 24, 201-208 (2015).</li></ol>

本文的目的是提供一种开源的、经过验证的方法来测量拉伸载荷下肌腱中的二维应变场。该软件的基础是基于公开可用的ALDIC算法12。该算法被嵌入到更大的 MATLAB 代码中，并增加了增量（相对于累积）应变分析的功能。然后将这种适应的算法应用于肌腱的拉伸测试，并通过两种不同的技术（即，数字转换图像和使用光漂白线的应变测量）评估其准确性。此外，还增加了一种功能?...

肌腱是机械敏感组织，响应机械负荷而适应和退化1，2，3，4。由于机械刺激在肌腱细胞生物学中的作用，人们对了解肌腱细胞在加载过程中在天然组织环境中经历的菌株非常感兴趣。已经开发了几种实验和分析技术来测量肌腱中的局部组织菌株。其中包括使用斑点图案或光漂白线（PBL）对表面应变进行2D/3D数字图像相关（DIC）分析5，6，7，8，测量组织内单个细胞核的质心到质心距离的变化9，10，以及最近的全场3D DIC方法，该方法考虑了面外运动和3D变形11.然而，这些技术的准确性和灵敏度仅在少数情况下被报道，并且这些技术都没有公开，这使得这些技术的广泛采用和利用变得困难。
这项工作的目的是创建一个经过验证的分析工具，用于测量肌腱外植体中的局部组织菌株，该工具易于获得且易于使用。所选择的方法基于由Yang和Bhattacharya12开发的用MATLAB编写的公开可用的增强拉格朗日数字图像相关（ALDIC）算法。该算法适用于分析肌腱样品，并通过将其应用于数字转换图像并将实际肌腱样品中测量的应变与从光漂白线获得的结果进行比较来验证。此外，算法中还实现了附加功能，即使在没有已知应变值或二次测量技术的情况下，也能确认计算出的位移场的准确性。因此，该算法是准确测量肌腱局部二维组织应变的非常有用且适应性强的工具。

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5-DTAF (5-(4,6-Dichlorotriazinyl) Aminofluorescein), single isomer</td>
			<td>ThermoFisher</td>
			<td>D16</td>
			<td></td>
		</tr>
		<tr>
			<td>Calipers</td>
			<td>Mitutoyo</td>
			<td>500-196-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal Microscope</td>
			<td>Nikon</td>
			<td>A1R HD</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning LSE Vortex Mixer</td>
			<td>Coning</td>
			<td>6775</td>
			<td></td>
		</tr>
		<tr>
			<td>DRAQ5 Fluorescent Probe Solution (5 mM)</td>
			<td>ThermoFisher</td>
			<td>62554</td>
			<td></td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>MathWorks</td>
			<td>R2022b</td>
			<td></td>
		</tr>
		<tr>
			<td>Tensile Loading Device</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Tensile loading device described in Peterson et al, 2020. (ref 13)&#160;</td>
		</tr>
		<tr>
			<td>Tube Revolver Rotator</td>
			<td>ThermoFisher</td>
			<td>88881001</td>
			<td></td>
		</tr>
	</tbody>
</table>

measuring local tissue strains in tendons via open-source digital image correlation

了解肌腱细胞原 位 经历的菌株以及这些菌株如何影响组织重塑具有相当大的科学兴趣。基于这种兴趣，已经开发了几种分析技术来测量加载过程中肌腱外植体内的局部组织菌株。然而，在一些情况下，这些技术的准确性和灵敏度尚未被报道，并且没有一种算法是公开可用的。这使得更广泛地测量肌腱外植体中的局部组织菌株变得困难。因此，本文的目的是创建一个经过验证的分析工具，用于测量肌腱外植体中的局部组织菌株，该工具易于获得且易于使用。具体而言，一种公开可用的增强拉格朗日数字图像相关（ALDIC）算法通过跟踪单轴张力下小鼠跟腱内细胞核的位移来测量2D菌株。此外，通过分析数字转换的图像，以及将应变与独立技术确定的值（即光漂白线）进行比较，验证了计算菌株的准确性。最后，将一种技术纳入算法中，利用计算出的位移场重建参考图像，可用于在没有已知应变值或二次测量技术的情况下评估算法的精度。该算法能够测量高达 0.1 的应变，精度为 0.00015。将重建的参考图像与实际参考图像进行比较的技术成功地识别了具有错误数据的样本，并表明在具有良好数据的样本中，大约85%的位移场是准确的。最后，在小鼠跟腱中测量的菌株与先前的文献一致。因此，该算法是准确测量肌腱局部组织应变的非常有用且适应性强的工具。

在分析实际组织样品中的应变场之前，首先使用小鼠跟腱内细胞核的数字应变/转换图像验证ALDIC方案。具体来说，将图像转换为在 2%、4%、6%、8% 和 10% 应变的 x 方向上以数字方式产生均匀应变，模拟泊松比为 115，16。然后通过将计算出的平均应变值与已知的数字应变值进行比较来评估ALDIC算法的准确性。此外，还评估了应变值的标准偏差以确定应变场的...

Watch this Scientific Journal Video about Measuring Local Tissue Strains in Tendons via Open-Source Digital Image Correlation at JoVE.com

Measuring Local Tissue Strains in Tendons via Open-Source Digital Image Correlation

本文介绍了一种用于测量肌腱外植体内局部二维组织菌株的开源数字图像相关算法。该技术的准确性已使用多种技术进行了验证，并且可供公众使用。

通过开源数字图像相关 测量 肌腱中的局部组织应变

There is considerable scientific interest in understanding the strains that tendon cells experience in situ and how these strains influence tissue ...

该协议能够在加载期间测量肌腱内的局部组织应变。了解肌腱的机械行为并适应其负载环境很有用。该技术的主要优点是所使用的软件可以在线公开获得，即使真正的组织菌株未知，也能提供有关测量精度的反馈。测量肌腱中的局部组织应变对于了解细胞在肌腱变性和修复过程中如何重塑组织很有价值。演示这一程序的将是本科生Stanton Godshall和我实验室的博士生Krishna Pedaprolu。在DTAF中染色收获的跟腱后，将组织从DTAF溶液转移到DRAQ5溶液中，并在室温下在黑暗空间中孵育组织10分钟。将肌腱放入拉伸加载装置的夹具中。在将夹具安装到装载装置中之前，请使用数字卡尺测量跟骨附件与另一侧夹具之间的距离。将夹具安装到含有PBS的装载装置中，以保持组织水合作用。将肌腱尽可能与显微镜图像的 x 轴或 y 轴对齐，以便算法的 X 应变和 Y 应变输出与肌腱轴相对应。用一克张力预加载肌腱。如果需要，在组织的中心区域对一组间隔80微米的四条线进行光漂白，并在夹具附近的左右极端重复该过程。每个组织区域中线之间的距离变化是可用于验证数据的局部组织菌株的二次测量。接下来，使用共聚焦显微镜，在一克预载荷下获取DTAF和DRAQ5荧光的体积图像。以每秒0.5%的速度将应变斜坡上升至2%应变。请注意，可以调整应变率和增量应变大小。让组织应力放松10分钟后，在变形后拍摄组织的另一张体积图像。根据需要对任意数量的应变增量重复该过程。要创建经过数字转换的图像，请下载代码digital_strain。m来自GitHub。下载后，打开并运行代码。出现提示时，在按 OK 之前插入最大施加应变、施加应变增量和泊松比的所需值。然后，当再次出现提示时，选择未变形的参考图像。对于每个应变增量，将显示参考图像和转换后的图像的叠加。经过数字转换的图像将保存到名为“数字转换的X%应变”的目录中，其中X是应变增量。打开具有显示名称的脚本，然后单击运行以开始图像分析。出现提示时，根据需要更改增强拉格朗日数字图像相关或 ALDIC 参数的值。出现提示后，选中 yes 复选框以自动保存所需变量集合的平均值、标准差和 2D 图。出现提示时，选择所需的变量，如 X 应变、Y 应变、剪切应变、坏区域等，然后按 OK。按照下一个提示，选择包含重命名的最大强度 Z 投影的文件夹。软件自动执行增量ALDIC以确定变形图像的应变场。出现提示时，左键单击以创建一个四点面，以定义用于测量应变的感兴趣区域。文件夹核跟踪结果（可通过调整行 555 和 556 重命名）存储先前指定的所有图。此文件夹还包含一个名为结果的电子表格，该电子表格存储之前指定的所有均值和标准差。当使用数字应变图像进行验证时，ALDIC算法始终低估了平均X应变，并且误差幅度随着施加应变的增加而增加。Y菌株也大多被低估了。然而，在所有情况下，应变误差的大小都非常小。计算出的X应变和Y应变的标准差虽然幅度较低，但随着施加应变的增加而增加。坏区分析显示，使用累积法分析的数字化转换图像中具有无效应变计算的坏区数量在施加6%应变后持续增加，而增量数量保持在1%在四个样本中的一个中，被视为异常值，近一半的图像在最大应变增量下被识别为坏图像。ALDIC计算的X菌株大于PBL测定的X菌株，差异在0.005以内，与所有样本中平均的PBL数据的标准差相似。确定拉伸载荷下肌腱局部应变的大小和空间分布表明，在所有样品中，X应变始终保持在施加的应变以下。对于所有增量，Y方向上的平均应变近似为零，但标准偏差很高。平均剪切应变在整个应变增量过程中稳步增加。要记住的最重要的一点是在施加更大的应变之前保存图像。如果未保存，图像将丢失且无法恢复。虽然该技术专门用于测量肌腱内的组织应变，但它可以提供对许多其他动物和人体组织的机械生物学和力学的见解。

measuring-local-tissue-strains-tendons-via-open-source-digital-image

Research

JoVE Journal

Engineering

Measuring Local Tissue Strains in Tendons via Open-Source Digital Image Correlation

Echo Particle Image Velocimetry

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.2 For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.3,4,5,6 In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine7 with a PC running commercial particle image velocimetry (PIV) software8 is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported.
For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/&delta;t. (See 9 for a review of ultrasound imaging.)
For a typical EPIV experiment, the frame rate is between 20-60 fps, depending on flow conditions, and 100-1000 B-mode images of the spatial distribution of the tracer particles in the flow are acquired. Once acquired, the B-mode ultrasound images are transmitted via an ethernet connection to the PC running the PIV commercial software. Using the PIV software, tracer particle displacement fields, D(x,y)[pixels], (where x and y denote horizontal and vertical spatial position in the ultrasound image, respectively) are acquired by applying cross correlation algorithms to successive ultrasound B-mode images.10 The velocity fields, u(x,y)[m/s], are determined from the displacements fields, knowing the time step between image pairs, &Delta;T[s], and the image magnification, M[meter/pixel], i.e., u(x,y) = MD(x,y)/&Delta;T. The time step between images &Delta;T = 1/fps + D(x,y)/B, where B[pixels/s] is the time it takes for the ultrasound probe to sweep across the image width. In the present study, M = 77[&mu;m/pixel], fps = 49.5[1/s], and B = 25,047[pixels/s]. Once acquired, the velocity fields can be analyzed to compute flow quantities of interest.

An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.

回声粒子图像测速技术

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

科研

工程学

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 ...

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

以减少液滴表面的相互作用来优化Bioanalytes运输中的数字微流体

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

Scanning SQUID Study of Vortex Manipulation by Local Contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

由当地接触式扫描涡操纵SQUID研究

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

通过时间分辨微波电导率重组动力学薄膜光伏材料

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer.
At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

管道单、两相流局部瞬时对流换热的测量

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer ...

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due to their potential applications for future device technologies such as sensors and storage. However, conventional approaches, which usually utilize materials containing magnetic metal ions (or radicals), have a major problem: only a few materials have been found to show the coupling phenomena at room temperature. Recently, we proposed a new approach to achieve room-temperature magnetoelectrics. In contrast to conventional approaches, our alternative proposal focuses on a completely different material, a &#34;liquid crystal&#34;, free from magnetic metal ions. In such liquid crystals, a magnetic field can be utilized to control the orientational state of constituent molecules and the corresponding electric polarization through magnetic anisotropy of the molecules; it is an unprecedented mechanism of the magnetoelectric effect. In this context, this paper provides a protocol to measure ferroelectric properties induced by a magnetic field, that is, the direct magnetoelectric effect, in a liquid crystal. With the method detailed here, we successfully detected magnetically-tuned electric polarization in the chiral smectic C phase of a liquid crystal at room temperature. Taken together with the flexibility of constituent molecules, which directly affects the magnetoelectric responses, the introduced method will serve to allow liquid crystal cells to acquire more functions as room-temperature magnetoelectrics and associated optical materials.

In this report, we present a protocol to examine direct magnetoelectric effects, i.e., induction of ferroelectric polarization by applying magnetic fields, in liquid crystals. This protocol provides a unique approach, supported by the softness of liquid crystals, to achieve room-temperature magnetoelectrics.

液晶中磁调谐铁电极化的测量

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due ...

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, with its peak locomotion speed reaching 150 cm/s. First of all, we observed the microstructure and hierarchy of water strider legs using the scanning electron microscope. On the basis of the observed morphology of the legs, a theoretical model of the detachment from water surface was established, which explained water striders' capability to slide on water surface effortlessly in terms of energy reduction. Secondly, a dynamic force measurement system was devised using the PVDF film sensor with excellent sensitivity, which could detect the whole interaction process. Subsequently, a single leg in contact with water was pulled upward at different speeds, and the adhesion force was measured at the same time. The results of the departing experiment suggested a deep understanding of the fast jumping of water striders.

The protocol here is dedicated to investigating the free and quick maneuvering of water strider on water surface. The protocol includes observing the microstructure of legs and measuring the adhesion force when departing from water surface at different speeds.

PVDF 薄膜传感器对水黾腿跳起动力的测量

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, ...

Full-field Strain Measurements for Microstructurally Small Fatigue Crack Propagation Using Digital Image Correlation Method

A novel measurement approach is used to reveal the cumulative deformation field at a sub-grain level and to study the influence of microstructure on the growth of microstructurally small fatigue cracks. The proposed strain field analysis methodology is based on the use of a unique pattering technique with a characteristic speckle size of approximately 10 &#181;m. The developed methodology is applied to study the small fatigue crack behavior in body centered cubic (bcc) Fe-Cr ferritic stainless steel with a relatively large grain size allowing a high spatial measurement accuracy at the sub-grain level. This methodology allows the measurement of small fatigue crack growth retardation events and associated intermittent shear strain localization zones ahead of the crack tip. In addition, this can be correlated with the grain orientation and size. Thus, the developed methodology can provide a deeper fundamental understanding of the small fatigue crack growth behavior, required for the development of robust theoretical models for the small fatigue crack&#160;propagation in polycrystalline materials.

Microstructurally small fatigue crack growth behavior is investigated using a novel methodological approach combining crack growth rate measurement and strain-field analysis to reveal the cumulative deformation field at sub-grain level.

基于数字图像相关的微结构小疲劳裂纹扩展的全场应变测量

A novel measurement approach is used to reveal the cumulative deformation field at a sub-grain level and to study the influence of microstructure on the ...

Intermediate Strain Rate Material Characterization with Digital Image Correlation

The mechanical response of a material under dynamic load is typically different than its behavior under static conditions; therefore, the common quasistatic equipment and procedures used for material characterization are not applicable for materials under dynamic loads. The dynamic response of a material depends on its deformation rate and is broadly categorized into high (i.e., greater than 200/s), intermediate (i.e., 10&#8722;200/s) and low strain rate regimes (i.e., below 10/s). Each of these regimes calls for specific facilities and testing protocols to ensure the reliability of the acquired data. Due to the limited access to high-speed servo-hydraulic facilities and validated testing protocols, there is a noticeable gap in the results at the intermediate strain rate. The current manuscript presents a validated protocol for the characterization of different materials at these intermediate strain rates. Strain gauge instrumentation and digital image correlation protocols are also included as complimentary modules to extract the utmost level of detailed data from every single test. Examples of raw data, obtained from a variety of materials and test setups (e.g., tensile and shear) is presented and the analysis procedure used to process the output data is described. Finally, the challenges of dynamic characterization using the current protocol, along with the limitations of the facility and methods of overcoming potential problems are discussed.

Here we present a methodology for the dynamic characterization of tensile specimens at intermediate strain rates using a high-speed servo-hydraulic load frame. Procedures for strain gauge instrumentation and analysis, as well as for digital image correlation strain measurements on the specimens, are also defined.

通过开源数字图像相关 测量 肌腱中的局部组织应变

通过开源数字图像相关测量肌腱中的局部组织应变