环境控制机械自适应聚合物纳米复合材料的微拉伸测试<em>体外</em>表征
1Advanced Platform Technology Center, Rehabilitation Research and Development,Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 2Department of Biomedical Engineering,Case Western Reserve University, 3Department of Electrical Engineering and Computer Science,Case Western Reserve University
Summary
一种方法的讨论<em>在体内</em>刺激响应性材料的机械行为进行监测作为时间的函数。测试样品<em>体外</em>与环境控制用微拉伸测试仪模拟生理环境。这项工作进一步促进理解<em>在体内</em我们的材料行为。
Abstract
植入微型器件获得重大关注的几个生物医学应用1-4。这样的设备已经从一系列的材料，提供自己的优点和缺点5,6。最突出的是，由于微尺度装置尺寸，高的弹性模量是必需的，以便植入到生物体组织。相反，该设备的刚度应与周围组织的匹配，以尽量减少引起的局部应变7-9。因此，我们最近开发的一类新的仿生材料，以满足这些要求，通过响应对环境刺激的机械性能的变化10-14。具体而言，为聚（乙酸乙烯酯）为基础的纳米复合材料（聚醋酸乙烯酯-NC）显示一个刚度降低时，接触到水和升高的温度（ 例如体温）。不幸的是，一些方法存在量化材料在体内 15的刚度，机甲外anical测试的生理环境，往往需要大样本，不适合植入。此外，刺激响应材料外植后可能会很快恢复其初始刚度。因此，我们已经开发了一种方法，通过它的机械性能植入microsamples可以测量体外模拟生理条件下保持使用的湿度和温度控制13,16,17。
为此，一个自定义的微拉伸测试仪的设计，以适应广泛不同的杨氏模量（在10MPa至5 GPA所在的范围）的微型样品13,17。由于大家的利益是在PVAC-NC的应用作为一种生物适应性神经探针底物，工具，能够在微尺度样本是必要的机械特性。这个工具被改编提供湿度和温度控制，干燥，冷却17最小化样本。其结果，技工密切反映这些人的特点，植样品的样品之前外植。
该方法的总体目标是在体内的机械性能，特别的刺激响应性，机械自适应聚合物为基础的材料的杨氏模量，定量评估。这是通过首先建立的环境条件下，将外植后的样品的机械性能的变化最小化，而不有助于减少刚度无关，因植入。制备的样品，然后注入，处理，和检测（ 图1A）。大鼠大脑皮质这里取出的大鼠脑组织，在指定的持续时间（ 图1B），这是代表每个样品的注入。在这一点上，将样品取出的，并立即装入的微拉伸测试仪，然后进行拉伸试验（ 图1C）。随后的数据分析提供了洞察这些创新材料的力学行为在大脑皮质的环境。
Protocol
1。样品制备制备聚醋酸乙烯酯-NC膜的厚度在25-100微米的范围内使用溶液流延法和压缩技术10-12。 粘附膜的硅晶片上的热板上加热两分钟，在70℃（玻璃化转变温度以上），以促进膜和晶片之间的紧密接触。此步骤可确保所制备的膜的硅晶片，这是必要的平面的微机械加工工艺保持平整，并且固定。 通过激光微加工（VLS 3.50，VersaLASER）到测试样品几何图案的电影。 CO <…
Representative Results
几乎所有的聚合物材料，包括聚醋酸乙烯酯-NC的机械性能取决于暴露于环境条件。最值得注意的是，这些包括对热和湿气的曝光。被塑化的材料时，由于水分的吸收，或经历了一个热转变时，它显示的杨氏模量的降低。在制备的水分的体外样品的机械特性和温度受控制的环境中，这是重要的，以确保有样品的水分含量非常少的改变，同时将样品加载到微拉伸测试仪，以及在机械测试。评估?…
Discussion
可植入生物医学微电子机械系统（微机电）与生物系统进行交互的进步是激励具有高度定制的特性的新材料的发展。其中一些材料的设计表现出材料性能的变化，发现在生理环境中对刺激的响应。一个最近开发的一类材料氢键形成的液体（ 例如水）和高温下的杨氏模量，材料的刚度的措施，减少了三个数量级10,11,18的存在下的反应。这些聚合物纳米复合材料具有柔软的聚合物基体?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
支持这项工作是由美国凯斯西储大学的生物医学工程部通过两个实验室启动资金（J. Capadona），美敦力的研究生奖学金（K.波特）。在此研究中，额外的资金支持部分由NSF资助ECS-0621984（C. Zorman），案例校友协会（C. Zorman）通过优异评论奖（B7122R），退伍军人事务部，以及高级平台技术中心（C3819C）。
Materials
| Name of Reagent/Material | Company | Catalogue Number | Comments |
| Silicon wafer | University Wafer | Mechanical grade | |
| Extruded acrylic sheet | Professional Plastics | SACR 062EF | Thickness 0.062″ |
| Razor blade | McMaster-Carr | 3962A3 | |
| Tweezers | McMaster-Carr | 8384A47 | #5 tip |
| Super Glue Gel | Loctite | 130380 | |
| Air Brush | Snap-on Industrial | BF175TA | |
| Air Compressor | Paasche | B002YKN8YO | D500 |
| Thermocouple | Omega | HH12A | |
| Hot plate | Cimarec | SP131325Q | |
| CO2 direct-write laser | VersaLaser | 3.5 | |
| Dessicator | Fisher Scientific | 08-595 | |
| Lamp | custom-built | ||
| Microtensile tester | custom-built |
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Cite This Article
Hess, A. E., Potter, K. A., Tyler, D. J., Zorman, C. A., Capadona, J. R. Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for ex vivo Characterization. J. Vis. Exp. (78), e50078, doi:10.3791/50078 (2013).