BIOMOMENTUM力学试验机--人发机械性能评估

EVALUATION OF THE MECHANICAL PROPERTIES OF HUMAN HAIR

We were recently asked if our mechanical tester has the capability of evaluating the mechanical properties of single fiber human hair. In our lab, a scientist has been devoted to this feasibility study.

The hardest part of this work was to develop the proper gripping fixtures to easily mount the hair on the tester to be able to perform tensile and torsion testing. Following few attempts, it was found that the simplest and most reproducible mounting method was based on the use of a pair of off-the-shelf syringe needle tips. On the bench, the hair fiber was inserted through the two needles facing each other and spaced by a predefined gauge gap. A single drop of cyanoacrylate glue was applied in the plastic cavity of each needle to secure the hair in place. Two needle tip holders with the same tapered shape as a regular syringe were mounted on the Mach-1. These two holders were fastened facing each other at the center of a testing chamber under a 17N multiaxis load cell. The double-needle hair assembly was then firmly inserted over the holder (see Image 1).

After zeroing the load, and considering the relative position of the vertical stage, the initial length of the hair at full extension (when no load is applied) was measured using the Mach-1 Motion's "Find Contact" function. A sinusoidal deformation in the elastic region was applied for 30 cycles at 0.5, 1 and 2 Hz. A Dynamic Mechanical Testing analysis was conducted as per MA056-SOP04-D to extract the complex tensile storage and loss modulus components. Dynamic testing showed an increase in phase magnitude with increased frequency. This result was expected and explains an increase in plastic deformation (loss modulus) with increased frequency.

The tensile modulus and ultimate tensile strength were also measured and calculated (Mach-1 Analysis software) during a tensile load ramp to failure (see Image 2 - Tensile test output until failure). The results were found to be in accordance with literature (Lee, 2012): 930 MPa ultimate tensile strength, 6.5 GPa elastic modulus. Other tests were completed using a rotational stage to apply torsion to the hair until rupture occurred. For two samples, the results were 175 and 179 turns before failure. A camera feed with a 10X lens was used to visualize the torsion of the fiber in real time.

The plastic torsion of the hair remains even after breakage and can be visualized under a microscope (see Image 3 - Post-torsion photograph using 20x microscope). 

During torsion, the generated torque around the Z-axis was too low to be measured by the 17N multiaxial load cell. However, the vertical contraction of the hair induced by torsion created a vertical contractile force that was measured by the Fz channel of the cell. It is assumed that through proper theoretical modelling of this test configuration, this axial load could be used to indirectly measure the torsional shear strength of the hair. 

Different indirect ways of quantifying the torsional properties of fibres have also been proposed in literature. For example, by relating the initial gauge length to the number of rotations before rupture, a theoretical value for fracture angle can be obtained. From a basic analysis, the fracture angle was found to be between 26 and 33°.

近，我们被问到我们的机械测试仪是否具有评估单纤维人发机械性能的能力。在我们的实验室中，一位科学家致力于这项可行性研究。

这项工作困难的部分是开发合适的抓持装置，以将头发轻松安装到测试仪上，以执行拉伸和扭转测试。经过几次尝试，发现简单，可重复的安装方法是基于使用一对现成的注射器针尖。在工作台上，将毛发纤维穿过彼此面对的两个针头插入，并以预定的标尺间隙隔开。将一滴氰基丙烯酸酯胶滴到每个针的塑料腔中，以将头发固定到位。在Mach-1上安装了两个具有与普通注射器相同的锥形形状的针尖支架。将这两个支架在17N多轴称重传感器下的测试腔室中心彼此相对固定。

将负载归零后，考虑垂直台的相对位置，使用Mach-1 Motion的“查找接触”功能测量在*伸展时（未施加负载时）头发的初始长度。在弹性区域以0.5、1和2 Hz的频率施加正弦形变形30个循环。根据MA056-SOP04-D进行动态力学测试分析，以提取复杂的拉伸存储和损耗模量分量。动态测试显示相位幅度随频率增加而增加。该结果是预期的，并解释了塑性变形（损耗模量）随频率增加而增加。

biomomentum多轴机械测试仪Mach-1
 Mach-1多轴机械测试仪是模块化集成压缩，拉伸，剪切，摩擦，扭转和3D压痕映射、电位分布等测试设备
   biomomentum至1999年以来，专注用于测试生物材料，组织和关节软骨机-电特性产品的设计、开发、制造和商业化的创新解决方案20余年。
    其mach-1多轴向多功能组织材料机械特性测试分析系统已经成为组织材料机械-电位测试分析的黄金标准。
  1、多功能、多轴向，适用样品范围广：
•1.1、从骨等硬组织材料到脑组织、眼角膜等极软的组织材料
•1.2、从粗的椎间盘的样品到极细的单纤维丝
2、力学类型测试分析功能齐全：
2.1、模块化集成压缩、张力、剪切、摩擦、扭转、穿刺、摩擦和非平面压痕、3D厚度、3D表面轮廓等各种力学类型支持,微观结构表征及动态力学分析研究
2.2、多物理场耦合加载测试
•3、通高量压痕、压缩测试分析（48孔板中压痕测试分析）
•4、高精度、高分辨率:
•4.1、位移分辨率达0.1um
•4.2、力分辨率达0.025mN
•4.3、样品直径小25um
•5、行程范围广：50-250mm
•6、体积小巧、可放入培养箱内
•7 、DIC （Digital Image Correlation)数字图像相关法非接触式的高精度位移、应变测量
•9、活性组织电位分布测试分析
•10、产品成熟，文献量达上千篇
biomomentum多轴机械测试仪Mach-1材料力学性能简介：
biomomentum多轴机械测试仪Mach-1材料力学性能是指材料在不同环境(温度、介质、湿度)下，承受各种外加载荷(拉伸、压缩、弯曲、扭转、冲击、交变应力等)时所表现出的力学特征。
可以放进标准培养箱里进行培养；
biomomentum多轴机械测试仪Mach-1测试意义及适用范围：
材料力学性能可以应用到生产的任何阶段，从测试原材料质量直到检查制成品的耐用性。 测试可对广泛多样的生物样品、材料和产品进行，包括软组织、软骨组织、皮肤组织、凝胶组织、高分子材料、生物产品、医学鉴定和水凝胶等。力学性能测试可帮助企业向客户证明其产品的力学性能、稳定性和安性，从而获得基础数据和竞争势。
1、多功能、多轴向，适用样品范围广：
1.1、从骨等硬组织材料到脑组织、眼角膜等极软的组织材料
1.2、从粗的椎间盘的样品到极细的单纤维丝
2、力学类型测试分析功能齐全：
2.1、模块化集成压缩、张力、剪切、摩擦、扭转、穿刺、摩擦和非平面压痕、3D厚度、3D表面轮廓等各种力学类型支持,微观结构表征及动态力学分析研究
2.2、多物理场耦合加载测试