Being able to precisely characterize the mechanical properties of soft microparticles is essential for numerous situations, from the understanding of the flow of biological fluids to the development of soft micro-robots. Here, we present a simple measurement technique for determining Poisson’s ratio of soft micron-sized hydrogels in the presence of a surrounding liquid. This method relies on the measurement of the deformation, in two orthogonal directions, of a rectangular hydrogel slab compressed uni-axially inside a microfluidic channel. Due to the in situ character of the method, the sample does not need to be dried, allowing for the measurement of the mechanical properties of swollen hydrogels. Using this method, we determined Poisson’s ratio of hydrogel particles composed of polyethylene glycol (PEG) and varying solvents fabricated using a lithography technique. The results demonstrate, with high precision, the dependence of the hydrogel compressibility on the solvent fraction and character. The method is easy to implement and can be adapted for the measurement of a variety of soft and biological materials.

中文翻译：

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水凝胶泊松比的微流控原位测量


从理解生物体液的流动到软体微型机器人的开发，能够精确表征软体微粒的机械特性对于许多情况都是至关重要的。在这里，我们提出了一种简单的测量技术，用于在周围液体存在的情况下确定柔软的微米级水凝胶的泊松比。该方法依赖于在微流体通道内单轴压缩的矩形水凝胶板在两个正交方向上的变形的测量。由于该方法的原位特征，样品不需要干燥，从而可以测量溶胀水凝胶的机械性能。使用这种方法，我们确定了使用光刻技术制造的由聚乙二醇（PEG）和不同溶剂组成的水凝胶颗粒的泊松比。结果以高精度证明了水凝胶可压缩性对溶剂分数和特性的依赖性。该方法易于实施，可适用于多种软质材料和生物材料的测量。