Background

Subsurface mechanisms can greatly affect the mechanical behavior of biological materials, but observation of these mechanisms has remained elusive primarily due to unfavorable optical characteristics. Researchers attempt to overcome these limitations by performing experiments in biological mimics like hydrogels, but measurements are generally restricted due to the spatio-temporal limitations of current methods.

Objective

Utilization of contemporary 3D printing techniques into soft, transparent, aqueous yield-stress materials have opened new avenues of approach to overcoming these roadblocks. By incorporating digital image correlation with such 3D printing techniques, a method is shown here that can acquire full-field deformation of a hydrogel subsurface in real-time.

Methods

Briefly, the method replaces the solvent of a transparent and low polymer concentration yield-stress material with an aqueous hydrogel precursor solution, then a DIC speckle plane is 3D printed into it. This complex is then polymerized using photoinitiation thereby locking the speckle plane in place.

Results

Full-field deformation measurements are made in real-time as the embedded speckle plane (ESP) responds with the bulk to the applied load. Example results of deformation and strain fields associated with indentation, relaxation, and sliding contact experiments are shown.

Conclusions

This method has successfully observed the subsurface mechanical response in the bulk of a hydrogel and has the potential to answer fundamental questions regarding biological material mechanical behaviors.

中文翻译：

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动态水下变形和应变的软水凝胶界面使用嵌入式斑点图像与二维数字图像相关。

背景

地下机制可以极大地影响生物材料的机械行为，但是主要由于不利的光学特性，对这些机制的观察仍然难以捉摸。研究人员试图通过在诸如水凝胶的生物模拟物中进行实验来克服这些局限性，但是由于当前方法的时空局限性，通常限制了测量。

客观的

将现代3D打印技术用于柔软，透明，含水屈服应力材料中，为克服这些障碍开辟了新途径。通过将数字图像相关性与此类3D打印技术结合在一起，此处显示了一种方法，该方法可以实时获取水凝胶表面的全场变形。

方法

简而言之，该方法用水凝胶前体水溶液代替透明且低聚合物浓度的低应力应力材料的溶剂，然后将DIC散斑平面3D打印到其中。然后使用光引发聚合该络合物，从而将斑点平面锁定在适当的位置。

结果

由于嵌入的散斑平面（ESP）对施加的载荷有很大的响应，因此可以实时进行全场变形测量。显示了与压痕，松弛和滑动接触实验相关的变形和应变场的示例结果。

结论

该方法已成功观察到了大部分水凝胶的地下机械响应，并有可能回答有关生物材料机械行为的基本问题。