Background

Soft tribology is increasingly important in the design and engineering of materials used in robotics, haptics, and biomechanics studies. When patterned surfaces are part of a lubricated tribopair that undergoes sliding and compressive deformation, the patterns experience a bending strain that affects the lubrication film thickness and elastohydrodynamic friction. The contribution of bending patterns to soft tribology is not well understood because earlier studies focused on hard tribopairs with effectively flat surfaces.

Objective

We investigate and model the differences in lubricated friction for poly(dimethyl siloxane) (PDMS) elastomer and PEGDA/alginate double network hydrogel patterns in order to determine the effect of height-to-width aspect ratio and bending angle on the elastohydrodynamic friction.

Methods

Photoresists of two different viscosities are spin coated onto silicon substrates to fabricate molds with pattern heights ranging from 20 μm to 50 μm.

Results

Tribological characterization of the tribopairs in the elastohydrodynamic lubrication regime shows that the patterns generate a friction peak that is independent of aspect ratio for short patterns but displays a “power-law fit” decrease with increasing aspect ratio for taller patterns. Two independent models are used to estimate the theoretical bending and deflection angles for the tribopairs.

Conclusions

The decrease in lubricated friction is attributed to taller patterns having large bending angles and a reduced effective surface for fluid load bearing. Results suggest that the bending of micropatterns could be harnessed to engineer lubricated friction in a variety of applications.

中文翻译：

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弹性流体动力润滑摩擦学中的软微模式弯曲

背景

软摩擦学在机器人技术，触觉技术和生物力学研究中使用的材料的设计和工程设计中越来越重要。当有图案的表面是经过润滑和摩擦变形的摩擦摩擦副的一部分时，这些图形会受到弯曲应变的影响，从而影响润滑膜的厚度和弹性流体动力摩擦。弯曲模式对软摩擦学的贡献还没有得到很好的理解，因为早期的研究集中在表面平坦的硬摩擦对上。

客观的

我们研究和建模聚二甲基硅氧烷（PDMS）弹性体和PEGDA /藻酸盐双网状水凝胶图案的润滑摩擦的差异，以确定纵横比和弯曲角度对弹性流体动力摩擦的影响。

方法

将两种不同粘度的光刻胶旋涂到硅基板上，以制造图案高度范围为20μm至50μm的模具。

结果

弹性流体动力润滑方案中的摩擦副的摩擦学表征表明，对于短模式，模式产生的摩擦峰与长宽比无关，但对于高模式，模式随长宽比的增加而显示出“幂律拟合”减小。使用两个独立的模型来估计摩擦对的理论弯曲角和偏转角。

结论

润滑摩擦的减少归因于较高的花纹，这些花纹具有较大的弯曲角度，并且减小了流体承载的有效表面。结果表明，可以在各种应用中利用微图案的弯曲来设计润滑摩擦。