Measurement of mechanical properties of liquid lubricants confined in nano gaps

被限制在纳米级间隙宽度的液体具有典型的粘弹性。在我们之前的研究中，我们开发了一种高灵敏度的剪切力测量方法，我们称之为“纤维摆动法（FWM）”，并揭示了液体聚合物在剪切时表现出增强的粘弹性。虽然解释这些现象的机制必须涉及限制在间隙中的分子取向，但细节尚不清楚。在这项研究中，我们成功地利用FWM结合双折射测量同时测量了受限液晶的粘弹性和分子取向。我们的实验结果表明，纳米尺寸的间隙宽度和粘弹性之间的关系强烈依赖于分子取向。

Liquids confined in nanometer-sized gap width have characteristic viscoelastic properties. In our previous study, we have developed highly-sensitive shear force measuring method, which we called the "fiber wobbling method (FWM)", and revealed that liquid polymers exhibit enhanced viscoelasticity when they are sheared. Although mechanisms to explain these phenomena must involve molecular orientation confined in the gap, details are not clarified. In this study, we succeeded in simultaneously measuring viscoelasticity and molecular orientation of confined liquid crystal using FWM combined with birefringence measurement. Our experimental results showed that the relationship between nanometer-sized gap widths and viscoelasticity strongly depends on the molecular orientation.