利用声学镊子进行软固体主动流变学研究
Active rheology of soft solids performed with acoustical tweezers
AI总结：
本文利用单束声学镊子操控水凝胶中电解产生的微气泡，结合弹性模型与辐射力计算测得局部剪切模量，并与流变仪体相测量结果一致，为复杂软材料的主动流变学表征提供了新工具。
摘要：
单束声学镊子被用于操控单个微气泡，并提供软水凝胶局部剪切模量的定量测量。微气泡通过水凝胶的电解直接产生，其位移在聚焦涡旋光束的焦平面内利用光学显微镜进行检测。偏离轴线的微气泡可被一个恢复性径向力分量拉回，从而形成稳定的二维陷阱。我们还观察到一种偏离轴线的切向微气泡运动，该运动源于光束角动量通量的传递。结合辐射力计算，一个简单的水凝胶变形弹性模型最终给出了介质剪切模量的局部值，这些值与使用流变仪进行的标准体相测量结果高度一致。我们的结果表明，声学镊子是表征复杂软材料局部力学性能的有效工具，为主动流变学领域开辟了新的机遇。
英文摘要：
Single-beam acoustical tweezers are used to manipulate individual microbubbles and provide quantitative measurements of the local shear modulus of soft hydrogels. The microbubbles are directly generated by electrolysis of the hydrogel and their displacement is detected using optical microscopy in the focal plane of a focused vortex beam. Microbubbles displaced off-axis can be pulled by a restoring radial force component that forms a stable two-dimensional trap. We also observe an off-axis tangential microbubble motion that is due to the transfer of the beam's angular momentum flux. A simple elastic model for the hydrogel deformation combined with radiation force calculations finally provide local values of the medium's shear modulus, which are found to be in good agreement with standard bulk measurements performed with a rheometer. Our results suggest that acoustical tweezers are relevant tools to characterize the local mechanical properties of complex soft materials opening new opportunities in the field of active rheology.
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