National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
Soft Matter. 2019 Apr 7;15(13):2817-2825. doi: 10.1039/c9sm00270g. Epub 2019 Mar 14.
Despite fascinating natural examples of switchable adhesives to wet surfaces, strategies for an artificially switching capillary adhesion system in situ remains a challenge. Here, we develop a smart reversible magnetic fluid (MF) meniscus adhesion system whose capillary effect can be regulated by external magnetic stimuli. It is revealed that the MF filled joint between two solid surfaces undergoes alteration of its adhesive properties in response to the external stimulus of a varying magnetic field. Compared with the original capillary force (without stimuli), the stimulated one increases or decreases depending on the distributions of applied magnetic field intensities, allowing for switchable adhesive behavior. In addition to the Laplace pressure, hydrostatic pressure induced by the intensity difference in the magnetic field between the inner and outer surfaces of the meniscus was found to contribute to wet adhesion, which accounted for the reversibility. Theoretical models of reversible adhesions have been built and solved as well, and agree well with the experiment results. Our findings not only provide a deep understanding of MF capillary adhesion, but also provide a new method to design reversible wet adhesion systems.
尽管有令人着迷的自然范例展示了可切换的湿表面粘附剂，但在原位实现人工切换毛细粘附系统的策略仍然是一个挑战。在这里，我们开发了一种智能可逆磁流体 (MF) 弯月面粘附系统，其毛细效应可以通过外部磁刺激来调节。结果表明，在两个固体表面之间填充 MF 的接头会根据外部磁场变化刺激的变化而改变其粘附性能。与原始的毛细力（无刺激）相比，刺激后的毛细力会根据施加磁场强度的分布而增加或减少，从而实现可切换的粘附行为。除了拉普拉斯压力之外，还发现由弯月面内外表面之间磁场强度差异引起的静水压力有助于湿粘附，这解释了其可逆性。还建立并求解了可逆粘附的理论模型，与实验结果吻合良好。我们的发现不仅提供了对 MF 毛细粘附的深入理解，还为设计可逆湿粘附系统提供了新方法。
