George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Lab Chip. 2017 Sep 12;17(18):3138-3145. doi: 10.1039/c7lc00556c.
Most microorganisms use hair-like cilia with asymmetric beating to perform vital bio-physical processes. In this paper, we demonstrate a novel fabrication method for creating magnetic artificial cilia capable of such a biologically inspired asymmetric beating pattern essential for inducing microfluidic transport at low Reynolds number. The cilia are fabricated using a lithographic process in conjunction with deposition of magnetic nickel-iron permalloy to create flexible filaments that can be manipulated by varying an external magnetic field. A rotating permanent magnet is used to actuate the cilia. We examine the kinematics of a cilium and demonstrate that the cilium motion is defined by an interplay among elastic, magnetic, and viscous forces. Specifically, the forward stroke is induced by the rotation of the magnet which bends the cilium, whereas the recovery stroke is defined by the straightening of the deformed cilium, releasing accumulated elastic potential energy. This difference in dominating forces acting during the forward stroke and the recovery stroke leads to an asymmetric beating pattern of the cilium. Such magnetic cilia can find applications in microfluidic pumping, mixing, and other fluid handling processes.
大多数微生物利用具有不对称运动的毛发状纤毛来执行重要的生物物理过程。在本文中，我们展示了一种新颖的制造方法，用于创建能够产生这种仿生不对称运动模式的磁性人工纤毛，这种运动模式对于在低雷诺数下诱导微流体输运至关重要。纤毛是通过光刻工艺与磁性镍铁坡莫合金的沉积相结合制造的，以创建能够通过改变外部磁场进行操纵的柔性细丝。旋转的永磁体用于驱动纤毛。我们研究了纤毛的运动学，并证明了纤毛的运动是由弹性、磁性和粘性力相互作用决定的。具体来说，前向冲程是由磁铁的旋转引起的，磁铁的旋转使纤毛弯曲，而恢复冲程是由变形的纤毛的伸直定义的，释放出累积的弹性势能。在前向冲程和恢复冲程期间起主导作用的力的这种差异导致了纤毛的不对称运动模式。这种磁性纤毛可用于微流体泵送、混合和其他流体处理过程。
