Hydrodynamically efficient micropropulsion through a new artificial cilia beating concept

Flow propulsion and manipulation in a microscale flow regime are essential for the rapid processing of biomedical analytical assays that are performed on lab-on-a-chip platform. However, inherited from typically conical movement of artificial cilia in a cyclic manner, the generated backflow and flow oscillations during artificial cilia actuation are inevitably significant and post a significant barrier to the practical use of artificial cilia for accurate flow control. To address this problem, in this study we have hypothesized that by minimizing the traversing path of the artificial cilia during the recovery stroke could minimize the generated back flow and will result in an increment in the net flow propulsion. In this aspect, we have initiated the concept of the triangular beating pattern and compared its performance with the typical circular beating pattern. Upon comparison, it was observed that in the case of triangular beating pattern, the generated peak net flow velocity is almost double than the case of circular beating pattern. In particular, the underlying hydrodynamics induced during the actuation of the aforementioned two distinct beating patterns of artificial cilia were visualized and quantified with delineated comparison. This comparison was conducted based on flow dynamic characteristics measured through a micro-particle image velocimetry method. These results are important given that previous researchers do not explicitly recognize the role of the triangular beating pattern which possesses a significantly hydrodynamic advantage that can reduce the amount of back flow and surrounding flow fluctuations. The proposed concept provides a novel perspective on the microscale flow manipulation with promising applications in micropropulsion.