Spontaneous motion of a solid object floating on an unsymmetrical geometric open channel is investigated. The open channel was created by selectively fabricating hydrophilic patterns on a superhydrophobic substrate, confining water within the hydrophilic region, thus forming a distinct open channel. As a rectangular foam block was placed on a triangular open channel, the variation of the spanwise width of the wetted area leads to a gradient of surface tension force along the centerline that is able to drive the foam block directionally. What is more, two open channels could be parallelly arranged together to drive even larger object. A theoretical model was developed to explain the mechanism, which agrees well with the experimental results. The findings of this work extend the application of capillary force, which could be used in areas such as self-driven microfluidics, surface lubrication, and open microchannels.

中文翻译：

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明渠上固体物体的自发运动

研究了漂浮在不对称几何明渠上的固体物体的自发运动。通过在超疏水基材上选择性地制造亲水图案，将水限制在亲水区域内，从而形成独特的开放通道，从而形成开放通道。当矩形泡沫块放置在三角形明渠上时，润湿区域展向宽度的变化导致沿中心线的表面张力梯度，能够定向驱动泡沫块。更重要的是，两个开放通道可以平行排列在一起以驱动更大的物体。开发了一个理论模型来解释该机制，该模型与实验结果非常吻合。这项工作的发现扩展了毛细管力的应用，可用于自驱动微流体、表面润滑和开放微通道等领域。