类似荷叶表面分形结构的润湿性研究

依据荷叶表面具有不规则自相似微纳双重结构,引入分形几何学构造类似荷叶的Koch分形结构,并建立相应的Cassie、Wenzel模型接触角方程,分析分形维数和结构参数对其润湿性的影响。研究表明:对于分形结构表面,随着分形维数的增大,结构越致密,接触角越大;同时,分形结构中微/纳尺度参数之比越大,接触角也越大。对于荷叶分形结构表面,当分形维数为2.261 8时,对应2种模型的接触角均为160°,Wenzel模型的微米乳突与纳米结构尺寸之比约为140,Cassie模型的微米乳突与纳米结构尺寸之比约为50;而且当Wenzel模型分形维数为2.273 5、Cassie模型分形维数为2.345 5时,接触角可达到180°。

Wettability on the Surfaces Similar to Fractal Structures of Lotus Leaf

Based on lotus leaf surface with irregular self-similar micro-nano dual structure,fractal geometry was used to construct Koch fractal structure similar to the lotus leaf.The corresponding contact angle equations with Cassie,Wenzel model were established,and the effects of fractal dimension and structural parameters on its wettability were analyzed.The results show that the structure is compacter and the contact angle is bigger with the increase of fractal dimension for the surface fractal structure,and the contact angle is greater with the larger ratio of micro/nano scale parameter.For the fractal structure for lotus leaf surface,the contact angles corresponding to the two models are all 160 degrees when the fractal dimension is 2.261 8,and the ratio of micron mastoid and nanometer structure size is about 140 for Wenzel model and is about 50 for Cassie model.But the contact angle could reach 180 degrees when the fractal dimension is 2.273 5 for Wenzel model or the fractal dimension is 2.345 5 for Cassie model.