Guo Jiali, Zhao Haoran, Lou Ching-Wen, Dong Ting
College of Textile and Clothing, Qingdao University, 308 Ningxia Road, Qingdao 266071, China.
Advanced Medical Care and Protection Technology Research Center, Qingdao University, 308 Ningxia Road, Qingdao 266071, China.
Biomimetics (Basel). 2025 May 15;10(5):319. doi: 10.3390/biomimetics10050319.
Motion control of droplets undergoing collisions with solid surface is required in a number of technological and industrial situations. Droplet dynamics after lifting off is often unpredictable, leading to a major problem in many technologies that droplets move in uncontrolled and potentially undesirable ways. Herein, this work shows that well-designed surface chemistry can produce an accurate control of force transmission to impinging droplets, permitting precise controlled droplet rebounce. The non-wetting surfaces (superhydrophobic), which mimics the water-repellent mechanism of lotus leaves via micro-to-nanoscale hierarchical morphology, with patterned "defect" of extreme wettability (hydrophilic), are synthesized by photolithography using only one inexpensive fluorine-free reagent (methyltrichlorosilane). The contact line of impinging droplet during flatting and receding is free to move on the superhydrophobic region and pinned as it meets with the hydrophilic defect, which introduces a net surface tension force allowing patterned droplet deposition, controlled droplet splitting, and directed droplet rebound. The work also achieves controlled vertical rebound of impinging droplets on inclined surfaces by controlling defect's size, impact position, and impact velocity. This research demonstrates pinning forces as a general strategy to attain sophisticated droplet motions, which opens an avenue in future explorations, such as matter transportation, energy transformation, and object actuation.
在许多技术和工业场景中，都需要对与固体表面碰撞的液滴进行运动控制。液滴脱离后其动力学行为往往难以预测，这在许多技术中引发了一个重大问题，即液滴会以不受控制且可能不理想的方式移动。在此，本研究表明，精心设计的表面化学性质能够精确控制传递到撞击液滴的力，从而实现对液滴反弹的精确控制。通过光刻技术，仅使用一种廉价的无氟试剂（甲基三氯硅烷），合成了具有微纳尺度分级形态的非润湿性表面（超疏水表面），该表面模仿荷叶的拒水机制，并带有具有极端润湿性（亲水）的图案化“缺陷”。撞击液滴在变平及后退过程中的接触线在超疏水区域可自由移动，而当遇到亲水缺陷时会被固定，这会引入一个净表面张力，从而实现图案化液滴沉积、可控液滴分裂以及定向液滴反弹。该研究还通过控制缺陷尺寸、撞击位置和撞击速度，实现了撞击液滴在倾斜表面上的可控垂直反弹。这项研究证明了固定力是实现复杂液滴运动的一种通用策略，为未来诸如物质运输、能量转换和物体驱动等探索开辟了一条道路。
