当今社会向智能化、柔性化等方向纵深发展, 社会运作机制发生着深刻变革. 在国家高端智能制造、产业全面升级以及抢占科技前沿制高点的发展形势下, 作为制造业的核心−马达的研究设计成为国家发展、科技强国的战略核心之一. 近些年设备柔性化、微纳尺度化等高速发展, 马达研究逐渐由固体向液体不断演化, 并引发了液体马达研究在世界范围内新一轮的崛起. 目前, 全球范围内, 各个研究机构基于不同机制, 开发和拓展出不同形式的液体马达及其应用场景. 在目前的研究机制中, 大多集中于外加电磁场, 或利用温度场/浓度场梯度以及生物活性粒子群体涌现行为等. 但这些机制在尺度、驱动速度、稳定性等方面具有明显的不足, 深入发展具有很大的局限性. 而液滴的自发运动及自发旋转在众多方面都表现出优异的性能, 为液体马达的设计提供了优异的载体. 因此, 本文从液滴动力学行为、界面物化诱导液滴自发旋转等现象出发, 对液滴的自发运动及旋转旋转现象进行了深入、系统性的研究, 为潜在的液体马达的设计提供了新的策略.

  在本文中, 首先, 针对酸性液滴在液态金属表面上的自发运动行为进行了系统性的分析和研究, 对其不同的运动状态进行了类别划分, 明确了液滴自发平动和自发转动的实验条件范围. 并对液滴的自发运动行为进行了分析, 确定了其发生自发运动的机理, 并厘清了其内部的流场流动、内部气泡的运动与分布以及液滴边界波动等情况.

  其次, 通过调控实验参数, 在实验中实现了液滴持续稳定的无外驱动自发旋转, 并对液滴在液态金属表面自发旋转的形成内在机制进行了分析, 提出了旋转形状形成的模型, 并通过实验进行了验证. 同时, 研究了实验参数对液滴自发运动及自发旋转等的影响, 确定了旋转周期及角速度的影响因素. 并对液滴的旋转行为进行了理论分析, 并给出了液滴旋转角速度的数量级估计、液滴发生旋转前后的转动惯量的变化, 以及液滴发生旋转的能量转化效率等, 为利用自旋液滴实现液体马达提供了实验及理论依据.

  最后, 对液滴在液态金属表面呈现出的多瓣旋转及分裂现象进行了研究和分析. 实验中, 通过控制液滴的体积等参数实现了液滴的多瓣旋转和分裂, 包括四瓣、三瓣、两瓣旋转现象等. 实验中, 随着液滴体积的增大, 液滴从四瓣逐渐过渡到两瓣, 同时, 旋转周期也逐渐增大. 实验中, 同时对有注入管和无注入管的情形进行了对比, 并从理论上分析了这种现象的成因. 本文中发现的这种旋转与分裂现象不需要以往研究中需采用外部设备来驱动液滴旋转, 从而简化了液滴多瓣旋转的实现条件, 极大的提高了该类研究的普适性, 为物理学液滴旋转研究提供了新的途径, 并有望为制造步进液体马达提供参考依据.

  综上所述, 本文中系统性的研究了物化反应体系下的液滴自发运动及自发旋转行为, 本文的工作对于深入理解液滴的自发运动现象、界面诱导机制等具有重要的意义, 并为液体马达、柔性设备驱动装置设计等提供了新的发展策略.

Nowadays, the technology development is in the direction of intelligence and flexibility. As the core of manufacturing industry, the research and design of motor have become one of the strategic points of national development. In recent years, with the rapid development of equipment in flexibility and micro/nano scale, the study of motor has gradually evolved from solid to liquid, and leads to a new round of rise of liquid motor research in the world. At present, research institutions around the world have developed different forms of liquid motors based on various mechanisms and expanded their applications. However, these mechanisms have obvious shortcomings in scale, driving speed, stability and so on. However, serious limitations may arise in the further development. The spontaneous motion and rotation of droplets show excellent performance in many aspects. It is an excellent carrier for the design of liquid motor. Therefore, in this dissertation, the spontaneous motion and rotation of droplet are studied systematically. It may provide a new strategy for the design of liquid motor.

Firstly, the spontaneous motion of acid droplets on the surface of liquid metal is studied systematically. The motion states of acidic droplets under different experimental conditions are classified. The conditions of spontaneous translation and rotation are defined. The mechanism of spontaneous motion is determined. The internal flow field, the movement and distribution of bubbles and the fluctuation of droplet boundary are clarified.

Secondly, by adjusting the experimental parameters, the continuous, stable and spontaneous rotation of droplets without external driving is realized. The mechanism of this rotation is discussed. A model of the formation process of comma shape of droplet is proposed and verified by experiments. The influential factors controlling the rotation period and angular velocity are analyzed and determined. Moreover, the motion of droplet is analyzed theoretically, including the order of magnitude of angular velocity, the change of the moment of inertia before and after the formation of comma shape, and the energy conversion efficiency of this rotation. This research provides the guidance for the design of liquid motor with rotational droplet in experiment and theory.

Finally, the phenomenon of multi-lobed rotation of droplet on the surface of liquid metal is studied. In the experiments, the multi-lobed rotation, including four-lobed, three-lobed, two-lobed rotation of droplet, are realized by controlling the experimental parameters, e.g., the volume of the droplet. In the experiment, with the increase of the droplet volume, the droplet gradually transits from four-lobed to two-lobed. The rotation does not need to be driven by external devices as reported in previous studies, which simplifies the conditions for the rotation of droplet. It greatly improves the universality and provides a new way for the study of rotational droplet, and also provides the help for the manufacture of stepping liquid motor

In summary, this dissertation systematically studied the spontaneous movement behavior of the droplet under the physicochemical conditions. This work may be of great significance to understand the spontaneous movement of droplet and the interfacial phenomenon. It may also provide the guidance for the design of liquid motor, flexible device driving device, etc.