论文标题
氧化液体金属中的Marangoni指法不稳定性
Marangoni Fingering Instabilities in Oxidizing Liquid Metals
论文作者
论文摘要
Eutectic Gallium-Indium（Egain）是一种室温液体金属合金，在室温下具有任何液体的最大张力，但仍可以承受指法的不稳定性。由于在施加的电压下，氧化物沉积在金属表面上，这会导致界面张力的降低，从而使重力下扩散。了解室温液体金属的扩散动力学对于开发软电子设备和了解具有极端表面张力的液体的流体动力学很重要。当施加的电压或氧化速率太高时，egain会经历指法不稳定性，包括尖端 - 分裂，这是由于界面上的Marangoni应力而发生的。我们的实验是用放置在电解质（氢氧化钠）中的egain液滴进行的；通过将egain放在铜电极上，铜电极很容易湿润，我们能够控制手指的初始宽度，从而设定了扩散的初始条件。观察到两个过渡：（1）最小电流密度，所有手指都变得不稳定的手指不稳定； （2）较宽的手指将单个分裂事件变成两个较窄的手指的当前密度。我们提出一个相图作为电流密度和初始手指宽度的函数，并确定最小宽度，以下是单个尖端拆分不会发生的。
Eutectic gallium-indium (EGaIn), a room-temperature liquid metal alloy, has the largest tension of any liquid at room temperature, and yet can nonetheless undergo fingering instabilities. This effect arises because, under an applied voltage, oxides deposit on the surface of the metal, which leads to a lowering of the interfacial tension, allowing spreading under gravity. Understanding the spreading dynamics of room temperature liquid metals is important for developing soft electronics and understanding fluid dynamics of liquids with extreme surface tensions. When the applied voltage or the oxidation rate becomes too high, the EGaIn undergoes fingering instabilities, including tip-splitting, which occur due to a Marangoni stress on the interface. Our experiments are performed with EGaIn droplets placed in an electrolyte (sodium hydroxide); by placing the EGaIn on copper electrodes, which EGaIn readily wets, we are able to control the initial width of EGaIn fingers, setting the initial conditions of the spreading. Two transitions are observed: (1) a minimum current density at which all fingers become unstable to narrower fingers; (2) a current density at which the wider fingers undergo a single splitting event into two narrower fingers. We present a phase diagram as a function of current density and initial finger width, and identify the minimum width below which the single tip-splitting does not occur.
