Synchronous Observation on the Spontaneous Transformation of Liquid Metal under Free Falling Microgravity Situation

Abstract

The unusually high surface tension of room temperature liquid metal is molding it as unique material for diverse newly emerging areas. However, unlike its practices on earth, such metal fluid would display very different behaviors when working in space where gravity disappears and surface property dominates the major physics. So far, few direct evidences are available to understand such effect which would impede further exploration of liquid metal use for space. Here to preliminarily probe into this intriguing issue, a low cost experimental strategy to simulate microgravity environment on earth was proposed through adopting bridges with high enough free falling distance as the test platform. Then using digital cameras amounted along x, y, z directions on outside wall of the transparent container with liquid metal and allied solution inside, synchronous observations on the transient flow and transformational activities of liquid metal were performed. Meanwhile, an unmanned aerial vehicle was adopted to record the whole free falling dynamics of the test capsule from the far end which can help justify subsequent experimental procedures. A series of typical fundamental phenomena were thus observed as: (a) A relatively large liquid metal object would spontaneously transform from its original planar pool state into a sphere and float in the container if initiating the free falling; (b) The liquid metal changes its three-dimensional shape due to dynamic microgravity strength due to free falling and rebound of the test capsule; and (c) A quick spatial transformation of liquid metal immersed in the solution can easily be induced via external electrical fields. The mechanisms of the surface tension driven liquid metal actuation in space were interpreted. All these findings indicated that microgravity effect should be fully treated in developing future generation liquid metal space technologies.