Title: 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.