Core Viewpoint - A research team led by Professor Ding Yang from Beijing University of Posts and Telecommunications has discovered a phenomenon called "thrust reversal" in propellers operating in specific fluid environments, challenging traditional understandings of propeller mechanics [1] Group 1: Research Findings - The study reveals that at millimeter to sub-millimeter scales, clockwise rotating propellers do not propel micro submarines forward but instead cause them to move backward [1] - The research indicates that in different Reynolds number environments, objects exhibit distinctly different motion characteristics [1] - At ordinary scales, propellers generate forward thrust by pushing water backward, while at smaller scales, the water flow is deflected outward, creating a suction effect at the propeller's center that pulls the submarine in the opposite direction [1] Group 2: Implications - This discovery has significant implications for applications such as micro medical robots and pipeline inspection devices, which often measure only a few millimeters in size [1] - Traditional propeller propulsion systems may fail in these small devices, necessitating research into how to adjust parameters to mitigate or utilize this centrifugal suction effect [1]