Hu Man, Li Yuqi, Chen Li, Wu Wenna, Huo Peng, Gu Xi, Wang Feng, Deng Daosheng
Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China.
Center for Combustion Energy, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China.
Proc Natl Acad Sci U S A. 2024 Oct 29;121(44):e2413880121. doi: 10.1073/pnas.2413880121. Epub 2024 Oct 24.
Active matters, characterized by multi-mode motions, have been emerging for both engineering and biological applications. Generally, active objects rely on the symmetry-broken structures, compositions, or interfacial activities through a physical or chemical approach. Here, we report an active bubble spontaneously hovering with a horizontal oscillation at the solid/liquid interface by impacting a stationary laser beam into a liquid through a transparent solid cover. This spontaneous oscillation mode of the bubble synchronizes with that of the interfacial temperature and hydrodynamical flow. A physical mechanism is proposed, and the scaling analysis of the oscillation frequency agrees well with experiments in various liquids under different laser powers. Additionally, the bubble trajectory rotates azimuthally, arising from the symmetry breaking of the vortex pair accompanying the oscillation. Moreover, the double pendulum of oscillation bubbles has been demonstrated, achieving a preferable oscillation direction in a controllable way. These findings would not only advance our understanding of active matters but also shed light on the bubble-mediated technological applications, such as microrobots and drug deliveries.
具有多模式运动特征的活性物质已在工程和生物应用中崭露头角。一般来说，活性物体通过物理或化学方法依赖于对称性破缺的结构、组成或界面活性。在此，我们报告了一种活性气泡，通过将固定激光束透过透明固体盖体射入液体，使其在固/液界面处自发地以水平振荡方式悬浮。气泡的这种自发振荡模式与界面温度和流体动力流的振荡模式同步。我们提出了一种物理机制，并且振荡频率的标度分析与不同激光功率下各种液体中的实验结果吻合良好。此外，气泡轨迹会发生方位角旋转，这是由伴随振荡的涡旋对的对称性破缺引起的。而且，已经证明了振荡气泡的双摆现象，能够以可控方式实现较好的振荡方向。这些发现不仅会增进我们对活性物质的理解，还会为气泡介导的技术应用，如微型机器人和药物递送，提供启示。
