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A New Mechanism of Light‐Induced Bubble Growth to Propel Microbubble Piston Engine
Author(s) -
Yan Xin,
Xu Jinliang,
Meng Zhijun,
Xie Jian,
Wang Hao
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202001548
Subject(s) - bubble , piston (optics) , radiation pressure , physics , mechanics , radiation , radius , momentum (technical analysis) , acceleration , optics , classical mechanics , computer security , finance , wavefront , computer science , economics
Radiation pressure refers to the momentum transfer of photons during light “particles” impacting a surface. The force is too small to drive microengines. Different from the classical radiation pressure, the indirect radiation pressure ( F m ) is introduced, coming from the momentum change of light‐induced bubble expansion. F m is shown to obey F m ∼ ( I · r b ) 2 , behaving faster growth of indirect radiation pressure versus light intensity I and bubble radius r b . An effective bubble size range is identified for F m to suppress other forces for bubble in liquid. The top laser irradiation on nanofluid is used in this experiment. A well‐defined bubble pulsating flow, being a new principle of bubble piston engine, is demonstrated. During pulse on (≈ns scale), F m exceeding other forces generates an extremely large acceleration, which is three to four orders larger than the gravity acceleration, propelling the bubble traveling downward. During pulse off, the bubble is floating upward due to the nonexistence of F m . In such a way, the piston engine sustains the oscillating ranges of 38–347 µm for bubble diameters and 2.7–457.9 µm for traveling distances of piston. This work is useful to manipulate bubble dynamics in solar energy systems, and can find various applications in optofluidics.