Bobbing chemical garden tubes: oscillatory self-motion from buoyancy and catalytic gas production

Chemical reactions can induce self-propulsion by the production and ejection of gas bubbles from micro-rocket like cylindrical units. We describe related micro-submarines that change their depth in response to catalytic gas production. The structures consist of silica-supported CuO and are produced...

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Bibliographic Details
Published in:Soft matter 2023-03, Vol.19 (11), p.2138-2145
Main Authors: Wang, Qingpu, Steinbock, Oliver
Format: Article
Language:English
Subjects:
Acceleration
Buoyancy
Chemical kinetics
Chemical reactions
Gardens & gardening
Gas production
Hydrogen peroxide
Oil and gas production
Oxygen
Reaction kinetics
Self-assembly
Silica
Submarines
Tubes
Vertical orientation
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Summary:Chemical reactions can induce self-propulsion by the production and ejection of gas bubbles from micro-rocket like cylindrical units. We describe related micro-submarines that change their depth in response to catalytic gas production. The structures consist of silica-supported CuO and are produced by utilizing the self-assembly rules of chemical gardens. In H 2 O 2 solution, the tube cavity produces O 2 (g) and the resulting buoyancy lifts the tube to the air-solution interface, where it releases oxygen and sinks back down to the bottom of the container. In 5 cm deep solutions, the resulting bobbing cycles have a period of 20-30 s and repeat for several hours. The ascent is characterized by a vertical orientation of the tube and a constant acceleration. During the descent, the tubes are oriented horizontally and sink at a nearly constant speed. These striking features are quantitatively captured by an analysis of the involved mechanical forces and chemical kinetics. The results show that ascending tubes increase their oxygen-production rate by the motion-induced injection of fresh solution into the tube cavity. Self-assembled hollow silica-CuO tubes show oscillatory bobbing motion in H 2 O 2 solutions. The ascent and descent characteristics are analyzed experimentally and reproduced by theory.
ISSN:1744-683X
1744-6848
DOI:10.1039/d2sm01681h