Light Fueled Manipulation of Bubble Motion Against Buoyancy via Photosensitive Substrate

Flexibly and precisely controlling bubbles is of paramount significance for biological and chemical analysis, reaction engineering, etc. However, the buoyancy force acting on bubbles is significant, making it difficult to precisely manipulate bubbles. Particularly, controlling the anti-buoyancy motion of bubbles remains a fundamental challenge. Herein, a versatile light strategy for manipulating the anti-buoyancy motion of bubbles via a photosensitive substrate is developed. Upon focused laser beam irradiation, an intense Marangoni effect associated with non-uniform temperature distribution is induced underneath the bubble. The created excess Laplace pressure drives the bubble to move against the buoyancy force downward to the focused-laser-acted region, manifesting an excellent phototaxis motion. Theoretical analysis demonstrates that the Marangoni effect is responsible for actuating the anti-buoyancy motion of a bubble. With this light strategy, the bubble collection, transportation, and on-demand release can be flexibly implemented. Moreover, the phototaxis motion of bubbles inspires a manipulation protocol via the integration of 3D-structured design of photosensitive substrate. This light strategy for manipulating bubbles not only possesses sufficiently high accuracy and quick response, but also circumvents the limitation of the liquid volatility and multi-dimensional motion, which provides new ideas for rational control of bubble behaviors.