Light-Patterned Electrochemical Microbubbles for Large-Scale Precision Assembly of Nanocolloids

Microbubbles in aqueous suspensions have enabled a variety of applications ranging from pumping, mixing, drug delivery, to nanoparticle assembly. However, as far as we know, it remains a formidable challenge to create arrays of bubbles and we are not aware of a method that permits custom patterns of bubbles to be dynamically formed and refreshed. In this work, we report a novel approach to achieve custom ‘on demand’ bubble patterns via an opto-electrochemical technique. It permits us to achieve controlled bubble sizes in the range from a few to ~140 micrometers. Entire patterns can be formed in ~1 second, including lattices, rings, squares, and arbitrary 2D images. The required minimum light intensity (532 nm) of ~0.1 W / cm² is similar to that of sun light, several orders of magnitudes lower than those of optothermal/optoelectronic printing methods, which makes the reported technique parallel and scalable. Interestingly, the bubble patterns can be used to assemble structures from nanocolloids. For a demonstration, we show that nanocolloids can be arranged into different patterns on substrates with light-addressed electrochemical microbubbles across a dimension of millimeters and at an accuracy of less than 1 um. This forms a new printing technique that is quite general and that enables fast and non-contact particle assembly and manipulation. We expect that it will find application in nanomanufacturing, single-cell biotechnology, and in arranging optoelectronic building blocks.