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During the laser driven synthesis cavitation bubbles filled with nanoparticles are formed. These cavitation bubbles along with already dispersed nanoparticles in the solution are the two major factors that limit the energy that can be coupled into the target material by shielding subsequent laser pulses. While the latter shielding effect can be avoided by suitable fluid handling avoiding the former is more difficult due to the lifetime (~100μs) and the size (~100μm) of cavitation bubbles which depend on the laser energy and pulse duration. In this work we present a strategy to scale up the process by enhancing the productivity of the synthesis. This approach utilizes a MHz-repetition rate laser system consisting of a 500W ps-laser source and a laser scanner that reaches a scanning speed of up to 500m/s. This unique system enables spatial bypassing the cavitation bubble and thereby applying most of the laser energy to the target. By using this system productivities of up to 5 gram per hour are demonstrated in a continuous process. |
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