Development of a desktop device for automated laser ablation in liquids

Laser Ablation in Liquids (LAL) has been evolved since the 1990s as a promising technique for producing pure colloids. LAL is a scalable method for producing nanoparticles (NPs), which show high catalytic activity, are easily functionalized, and, when supported onto polymer and metal powders, enhance the 3D printing powders' properties. However, in-depth knowledge of the process and suitable equipment are essential to ensure a highly reproducible process. Moreover, the process is only economically feasible if high productivities and a high automatization degree are achieved due to substantial investment and labor costs. A desktop-sized device enabling the automated production of NPs can be the solution to these challenges. A compact laser is required to ensure the compact device design. However, these lasers are limited in their power and, consequently, limit NP productivity. An intermediate pulse duration could provide an increased ablation efficiency and, thus, enhance the NP productivity. Therefore, in this work, the influence of pulse duration on the ablation efficiency is examined. Additionally, the process parameters are optimized, a safety analysis is performed, and future perspectives are analyzed to maximize the device's productivity.

At first, a suitable laser system for the device is identified by comparing different laser systems' ablation efficiencies. An intermediate laser pulse duration of about several hundred ps to ~2 ns is determined as a system leading to the highest efficiency. Shadowgraph imaging and pump-probe microscopy revealed that that for pulse durations >5 ns, more energy is absorbed by a laser-induced vapor layer leading to an energy loss for the ablation. The vapor layer expansion starts approximately 2 ns after the laser pulse impact allowing higher efficiencies for short pulse durations.

Second, the process parameters for a device for automated LAL are optimized. Here, the relation between productivity and particle size is demonstrated and explained by in-process fragmentation. Due to a low-power laser chosen for the device, the parameters, as the focal distance and liquid flow rate, are adjusted, focusing on high productivity. It is found that the focal distance, liquid flow rate, and laser energy can be combined to the volume-specific energy dose, which determined the NP size.

Third, the safety of the device is evaluated. Therefore, different sensors are implemented and evaluated. The future perspectives and possibilities of the device are considered. The current capacities are sufficient to provide enough colloid for laboratory-scaled testing of functionalized materials as catalysts, bio-inks, and 3d printing powder. The efficiency of the device could be increased by beam splitting.

Overall, this work shows that a high LAL efficiency is found for a pulse duration of about several hundred ps to ~2 ns. This finding enabled the development and construction of a compact and automated LAL device.


Citation style:
Could not load citation form.


Use and reproduction:
All rights reserved