Microgrooves with diverse cross-sections are required in various fields but remain a significant challenge in precision machining, especially for hard-to-machine materials. Patterned laser ablation offers an avenue for fabricating microgrooves on any material with notably enhanced shape diversity. However, it is hard to precisely control the grooves’ cross-sectional profiles due to the complex ablation process, including the diffraction-induced energy distribution variations away from the focal plane and the inconsistent polarization-related energy absorption. These factors complicate the relationship between beam spot shape and ablated groove shape, making it challenging to design appropriate spot shapes for specific groove requirements. Here, we propose an adaptive beam-shaping method for laser spot design to improve microgrooves’ shape accuracy. Combining laser diffraction and polarization effects, a profile evolution model of the laser ablation is established to accurately predict groove shapes, guiding the iterative beam-shaping procedure. The beam spot shape is iteratively fine-tuned until the deviation between the simulated and the target grooves’ profile meets the accuracy requirements. The grooves’ profile deviations are significantly reduced, with the final profile’s root mean square error decreased to less than 0.5 μm when processing microgrooves with a width of 10 μm. Various microgrooves with precise cross-sections, including triangles, trapezoids, and functionally contoured microstructures, are achieved by patterned laser direct writing assisted with the adaptive beam-shaping method. This method paves the way for laser ablation of microgrooves with high shape accuracy for traditional hard-to-machine materials.

The practical application of lithium (Li) metal anodes in high-capacity batteries is impeded by the formation of hazardous Li dendrites. To address this challenge, this research presents a novel methodology that combines laser ablation and heat treatment to precisely induce controlled grain growth within laser-structured grooves on copper (Cu) current collectors. Specifically, this approach enhances the prevalence of Cu (100) facets within the grooves, effectively lowering the overpotential for Li nucleation and promoting preferential Li deposition. Unlike approaches that modify the entire surface of collectors, our work focuses on selectively enhancing lithiophilicity within the grooves to mitigate the formation of Li dendrites and exhibit exceptional performance metrics. The half-cell with these collectors maintains a remarkable Coulombic efficiency of 97.42% over 350 cycles at 1 mA cm⁻². The symmetric cell can cycle stably for 1600 h at 0.5 mA cm⁻². Furthermore, when integrated with LiFePO₄ cathodes, the full-cell configuration demonstrates outstanding capacity retention of 92.39% after 400 cycles at a 1C discharge rate. This study introduces a novel technique for fabricating selective lithiophilic three-dimensional (3D) Cu current collectors, thereby enhancing the performance of Li metal batteries. The insights gained from this approach hold promise for enhancing the performance of all laser-processed 3D Cu current collectors by enabling precise lithiophilic modifications within complex structures.

Liquid-assisted laser ablation has the advantage of relieving thermal effects of common laser ablation processes, whereas the light scattering and shielding effects by laser-induced cavitation bubbles, suspended debris, and turbulent liquid flow generally deteriorate laser beam transmission stability, leading to low energy efficiency and poor surface quality. Here, we report that a continuous and directional high-speed microjet will form in the laser ablation zone if laser-induced primary cavitation bubbles asymmetrically collapse sequentially near the air-liquid interface under a critical thin liquid layer. The laser-induced microjet can instantaneously and directionally remove secondary bubbles and ablation debris around the laser ablation region, and thus a very stable material removal process can be obtained. The shadowgraphs of high-speed camera reveal that the average speed of laser-induced continuous microjet can be as high as 1.1 m s⁻¹ in its initial 500 μm displacement. The coupling effect of laser ablation, mechanical impact along with the collapse of cavitation bubbles and flushing of high-speed microjet helps achieve a high material removal rate and significantly improved surface quality. We name this uncovered liquid-assisted laser ablation process as laser-induced microjet-assisted ablation (LIMJAA) based on its unique characteristics. High-quality microgrooves with a large depth-to-width ratio of 5.2 are obtained by LIMJAA with a single-pass laser scanning process in our experiments. LIMJAA is capable of machining various types of difficult-to-process materials with high-quality arrays of micro-channels, square and circle microscale through-holes. The results and disclosed mechanisms in our work provide a deep understanding of the role of laser-induced microjet in improving the processing quality of liquid-assisted laser micromachining.