Chenbin Ma

Microstructures with narrow openings and enlarged internal volumes are highly desirable for durable superlubricating surfaces, as they enable increased lubricant storage and improved lubrication stability. However, conventional laser texturing typically produces tapered features with wider openings due to the intrinsic Gaussian energy distribution of laser beams, limiting the achievable internal volume. To overcome this limitation, this study investigates an oblique dual-beam femtosecond laser ablation strategy for polyamide 6 (PA6) using a mechanism-informed optimization framework integrating COMSOL-based multiphysics simulations with response surface methodology (RSM). The effects of pulse energy, incident angle, and beam separation on micro-pit morphology are systematically analyzed. Pulse energy governs ablation intensity and feature scaling; increasing incident angle suppresses depth while promoting lateral expansion; and reduced beam separation enhances depth through local energy overlap. Quadratic regression models for pit depth, inner width, outer width, and ablated area are established via a central composite design and exhibit strong predictive capability. Multi-objective optimization identifies an effective processing window of 30–40 μJ pulse energy, 20–40° incident angle, and −12 to 12 μm beam separation, enabling uniform micro-pits with narrow openings and depths of 70–80 μm. Overall, this work provides a concise and predictive framework for oblique dual-beam laser texturing for predicting and guiding the future fabrication of narrow-opening, enlarged-interior microstructures.

Laser-induced plasma micromachining (LIPMM) process is an effective approach to create microfeatures with high aspect ratio (AR) and reduced heat affected zone (HAZ). Therefore, LIPMM plays a crucial role in improving the morphology of microchannels. In this study, microchannels were fabricated using a femtosecond laser with two distinct sets of process parameters under three different processing methods: overflow-water-assisted laser-induced plasma micromachining (OF-LIPMM), laser direct writing (LDW), and static water laser-induced plasma micromachining (S-LIPMM). Furthermore, single-factor experiments were conducted to systematically analyze the effects of four parameters, namely single-pulse energy, scanning speed, scanning times, and frequency, on the HAZ, AR, and material removal rate (MRR) of the microchannels. Finally, the optimized parameters determined from the single-factor experiments were applied for large-scale grid fabrication on a surface. The experimental results revealed that OF-LIPMM enables the creation of two different kinds of microchannel surfaces: one microchannel was fabricated with a higher AR of 3:1 and a larger HAZ, while another microchannel was created with a lower AR of 1:1 and a reduced HAZ. Moreover, the parameters investigated in the single-factor experiments can be applied to large-scale processing. The results also indicate that variations of the scanning speed, frequency, and single-pulse energy have similar effects on the machining characteristics of the three processing methods. The findings enable the generation of microchannels with favorable morphological characteristics and have significant implications for the large-scale production of both types of microchannels.

Inspired by natural creatures, superhydrophobic surfaces with various adhesion behaviors have attracted significant scientific interest. In this study, by controlling the laser fluence, the scanning times, and the subsequent cleaning method, microcolumn arrays with different morphologies were fabricated on 304 stainless-steel surfaces using picosecond laser direct writing. To achieve wettability transition, the laser-processed samples were then subjected to heat treatments (120 °C) in air and in a low vacuum environment (6 kPa). The results show that after heat treatment in different environments and with various time lengths, the laser-processed surfaces become hydrophobic surfaces with different adhesion properties. It is worth noting that while surfaces heat-treated in air exhibit weak wettability transition potential and high adhesion, the surfaces heat-treated in a low vacuum environment present superhydrophobic and low adhesion properties with a minimum sliding angle of about 3.14°. Moreover, the low-vacuum heat-treated surfaces retain good superhydrophobic properties after 1 month of observation as well as an abrasion test. These transitions in hydrophobic behavior and adhesion properties may be mainly attributed to the heat treatment-induced (in the air or in a low vacuum environment) redistribution of surface compounds and the microstructure-induced alternation of the solid–liquid contact state. By controlling the laser processing parameters and the heat treatment time and environment, stable wettability transition and flexible adhesion control of stainless steel can be easily achieved.