Magnetically-Assisted Laser-Induced Plasma Micro-Machining for Flexible and Fast Texturing of Functional Surfaces

能源、环境和卫生部门面临的挑战表明，对灵活且可扩展的微加工工艺的需求日益增长，这些应用包括用于组织粘连和抗生物污染的纹理表面，减少工具和发动机系统的磨损，以及用于生物医学设备(如针头和植入物)的功能表面。该奖项资助了一种新型微加工工艺的研究，该工艺解决了几个现有的挑战，即材料可加工性的限制，以经济可行的材料去除速度绘制大片区域的图案，以及生成不同尺寸和形状的微特征。一个完全实现的磁助激光诱导等离子体微加工过程将能够快速、直接地产生具有可控几何特征的微特征。在磁助激光诱导等离子体微加工中，皮秒激光脉冲在液体介质中诱导等离子体羽流。等离子羽流通过热汽化和机械侵蚀相结合的方式从工件表面去除材料，以创建具有所需几何形状的机械加工特征。该项目旨在利用外部磁场对等离子体羽流的影响，通过两种机制提高加工速度和精度：(1)增加其能量密度，从而提高材料去除速率；(2)通过改变其形状，几乎直接创建所需的微特征几何形状。研究的目的是了解这一过程的电磁和热机械机制之间的相互作用，即激光、介质、等离子体、磁场和工件材料之间的相互作用。实现这一目标的方法包括使用磁流体力学、细胞内质点和有限元分析方法进行模拟，以确定每种相互作用的结果。各种材料的实验，包括钛合金、硅、聚合物，以及透明、易碎和反射材料，如玻璃，将使用波长为532 nm的皮秒激光系统、计算机控制的电磁铁阵列和基于焦点变化的计量方法进行。在生成特征的深度、形状和材料去除率方面，将实验结果与模拟结果进行比较。

Challenges in the energy, environmental, and health sectors present a growing need for flexible and scalable micro-machining processes for applications such as textured surfaces for tissue adhesion and anti-bio-fouling, reduced wear in tooling and engine systems, and functional surfaces for biomedical devices such as needles and implants. This award funds research on a novel micro-machining process that addresses several existing challenges, namely limitations in the machinability of materials, patterning large areas at economically feasible material removal rates, and generating micro-features of different sizes and shapes. A fully realized magnetically-assisted laser induced plasma micro-machining process will be capable of fast and direct generation of micro-features with controlled geometrical characteristics.In magnetically-assisted laser-induced plasma micro-machining, picosecond laser pulses induce a plasma plume within a liquid dielectric. The plasma plume removes material from the workpiece surface by a combination of thermal vaporization and mechanical erosion to create machined features with desired geometry. This project aims to advance processing capabilities in terms of machining rate and precision by utilizing the external magnetic field's influence on the plasma plume through two mechanisms: (1) by increasing its energy density, leading to increased material removal rates; and (2) by modifying its shape, leading to the nearly direct creation of desired micro-feature geometries. The research objective is to understand the interaction between the electromagnetic and thermo-mechanical mechanisms of the process, i.e., interactions between the laser, dielectric, plasma, magnetic field and workpiece material. Methods to achieve this objective include simulations using magneto-hydrodynamic, particle-in-cell and finite element analysis methods to determine the outcomes of each interaction. Experiments with a wide variety of materials, including titanium alloys, silicon, polymers, and transparent, brittle and reflective materials such as glass, will be conducted using a picosecond laser system with a 532 nm wavelength, a computer-controlled array of electromagnets, and focus variation-based metrology. Experimental results will be compared with simulation results in terms of the depth and shape of the generated features and material removal rate.