Femtosecond-laser sharp shaping of millimeter-scale geometries with vertical sidewalls

Abstract

As femtosecond (fs) laser machining advances from micro/nanoscale to macroscale, approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand. In this research, an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining (i.e. defects on edges and tapered sidewalls). The evolution of edge sharpness (edge transition width) and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed. Through decreasing the angle of incidence (AOI) from 0° to −5°, the edge transition width could be reduced to below 10 µm but at the cost of increased sidewall tapers. Furthermore, by analyzing lateral and vertical ablation behaviors, a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls. The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications. The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions. Both mm-scale diameters and depths were realized with dimensional precisions below 10 µm and surface roughness below 1 µm. This research establishes a novel strategy to finely control the fs laser machining process, enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.

Meniscus-Induced Directional Self-Transport of Submerged Bubbles on a Slippery Oil-Infused Pillar Array with Height-Gradient

“…To control the height of the pillar array, a unique silicone template with thickness-gradient was prepared in advance (Figures S1 and S2). A series of through holes were machined in the corresponding thickness areas using a femtosecond laser drilling system with the advantages of high precision, low thermal effect, and good controllability. − The cavity at the bottom of the silicone template was blocked with a preprepared unit template, and then, the mixture of epoxy resin was coated on the silicone template for complete curing. After peeling off from the silicone template, the obtained height-gradient pillar array was modified by the femtosecond laser system and hydrophobic agent (Glaco) to endow the surface superhydrophobic (Figures S3 and S4).…”

Femtosecond laser polishing of additively manufactured parts at grazing incidence

“…In the past decade, femtosecond (fs) lasers have been recognized as a powerful tool for precision machining and micro/nanofabrication [32][33][34][35] due to their advantages over CW and longpulse lasers, including having less thermal effect and minimal influence on the initial surface compositions. Different from the CW and long-pulse laser polishing, which is mainly an equalmaterial manufacturing process, fs laser processing mainly utilizes a subtractive ablation process that can not only reduce the surface roughness but also provides a second chance to improve the dimensional accuracies of three-dimensional (3D) parts.…”

High-Precision and Low-Damage Microchannel Construction via Magnetically Assisted Laser-Induced Plasma Ablation for Micro-Thermoelectric Devices

“…The above mentioned issues will significantly deteriorate the semiconductor film performance and surface flatness near the etching paths, which have adverse effect on the bonding of high-density thermoelectric legs to the electrode as well as the device output performance. , Even for the femtosecond laser with ultrashort pulses, a distinct recast area due to Marangoni effects with higher temperature materials flowing to the lower zone will still be formed, leading to a nonuniform melting of the material surface. In addition, depth fluctuation may induce laser beam defocus, thus limiting effective ablation for thick films during multiple removal and resulting in tapered sidewalls in the machined microchannel. , Hence, precisely controlling the distribution of effective laser energy above the material ablation threshold during laser–material interaction, avoiding the uneven energy distribution due to laser defocus, and reducing recast and elemental thermal segregation are urgent to realize the high-aspect-ratio etching as well as high-precision and low-damage 3D microchannel construction for thick films in micro-thermoelectric devices.…”

“…In addition, depth fluctuation may induce laser beam defocus, thus limiting effective ablation for thick films during multiple removal and resulting in tapered sidewalls in the machined microchannel. 14,15 Hence, precisely controlling the distribution of effective laser energy above the material ablation threshold during laser−material interaction, avoiding the uneven energy distribution due to laser defocus, and reducing recast and elemental thermal segregation are urgent to realize the highaspect-ratio etching as well as high-precision and low-damage 3D microchannel construction for thick films in microthermoelectric devices.…”