Laser precision processing exhibits an accuracy that ranges from microns to tens of microns and provides advantages such as high processing accuracy, application to a wide range of materials, and minor thermal damage. In 1986, Dr. Mourou and Strickland used microwave amplification technology to amplify and compress laser-chirped pulses and achieved results better than those of traditional methods such as Q-switching and mode-locking, leading to the rapid development of laser precision processing technology.
Because of the increasing demand for lightweight components and high-value-added products in critical industries such as aerospace, automobile, electronics, and medical devices, laser precision processing technology has become essential in precise machining, surface finishing, high-performance joining, and functional surfaces for drag reduction, stealth, and anti-icing.
In this paper, we summarize our current work on laser precision processing in recent years. The work includes laser precision polishing, metal-composite high-strength joining, one-stop fabrication of functional surfaces, ultrafast laser drilling on bones, and ultrafast laser-assisted silicon wafer manufacturing.
The laser precision polishing technique offers an adaptable, accurate, and environmentally friendly solution for enhancing the surface quality of additive-manufactured metallic components. The technique can considerably reduce the surface roughness and average grain size of the original laser-additive-manufactured metallic alloys. Moreover, porosity can be reduced in the laser-polished layer. Laser precision polishing can substantially improve mechanical properties, such as microhardness, residual stress, tensile strength, and fatigue performance, and reduce corrosion resistance. Magnetic-field-assisted polishing methods are also proposed to improve the uniformity in surface quality and performance.
The high-strength laser-joining method is proposed to produce hybrid joints of titanium alloys and carbon-fiber-reinforced polymers (CFRPs). Before the laser-joining process is implemented, a surface-texturing treatment is employed on the metal surface to improve joint strength through the formation of interlock structures between the titanium alloy and CFRP. This method effectively eliminates micropores in the joints, thereby increasing the fracture strength of the joints to up to 60 MPa.
The one-stop fabrication method for functional micro/nano surfaces is proposed to achieve excellent anti-icing properties on laser-fabricated hierarchical structures consisting of micropillars and nanoparticles, with water droplets retaining their liquid state for over 8 h at -8.5±0.5 ℃. Distinct micro/nano hybrid structures, including regular laser-induced periodic surface structures (LIPSSs), semi-continuous nano-bumps, and nanoscale-to-microscale protrusions, are induced on a tungsten-carbide-cobalt (WC-Co) alloy by applying the laser precision machining technology, thus significantly reducing the optical reflectance at the laser-treated surfaces in the visible wavelength range.
We demonstrate the feasibility of ultrafast laser drilling in vitro large-size holes in an animal bone with high efficiency and minimal collateral damage. The laser precision machining technology is utilized to drill millimeter-scale holes in the bone under different cooling conditions, including gas- and water-assisted processes. A 4 mm hole with a smooth and clean surface is successfully drilled, and the highest removal rate of 0.99 mm3/s is achieved. The bone and bone marrow are distinguished by using a real-time monitoring system based on real-time spectral responses during laser drilling.
We employ laser precision processing for wafer thinning and grinding. The wafer thickness is reduced from 199 to 102 μm, and compressive stress is achieved at the laser-machined surface with the depth of the heat-affected zone (HAZ) being less than 1 μm. Laser grinding of silicon wafer effectively eliminates damages such as micro-cracks, micropores, and saw-marks on the surfaces and reduces surface roughness. Laser thinning and grinding technologies have limited influence on the electrical properties of the silicon wafer.
In this paper, we review the recent achievements in the research on laser precision technologies conducted by our group. We show that laser precision processing is a promising method for practical applications in the aerospace industry, medical devices, and integrated circuits, mainly because of its multiple functions, high flexibility, high precision, and applicability to various materials. Although industrial mass production may still be challenging, emerging technologies, including online monitoring systems, ultra-precision operation platforms, and high-power laser sources, have potential to improve the quality, efficiency, and reliability of laser precision processing.
