Laser Micromachining

Purpose – Laser milling is a recent process in mould making, providing several advantages over traditional mould making technologies by reducing manufacturing time, shortening the number of machining operations and avoiding expensive electrodes. This paper investigates the ...

As patients who receive orthopedic implants live longer and opt for surgery at a younger age, the need to extend the in vivo lifetimes of these implants has grown. One approach is to pattern implant surfaces with linear grooves, which elicit a cellular response known as contact guidance. Lasers provide a unique method of generating these surface patterns because they are capable of modifying physical and chemical properties over multiple length scales. In this paper we explore the relationship between surface morphology and laser parameters such as fluence, pulse overlap (translation distance), number of passes, and machining environment. We find that using simple procedures involving multiple passes it is possible to manipulate groove properties such as depth, shape, sub-micron roughness, and chemical composition of the Ti-6Al-4V oxide layer. Finally, we demonstrate this procedure by machining several sets of grooves with the same primary groove parameters but varied secondary characteristics. The significance of the secondary groove characteristics is demonstrated by preliminary cell studies indicating that the grooves exhibit basic features of contact guidance and that the cell proliferation in these grooves are significantly altered despite their similar primary characteristics. With further study it will be possible to use specific laser parameters during groove formation to create optimal physical and chemical properties for improved osseointegration.

In this paper we investigate the effects of visible to near infrared (NIR) laser illumination on the optical transmission (OT) and morphological (MC) alterations of thin, curved surfaces of polycarbonate (PC). The second harmonic of Nd:YAG laser (532 nm) and two diode lasers (665 and 980 nm) were used as illuminating sources. The morphological changes of the PC surfaces are determined using atomic force microscopy (AFM), demonstrating the appreciable changes caused by shorter wavelengths (higher energy). When analyzing the OT spectra of PC thin films, a measurable decrease in the OT of the PC samples which were illuminated by 532, 665 and 980 nm, in particular 532 nm, for energy densities greater than 25 J/cm 2 can be seen.

This paper reports on UV laser micromachining of a biodegradable polymer for applications in biomedical engineering. Parametric studies have been conducted on Poly-vinyl Alcohol (PVA), a biodegradable polymer, to produce micro channels and micro holes. Laser micromachining of micro channels is studied using a XeCl excimer laser at 308 nm wavelength and laser micro drilling is studied using a Q-switched Nd: YAG laser at 266 nm wavelength. Feature sizes ranging from 4 to 10 μm were obtained for the micro holes and the features of micro channels ranged from 33 to 65 μm wide and 22 to 123 μm deep. This work demonstrated that UV laser micromachining is a well-suited technique for biodegradable polymers with minimum thermal damage to the surrounding material.

An active catheter intended for controllable intravascular maneuvers is presented and initial experimental results are shown. A commercial catheter is coated with polypyrrole and laser micromachined into electrodes, which are electrochemically activated, leading to bending of the catheter. The catheter's electro-chemo-mechanical properties are theoretically modeled to design the first prototype device, and used to predict an optimal polypyrrole thickness for the desired degree of bending within ∼30 seconds. We compared the experimental result of catheter bending to the theoretical model with estimated electrochemical strain, showing reasonable agreement. Finally, we used the model to design an encapsulated catheter with polypyrrole actuation for improved intravascular compatibility and performance.

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric

In this paper the results of micromachining of polycarbonate polymer foils and SUS304 stainless steel thin sheets are reported, performed by an industrial femtosecond laser operated at 1030 nm and 515 nm (SHG) wavelength. For a typical Galvoscanner setup the ablation scribing was investigated at a spotsize of 20 µm which is typical for contemporary feature size used for medical stents. At this value a maximum peak intensity of 6.4*10 13 W/cm² can be reached, which enables significant nonlinear absorption in the polymer. Laser pulse overlap was varied to optimize overlap values for best edge quality and for best ablation rate. From the results some guidelines for complete cutting of thin sheets were derived. For an acceptable edge quality a maximum ablation rate of 2.6 mm³/min was demonstrated for stainless steel thin sheets, whereas up to 9,4 mm³/min have been reached for polycarbonate. For SUS304 the use of the SHG does not increase ablation rate or edge quality, whereas for polycarbonate the cutting quality is better, but at a smaller ablation rate.

In this article, we explore a new fabrication process for a flexible, all polymer, active fluidic delivery system, incorporating a fusion of laser micromachining and microfabrication techniques as well as rapid prototyping technology. Here, we show selective fluidic delivery from isolated microchannels through an electrochemically driven pumping reaction, demonstrate the dispensing of dose volumes up to 5.5 μl, and evaluate the device’s performance in terms of its delivery speed and ejection efficiency. Finally, we move this work toward an implantable microfluidic drug delivery device by investigating the device’s biocompatibility through a statistical approach that overviews the viability of bovine aortic endothelial cells on polyimide and silicon substrates.

We report the results of an investigation of the laser-material interaction processes involved in laser drilling of alumina, through the use of an enhanced peak power (2.5 kW) CO2 laser and novel temporal pulse formats. Peak power was varied from 30 W to 2 kW for pulses of constant energy to observe the effect produced on scribe depth. High-speed videography of hole formation has been combined with microscopic analysis to investigate the key processes involved in laser processing of alumina. Plasma screening was observed for short, high peak power laser pulses, and optimal scribing was achieved in the weakly plasma absorbing regime. A new processing technique for scribing alumina has been developed, which exploits the fast response of the laser to produce novel temporal pulse shapes, which can be modified to generate cleaner holes. Scribe speeds of up to 280 mm·s-1 were obtained for scribe holes >200 μm deep and 150 μm apart, with no material plugging the hole, in 0.635-mm-thick 96% alumina.

— Pitch adapters (PAs) are passive electronic components widely used to adapt different pitches between silicon strip detectors and readout electronics. This paper presents an optimized process to fabricate high-density PAs using laser ablation of metal-on-glass layers. Minimum pitch sizes of 40 µm for the pads and 25 µm for the conductive traces were achieved. The resolution of the method allowed the cutting of traces as narrow as 15 µm. Different prototypes and small production series have been successfully manufactured and tested for electrical parameters, bondability, and metrology. Ageing tests were also performed to ensure long-term reliability. The production yield reached 80%. Fully functional particle detectors for high-energy physics have been assembled using these PAs, characterized and tested with lasers and radioactive sources. [2014-0371]

The application of the copper bromide (CuBr) laser as an attractive tool in the micro-machining of different materials has been demonstrated. High-quality drilling by trepanning and precision cutting was established on several materials with a negligible heat-affected zone (HAZ). That good performance was a result of the combination of high power visible radiation, short pulses, and close to the diffraction-limited laser beam quality with high-speed galvo scanner beam steering.

Microsurface scale characteristics (roughness, waviness and form) and the workpiece mounting fixture effects must be accounted and compensated for during laser micromachining such that the focused laser spot position is known in the coordinates of the measured surfaces. Thus, allowing rapid and accurate micromachining on the true workpiece engineering surface. The thin-plate splines (TPSs), a mathematically simple theory, is modified