The Development of Biomedical Devices with Excimer Laser Micromachining, Modeling and Simulations

This paper presents a new method of developing micro-scale medical devices by using excimer laser with analytical modeling and simulation of the processes. In recent years, The laser has attracted a significant interest of finding feasible techniques for developing new biomedical devices such as micro scaffolds for nerves, micro arrays for DNA, micro channels for drug delivery or bio-MEMS for bioelectronics devices. This paper focuses on exploring the applications of laser micromachining and advanced surface modification techniques for the development of the biomedical devices. Analytical modeling was conducted and constructed for laser micromachining processes such as pulse laser deposition, 3D material printing and spin coating to fabricate user-defined microstructures on a silicon wafer. Because laser micromachining with the excimer laser is a flexible and controllable process that has high resolution and contactless cutting, it is a good candidate to machine the silicon wafer that is hard, brittle and biocompatible as well as difficult to be machined by other traditional machining methods. The laser micromachining is complex and depends on the interaction of laser energy, material properties and the beam delivery system that has several parameters and need to be investigated before the actual operation so this research began with the study of laser process parameters relating to the laser ablation on a silicon wafer such as laser energy, spot size, working plane, feed rate of XYZ translation stage and number of pass. From the study, the shape of laser ablation was measured and used as the cutting profile of a laser machine tool.;To support the users at the design stage of biomedical devices, the 3D analytical model of laser ablation is essential to predict the microstructure virtually in CAD/CAM system. There are many researches developing their models to simulate the laser ablation for micromachining but there are errors in the simulation of laser phenomenon because it depends on their assumptions and methods used to formulate the model. Therefore, this research proposed the better analytical model to calculate the laser cutting profile from the essential laser process parameters and material properties studied from the fundamental study. The analytical model starting from laser energy profile, modified beam propagation with Gaussian function and laser ablation modeling with cutting angle reduced the laser-machined surface errors compared to the previous work. Moreover, the model was further applied in the computer simulation of laser micromachining to get the optimal laser process parameters for minimal surface roughness. It demonstrated that this model is a great tool for engineer to design and develop the biomedical devices.;When the device meets the functional requirement, it does not mean that it can be used as a biomedical device because the quality and biocompatibility are other crucial factors in the biomedical device development. This research also proposes the surface modification techniques to improve the surface quality and biocompatibility of machined substrate. The improvement on quality of laser ablation by using the cyanoacrylate is proposed to protect the falling debris on the substrate while the diamond-like carbon coating with PLD and polyethylene glycol with UV lithography are introduced to reduce the protein adsorption on the laser-machined area. Moreover, the technique to detect the fluorescent protein adsorption by using the fluorescent spectrophotometer is proposed to quantitatively measure the amount of albumin on the substrate. All proposed methods make the micro devices fabricated from the laser micromachining become more feasible in the biomedical device applications. In conclusion, the techniques presented in this paper provide the essential tools of laser micromachining on a silicon substrate for developing and prototyping biomedical devices. In this paper, the presented new method can be used in modeling and applying excimer laser in design, planning and fabrication of micro-scale biomedical devices.