Optimization of micropipette fabrication by laser micromachining for application in an ultrafine atmospheric pressure plasma jet using response surface methodology

Abstract

The optimization of the laser micromachining process for special tapered micropipettes was investigated using response surface methodology. Three process parameters for the CO2 laser-based micropipette puller (P-2000, Sutter Instrument) were chosen as variables, namely heat, velocity and pull. The targeted length LTVS of the tapered variant section with a tip diameter of 10 μm was taken as a response. The optimum process parameters with LTVS of 7.3 mm were determined by analyzing the response surface three-dimension surface plots. The central composite design was selected to optimize the process variables, and the experimental data were fitted into a reduced cubic polynomial model. The high R2 value (99.66%) and low coefficient of variation (0.73%) indicated the statistical significance of the model and good precision for the experiment. The optimization result showed that the best parameters were with the heat, velocity and pull values of 850, 53 and 170, respectively. The result was verified by a CO2 laser-based micropipette puller three times with length LTVS at 7.26 mm, 7.35 mm and 7.36 mm with the same optimized parameters. Then, the application to the ultrafine atmospheric pressure He/O2 plasma jets was carried out and micro-hole etching of the parylene-C film was realized with length LTVS at 6.29 mm, 7.35 mm and 8.02 mm. The results showed that the micro-plasma jet with an LTVS of 7.35 mm had the minimum applied voltage of 12.7 kV and the minimum micro-etching diameter of 45 μm with the deepest etching depth of 2.8 μm.