Investigation On The Ablation Mechanism And Process Of 266nm Nanosecond Laser Machining Of PDMS

PDMS(Polydimethylsiloxane),a silicon-based elastomeric polymer,is one of the most widely used technical polymers due to its mechanical flexibility and stability,high biocompatibility,and high transparency in the UV to visible light range.It is extensively used in the fabrication of microelectromechanical systems(MEMS).When manufacturing MEMS,micropores and microgrooves need to be processed on PDMS.Laser processing technology has advantages such as non-contact and high efficiency,making it increasingly used in PDMS processing compared to other technologies.The266 nm nanosecond laser is a cost-effective and efficient light source,rendering it an important tool for PDMS processing.Based on this,this thesis proposes to process PDMS with a 266 nm nanosecond laser and conducts investigation on the ablation mechanism and process of 266 nm nanosecond laser machining of PDMS via theoretical analysis,simulation,and process experiments.The photothermal and photochemical ablation mechanism of PDMS processed by UV-nanosecond laser are discussed,as well as the mechanism of microcrack when processing micropores and microgrooves on PDMS with UV-nanosecond laser.The results showed that the ablation mechanism of PDMS by 266 nm nanosecond laser was a combination of photothermal and photochemical effects.Thermal stress caused radial and circumferential microcracks to form on the surface of the micropores.Divergent microcracks were produced on the surface of the microgrooves as a result of thermal stress.A finite element simulation model was developed to simulate the temperature and stress fields of PDMS under nanosecond laser irradiation,and the temperature field and stress field distribution under nanosecond pulse laser irradiation were obtained.During the duration of the laser pulse,the temperature difference between the laser irradiation area and the surrounding area rapidly increased,from the spot center along the radial direction,the glass transition width is greater than the width of the ablation.Thermal stresses occur in the shallow area of the surface in the micron range of depth.A 266 nm nanosecond laser experimental processing system was built to conduct process experiments on micropore and microgroove machining on PDMS surface.Through single-factor tests,process rules were derived for the effect of processing parameters,such as pulse energy and pulse quantity,on the dimensions of micropore diameter and depth,as well as on the thermal characteristics such as microcrack width,spatter width,and vitrification width on the micropore surface during processing micropores.Similarly,process rules were derived from the effect of processing parameters such as pulse energy,scanning speed,and scanning times on the dimensions of microgroove width and depth,as well as on the thermal characteristics such as microcrack width,spatter width,and vitrification width on the microgroove surface during processing microgrooves.This investigation provides a reference for 266 nm nanosecond laser machining of PDMS.