Research On Device And Experiment Of Cryogenic Abrasive Air Jet Machining Of PDMS

With the development of microfluidic chip industry,the demand for microfluidic chips is increasing,therefore,the research on the backing material polydimethylsiloxane(PDMS)is also increasing.At present,soft lithography and laser ablation are commonly used in PDMS processing.Soft lithography can distort PDMS,laser ablation technology has high production cost and low efficiency.Abrasive air jet machining(AAJM)is a new micro-fabrication technology,which has such advantages as low cost,high material removal rate and ability to process complex microstructures.But AAJM of PDMS at room temperature is impossible.Aiming at the processing problem of PDMS,this thesis proposed to process PDMS by using cryogenic abrasive air jet.A cryogenic abrasive air jet machining(CAAJM)device was designed and built according to the processing requirements,the basic research and exploration on heat transfer rate,material removal mechanism and processing technology of CAAJM of PDMS were conducted.The main contents of this thesis are as follow:A CAAJM device was designed and built.According to the target parameters of the device,the overall scheme design,jet generator selection,cooling cylinder structure design,snaked-shaped tube length calculation,nozzle size design,movement platform design and air source device selection were completed.The CAAJM device built in this thesis has such advantages as controllable jet temperature,small fluctuation range of jet parameters,automatic liquid nitrogen replenishment,high processing accuracy,simple structure,convenient construction,easy operation and high security.Based on the analysis of jet structure and glass transition mechanism of PDMS,the simulation of heat transfer during CAAJM of PDMS was carried out,the mechanism of material removal was studied.The model of heat transfer during CAAJM of PDMS was established,and the distribution of heat transfer coefficient on PDMS surface was calculated.The simulation results indicate that PDMS is cooled to glass state first by CAAJ and then eroded,which meets the processing requirements.The surface morphology of processed PDMS was analyzed by SEM and the surface composition was analyzed by EDS.It was found that the material removal mechanism was a mix of ductile removal mode and brittle removal mode.The experiment on CAAJM of PDMS was carried out.The effects of processing parameters(feed speed,processing distance,processing times,erosion angle and abrasive particle size)on the results of processing was analyzed by using single-factor experiments.In this thesis,a CAAJM device was designed and built,the theoretical and experimental research on CAAJM of PDMS was carried out.That provides a new processing method for PDMS with high efficiency and low cost,which is of certain reference value for solving the difficulties in processing of PDMS.