The Optimization Simulation And Experiment Of Traction Electrode In Nano Electrospray

Because of The electrospray ionization versatility in the biological macromolecules detection, easy usability and effectiveness. It has become one of the most common ionization technology. Because ion transport efficiency from electrospray ion source to the mass spectrometer is very low (0.01%0.1%),so the scientists are working to improve the mass spectrometry detection sensitivity. In this paper, we designed a traction electrode near the electrospray needle tip, the traction electrode can change the shape equipotential line near the needle tip, and then focus on the ion in the electrospray. After summarized by lots of experiments, we design the basic structure of traction electrode, this parameters in this design is for small amplitude fluctuation, we hope to be able to get the optimal traction electrode structure under certain experimental conditions.First we use COMSOL simulation software to make electrostatic field analysis, in the process, using Taguchi DOE (Taguchi design) method, multiple sets of orthogonal experimental design, then according to the response factors of the influence degree of the potential line near the injection needle tip, we obtained the best structure of traction electrode in a certain conditions. Under the condition of the needle injection voltage of2100V,the electrode voltage is800V,8mm inside diameter of the traction electrode,3mm from the needle tip to the traction electrode, electrode thickness is4mm, traction electrode diameter is14mm,the counter electrode diameter is4mm,the electrostatic field distribution of equipotential line to the focusing effect of electrospray ion is best.Using MEMS technology to design and manufacture a kind of electrode structure using for electrospray ion focusing. First we use laser cutting technology manufacture the electrode structure on the PMMA, and then after processing of the PMMA in the ultra clean laboratory, we use cleaning fluid for ultrasonic cleaning, After cleaning we dry the PMMA, then we use metal film deposition technique on PMMA surface evaporation on1micron copper metal layer. We use this layer to continue the electroforming. Finally use the micro electroforming technology in copper basal layer make nickel layer about5micron. This kind of electrode metal layer is relatively smooth and good experimental, and the metal layer and PMMA substrate has a certain binding force, can satisfy the experimental requirement. Finally, built up electrospray experiment platform, and through the experiment method to optimize the structure of traction after the best electrode verified one by one. Finally in the following experimental conditions, the rate of200nL/min,injection needle diameter15μm, spray needle voltage2100V,the traction electrode voltage is800V,8mm inside diameter of the traction, electrode needle injection to traction electrode distance of3mm,traction electrode diameter14mm,compared.with no traction electrode, can be achieved2times the magnification of a nano electrospray current. After we obtained this conclusions, we recognize that it is very meaningful to the other electrospray focus process. The focus device such as air amplifier, ion funnel. Ion funnel focusing device, the relative position of needle and the voltage on the focus device all has a certain guiding role.