Design, Simulation, Fabrication And Evaluation Of MEMS Based Air Amplifier For Electrospray Lonization

Electrospray ionization (ESI) is a unique technique to effectively produce gas-phase ions of polar, involatile and thermally labile molecules, which greatly widens the application of mass spectrometry (MS) in the biomedical field. The sensitivity of ESI-MS is determined by the electrospray ionization efficiency and ion transport efficiency. Due to the development of nano-ESI systems, the ionization efficiency has been improved. However, ion transport efficiency is still very low and the miniaturization of ESI-MS systems makes former designed devices no longer meet the requirements. This paper demonstrates a computer simulation and a microfabrication process for a miniature air amplifier. Main contents include:According to the structure of commercial air amplifier, a novel small-sized air amplifier is designed. The flow field property of the air amplifier is studied bases on the micro fluid dynamics theory. The PDMS is chose as the main material.The designed device is simulated by ANSYS FLOTRAN module. The basic structure parameters of air amplifier and the nitrogen pressure are optimized using2D and3D simulations. These optimized results provide a design guideline for the device fabrication. This process reduces cost and put a solid theory foundation for ESI test.The air amplifier is formed by micro electro mechanical system (MEMS) technology. This process mainly includes:a bonding process of two polydim ethylsiloxane (PDMS) parts; Each PDMS part is fabricated through molding process using a micromachined, two-layer SU-8mold structure. Oxygen Plasma Treatment Method and Partial Curing、Varying Curing Ratio PDMS Bonding Technologies are conducted. A good bonding performance of air amplifier is obtained using the optimized bonding method.The ESI system is set up and a series of experiments have been carried out. Firstly, the basic characters of ESI are studied. Then, the air amplifier is embedded in the ESI system. Results show that more than30-fold improvement in ion current for certain operation conditions when the air amplifier is embedded in an electrospray ionization system.