Electron Beam Induced Radiolysis In Liquid And Its Application In Electron Beam Induced Hydrogel Printing

With the developments of microfabrication,the application of various techniques,such as sensor engineering,have been enhanced based on the improvement of micro-electrical system(MEMS).Meanwhile,hydrogel materials are applied in different MEMS technologies for their advantage on high biocompatibility.However,most hydrogel devices with a size of millimeters or centimeters limit their application in microdevices.Up to now,electron beam lithography has been well applied for patterning in the fabrication of nanodevices.However,the fabrication of hydrogel devices with micrometer and nanometer scales is still a big challenge due to the high saturated pressure of their aqueous precursors.In this project,the author performs the research through simulation and experiments.For theory investigation,the author analyzes the influence of electron beam parameters on the morphology of the hydrogel formed by electron beam printing in aqueous precursors.Models about the electron beam scattering in the solution and the hydrogel cross-linking are created.For experiments,a plan for electron beam printing of nano-scale hydrogel was designed,including fabrication,encapsulation,application of the devices,and printing result analysis.Parameters to influence the morphology of printed hydrogel are analyzed.This project provides the theoretical basis and a practical method for the preparation of nano-scale hydrogels.The works of this thesis are as follows:1.Study the influence of electron beam parameters on the energy distribution in scattering space.The electron scattering model was established based on theories,and the influence of electron beam parameters on the electron scattering process in hydrogel precursor solution was analyzed.Based on Mott cross section formula and Joy modified Bethe formula,the random process of electron scattering is modeled by Monte Carlo method,and the relevant data analysis method is established according to the particularity of this subject.2.Study the principle and process of electron beam induced hydrogels fabricating method.Based on the chemical kinetic equation,a hydrogel crosslinking model was constructed to analyze the effect of electron beam on the crosslinking process.The interactive model between electron beam and crosslinking is established by integrating water radiolysis theory and polymer crosslinking theory in the kinetic equation.3.Design and prepare hydrogel solution cell,encapsulation method and printing scheme of hydrogel.An in-situ liquid phase analysis device compatible with high vacuum environment is designed by micromachining method,which can be applied to conventional electron beam printing equipment.Several research methods and printing schemes are designed to explore the influence of electron beam parameters to the hydrogel morphology.The hydrogel printing is completed by using scanning electron microscope,and the printing accuracy reaches 450 nm.4.The effects of different electron beam parameters on the morphology of hydrogels and the characteristic size of hydrogels prepared are systematically analyzed.Through sorting and analyzing the hydrogel data with different parameters,it is found that the current is positively correlated with the hydrogel size,and the hydrogel size first increased and then decreased with the voltage rise.The hydrogel characteristic size under specific parameters is measured,and other conclusions are made.This work provides empirical guidance for the parameters design of small-size hydrogel printing in the follow-up study.