面向生物医疗器件制造的硅电极三维微细电解加工机理与工艺研究

For biomedical devices manufacturing, a novel servo scanning micro electrochemical machining (ECM) process with silicon electrodes is presented to machine 3D micro structures, to meet the requirements of high machining accuracy and surface quality on alloy steel materials. Compounds and metallographic structures of different alloy steels are researched and electrochemical reaction characteristics of each alloy phase in steels are tested. Then the dissolving mechanism and rules of alloy steel with multiple alloy phases are studied in micro ECM. Considering the metallographic structures as physical model, material removing simulation for alloy steel machining is employed to get the quantitative rules between the material removal rate and machining parameters. In order to remove different alloy phases in the alloy steel body controllably, uniformly and quickly, electrochemical polarization resistance is researched on the interface of alloy steel and inactive electrolyte. Resistance and capacitance parameters in the equivalent circuit are analyzed by electrochemical impedance spectra (EIS) method and material removing process is analyzed with different alloys and different electrolyte. Aiming at the manufacturing object, the electrolyte constituent is optimized for good machining accuracy and efficiency. In order to shape 3D structures precisely, a novel sidewall insulation layer preparation method for micro electrode is presented. Monocrystal silicon material is used as electrode body. A thin and uniform silicon dioxide layer is deposited on its sidewall surfaces, which adheres the electrode body quite firmly. In addition, an inter-electrode gap detecting and controlling strategy are used in ECM experiments. By optimizing the motion trail of workpiece and controlling the output machining parameters, the machining accuracy can be improved. It is expected to achieve an ECM process for 3D micro structures, which has the integrated characteristics of alloy machining, good machining accuracy and surface finishing. And the research results are expected to be used in the manufacturing for micro biomedical devices especially the microfluidic chip moulds and micro navigating robots.

面向生物医疗器件的精密制造，以实现合金钢上具有三维微结构、较高精度和表面质量要求的微加工为目标，提出一种采用硅电极的微细电解加工技术路线。在研究合金钢金相组织和各合金相的电化学特性基础上，探索电解材料蚀除机理，建立考虑金相组织的电解材料蚀除模型，确定合金材料蚀除速率与工艺参数间的量化规律。为了实现合金钢电解蚀除的可控性、均一性和快速性，测量其在钝化电解液中的电化学反应极化阻抗，分析阻抗参数对材料蚀除的影响，优化电解液化学成分。探索一种新型的工具电极侧壁绝缘层制备工艺，单晶硅作为工具电极基体，表面沉积厚度薄且均匀、绝缘性能好、与基体紧密结合的二氧化硅作为绝缘层；提出了间隙检测和控制策略，优化工件的运动轨迹。从机理研究和关键技术突破两个方面，形成适用于合金钢材料、具有高精度定域性加工和表面光整综合特征的三维微结构加工的新工艺。并应用于微流控芯片模具、微创介入医疗器件等生物医疗关键部件的制造中。

项目研究涉及金属合金的电解加工材料蚀除机理、电解液成分优化、电解材料蚀除模型等基础科学问题，以及创新的侧壁可靠绝缘的微细硅电极制备和微细电解加工工艺的关键技术问题。研究获得主要成果如下：. 在材料蚀除机理研究中，提出了基于界面等效电路的材料蚀除分析方法，通过对工件/电解液界面等效电路阻抗参数的测试，定量分析金属溶解电化学反应条件和电流密度，计算工件材料蚀除速率，建立材料去除模型。从而可预测并改善微细电解加工中Fe-Cr-Ni基合金的材料蚀除速率。. 在分析影响材料蚀除速率的因素和络合添加剂对固体沉淀物溶解作用的基础上，提出了针对铁基合金材料的复合电解液成分优化选用方法：采用电流效率较大、电化学反应阻抗和界面电容较小的钝性成分，采用配位体络合能力强、亲水基团数量多、生成的络合物表面活性弱的络合添加剂。为微细电解加工中电解液成分优化选取提供一指导性理论依据。. 基于合金钢蚀除的电化学反应极化阻抗和材料蚀除规律，通过计算金属溶解电流密度和材料蚀除速率的瞬态变化规律，结合网格变形技术，预测了微结构的加工轮廓。仿真模型对加工结果的预测精度较高，且可用于深入的电解加工机理研究。. 创新性地提出微细硅工具电极的设计制作思路。以重掺杂硅为电极基体、二氧化硅/氮化硅薄膜为绝缘层的硅电极，实验验证了其优秀的加工可靠性和耐久性。采用微细硅电极形成的电解加工新体系有望解决加工中的杂散腐蚀和可控性问题，形成新的微细电解加工技术途径。. 在对材料去除区域和单层深度的数学理论分析基础上，提出了系统优化的分层扫描加工轨迹规划、控制策略和工艺路线，用于微结构的成型加工。在微流控生物芯片模具微小结构的精密加工中，验证了材料蚀除机理、电解液优化方法、加工仿真模型、微细硅工具电极和分层扫描加工工艺等项目研究可行性，使用加工的芯片模具注塑出相应的微流控生物芯片。