基于针尖阵列的柔性干电极制备与测试
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摘要
针对目前Ag/AgCl湿电极存在导电膏干涸而导致的信号质量变差、电极-皮肤接触阻抗变大等问题,提出一种可测量生物电信号的柔性干电极的制备方法。结合深反应离子刻蚀(DRIE)和湿法腐蚀工艺制备出硅针尖模具,后经聚对二甲苯薄膜的保形淀积完成聚二甲基硅氧烷(PDMS)两次翻膜工艺,并有效解决了PDMS与金属种子层之间的黏附性问题。使用COMSOL软件对干电极和湿电极进行电场仿真,结果显示干电极能显著提高生物电信号提取的有效性和稳定性。通过对干电极与湿电极进行电极-皮肤接触阻抗的对比测试,表明湿电极随着导电膏干涸而导致接触阻抗逐渐变大并超过干电极,相反干电极的接触阻抗则较为稳定。该方法制备的柔性干电极具有工艺简单、成本较低、适于批量化生产、材料生物兼容性好、接触阻抗稳定等优点。
For resolving the problems of poor signal quality and large electrode-skin contact impedance caused by the dryness of conductive paste on Ag/AgCl wet electrode,the preparation method of the flexible dry electrode for measuring bio-electrical signals was proposed.The silicon tip mould was fabricated by deep reactive ion etching(DRIE)process and wet etching process.With parylene film conformal deposition,the double-transfer pattern process of the polydimethylsiloxane(PDMS)was accomplished,and the adhesion problem between the PDMS and metal seed layer was solved effectively.The electric field simulations of the dry electrode and wet electrode were carried out by the COMSOL software.The results show that the dry electrode can significantly enhance the validity and stability of bio-electrical signal extraction.The electrode-skin contact impedances of the dry electrode and wet electrode were compared and tested.It shows that with the conductive paste drying,the contact impedance of the wet electrode gradually becomes larger and exceeds the contact impedance of the dry electrode.On the contrary,the contact impedance of the dry electrode is relatively stable.The proposed flexible dry electrode prepared with the method has the advantages of simple process,low cost,mass production,good material bio-compatibility and stable contact impedance.
For resolving the problems of poor signal quality and large electrode-skin contact impedance caused by the dryness of conductive paste on Ag/AgCl wet electrode,the preparation method of the flexible dry electrode for measuring bio-electrical signals was proposed.The silicon tip mould was fabricated by deep reactive ion etching(DRIE)process and wet etching process.With parylene film conformal deposition,the double-transfer pattern process of the polydimethylsiloxane(PDMS)was accomplished,and the adhesion problem between the PDMS and metal seed layer was solved effectively.The electric field simulations of the dry electrode and wet electrode were carried out by the COMSOL software.The results show that the dry electrode can significantly enhance the validity and stability of bio-electrical signal extraction.The electrode-skin contact impedances of the dry electrode and wet electrode were compared and tested.It shows that with the conductive paste drying,the contact impedance of the wet electrode gradually becomes larger and exceeds the contact impedance of the dry electrode.On the contrary,the contact impedance of the dry electrode is relatively stable.The proposed flexible dry electrode prepared with the method has the advantages of simple process,low cost,mass production,good material bio-compatibility and stable contact impedance.
引文
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[2] CHOU N,YOO S,KIM S.A largely deformable surface type neural electrode array based on PDMS[J].IEEE Transactions on Neural Systems and Rehabilitation Engineering,2013,21(4):544-553.
[3]浦小飞.穿戴式电生理监测系统的超低功耗、低噪声模拟前端集成电路研究与设计[D].上海:复旦大学,2013.
[4] GRISS P,ENOKSSON P,TOLVANEN-LAAKSO H K,et al.Micromachined electrodes for biopotential measurements[J].Journal of Microelectromechanical Systems,2001,10(1):10-16.
[5] HOCHBERG L R,SERRUYA M D,FRIEHS G M,et al.Neuronal ensemble control of prosthetic devices by a human with tetraplegia[J].Nature,2006,442(7099):164-171.
[6] HONG S,LEE S,YOO H,et al.Mechanical and electrical evaluation for the long-term stability of implanted 3D retinal microelectrode[C]//Proceedings of the 16th International Solid-State Sensors,Actuators and Microsystems Conference.Beijing,China,2011:202-205.
[7] SHMACK G,DUTSCHK V,PISANOVA E.Modification of polyamide fibres to improve their biocompatibility[J].Fibre Chemistry,2000,32(1):48-55.
[8] WANG L F,LIU J Q,YANG B,et al.PDMS-based low cost flexible dry electrode for long-term EEG measurement[J].IEEE Sensors Journal,2012,12(9):2898-2904.
[9] CHEN C Y,CHANG C L,CHANG C W,et al.A low-power bio-potential acquisition system with flexible PDMS dry electrodes for portable ubiquitous healthcare applications[J].Sensors,2013,13(3):3077-3091.
[10] WANG R X,HUANG X J,LI G F,et al.Fabrication and characterization of a parylene-based three-dimensional microelectrode array for use in retinal prosthesis[J].Journal of Microelectromechanical Systems,2010,19(2):367-374.
[11] MENG Y,LI Z B,CHEN X,et al.A flexible dry microdome electrode for ECG monitoring[J].Microsystem Technologies,2015,21(6):1241-1248.
[12] YAMAMOTO T,YATOMOTO Y.Electrical properties of the epidermal stratum corneum[J].Medical and Biological Engineering,1976,14(2):151-158.
[13]任子明,白冰,王任鑫,等.基于梳齿式电容加速度计的深硅刻蚀[J].微纳电子技术,2017,54(9):633-638.
[14]孟莹.基于柔性MEMS干电极阵列的智能心电监护系统关键技术研究[D].上海:上海交通大学,2015.
[15]王任鑫.基于柔性衬底的三维针尖电极阵列研究[D].北京:北京大学,2013.
[16] HUCLOVA S,ERNI D,FRHLICH J.Modelling and validation of dielectric properties of human skin in the MHz region focusing on skin layer morphology and material composition[J].Journal of Physics:D,2012,45(2):025301-1-025301-17.
[17] BIRGERSSON U H,BIRGERSSON E,OLLMAR S.Estimating electrical properties and the thickness of skin with electrical impedance spectroscopy:mathematical analysis and measurements[J].Journal of Electrical Bioimpedance,2012,3(1):51-60.
[18] MENG Y,LI Z B,CHEN J P.A flexible dry electrode based on APTES-anchored PDMS substrate for portable ECG acquisition system[J]. Microsystem Technologies,2015,22(8):2027-2034.
[19] BAEK J Y,AN J H,CHOI J M,et al.Flexible polymeric dry electrodes for the long-term monitoring of ECG[J].Sensors and Actuators:A,2008,143(2):423-429.
[20]MOON J H,BAEK D H,CHOI Y Y,et al.Wearable polyimide-PDMS electrodes for intrabody communication[J].Journal of Micromechanics and Microengineering,2010,20(2):025032-1-025032-11.