视网膜前假体中柔性凸起微电极的研制

采用聚对二甲苯（Parylene C）作为结构材料，借助微细加工技术设计并制作了按6×6矩阵排布的柔性凸起微电极阵列．微电极直径为80μm，引线线宽40μm，电极间距为280μm，引线间距为80μm．电极位点高度约为10μm，呈明显的圆滑凸起结构特征．电极和引线表面均平整光滑，轮廓清晰，结构完好．阻抗测试结果表明：随着频率的增加，凸起微电极的阻抗呈下降趋势，显示出明显的高通特性；1kHz时凸起微电极的阻抗约为10kΩ，较具有相同基底面积的平面电极约低30％，有助于提高电极的信噪比，可望用于视网膜前假体中．柔性凸起微电极制作工艺简单，利于高效率批量制作并提高微电极的集成度．     

基于MEMS技术的植入式柔性多触点平面电极阵列

为提高植入式电极阵列的分辨率,降低生物组织损伤,保证其在生物体内稳定工作,本文提出了一种基于聚对二甲苯(Parylene C)的柔性多触点平面电极阵列.该电极为Parylene C/Au/Parylene C 3层结构,共24个通道.电极采用标准MEMS工艺加工,触点分布精确,轮廓清晰,表面平整,粗糙度为23.8 nm.为评估电极的工作性能,采用磷酸缓冲液(PBS溶液)模拟生物组织液,对电极阵列进行了电化学阻抗测试及循环伏安测试.测试表明,电极在100 Hz与1 000 Hz的阻抗值约为400 kΩ与50 kΩ,满足记录电极对阻抗的要求,同时,不同通道之间具有良好的一致性.此外,对随机选取的一个通道进行的循环伏安法测试表明,电极在刺激模式下具有良好的可逆性,对组织无影响,该通道的电荷储存能力约为650μC/cm2,与文献报道电极相当.     

硅基MEMS三维微电极阵列的超电容特性

三维微电极是一种具有空间结构优势、电化学性能比二维微电极更加优越的微型储能结构.本文提出一种基于光刻、感应耦合等离子体刻蚀和溅射等MEMS工艺加工三维结构硅基微电极阵列的新方法.采用电化学阴极沉积工艺在微电极表面制备了纳米氧化钌功能薄膜.借助扫描电子显微镜、循环伏安测试和电化学交流阻抗谱测试等手段对三维微电极的表面形貌和电化学性能进行了表征,系统研究了阴极沉积电流密度、电沉积时间以及硅基微结构表面"微草效应"对三维微电极超电容特性的影响.所制备三维微电极的比电容达到1.57 F/cm2,与平面电极比电容0.42 F/cm2相比明显提高,而电化学阻抗比二维平面微电极显著降低.相关实验数据表明基于MEMS技术加工的三维结构微电极具有优于平面电极的电化学电容储能特性.     

导电聚合物修饰的柔性神经微电极的制备与界面性质

本研究提供了一种简易、低成本的工艺和方法,进行神经微电极的性能改进,来改善神经电极/神经组织的界面特性。首先采用光敏型聚酰亚胺(Durimide 7510)作为微电极基质材料制备了一种柔性神经微电极;然后电化学合成导电聚合物聚噻吩PEDOT/LiClO4,进行神经微电极位点的表面修饰;最后测试和评价了神经微电极的表面形貌、电学性能及其生物相容性。结果表明导电聚合物粗糙的菜花状表面形貌提供了更大的界面表面积,因此电极阻抗降低到原来的1/20,微电极的电荷注入能力也增加了约100倍。细胞生物学实验也表明,导电聚合物修饰的柔性微电极上,细胞生长状态良好,与未修饰的柔性微电极下相比,粘附率与存活率均有明显改善,粘附率较修饰前增加了92.5%,存活率也由69.2%提高到85.4%。     

用于电刺激的植入式铂黑微电极

传统的植入式电刺激微电极表面积小,电极／组织界面阻抗高,并且电荷存储容量（CSC）小,这些都会增加植入式系统的功耗并影响电刺激效果．提出了一种在电极点电镀铂黑的方法来增加微电极的有效面积（ESA）．通过在超声波浴下使用脉冲电流电镀的方法,可以极大地增加微电极的ESA,降低界面阻抗并增加CSC和电荷注入容量．铂黑微电极的几何特性和电学特性分别由扫描电子显微镜（SEM）和电化学分析仪测定,并与未镀铂黑的电极特性进行了对比,对铂黑镀层的机械稳定性也做了相应的测试．实验结果表明,铂黑镀层的纳米结构使铂黑电极相比普通铂电极界面阻抗降低了1／16,CSC扩大13倍．在5min的室温超声波衰减实验中,阴极电荷存储容量（CSCc）仅减小20％．     

一种集成纳米金柱结构的神经薄膜微电极阵列

在神经假体系统中,神经微电极是实现信号检测以及激励任务的重要组成部分.然而,神经微电极由于尺寸微小,往往具有很高的电极/组织界面阻抗.本文提出了一种在电极位点表面处集成纳米结构来增大电极有效表面积的方法.这种方法结合了光刻、局部氧化铝以及电子束蒸发等技术,在薄膜微电极的表面集成了纳米金柱结构.最后,本文测试和评价了此微电极的表面形貌以及电学性能.实验结果表明,这种集成有纳米金柱结构的微电极其界面阻抗降低了约25倍,促进了这种微电极在神经工程领域的广泛应用.     

聚苯胺-碳纳米管涂层的电化学合成及其对神经微电极界面性能的影响

研究提供了一种简易、低成本的方法进行神经微电极的性能改进,来改善神经电极/神经组织的界面特性。采用电化学方法合成导电聚合物聚苯胺PA-NI和PANI-MWCNT(多壁碳纳米管)复合涂层,对神经微电极位点进行表面修饰;对修饰电极的表面形貌与电学性能进行测试,对比分析了MWCNT掺杂对PANI涂层的影响。结果表明,MWCNT掺杂改善了PANI涂层的表面形貌;与PANI修饰电极相比,PA-NI-MWCNT修饰电极界面通过的电荷量提高了近14倍,电学性能稳定性更好,在神经信号相关的1kHz频率处阻抗降低到原来的1/8,PANI-MWCNT复合涂层能更好地提高电极的电学性能。     

基于碳膜的柔性神经微电极阵列加工

为了实现长期安全有效的神经电刺激,避免电极腐蚀情况,提出了一种基于热解光刻胶形成碳膜作为导电材料的柔性视网膜神经微电极阵列．首先,通过高温热解图形化的光刻胶形成导电碳膜,然后利用光敏性聚酰亚胺（Durimide 7510）作为基底材料,通过光刻结合转膜、键合和牺牲层腐蚀技术,实现了具有柔性特征的碳膜神经微电极阵列．实验结果显示这种碳膜电极的电荷存储能力达到6．625mC／cm2．是金电极的12．4倍,显示了良好的电化学稳定性和电荷注入能力,有利于其长期植入和安全有效地工作,可应用于新一代人工视网膜系统的构建．     

基于MEMS技术的三维氧化钌微电极准电容特性

为增强电极在单位底面积上的电荷储存能力,设计利用MEMS技术制作高深宽比三维微电极结构,以增大电极结构表面积,并在结构表面制作功能膜形成电极.以硅为基底,SU-8光刻胶为材料制作了三维微电极结构,在结构表面溅射金作为集流体,用两电极体系进行方波脉冲电沉积,在三维微电极结构表面沉积氧化钌作为活性物质,制备了三维微电极.用扫描电镜和能谱对微电极表面形貌和物质组成进行表征,用循环伏安法等对微电极的电化学特性进行测试,三维微电极的比容量达0.79 F/cm2.     

基于聚酰亚胺的神经微电极的制备及特性研究

提出了一种基于非光敏型聚酰亚胺PI-5J的柔性薄膜神经微电极的制作方法,利用常规光刻技术设计和制作出了适合植入的柔性神经刺激微电极阵列,并通过离体实验对其进行了微电极的老化测试和电学特性测试,通过在体实验进行了微电极的生物相容性测试.测试结果显示,制作出的微电极不容易老化,而且具有很好的生物相容性和电学性能,此实验结果...     

Neural signal recording using microelectrode arrays fabricated on liquid crystal polymer material

Microelectrode arrays have been developed for simultaneous multi-channel recordings from nervous systems, typically using silicon substrates. However, it has been known that it is difficult to meet the biocompatibility and durability requirements using silicon and other dielectric materials (SiO₂, Si₃N₄), due to environmental moisture and ions. Additional disadvantage of silicon being the rigid material makes it hard to apply these materials in chronic recording situations.Liquid Crystal Polymer (LCP) was recently introduced as a candidate material for electronic packaging purposes. The material acts as efficient barrier against ions and moisture, a desirable feature for a substrate material of microelectrode arrays. In this paper, we report on the neural recording performed using the LCP-based microelectrode arrays.The cell adhesion on the new material was compared very favorably with that using silicon, SiO₂, or polyimide material. The microelectrode arrays were patterned with Ti (500 Å)/Au (3500 Å) on the LCP film and were employed in both stimulation and recording from rat sciatic nerve. The electrical characteristic of the recorded signal was as good as those using other substrate materials, proving this material as an excellent candidate for next generation microelectrode arrays.     

三维微柱阵列电极的电化学性能(英文)

随着MEMS技术的发展,对微纳尺寸器件的需求日益凸显,微能源的研究变得尤为重要,而微型超级电容器则是其中一种基于电化学电容实现储能的微型能量存储器件.设计了一种基于氧化钌功能薄膜的三维微柱阵列电极,并进行了相关的扫描电镜(SEM)、循环伏安(CV)和交流阻抗谱(EIS)测试.测试表明在2 mm×2 mm的硅片上,直径为50μm、高为100μm的三维微柱阵列电极的比电容为2.43 F/cm2,具有良好的电化学性能.与同容量的二维平面电极相比,基于三维结构的微型超级电容器具有明显的小尺寸优势.     

Interfacing cell-based assays in environmental scanning electron microscopy using dielectrophoresis

Development of the dielectrophoretic (DEP) live cell trapping technology and its interfacing with the environmental scanning electron microscopy (ESEM) is described. DEP microelectrode arrays were fabricated on glass substrate using photolithography and lift-off. Chip-based arrays were applied for ESEM analysis of DEP-trapped human leukemic cells. This work provides proof-of-concept interfacing of the DEP cell retention and trapping technology with ESEM to provide a high-resolution analysis of individual nonadherent cells.     

Optimization of the geometry and porosity of microelectrode arrays for sensor design

This paper describes the systematic investigation of a range of microelectrode arrays with varying dimensions fabricated by standard photolithographic and reactive-ion etching techniques. As expected from theory, the electrochemical behavior of microelectrode arrays with a constant individual diameter varied strongly with center-to-center spacing, the larger the spacing the more sigmoidal the recorded voltammogram. Furthermore, the behavior of arrays with a constant relative center-to-center spacing is shown to vary with individual electrode diameter, the arrays with the smallest electrodes producing strongly peaked voltammograms. Peak current densities and signal-to-noise ratios were also obtained for a variety of array geometries, and the use of electrodeposited platinum black electrodes was investigated. To demonstrate one advantage of using a loosely packed microelectrode array in electroanalysis, a ferrocene-mediated enzyme-linked assay involving the biocatalytic reduction of H2O2 was investigated. Results showed an improved temporal response, with current-time transients reaching a steady-state response more quickly using arrays with increased center-center spacings.     

Nanoelectronic interface for lab-on-a-chip devices

Innovations in microfabricated analytical devices integrated with microelectronic circuits and biological cells show promising results in detection, diagnosis and analysis. Planar metallic microelectrodes are widely used for the electrical interface with the biological cells. Issues with the current microelectrode array design are the difficulty in selective integration with a cell, the size dependency of its impedance and the large amount of noise in the circuit due to this mismatch. It is quite evident that an approach utilizing nanotechnology can solve some of these problems by yielding efficient electrical interconnections. The design and development of a planar microelectrode array integrated with vertically aligned nanowires for lab-on-achip (LoC) device applications are presented. The nanowire integrated microelectrode arrays for LoC devices show promising results with respect to impedance control due to increased surface area. The authors have fabricated nanowire integrated microelectrode arrays on silicon and flexible polymer substrates using the template method. A high degree of specific growth is achieved by controlling the nanowire synthesis parameters. An attempt has been made to integrate biological cells into the nanowires by culturing endothelial cells onto the microelectrode array.     

Effect of diffusion coefficient diversity on steady-state voltammetry when homogeneous equilibria and migration are encountered

An exact treatment is developed to predict the steady-state limiting voltammetric current, I(L), for a system in which the reaction O(+) + A(-) ? N occurs reversibly in solution, in the presence of supporting electrolyte C(+)A(-). Either or both O(+) and N undergo a one-electron reduction at the hemispherical microelectrode. The dependence of I(L) on the formation constant of the equilibration reaction, the electrolyte concentration, and the support ratio is derived for any trio of values of these parameters and for any combination of diffusivities of the O(+), N, and A(-) species.     

Nanostructured gold microelectrodes for extracellular recording from electrogenic cells

We present a new biocompatible nanostructured microelectrode array for extracellular signal recording from electrogenic cells. Microfabrication techniques were combined with a template-assisted approach using nanoporous aluminum oxide to develop gold nanopillar electrodes. The nanopillars were approximately 300-400 nm high and had a diameter of 60 nm. Thus, they yielded a higher surface area of the electrodes resulting in a decreased impedance compared to planar electrodes. The interaction between the large-scale gold nanopillar arrays and cardiac muscle cells (HL-1) was investigated via focused ion beam milling. In the resulting cross-sections we observed a tight coupling between the HL-1 cells and the gold nanostructures. However, the cell membranes did not bend into the cleft between adjacent nanopillars due to the high pillar density. We performed extracellular potential recordings from HL-1 cells with the nanostructured microelectrode arrays. The maximal amplitudes recorded with the nanopillar electrodes were up to 100% higher than those recorded with planar gold electrodes. Increasing the aspect ratio of the gold nanopillars and changing the geometrical layout can further enhance the signal quality in the future.     

Soft microelectrode linear array for scanning electrochemical microscopy

A linear array of eight individual addressable microelectrodes has been developed in order to perform high-throughput scanning electrochemical microscopy (SECM) imaging of large sample areas in contact regime. Similar to previous reports, the soft microelectrode array was fabricated by ablating microchannels on a polyethylene terephthalate (PET) film and filling them with carbon ink. Improvements have been achieved by using a 5 μm thick Parylene coating that allows for smaller working distances, as the probe was mounted with the Parylene coating facing the sample surface. Additionally, the application of a SECM holder allows scanning in contact regime with a tilted probe, reducing the topographic effects and assuring the probe bending direction. The main advantage of the soft microelectrode array is the considerable decrease in the experimental time needed for imaging large sample areas. Additionally, soft microelectrode arrays are very stable and can be used several times, since the electrode surface can be regenerated by blade cutting. Cyclic voltammograms and approach curves were recorded in order to assess the electrochemical properties of the device. An SECM image of a gold on glass chip was obtained with high resolution and sensitivity, proving the feasibility of soft microelectrode arrays to detect localized surface activity. Finite element method (FEM) simulations were performed in order to establish the effect of diffusion layer overlapping between neighboring electrodes on the respective approach curves.     

A Hemispherical Image Sensor Array Fabricated with Organic Photomemory Transistors

Hemispherical image sensors simplify lens designs, reduce optical aberrations, and improve image resolution for compact wide-field-of-view cameras. To achieve hemispherical image sensors, organic materials are promising candidates due to the following advantages: tunability of optoelectronic/spectral response and low-temperature low-cost processes. Here, a photolithographic process is developed to prepare a hemispherical image sensor array using organic thin film photomemory transistors with a density of 308 pixels per square centimeter. This design includes only one photomemory transistor as a single active pixel, in contrast to the conventional pixel architecture, consisting of select/readout/reset transistors and a photodiode. The organic photomemory transistor, comprising light-sensitive organic semiconductor and charge-trapping dielectric, is able to achieve a linear photoresponse (light intensity range, from 1 to 50 W m⁻²), along with a responsivity as high as 1.6 A W⁻¹ (wavelength = 465 nm) for a dark current of 0.24 A m⁻² (drain voltage = −1.5 V). These observed values represent the best responsivity for similar dark currents among all the reported hemispherical image sensor arrays to date. A transfer method was further developed that does not damage organic materials for hemispherical organic photomemory transistor arrays. These developed techniques are scalable and are amenable for other high-resolution 3D organic semiconductor devices.