Papers by Keyword: Microelectrode

Abstract: Measuring deep brain neural activities with a microelectrode is of greatest importance in uncovering the mechanism of various brain disorders. In this operation, a microelectrode needs to be accurately inserted into deep the brain. However, a microelectrode of high flexibility would bend at encountering a layer of tough tissue during insertion, which would lead to deflection and impaired targeting accuracy. To deal with this problem, a rotational insertion method has been developed in this paper for deflection-free insertion. Rotation helps generate a dynamic anti-bending force to prevent buckling, and this force becomes larger with the increase of rotational speed. Thus, by controlling the rotational speed at which insertion is carried out, deflection-free insertion of a microelectrode deep into brain can be realized. The effectiveness of this method has been experimentally confirmed.

Abstract: This work was to study the dissolved CO in solution phase by using rotating disk electrodes and the solution phase CO demonstrate the limiting currents dependence of rotating speeds. Gold and gold-platinum metals clusters are used in glassy carbon supported rotating disk electrode for electrochemical oxidation of the solution phase CO. Small metal clusters and Au-Pt alloy effects are observed in the measurements. The comparison of microelectrode and RDE study of solution phase CO electrochemical oxidation is confirmed the limiting currents dependence of the boundary layers concentrations.

Abstract: Rapid-response biosensing systems are necessary to counteract threats due to high-consequence pathogens. A disposable immunosensor suitable for quantitative determination of E.coli O157:H7 in pure cultures was investigated by electrochemical impedance spectroscopy (EIS). Electric responses of this biosensor for different cell concentrations at multi-frequencies were explored utilizing disposable screen-printed silver four-wire interdigitated microelectrodes (IMEs). Additionally, the best response frequency for the detection was studied, and the relationship between the impedance at this frequency and the concentrations of E.coli O157:H7 was established. The results showed that the impedance biosensor showed linearity from 1.15×10³ CFU/mL to 1.15×10⁶ CFU/mL at 100Hz, which yielded the model coefficient to 0.951.

Abstract: We present a new design of biochip for application in clinical diagnostics by using a conventional method of pattern transfer process in microelectronic fabrication. Although there are many advanced techniques available to produce nanostructures such as electron beam lithography (EBL), ion-beam lithography (IBL), focused ion beam milling and nanoimprint lithography, these methods often requires high maintenance costs, time consuming and very complicated compared to conventional photolithography. This conventional technique is still a good choice for a feature size more than 1 micron. In this work, microbridge and microgap design from chrome mask are transferred on silicon wafer to fabricate a biochip. The pattern transfer of the first mask of electrode is presented in this paper to test the repeatability of pattern transfer during photolithography process. Therefore, during the process, the resolution and precise alignment factors are taken into account to prevent circuit and device failure. Post-exposure bake time and development limitations are recorded for both designs.

Abstract: In order to fabricate micro holes by EDM process, microelectrodes with high accuracy of form are needed. At present, micro electrodes are generated by grinding and/or on-machine EDM operations and then it is well known that efficient productivity of micro electrodes cannot be realized. Controlling method of thrust force for micro shaft is already proposed. Applying this method, thrust force is controlled to be 0 in turning operation, therefore microelectrodes are generated efficiently. Actually, microelectrode which diameter is less than 0.1 mm can be easily machined in short time. high-precision micro hole machining requires microelectrodes with high cylindricity. In this study, turning method for microelectrodes with high cylindricity is discussed.

Abstract: LiFePO₄ is becoming promising lithium ion cathode material. Because period of testing call is long, sometimes it cannot accurately characterize for cathode materials. By using Electrochemical Impedance Spectrum, it would be better to describe performance of materials. The electrochemical parameters have been obtained by modeling process of insertion and desertion by Electrochemical Impedance Spectrum, which is helpful to analyze LiFePO₄ electrochemical performance. Because of quick response and preciseness of electrochemical method, it would be better to analyze cathode materials.

Abstract: A new turning method to control the thrust force to be zero has already been proposed in our laboratory, and it is shown that micro shafts which diameters are less than 1 mm can be generated stably and repeatedly by applying this turning method. As an application of this turning method, a generating method of electrodes of micro electric discharge machining, EDM, for micro holes is proposed. When drilling a micro hole by EDM using an electrode with high aspect ratio, machined chip is difficult to be exhausted. Therefore, machining time has a tendency to be long and the electrode consumption becomes large. Standing in such a viewpoint, a new method to exhaust the chip smoothly by forming the micro electrode geometry is proposed in this paper. As the results of this study, it is confirmed that the machining time of micro holes can be shorted and the consumption of electrode can also be decreased experimentally.

Abstract: In this paper micro-electrochemical turning for fabricating microelectrode is presented. A stainless steel film with 50 μm thickness as turning tool is the cathode and a rotary tungsten rod for the proposed microelectrode fabrication is the anode. By applying ultra short pulses in micro seconds, dissolution of the anode can be restricted to the small region very close to the cathode. Due to rotation of the anode and movement of the cathode along the rotary axis direction, the anode uniformity corrosion was improved and its rotating concentricity was ensured simultaneously. A micro-electrode with a high aspect ration, namely 20 μm in diameter and 2500 μm in length has been fabricated in the low concentration electrolyte, 4%NaOH.

Abstract: Restoring peripheral nerve trauma is an important research field in regenerative medicine. One therapeutical approach is to use tissue engineered nerve conduits consisting of biodegradable polymers. These materials can be designed to include active agents to further stimulate or influence proliferation, maturation, differentiation or migration of specific neuronal cell in these nerve guides. We have developed a method to electrically deposit and immobilize neuronal cells and extracellular matrix proteins on self structured micro electrodes. These electrodes also present a feasible methodology to investigate electrical stimulation of nerve cells. In our approach, poly-D,L-lactide-co-glycolides (PLGA) were investigated as possible substrate for these electrodes, while further allowing for the integration of model substances in a drug release concept. In a first approach, caffeine was used due to its well known effect of both stimulating and inhibiting effects on certain neuronal cells, while also allowing easy incorporation into PLGA via chemical means. A Plackett-Burman experimental design was used to find the optimum composition among different parameters such as drug concentration, polymer concentration, type of solvent and film-drying condition. The optimized drug loaded polymer films were tested for their release and degradation profile, and their behavior in cell culture. Finally, we are currently establishing an integrated experimental setup, combining caffeine modified PLGA film substrates with the manufacturing of the electrode structures to investigate cell deposition via electrical means and stimulation/ inhibition via chemical release.

Abstract: The machining of materials on microscopic scales is considered to be great importance to a wide variety of fields. Electrochemical Micro-machining (EMM) appears to be promising to machine the micro-structures in future due to the material is dissolved at the unit of ion. This paper is focused on developing a micro electrochemical machining system in which the micro-structures such as micro-cylinder, multiple micro-electrodes, micro-holes and micro-slot were processed. The micro-electrodes were prepared in a precisely controlling the electrochemical etching process. Mathematical model controlling the diameters of electrodes was built up. Furthermore, the obtained micro-electrodes were selected as the cathode tool for micro holes drilling and micro-slot milling using pulse power in Micro-ECM.