Advanced Materials Research Vols. 60-61

Abstract: This paper presents deep-hole etching process by inductively coupled plasma (ICP),the hole is higher than 400um ,and its diameter is 200um wide. Etching process successfully used in anchor fabrication below 150 um deep in micro-inertial devices, is first used in deep-hole etching .The result is badly, the sidewall surface is coarse, and the sidewall perpendicularity is poor,the dimension difference between upper and down diameter is as large as 35um.Because with the depth increasing , deep-hole etching brings new problem, such as fluorine(F) radical and ions distributing very differently between in down and upper area, also extracting reactant and temperature distribution . To solve above problems, process parameters such as gas flow mass and time in one reaction cycle, source and substrate power, reaction pressure and temperature should be adjusted. Through several experiments, optimal process is applied and the result is satisfied .From SEM figure, The the sidewall surface is smoother, the sidewall perpendicularity is good, the dimension difference between upper and down diameter is controlled in 1.6um,the sidewall angle is 89.78°. The process has been used in deep-hole fabrication of micromachined filter, and the rate of device enhances largely at present.

Abstract: In this paper, a Z-axis micromachined gyroscope with a new decoupled design was presented. The gyroscope consists of dual proof mass, sense frame and drive frame structure. The sense frame is constrained in the sense direction and anchored on the substrate, which minimize the influence from the motion of the proof mass in the drive direction. The drive frame is also restricted to oscillate in the drive direction. ANSYS has been used to make modal analysis and harmonic analysis to determine the vibration characteristics of the decoupled gyroscope. We introduce the decoupling ratio (ηDtS) of drive mode to sense mode and the decoupling ratio (ηStD) of sense mode to drive mode to determine the decoupling design. The results show that the drive mode and the sense mode are well decoupled.

Abstract: A method of fabrication of micro via-hole by wet-etching of Pyrex glass is presented in the paper. The through holes with double funnel-shape have been fabricated attribute to isotropic etching. Furthermore, the funnel-shape holes are advantageous to the joint sealing and have been applied to fabricate microfluid chips. The results show that the proportioning of corrosion solution is HF:HCl:H2O=3:6:10, and the corrosion rate is about 0.67um/min, the diameter of the holes on the both-side of the wafer is only 750 um, the middle ones are 300um

Abstract: This paper discusses the nonlinear errors for a novel gap variation-type thick film capacitive micro-displacement sensor. The micro-displacement sensor is developed for measuring the PZT displacement based on the pattern of PZT deformation-force sensing-displacement. In theory, The capacitor detects the micro-displacement driven by the PZT ceramic，and the variation of capacitance can be transformed into real-time output voltage signals. In this process, there would be some nonlinear errors. Based on the structure and operational principle of the sensor, possible nonlinear errors and their causes are analyzed. Then targeted measures are adopted to deal with them. Results show that the sensor’s linearity can be improved by effective compensating methods.

Abstract: A biosensor based on gold electrode modified by Pt nanaoparticles/Osmium redox polymer/Nafion trilayer film was fabricated and used for selective and sensitive determination of dopamine. The biosensor is explored for DA sensing using the cyclic voltammetry (CV), amperometric and differential pulse voltammetric (DPV) methods. The CV anodic peak currents showed a linear range with a correlation coefficient of 0.996, localized in the concentration range 0~192 μM. The differential pulse voltammetric (DPV) peak currents were linear with DA concentration during 2~425 μM with correlation coefficient of 0.99. The biosensor showed high sensitivity of 0.5 nA /nM cm2 and excellent reproducibility with the detection limit of ~10 nM (S/N=3) for the determination of DA. The easy fabrication, low detection limit and high sensitivity of the integrated biosensor making it particularly suitable for the analytical purposes.

Abstract: Molecular dynamics simulations are carried out to characterize the mechanical properties of [001] and [110] oriented silicon nanowires, with the thickness ranging from 1.05nm to 3.24 nm. The nanowires are taken to have ideal surfaces and (2×1) reconstructed surfaces, respectively. A series of simulations for square cross-section Si nanowires have been performed and Young’s modulus is calculated from energy–strain relationship. The results show that the elasticity of Si nanowires is strongly depended on size and surface reconstruction. Furthermore, the physical origin of above results is analyzed, consistent with the bond loss and saturation concept. The results obtained from the molecular dynamics simulations are in good agreement with the values of first-principles. The molecular dynamics simulations combine the accuracy and efficiency.

Abstract: A new method has been developed and applied in a micro amperometric immunosensor to immobilize antibody with electropolymerized staphylococcal protein A (SPA). SPA is usually used directly as an immunoadsorbent and can achieve the binding of IgG very well. In this paper, pyrrole doped with SPA was co-electropolymerized onto the working electrode surface by cyclic voltammetry in 10 minutes. It effectively immobilized SPA on the surface of the working electrode for orientation-controlled immobilization of capture antibodies. This method as a controllable and convenient manipulation can modify the sensing surface more rapidly with less consumption of reagent (10μL), which is proper to the micro immunosensor. As an application to test the validity of this method, Salmonella typhimurium (S. typhimurium) with the concentration of 102cfu/ml could be detected by this immunosensor, which shows the good property of the sensor and proves the feasibility of the method applied for the immobilization of antibody. It is potential to develop a biosensor that can be used for convenient, low-cost and real-time sensing of pathogens in food products.

Abstract: The study is performed to implement the Gold-Gold thermocompression bonding for the wafer-level packaging of MEMS chips. Numerous experimental attempts have been carried out to select the metal film adhesive to avoid the Au-Si melt together and optimize bonding processes to intensify the Au-Au eutectic bonding. Finally the results display that the eutectic bonding of the gold-gold are arrived as electrical as well as mechanical interconnection of the MEMS structure and as seal as well as bonding intension.

Abstract: This paper presented a parametric experimental study of electrokinetic instability phenomena in a cross-shaped configuration microfluidic device with varying channel depths and conductivity ratios. The flow instability is observed when applied electric field strength exceeds a certain critical value. The critical electric field strength is examined as a function of the conductivity ratio of two samples liquid, microchannel depth, and the treatment of microchannel wetted surface. It is found that the critical electric field strengths for the onset of electrokinetic instability are strongly dependent on the conductivity ratio of two samples liquid, and decrease as the channel depths increasing of microfluidic devices. In the present study, the surface inside microchannels is treated utilizing hydrophilic and hydrophobic organic-based SOG (spin-on-glass) nanofilms for glass-based microchips. The experimental results indicate that no significant difference for the critical electric fields for the onset of electrokinetic instability phenomena in both hydrophilic and hydrophobic SOG coating in the surface of microchannels. The critical electric fields for the onset of electrokinetic instability phenomena are slightly lower in both SOG coated cases in compare with that of the non-coated microchannel.

Abstract: A design and simulation of a fully CMOS compatible micromachined multilayer cantilevers-based environmental thermometer are presented. The operation principle of the structure is depending on the mismatch effect of thermal expansion coefficient and the piezoresistive effect of polysilicon in CMOS process. Upon temperature variation, the deformation of the multilayer cantilever resulted from the large thermal expansion coefficient mismatch of different materials can be sensed and translated to an electrical voltage output by using a symmetric piezoresistive Wheatstone bridge. The mechanical characteristics of the device are analyzed with the extension of bi-layer Timoshenko model and the output of the read-out circuit is also simulated. The calculation and simulation show that the device with bi-direction deformation may have wide temperature range from -100 to 100°C and sensitivity about 0.15mV/°C, which fit the demand of radiosonde for environmental temperature measurement. This sensor may also have other favorable features, such as micro size, low-cost due to its working principle and compatibility with commercial CMOS process.