Key Engineering Materials Vols. 562-565

Abstract: In this paper, a novel microdevice-based solid phase extraction (SPE) method has been developed to extract genomic DNA from real biological samples, such as whole blood, by using a green reagent NaCl as the new binding salt. Guanidine as a bind salt was widely used for extraction DNA with a high extraction efficiency. But it was proved that guanidine was a kind of polymerase chain reaction (PCR) inhibitors, which is also toxic and the waste of guanidine might contaminate environment. NaCl is a natural, nontoxic, cheap, and green reagent, which would be a perfect candidate to replace guanidine. Silicon - polydimethylsiloxane (PDMS) - glass microdevice with a microchannel was designed and fabricated by micro electromechanical system (MEMS) technology. The DNA adsorption on the surface of the microchannel was observed by scan electron microscopy (SEM) technology. Then both NaCl and guanidine were used as the binding salt to extract genomic DNA from real biological sample. Compared with the binding salt of guanidine, the microdevice-based SPE method using NaCl is able to extract enough genomic DNA from rat whole blood in 30 min. About 725.2-1279.3 ng/mL genomic DNA was successfully extracted from whole blood by using NaCl. This highly efficient, effortless, and green method can be widely used as a lab-on-a-chip component for initial biologic sample preparation.

Abstract: We present a single mask selective release process for complex SOI MEMS device. Comparing to the one-step dry release process, there are two improvements, the first one is to ensure that the bottom of the suspension beams will not be notching, and have sufficient strength and rigidity, the second one is to ensure that the released structures will not be damaged during wafer dicing. According to the proposed design rules, in the dry release step, most of the device area is released, except the boundaries of the proof mass and the suspension beams. Then, in the wet release step, all the structures will be released, and also increased the gap below the structure. So the suspension beams is protect enabled that the device has sufficient rigidity and not easy to break. To verify this method, a micromachined gyroscope is fabricated and test.

Abstract: As an important part of MEMS, the micro-comb electrostatic driving structure is the main source of mechanical movement in many MEMS devices. Its reliability will directly affect the using performance of the MEMS devices. The electrostatic driving system of micro-comb capacitive micro-machined gyroscope can be equivalent to a second order system. If the applied voltage is less than the pull-in voltage, the movable micro-comb will maintain a steady state. Otherwise, the micro-combs will stick together because the applied voltage is greater than the calculated pull-in voltage. If the distance between micro-combs is too narrow, the role of these micro forces will be very significant. The pull-in phenomenon occurring in the process that the micro-machined gyroscope is applied on a phase step input voltage will lead to the very narrow comb spacing. As a result that the role of micro-forces such as the capillary force, Van der Waals force and Casimir force will become very significant, and the micro-combs will stick together permanently.

Abstract: With the development of micro-nanomachining technology (MNMT), micro heat radiator is getting attention. In this paper, the heat dissipation mechanism of light emitting diode (LED) ball lamp is introduced. And the LED heat radiator is simplified. On the basis of that, a new type of micro metal-plastic heat radiator of LED is put forward. And the LED heat radiator is simplified. A series of numerical simulations are carried out to compare the heat dissipation performance of micro heat radiator respectively made by metal, plastic, metal-plastic composite by the FloEFD software. Micro metal-plastic heat radiator structures, including fin spacing, fin thickness, fin height and substrate thickness, are carry out to be simulated.

Abstract: In this paper, we design a high-order switched capacitor filter for rapid change parameter converter. This design uses a structure which consists of three biquads filter sub-units. The design is a 6^th-order SC elliptic low-pass filter, and the sample frequency is 250 kHz. By the MATLAB Simulink simulation, the system can meet the design requirements in the time domain. In this paper, the 6^th-order switched capacitor elliptic low-pass filter was implemented under 0.5 um CMOS process and simulated in Cadence. The final simulation results show that the pass-band cutoff frequency is 10 kHz, and the maximum pass-band ripple is about 0.106 dB. The stop-band cutoff frequency is 20 kHz, and the minimum stop-band attenuation is 74.78 dB.

Abstract: We prepared the polyaniline@polypyrrole (PAn@PPy) conductive composite by a novel method. The struction like Pre-prepared PAn as the core and PPy as the shell for the composite has been prepared by in-situ polymerization. The PAn@PPy conductive composite presents an electrical conductivity of 12.5 S/cm, which is much higher than pure PAn. The synthesized polymer composites are characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric analysis (TG). The results indicated that PPy successfully grafted on PAn and the heat resistance of nanocomposite is remarkably increased.

Abstract: This paper presents a novel micro-electromechanical system (MEMS) piezoelectric vector hydrophone based on ZnO thin film. The approximate theory analysis is introduced in sensitivity and resonant frequency, and a simulation on the vector hydrophone is carried out by finite element method (FEM). Results of the theory analysis and FEM simulation agree well. The results show that the ratio of the piezoelectric layer thickness and Si layer thickness exists an optimum value for sensitivity, and MEMS piezoelectric vector hydrophones in smaller size have higher sensitivity than piezoresistive ones and are of passivity.

Abstract: In this paper, we study the MEMS wireless air-mouse system(MWAMS), which based on three-axis gyroscope、three-axis accelerometer、magnetometer and wireless RF technology. It makes use of MEMS motion sensing technology、information fusion algorithm and DCM complementary filter algorithm to sensing air-mouse's motion. This paper presents a new multi-sensor optimal information fusion and mapping algorithm. Compared to the traditional algorithm, this new algorithm based on MEMS technology not only has higher performance-higher location accuracy and better smoothness, but also has lower power consumption.

Abstract: Stability jet ejection and precision deposition are the two keys for industrial application of electrohydrodynamic printing. In this paper, inserted conductive probe is utilized to gain stability jet, which would increase the electrical field strength, reduce the back flow, onset and sustaining voltage. Lower applied voltage would enhance the stability of electrospun jet, in which fine jet can be used to direct-write orderly Micro/Nano-structure. With the guidance and constrain of inserted probe, the oscillating angle range of electrohydrodynamic jet is decreased to 3°from 15°, and the width of printed structures is 21μm in average that is much narrower than that printed from spinneret without probe (74μm in average). Spinneret with tip provides a good way to improve the control level of electrohydrodynamic printing, which would accelerate the industrial application of electrohydrodynamic printed Micro/Nano structure.

Abstract: Using first-principle calculations based on density function theory (DFT), the geometry , band structure and electronic density of states of Co-doped anatase titanium dioxide (Co/TiO₂) have been studied at plane wave ultra-soft pseudo-potential (PWPP). The states of the valence bands and conduction bands of pure and Co doped TiO₂ with anatase structure were calculated. The density of states of pure anataseTiO₂ and Co-doped TiO₂ is analyzed in detail based on the calculations using the first-principles. From the calculated results, the band gaps of anataseTiO₂ and Co doped TiO₂ are about 2.15 and 0.78eV, respectively. It shows that Co doped anatase titanium dioxide may lead to the narrowing of the band gap in Co/TiO₂. The Co doped anataseTiO₂ could be a potential candidate for photocatalyst because it can enhance the photocatalytic activity of anatase TiO₂.