Advanced Materials Research Vols. 60-61

Abstract: We study some microstructures fabricated by designed 355nm ultraviolet nanosecond pulse laser micromachining system, which consists of LASER, mechanical and optical structure, 3D work platform, and control system. Nanosecond pulse LASER, with 40ns pulse duration, is chosen as the light source. Mechanical and optical structure is designed for laser beam focusing. Computer software resolves the graphics. And control system based on DSP and FPGA is designed to drive the 3D work platform. Raster sensor is used to measure the real distance that the platform moves. Using this system, some experiments are analyzed and some parameters are optimized. Some microstructures are also fabricated on single crystal silicon wafer and organic glass. The lines of fabricated graphics are 20-40um wide and smooth, with less effect of heat.

Abstract: The compound of micron powders and nanometer powders is a magnificent step in the application and development of metal matrix composite reinforced by nanometer particles. By taking nano-Al2O3 powders and Ni-based micron powders as the research object, the preparation process of metal matrix micro/nano-powders reinforced by nanometer particles with high energy ball-milling is discussed from three aspects: the additive process of nanometer powders, the additive content of nanometer powders, and the required ball-milling time in the paper. The results show that the additive process of nanometer powders which uses directly the dispersed uniformly nanometer suspensions as grinding medium can effectively decrease and avoid nanometer powders’ agglomeration of composite powders. Nanometer particles are well distributed in the composite powders. The optimum additive content of nanometer powders is consistent with the theoretical model of mixture ratio, which is determined by the ratio of the average diameter of micron powders and nanometer powders and their density of corresponding solid materials. Meanwhile, the required ball-milling time for preparation of better uniformity composite powders is no more than 0.5hr. This implies that the preparation process has a high productivity. Moreover, the preparation process is verified through other nanometer powders including nano-SiC powders and nano-CeO2 powders.

Abstract: The armature fabricated with the sacrificial layer techniques is an important part of micro electromagnetic relay. So the sacrificial layer is one of the key fabrication processes in the realization of prototype of micro electromagnetic relay. In this paper several sacrificial layers including Copper, Polyimide and Positive photoresist are studied based on the investigation of the research on sacrificial layer and binding the characteristic of micro electromagnetic relay’s fabrication process.

Abstract: Core-shell quantum dots are colloidal particles consisting of a semiconductor core and a shell material as an outer coating layer. It can be utilized to develop sensitive methods for the detection of specific biological entities, such as microbial species, their transcription products, and single genes etc. The goal of current research is to synthesize CdTe and core-shell CdTe/ZnS quantum dots (QDs) with an improved process, and to investigate their properties. Well-dispersed CdTe core was prepared in aqueous phase with using 3-mercaptopropionic acid (MPA) as stabilizer under conditions of pH 9.1, temperature of 100 °C, refluxing for 6h, and mol ratio of Cd2+/Te2-/MPA is 1:0.5:2.4. Average size of 8 nm CdTe core was conformed via transmission electron microscopy (TEM). Core-shell CdTe/ZnS QDs were then synthesized to improve the optical properties and biocompatibility of CdTe core. Various conditions were researched to obtain the core-shell QDs with the best optical properties, such as quantum yields, fluorescence intensity etc. The results indicated that the core-shell qualified CdTe/ZnS was prepared under conditions of pH 9.0, temperature of 45 °C, refluxing for 1h, and mol ratio of CdTe/S2-/Zn2+ is 4/1/1. CdTe/ZnS with average size of 10 nm were achieved and conformed via TEM. Moreover, red shift of a maximum emission wavelength from 547 nm of CdTe to 587 of CdTe/ZnS was observed via fluorescence spectrum (FS), which inferred the growth of QDs and formation of ZnS shells. The achieved ZnS shell make CdTe core less toxic and more biocompatible, it will be useful in biological labeling, diagnostic process and biosensing system based on fluorescence resonance energy transition (FRET).

Abstract: A novel electrochemical DNA biosensor system based on multi-walled carbon nanotubes(MWCNTs) was presented in this paper. In order to make multi-walled carbon nanotubes being perpendicularly standing on Au electrode via Au-S chemical bonding, we cut multi-walled carbon nanotubes (1.5 m) into short pipes (200-300 nm). Then, the shortened nanotubes were further modified by thiolization reaction with cysteamine (NH2CH2CH2SH). The –SH modified MWCNTs, gold nanoparticles and 5’ end –SH modified DNA (HS-DNA) as nucleotide probes were self-assembled onto the surface of Au electrode respectively. The DNA biosensors based on self-assembled MWCNTs had a higher current response compared to those based on random MWCNTs. When the target DNA concentration was 4.0×10–9 mol/L to 1.2×10-8 mol/L, the cathodic peak current of Au electrode system with the AQDS as indicator was linearly related, and the detection limit was about 6.5×10-9 mol/L. In addition, the developed DNA biosensors also had a high selectivity of hybridization detection.

Abstract: Based on the refraction theory of the lens, the SU-8 photoresist hard X-ray hourglass lenses with three different structure parameters are fabricated. The mask-back exposure technique is introduced to fabricate the lenses. The focusing performance of this device is tested at Beijing Synchrotron Radiation Facility (BSRF). At the distance of 1.65m from the lenses, an obviously focusing performance in one dimension is observed. The relative intensity of the lenses with the largest gain is about 217.7, the gain of the lens is about 1.15, and the dimension of the focus is about 33µm. The focusing performance of this device can be improved through the developing of the mask-back exposure technique.

Abstract: Based on a new micro programmable grating with changeable blazed angle, the control system was recently designed and developed, enabling the normal operation for the fabricated grating. The basic requirements for the control system are high reliability, efficiency and miniaturization. This paper presents the specific design objectives for the control system according to the grating’s operation characteristics. The whole control system contains three key modules—generator & communication module, high-voltage amplifier module and computer software module. Generator & communication module includes a high-performance microcontroller (C8051F020), a D/a converter (AD7305) and universal serial bus (USB) interface. As for the considered performances, PA69 is complete capable of magnifying the driving voltage signals to drive the grating in high-voltage amplifier module. After the development of the control system, an experiment was performed for investigating the dynamic frequency response of the grating. In conclusion, it has the advantages of wide output of voltage, high frequency response, driving ability in wide capacitive load range and real-time control properties. Hence, it is appropriate for controlling MEMS programmable grating in complicated and dynamic conditions.

Abstract: A new type of continuous face-sheet micro deformable mirror was designed and fabricated based on SOI (Silicon-on-Insulator) technology for high optical efficiency applications in adaptive optics system. SOI provided a Silicon-Insulator-Silicon structure, and the insulator-layer of the three-layer structure was taken as etch-stop layer in deep silicon etching, which made the suspended bulk silicon membrane obtained easily. And the reflective face did not suffer etch-step due to the protection of insulator-layer. The mirror was composed of 5-um-thick and 10-mm-diameter flexible bulk silicon membrane, and actuated by 69 electrostatic actuators which evaporated on glass substrate. SOI and glass wafer were bonded together by anodic bonding, forming a separation gap of 15um between the mirror face and electrostatic pad, which offered a maximum effectual displacement of 5um by considering the pull-in effect. Fabrication process was introduced in detail. Bulk silicon micromachining was employed, methods mainly include Inductivity Coupled Plasma (ICP) etching and Si/Glass anodic bonding technique.

Abstract: This paper introduces a novel approach for human motion recognition via motion feature vectors collected by A Micro Inertial Measurement Unit (µIMU). First, µIMU that is 56x23x15mm3 in size was built. The unit consists of three dimensional MEMS accelerometers, gyroscopes, a Bluetooth module and a Micro Controller Unit (MCU), which can transmit human motion information through a serial port to a computer. Second, a human motion database was setup by recording the motion data from the µIMU. The motions include fall, walk, stand, run and step upstairs. Third, Support Vector Machine (SVM) training process was used for human motion multi-classification. FFT was used for feature generation and optimal parameter searching process was done for the best SVM kernel function. Experimental results showed that for the given 5 different motions, the total correct recognition rate is 92%, of which the fall motion can be classified from others with 100% recognition rate.

Abstract: A microfluidic chip with in-situ prepared chitosan membrane immobilized with Glucose Oxidase was developed as glucose oxidase reactor to detect human serum. The chitosan was prepared in-situ in the micro-channel as the immobilization material.Then,GOD was immobilized in the chitosan membrane, in which factors, such as the glutaraldehyde concentration, time of crosslinking and immobilization, buffer pH, were optimized with orthogonal experiments. The concentration of glutaraldehyde was finally chosen as 0.15%, time of crosslinking as 60 min, immobilization time as 15 h, and buffer PH as 8.0. The immobilization efficiency could reach up to 5U•cm2. The homemade microchip could be applied for rapid determination of glucose in serum, combining with the Luminol-K3Fe(SCN)3 Chemiluminescence reaction system. Under optimized conditions of sample velocity of 500uL•min-1, the concentration of K3Fe(SCN)3 of 1×10-2mol•L-1 and the concentration of luminol of 5×10-4 mol•L-1, the detection limit could achieved 1ug•mL-1.