Papers by Author: Ming Chang

Abstract: In this paper, a method combining stereo vision and digital phase-shifting techniques is presented, which can measure the profile of complex freeform surfaces expeditiously and accurately. A chessboard is used to determine the camera parameters for the camera calibration of the system and the epipolar line rectification is executed based on the stereo calibration result. The stereo matching is processed with the combination of four-step phase-shifting and Gray code techniques, and the maximum probability method is proposed to remove the fringe order confusion problem between Gray code and phase shifting measurement. Bilinear interpolation method is also adopted to improve the speed and accuracy of stereo matching. Experiments were carried out with measuring a step gauge block and a shoe last model. Experimental results show that the measurement can be completed within 3 s for a measuring region of 640 mm × 480 mm, and the average measurement error is less than 0.054 mm.

Abstract: In this study, the electrical characteristics of gold nanowire (NW) under external tensile force were experimentally investigated. Experiments were carried out with a self-developed nanomanipulator inside the vacuum chamber of a scanning electron microscopye. A resistivity of for an individual gold NW was first obtained with the nanomanipulation system when no tensile force is applied, approximately 4.36 times larger than that of bulk gold. The results agree with the works of previous investigations. The electric characteristics of gold NWs under uni-axial tensile force was then investigated via the nanomanipulator. Experimental results show that the resistivity of gold NWs decreases as the applied tensile force increases, while the conductivity of the NWs as well as the mobility of electrons increases as the force increases. This indicates that the electrical characteristics of gold NWs are indeed affected by the external tensile forces applied to it.

Abstract: With the rapid expansion of nanotechnology, assembling nano-materials and to create electrical/mechanical devices at micro and nano scales has become an increasingly important research area. An “OR” logical gate at nano-scale has been constructed with ZnO nanowires (NWs) via a mechanical nano-manipulator which placing inside the vacuum chamber of a scanning electron microscope (SEM). By means of the electrostatic interactions and the characteristics of ZnO NWs, the on/off effect between probe tip and NW can be controlled by controlling the voltage between them. Experimental results show that the fabrication of nano logic gates based on ZnO NWs is possible.

Abstract: A mechanical nanomanipulation system has been developed for the assembly and fabrication of nano-devices inside a scanning electron microscope (SEM). The mechanical manipulator is made up of commercially available actuators and positioning stages which consists of three individual operation units each having three linear stages and one rotational stage. Experiments were performed to construct 2D and 3D nanostructures with Au nanowires. Versatile manipulations including shape modification, length amendment, and connection of nanowires were carried out. An electron beam induced deposition (EBID) technique was used to grasp nano-materials and assemble them, enabling 2D and 3D manipulation to be easier to conduct. Experimental results show that this manipulator is possible to play an important role in enabling the technology of assembling nano-scale mechanical and electronic devices from prefabricated nano-scale components.

Abstract: One-dimensional (1D) nanostructure such as nanowires (NWs), nanobelts and nanorods have attracted tremendous attention in recent years due to their exceptional micro-structural properties and novel potential applications. In the present investigation, titania (TiO2) nanowires are synthesized by microwave hydrothermal process (MHP) treating TiO2 nano powder with NaOH inside a microwave oven for 5h at 210°C and 350W. The mechanical properties of as synthesized TiO2 nanowires are determined by bending it with a nanomanipulator inside a scanning electron microscope (SEM). Young’s moduli of the nanowires are measured to be approximately 11.870.923GPa.

Abstract: With rapid expansion of nanotechnology, microminiaturization has become imperative in the field of micro/nano fabrication. A nanomanipulation system with high degrees of freedom that can perform nanomachining, nanofabrication and mechanical/electrical characterization of nanoscale objects inside a scanning electron microscope (SEM) is presented. The manipulation system consists of several individual operating units each having three linear stages and one rotational stage. The body of the manipulator is designed using the idea of superposition. Each operating unit can move in the permissible range of SEM’s vacuum chamber and can increase or decrease the number of units according to the requirement. Experiments were executed to investigate the in-situ electrical resistance of nano materials.

Abstract: Nanostructures materials have stimulated broad attention in the past decade because of their potential fundamental characteristics and its promising applications in nano electronic devices. In the present investigation, crystalline boron nanowires (BNWs) were synthesized by vapor liquid solid (VLS) technique and its mechanical properties were studied using a nanomanipulator inside a scanning electron microscope (SEM). Electron beam induced deposition (EBID) method was used to clamp boron nanowire to the AFM tips. The Young’s modulus of the NWs were determined from the buckling instability of NW and computed to be approximately 131.7 ± 14.6GPa. In addition, the nanomanipulation system was used to manipulate nanowire and built a nanoring.

Abstract: The dynamic characteristic of CNC (computer numerical control) machine tools is a critical role to decide the accuracy and speed of machine. It is very important to improve the precision and reduce the motion error so as to manufacture complex and fine products. In general, the motion error is estimated by a two or three-dimensional ball bar measurement system. Although this technology is capable of dynamical measurement, its condition should be confined to a low speed or a large radius. A new measurement method for measuring circular motion error of CNC machine tools is proposed in this paper. The instrument consists of a dual-frequency laser interferometer, a beam splitter and two corner cubes. In order to evaluate the exactness of the results we get from our measurement system, we use RSF’s grid encoder to do another experiment and compare both the results. According to the results shown, our measurement system can measure both of the X and Y axes of the plane of the CNC stage in a small scale at the same time and can simplify the calibration procedure as well as shorten the time of measurement. This method can accomplish the two-axis measurement at a high speed, without being restricted by radius variations. It is a good, simple and effective measurement method.

Abstract: The optical-fiber alignment system is a critical role on micro/nano precision engineering. In this paper, the design and fabrication of a novel, six-axis compliant nano-stage which uses flexure hinge and negative Poisson’s Ratio is presented. Every single axis is a designed planar geometry, so it is easily fabricated via laser cutting processes that enable cost down to achieve batch products. The material of six-axis mechanism is aluminum. The micromechanism consists of six trapeziform displacement structures and two hexagonal plates which are on the top and bottom. The displacement structures includes of a signal layer flexure hinge toggle mechanism stage and asymmetrical multi-layer flexure hinge toggle mechanism stage. The computer simulation of the transferring behavior was performed with a commercial package, named SolidWorks ANSYS@. The model states of stress, strain and the displacement of ratio can be estimated. The experiment was carried out with Piezoelectric(PZT) actuators and LVDT which drives and measures the displacement. Comparison of the simulation and experimental result between the single-axis and six-axis stage are presented. The results shown that the displacement of ratio is 32 times as the single-axis structures. The system maximum displacement of vertical translation, horizontal translation, tilt angle and rotational angle is 50 µm, 50 µm, 0.5° and 0.5°. In experimental, the results not only demonstrate that this micromechanism of flexure hinge and negative Poisson’s Ratio increases the displacement of ratio and reduces the size of system, but can also be applied on the optical-fiber alignment system.

Abstract: A membrane thickness process control expert system of chemical vapor deposition (CVD) based on neural network is presented. In general, there are many factors would influence the membrane quality. Most of them can be adjusted by changing the recipe, which are the process parameters of the working machines. Finding out a suitable and steady recipe and on-line real-time controlling the recipe is the target that process engineers devote to. Generally speaking, the recipe adjustment is based on the accumulation of experiences or learning from the try and error results. However, the process of thin film deposition is a very complicate and nonlinear system. It is very difficult to find out the relationships between the variation of process parameters and membrane quality. Therefore, a system was developed to simulate the CVD’s process using a technique of neural network. An expert system was then set up by extracting out the regular rule between process input and output from the trained neural network, which would provide references to engineers for the need of on-line recipe adjustment.