Progress of Precision Engineering and Nano Technology

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Authors: Pei Jing Shi, Bin Shi Xu, Yi Xu, Q. Liu
Abstract: A special kind of surface modified copper nanoparticles was selected as the auto-reconditioning materials to in situ generate a copperized protective film on iron-base metal surfaces under designed tribological conditions. The morphologies and element distributions of the formed film were observed and determined by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The micro mechanical properties and tribological behaviors were investigated by nano test system and ball-on-disc tribotester. The results show that the morphology of the protective film is smooth, the nano-hardness decreases by 46% and the friction coefficient of the copperized protective film is about 0.10. The forming mechanism of the auto-reconditioning film can be described that the copper nanoparticles deposit on the worn surfaces and form iron-copper alloy film with lower hardness and shear strength, which has better friction-reducing, antiwear and surface-optimizing behaviors.
Authors: Yong Da Yan, Tao Sun, Shen Dong, Ying Chun Liang
Abstract: A three dimensional molecular dynamics model is employed to simulate AFM-based lithography process. To investigate effects of tip geometry, three kinds of tip models are proposed: a cone-shape tip with a hemisphere at the end, a round-edged three sided pyramid tip with a hemisphere at the end and a sharp-edged three sided pyramid tip. These models simulate scratching behaviors of AFM tip at different scratching depths. Results showed that materials removal behavior and scratching forces were significantly affected by tip geometry, depending on the scratching depth and scratching directions. The specific energy using a sharp-edged three sided pyramid tip displayed a different behavior comparing to that using a round-edged three sided pyramid. However, scratching orientations exhibited no effects on the specific energy.
Authors: D.P. Zhao, D. Wu, K. Chen
Abstract: This paper introduces a fluidic technique based on patterned shapes of hydrophobic self-assembly monolayers (SAMs) and capillary forces to self-assemble micro-parts onto substrates. Self-assembly is defined as a spontaneous process that occurs in a statistical, non-guided fashion. More specifically, the fluidic self-assembly with capillary force is driven by the gradient in interfacial free energy when a micro-part approaches a substrate binding site. In this paper, the mechanism of self-assembly with capillary forces is proposed. The hydrophobic-hydrophilic material system between the binding sites and micro-parts is then simulated. Finally, the surface energy of a self-assembling system in the liquid phase under different conditions is calculated. The results show that shift, twist, lift and tilts displacements are detected to be rather uncritical and the system turns out to be rather stiff with respect to such displacements. The theoretical result is supported by the experiments and gives quantitive explanations why and how the capillary force works in the self-assembly process.
Authors: Y.G. Cui, Wei Jie Dong, C.Y. Gao, Q.Y. Zeng, Bao Yuan Sun
Abstract: This paper aims to make piezoelectric ceramic actuator self-sense its own displacement in the absence of independent sensor. It is derived from the basic piezoelectric equation that the free charge on the wafer of piezoelectric ceramic actuator contains displacement information. So a displacement self-sensing method based on integrate circuit is presented. Voltage driving circuit for the piezoelectric ceramic actuator and integrated circuit for gathering free charge are designed. Based on the proposed compound circuits, the actuator can sense its own displacement while actuation. It is convenient to adjust the circuit and easy to acquire sensitive signal by using this method, and the impedance mismatching problem met in bridge method is overcome. The experimental results show that piezoelectric self-sensing actuator can effectively measure its displacement signal under the conditions of different wave form of driving voltage and different driving voltage frequency.
Authors: L.Q. Du, C. Liu, H.J. Liu, J. Qin, N. Li, Rui Yang
Abstract: Micro hot embossing mold of microfluidic chip used in flow cytometry is designed and microfabricated. After some kinds of microfabrication processes are tried, this paper presents a novel microfabrication technology of micro hot embossing metal mold. Micro metal mold is fabricated by low-cost UV-LIGA surface micro fabrication process using negative thick photoresist, SU-8. Different from other micro hot embossing molds, the micro mold with vertical sidewalls is fabricated by micro nickel electroforming directly on Nickel base. Based on the micro Nickel mold and automation fabrication system, high precision and mass-producing microfluidic chips have been fabricated and they have been used in flow cytometry
Authors: K. Jia, H.H. Zhang, X.Q. Fan, X.P. Jiang, S. Liu
Abstract: In this paper, nonequilibrim molecular dynamics (NEMD) was used to simulate liquid flow in microchannels with ‘lotus effect’ coating. Without considering atomic structure and long-range interaction, we have been dedicated in establishing a two-dimensional geometric model based on the coating and studying the behavior of liquid near the inner surfaces of ‘lotus effect’ microchannels. The shape of a single pattern in the coating and the thickness of one microchannel were varied to study the influences of these parameters on velocity profile of liquid in the flow direction, the maximum of this velocity, and its position perpendicular to flow direction. The proper conditions which made the velocity slip of liquid near the boundary layer of microchannels maximum and liquid move most fast were decided.
Authors: Jun Hui Li, Lei Han, Ji An Duan, Jue Zhong
Abstract: An assembly bed on thermosonic flip chip bonding was set up, two different structures of tool tips were designed, and a series of experiments on flip chip and bonding machine variables were carried out. Lift-off characteristics of thermosonic flip chip were investigated by using Scanning Electron Microscope (JSM-6360LV), and vibration features of tool tips driven by high frequency were tested by using PSV-400-M2 Laser Doppler Vibrometer. Results show that, for chip-press model, slippage and rotation phenomena between tool tip and chip have been solved by using tool with greater area tip pattern during flip-chip bonding process, and welding failures appeared in chip-collet model have been controlled. Greater area pattern on tool tip is better than small area pattern. The power of ‘n’ bumps on flip chip bonding is far smaller than that of n×(the power of single wire bonding). The power is directly proportion to vibration displacement driven by the power, high-power decrease positioning precision of flip chip bonding or result in slippage and rotation phenomena. The proper machine variables ranges for thermosonic flip chip had been obtained.
Authors: Y.S. Lu, Yasuhiro Tani, K. Soutome, Yasushi Kamimura
Abstract: This paper deals with a novel polishing technology using polymer particles. It has been proposed and developed by the authors for the purpose of solving the problems associated with polishing pads such as pad deterioration, process inconsistency and poor accuracy. Single side polishing of silicon wafers and double side polishing of quartz crystal square wafers were performed to clarify the basic characteristics of the technology. The results showed that appropriate combination of tool plate with polymer particles could greatly improve polishing characteristics. In particular, the edge profiles can be controlled to have desirable shape as well as amplitudes.
Authors: Wen Jin Wang, Tai Yong Wang, Sheng Bo Fan, W.Y. Wang, G.F. Wang, W. Zhang
Abstract: For the problem of process monitoring of chip generation in CNC machining, the dynamic modeling of predicting chip formation using artificial neural networks based on real-time condition intelligent monitoring was studied. The dynamic model of predicting chip formation is established in this paper. Based on mathematical model of chip space motion path, the 3D model of chip shape was developed. The real-time simulation of chip generation was realized in the virtual reality environment.
Authors: Y.T. Yu, Wei Zheng Yuan, D.Y. Qiao
Abstract: Bifurcation of multi-layer microstructures subjected to thermal loading can be harmful for reliability and stability of MEMS structures. In this paper, three imperfections of geometry, coefficient of thermal expansion and thermal loading were introduced to investigate their effects on structural bifurcation by finite element simulation. Results show that bifurcation is strongly influenced by the imperfections. With larger deviation of imperfections, it results in a decreasing temperature to trigger the bifurcation and a gradual beginning of it.

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