In this paper, a micro-knife for minimally invasive surgery is proposed. It is a silicon horn shape and works in an ultrasonic longitudinal vibration mode to realize the precise incision with its sharp tip at one end. Finite element method in ANSYS is used to analyze and design the device to obtain the vibration frequency and displacement amplitude of the longitudinal mode. In the end, microfabrication of the proposed micro-knife is presented.

Development of intelligent and ecological energy absorption systems (EAS) is important to various fields such as automotive (vehicle suspensions, bumpers, engine mounts), construction (protections against seismic and wind-induced vibrations), and defense (parachuted objects, armors). Usual EAS use composites, shape-memory alloys and foams. Recently, liquid adsorption/desorption in/from nanoporous solids was employed to develop high-performance nano-EAS. Energy loss is based on the well-known capillary phenomenon: external work must be done to spread a non-wetting liquid on a solid surface. Nano-EAS provide considerably higher dissipated energies, about 1–10J/g at deformability of 30–70%, compared with the energy absorption of Ti-Ni alloys, about 0.01–0.05J/g at deformability of 5–8%. For water against hydrophobic nanoporous silica gel (artificial sand), the nano-EAS become ecological; they can be also made intelligent by thermo-electrical control. Relative to thermal effects, Qiao et al. have investigated, for nanoporous silica gel with insufficient coverage of the alkyl-based hydrophobic coating, the problem of hysteresis recovery by increasing the temperature in the range 20∼80°C. Energy loss capacity reduced severely after the first loading-unloading cycle, so, the hysteresis was found as irreversible. Shape of the first hysteresis, the accessible specific pore volume and the desorption pressure were almost unaffected by the temperature change. At temperature augmentation the second hysteresis was partially recovered and when the temperature exceeded 50°C the system became almost fully reusable. Water inflow was found as governed by Laplace-Washburn equation but the outflow process was perceived as thermally aided. On the other hand, Eroshenko et al. have contradictorily obtained for nanoporous silica gel with full coverage of the alkyl-based hydrophobic coating, a stable hysteresis at repeated working cycles. Adsorption pressure decreased and desorption pressure increased at temperature augmentation, this producing a reduction of the hysteresis area and damping. However, the accessible specific pore volume was found as thermally unaffected. Oppositely, both the in- and out-flows were found as governed by Laplace-Washburn equation. In this work, for nanoporous silica gels with partial and full coverage of the alkyl and fluorocarbon based hydrophobic coatings, the thermal effects on the hysteresis and damping performances are studied. Test rig used is a compression-decompression chamber introduced inside of an incubator that allows temperature adjustment in the range of −10∼50°C. Results reveal that, depending on the hydrophobic coating coverage, findings reported by Qiao et al. and Eroshenko et al. are in fact not contradictory but complementary. However, as expected, the accessible specific pore volume was found to decrease at temperature reduction. In order to explain all these apparently opposite experimental findings, a model based on the water cluster size distribution versus temperature, the pore size distribution of silica gel and the ability of water molecules to form hydrogen bonds with the uncovered hydroxyl groups on the solid surface is proposed.

It was found that with carbon nanotube (CNT) addition, epoxy resin composites could greatly enhance damping ability while the stiffness is kept high. A composite unit cell model containing single CNT segment is developed by using finite element method (FEM). CNT orientation is varied in order to describe the behaviors of the randomly oriented CNTs inside the epoxy matrix. Composite loss factors are calculated based on the ratio of the unit cell energy loss to the unit cell energy input. Calculated loss factors under different strain levels are compared to experimental data. As the CNT/matrix model gives smaller loss factors as compared with experimental data, a CNT/CNT model is further developed in order to improve model accuracy.

This paper presents a numerical method for predicting thermoelastic damping (TED) in micromechanical resonators with any arbitrary structural geometry. In this numerical method, TED is interpreted as the generation of thermal energy per cycle of vibration from the viewpoint of thermal field. Consequently, TED is mathematically expressed in terms of entropy — a parameter measuring the irreversibility in heat conduction, and then numerically calculated in ANSYS/Multiphysics. The validity of this numerical method has been verified using the well-known solution to TED in a beam resonator and experimental data in the literature. Compared to the commonly used interpretation of TED in the elastic field-complex frequency, this numerical method does not involve complex values and thus offers the advantages of simplicity and compatibility with finite element modeling software.

This paper presents a design optimization of a membrane-based ultrasonic piezoelectric transducer using micromachining by finite element simulation. The transducer can be used to generate ultrasound using the piezoelectric film to excite the vibration of the transducer membrane. The objective is to maximize the vibration magnitude of the membrane by optimizing the structure of the transducer, when the exciting signal is fixed. The size and the shape of the piezoelectric film were selected as the design parameters to optimize the structure of the transducer. Based on the theoretical analysis, it is found that the absolute values of the stresses in the center and the boundary of the diaphragm are greater than that on the other regions of the film, with the directions of the stress on center and boundary opposite to each other. In order to achieve the maximum exciting efficiency, the discrepancy in the stresses between the center and the boundary on the diaphragm should be maximized. In this paper, totally four different piezoelectric film structures are analyzed for optimizing the exciting efficiency of the transducer. The finite element models of the transducer were created using ANSYS. The simulations based on the three design options were performed; and through the comparison of the simulation results, the optimal structural parameters of the piezoelectric film are identified. Finally, the direction of the design improvement for the exciting efficiency of the transducer is provided.

The objective is to develop improved microvalve and micropump designs to simplify fabrication process, decrease manufacturing cost and increase efficiency. In this paper, a new prototype model of a micropump using piezoelectric (PZT) disc as the actuator is designed. This paper describes the structure and the working principle of new micropump using PZT disc as an actuator. The main basic structure includes a pump body with valveless structure and piezoelectric disc. The overall size of this prototype is the same as the diameter of a PZT disc about 4cm × 5cm. The working principle relies on the vibration of a membrane by applying a.c. voltage to the PZT actuator. The fabrication process is simplified, comparing with traditional manufacturing method and save time and cost. While fabrication and design are discussed herein, experimental results and pump performance will be reported separately. The developed micropump is able to produce a micro-flow rate suitable for medical applications such as drug delivery system.

Heat transfer due to forced convection caused by acoustic streaming in microfluidic devices is shown to have potential in cooling effect. However, few studies are made for theoretically studying the fluid motion induced by the acoustic field and forced heat transfer for micro cooling in microdevices. In this paper, Navier-Stokes equations are first employed to study acoustic radiation force and acoustic streaming in microchannel actuated by ultrasonic vibration. Then, an analytical study of fluid motion acoustically induced and the temperature field in microchannel is investigated to determine the enhancement of cooling effect in microchannel with acoustic streaming.

Air bearing linear motion stages with high speed and ultra high positioning performances are always used in steppers or scanners which are the most important equipments in microlithography process. Excellent air bearing design is one of the keys to archive those performances. Good load capacity and stiffness are always the main design objective for designers. But experiment shows that air bearing stage with high stiffness and load capacity may suffer from micro vibration. The micro vibration is not the “pneumatic hammer” which usually happens to air bearing due to poor restrictor design. Its amplitude ranges from tens to hundreds of nanometers and frequency from tens to thousands of Hz. For an ultra precision linear motion stage which positioning accuracy level is about ten nanometers, the vibration amplitude is obviously unacceptable. Further more, the micro-vibration seriously lower system’s dynamic characteristics. To find the reason of micro-vibration, finite element method is used to analyze the air flow in the air channel of air bearing. The result shows that the turbulence flow in the air channel will induce the micro-vibration. So the laminar flow in the air channel is the key way to eliminate the micro-vibration of air bearing stage. To turn the turbulence flow into laminar flow, the designer must consider the radius of the air channel, the number of air inlet and mass flow rate of air bearing comprehensively.

This paper presents the development of a micro-EDM system which is aimed to improve micro machining capability. The system consists of high precision X-Y-Z stages with quick response, a high precision granite machine body, a pulse power generator, a CCD microscopic computer vision system, etc. The X-Y-Z stages are driven by ultrasonic linear motors with a resolution as high as 0.05 μm. The granite machine body can reduce stray capacitance and absorb vibrations. RC pulse power generator can supply discharging energy as small as 10 −9 J. Micro electrode can be measured with a resolution of 1.6 μm by the microscopic computer vision system online. In order to machine precision 3D microstructures, a special CAM software package based on the commercial CAD/CAM software Unigraphics (UG) is developed to generate tool path and NC codes and compensate the electrode wear. Experiments carried out on this machining system show that micro shafts with a minimum diameter of 6 μm and micro holes of 10 μm in diameter can be obtained stably. With the aid of the self-developed CAM software packages, complicated 3D microstructures are machined on this micro-EDM machining system.

Burr formation is a common phenomena in metal cutting. The burr not only effect precision of parts directly but influence the assembly quality badly. Therefore, the control and deburring technology of machining burrs has become one of the key problem in precision or ultra-precision and automatic procession. In traditional drilling, the exit burr is bigger than the entrance burr, and its hazard is more larger. Moreover deburring process is very complex. According to these status quo, a new method of active control of the exit burr is put forward using vibration drilling. Mechanism of chip broken and burr formation in vibration drilling are analysed systematically and an equipment of vibration drilling is developed based on drilling experiment. Cutting test on A3 material, brass (H62) and 1Cr18Ni9Ti stainless steel is carried out using the method of vibration drilling. As a result, cutting character is improved because of the using of this method. Also, machining accuracy and surface integrality of parts are improved remarkably and the size of the exit burr is controlled effectively in vibration drilling. The development of vibration drilling device provides a new approach for the progress of ultra-precision drilling technology. Vibration drilling device and technology developed in this study can be widely used to ultra-precision machining.

With the wide applications of the hard brittle materials in micro electromechanical system (MEMS), the high precision micromachining technology of hard brittle materials has become an important subject. In order to enhance the machining accuracy and the degree of the micro ultrasonic machining (USM), the key technologies in micro USM are discussed. They include high precision machine body, rotated tool, on-line tool preparation, applying vibration to the workpiece, choosing the parameters of micro tool and so on. The buckling dynamic stability of the micro tool is analyzed. It not only depends on the static pressure but also on the ultrasonic amplitude. The formula for calculating the critical length of the tool is given. It can solve the problem of the tool’s bend, breakage, and deteriorating the hole shape accuracy in machining process caused by the improper choice of tool length, static pressure and ultrasonic amplitude. The experiment is carried out on the micro USM system, and the machined samples are presented.

MEMS line vibration gyroscope is always drove by electrostatic. When the configuration of the MEMS line vibration gyroscope is symmetry, its mass is vibrated in line at one direction (it is x direction here) and balanced in force at the other direction that vertical to x direction (it is y direction here) in horizontal. But when the configuration of the MEMS line vibration gyroscope is not asymmetry, the electrostatic that putted on the mass at y direction is destroyed. At this condition, one is that the mass is vibrated in line at y direction and produced zero signals; one is that the combs are distorted at y direction because of the destroyed of the balance of the electrostatic at y direction. This paper analyzed the second condition. The model of the distortion was built because the configuration is asymmetry. And it was simulated in Matlab. At the same time, it was analyzed by ANSYS according to the method of the Limited Element. And we got the electrostatic distributing fig and the distortion fig by using ANSYS. Through the compare of two methods, we know that the built model is correct whether or not.

Low level mechanical vibrations exist in many environments. The primary frequencies can spread about decades and the acceleration amplitudes of the ambient vibrations can be in the range from about 1 to 10 m/s 2 . Vibration energy harvesting is the promising electric power sources for micro-electric-mechanical system (MEMS). The piezoelectric cantilever model has been proved as a preference structure for vibration energy harvesting. An efficacious computational model of the vibration energy harvesting is established to predict the output of open-circuit voltages in this paper. Meanwhile, a prototype piezoelectric cantilever generator is set up. The calculated results were compared well with that of tests.

Spacer technology has been developed to fabricate nano-structures for NEMS application. It provides a parallel nano-fabrication method with double or quadplex device density at a certain lithography node. By controlling the deposited film thickness, the feature size of the SiO 2 spacer hard mask is reduced down to 35 nm. After the spacer pattern is transferred to Si, a precise thermal oxidation is performed to improve the profile and reduce the plasma damage. Finally, sublimation or HF vapor phase etching is introduced to release the nano-structures according to different structure dimensions. As a result, with better surface morphology, suspended Si nano-beams with a width of 20 nm are obtained. Actuated by mechanical vibration and electrostatic forces, vibrations of the obtained cantilever beams and fixed-fixed beams are observed in SEM. In addition, a metallic nano-nozzle with a diameter of 140 nm is established by electroless plating around the suspended Si nano-beam served as a mold. As a development of the spacer technology, nano-needle array is demonstrated at the cross points of crossed SiO 2 spacers by anisotropic etching. The diameters of the hybridized nano-needles are 300 nm so far and can be further reduced by smaller spacer dimension.