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A method of mode tracking based on modal participation factor (MPF) is developed and integrated into topology optimization of head suspension assemblies (HSAs). This method is devised to track the lowest torsional and the lowest sway frequencies, which are maximized as design goals for suspension assembly. Topology optimization based on this method is successfully used to find optimum designs for maximum torsional frequency, maximum sway frequency, or maximum both goals. The resulting topology images are then interpreted and reduced into physical form with three thickness levels among which reduced thickness helps improve the lowest torsional frequency.

This paper focuses on the development of a computational method to be used as a tool for air bearing simulation and design in modern hard disk drive. A data density of 100 Gb/in.2 has already been achieved in today’s production. The hard disk drive industry’s next goal is to increase the data density to 1 Tb/in.2 . New features in air bearing designs include shaped rails, multiple etching depths and negative pressure pockets. Thus, mesh generation is a difficult task in the air bearing simulation. This, in turn, demands the development of an accurate and easy-to-use computational method to solve Reynolds equations based on various flow models. Least square finite difference scheme, one of mesh-less methods, is presented to solve the slider air bearing problems of hard disk drives. For each specified attitude, the air bearing pressure is obtained by solving the Reynolds equation using the mesh-free method. The discretized nonlinear systems of equations are solved by successive over-relaxation (SOR) implementation, and the results of the numerical solutions are compared with other numerical and experimental data.

The implementation of all-optical telecommunication networks requires more efficient optical-to-optical wavelength routing devices to replace the conventional optical-to-electrical cross connects. In this paper, we demonstrate a novel rotary micromirror for directly fiber-optic switching. To fabricate this electrostatically actuated rotary micromirror, a very simple micromachining process has been developed using SOI wafer and DRIE technology. Based on this one-mask process, all the components for an NxN cross-connect with 2N-switch-architecture can be fabricated on a monolithic silicon substrate, including the optic fiber couplers, electrostatic comb drives and reflective vertical mirror arrays.

This paper presented design concepts to improve stroke magnification and to retain high torsional frequencies for piezoelectrically actuated suspension. Flexural rotation is employed to enhance stroke magnification at the dimple point of a load beam. As such, the two piezoelectric push-pull elements can be placed apart to make room for stiffening base portion of the load beam while attaining an adequate level of stroke. As a stiffening structure, an extended base plate is deployed to raise the torsional frequency of the actuated suspensions. The improved performances were verified numerically and experimentally. Also, prototypes in accordance to the present design concepts were fabricated and tested.

TiNi films with different Ti/Ni ratios were deposited on Si substrates with and without silicon nitride interlayer. Near-equiatomic TiNi films were found to have the lowest residual stress and the highest recovery stress regardless of the existence of silicon nitride interlayer. The addition of silicon nitride interlayer between film and Si substrate did not cause much change in phase transformation behavior as well as adhesion properties. X-ray photoelectron spectroscopy (XPS) analysis revealed that there is significant interdiffusion of elements and formation of Ti–N and Si–Si bonds at TiNi film/silicon nitride interface. Scratch test results showed that adhesion between the TiNi film and substrate was slightly improved with the increase of Ti content in TiNi films.

In this work, Ti–49.8 at.% Ni shape memory alloy (SMA) thin films were irradiated by 60-keV protons with two types of doses: 5×1016 and 1×1017 H+/cm2. The influence of proton irradiation on the transformation behavior of TiNi shape memory alloy films was investigated by differential scanning calorimetry (DSC) and glancing-incidence X-ray diffraction (GIXRD). The martensite transformation temperatures and austenite transformation temperatures shifted to lower value after proton irradiation, whereas proton irradiation has little effect on the R-phase transformation temperatures. This observation can be attributed to the formation of hydrides after proton irradiation.

Nanocrystalline TiN (or nc-TiN) has been imbedded in amorphous silicon nitride (a-SiNx)matrix to form a nanocomposite thin film (nc-TiN/a-SiNx) via magnetron sputtering deposition on silicon wafer. Two important effects of the Si3N4 sputtering target power on the formation of nc-TiN/a-SiNx have been studied: (1) Aside from forming a-SiNx in the matrix, Si atoms also imbed into TiN to form (Ti,Si)N solid solution crystallites. At low target power, the solid solution is substitutional. With increase of power, the amount of silicon “dissolved” in the TiN crystallite increases, and in the meantime, the interstitial components increase which is manifested in the increase in the TiN lattice parameter. (2) The crystallites have a preferred orientation varying with the deposition target power. As conveniently described by the coefficient of texture, the degree of preferred orientation along [111] direction decreases and finally tails off with increase of power. At the same time, the crystallites orient along [200] and [220] direction and eventually [220] direction dominants.

X-ray photoelectron spectroscopy (XPS) analysis of amorphous carbon ( a - C )-based nanocomposite films has been carried out. Four bonding types of carbon are revealed from the C 1s spectra: C – C sp 2 and sp 3 bonding, C – O and C – Ti bonding. With the introduction of Ti and Al into the a - C matrix, the carbon sp 3/ sp 2 ratio decreases significantly. XPS results also confirm that the Al doped in the film basically exists as an elemental Al in the a - C matrix, and the titanium is mostly bonded with carbon to form nc - TiC .

Fracture toughness of bulk materials is a topic of classical measurements, but that of thin films, especially hard and superhard thin films, is a different matter owing to specimen dimensions (thickness) and lack of convincing test procedure. Fracture toughness is the ability of a material to resist the growth of a pre-existing crack. For thin films, however, the testing usually includes crack initiation together with crack propagation thus the result is not the same as the classical “fracture toughness”. For thin films, it is better to use term “toughness” to avoid confusion. For engineering applications, it is of vital importance that the toughness of thin films be evaluated with a convincing method and procedure. This paper presents a new and relatively easy method in which two-step uniaxial tensile test is performed to characterise toughness of ceramic thin films. In the test, the film/substrate system is subjected to uniaxial tensile stress until the film fractures. After the load is removed to allow complete elastic recovering, this system is subjected to a second loading to the earlier extension. The toughness of the thin film is derived from the energy difference between the two subsequent loading extension curves. The crack initiation and propagation patterns are examined with scanning electron microscope (SEM). As an example, toughness of a nc-TiN/a-SiNx nanocomposite thin film has been tested with satisfactory results.

The residual vibration is one of the primary mechanical problems that affect the dynamic characteristics of the head actuator assembly in hard disk drives, and the data access speed and positioning resolution. A discrete damping device has been developed to suppress the quasi-rigid-body mode and a reduction of 10 dB in amplitude is shown possible. The servo performance of the head actuator assembly with and without the damping device is presented in this paper, together with the measurement and prediction of the dynamic characteristics. Both closed- and open-loop transfer functions of the plant are measured in the actual operating environment on a servo test stand and compared with the simulation. It is found that the use of passive damping in the structure design allows for a greater margin of error at the crossover frequency since less phase loss results when notch filters are used, thus improving the stability robustness in feedback control.

Topology optimization method is applied to improve shock resistance of suspension using a formulation that maximizes resonant frequencies while reducing effective mass. The design method is successfully used to obtain optimum solutions, which have tapered features in width and thickness and thin flexural linking to a dimple pad. The design features of suspensions impart less inertial force to the slider and thus are able to suppress tendency of head lift-off.

Nanocrystalline TiN (nc-TiN) has been imbedded in amorphous silicon nitride (a-SiNx) matrix to form a nanocomposite thin film (nc-TiN/a-SiNx) via magnetron sputtering. Adjusting Ti and Si3N4 target power ratio alters film composition, morphology, microstructure and residual stresses. The effects of silicon nitride target power density on surface morphology and residual stress have been studied. Atomic force microscopy (AFM) shows that the film surface becomes increasingly smoother and the roughness (Ra) drops from about 6 nm down to less than 1 nm as the silicon nitride target power density increases from 1.1 to 5.5 W cm−2. The surface topography is quantitatively described by calculation of two parameters: the interface width (w) and the lateral correlation length (ξ). The interface width (w) describes the vertical growth, and the lateral correlation length (ξ) characterizes the lateral growth of the surface. The growth-induced residual stress during the sputtering deposition of nc-TiN/a-SiNx nanocomposite thin film increases with sputtering power density, but only reaches about −1 GPa even at the highest experimented Si3N4 target power density of 5.5 W cm−2. The growth-induced stress is opposite in sign and roughly equal in quantity to the thermal stress induced by the difference in the coefficient of thermal expansion (CTE) between the films and the silicon wafer substrate. As a result, the magnetron sputtered nc-TiN/a-SiNx nanocomposite films become almost stress-free (as low as 0 to −0.15 GPa residual stress).

Ultrasonic C-mode scanning acoustic microscopy (C-SAM) is widely used in the semiconductor industry for reliability testing and product inspection due to its ability to nondestructively detect defects in IC packaging. However, image interpretation and defect identification depend largely on the experience of operators, and there is no defect recognition system; this is partly due to current recognition systems, which are based on computer vision algorithms and are not robust for C-SAM images. A new robust defect recognition system and its application to C-SAM images are described in this paper. The iconic domain of two-dimensional C-SAM grey-level image analysis based on the non-linear Mumford-Shah model is used, and defect recognition is achieved through the use of Support Vector Machines (SVMs). The system is verified through experiments on a sequence of C-SAM images corrupted by synthetically generated noise, bias and different shape. The remarkable defect recognition rates achieved indicate that Support Vector Machines (SVMs) are suitable for IC package defect identification.

Metallic Al was doped into amorphous carbon (a-C) to form a matrix of a-C(Al) of very low residual stress and high toughness at the expense of some hardness. Nanocrystallites of TiC (nc-TiC) of a few nanometers in size were embedded in this matrix to bring back the hardness. The nanocomposite coating of nc-TiC/a-C(Al) was deposited via co-sputtering of graphite, Ti , and Al targets. Although the nanocomposite coating exhibited a moderately high hardness (about 20 GPa), it possessed extremely high toughness (about 55% of plasticity during indentation deformation) and low residual stress (less than 0.4 GPa), smooth (Ra=5.5 nm ), and hydrophobic surface (contact angle with water reaches 100°).

NiTi shape memory thin films are potentially desirable for micro-electro-mechanical system (MEMS) actuators, because they have a much higher work output per volume and also a significantly improved response speed due to a larger surface-to-volume ratio. A new technique using a temperature controllable atomic force microscope (AFM) is presented in order to find the transformation temperatures of NiTi shape memory thin films of micrometer size, since traditional techniques, such as differential scanning calorimetry (DSC) and the curvature method, have difficulty in dealing with samples of such a scale as this. This technique is based on the surface relief phenomenon in shape memory alloys upon thermal cycling. The reliability of this technique is investigated and compared with the DSC result in terms of the transformation fraction (ξ). It appears that the new technique is nondestructive, in situ and capable of characterizing sputtering deposited very small NiTi shape memory thin films.

This paper presents a new design of an integral flexure that serves both the functions of a load beam and a gimbal for application in rotary actuators of hard disk drives (HDD). The design has optimized geometry that improves resonant frequency while retaining adequate rotational flexibility. Prototypes of the integral flexure are fabricated from a single piece of stainless-steel foil by photochemical machining techniques without involving welding and extra alignment. Its performance is simulated using finite element method and resonant frequencies of its prototype are measured. The numerical simulation and experimental results are in good agreement.

This paper presents design and development of an ankle physiotherapy device using a linear MR (magnetorheological) damper. After exploring many possible configurations of the MR valve, the proposed design makes sure that the damper is test- and research-friendly in that the damper can be easily assembled and disassembled with simple tools and procedure. The structural and functional integrity of the damper was maintained even with the simple layout of the damper. The dimensions of the MR valve are optimally determined using finite element analysis. The damper performance under steady shear is experimentally evaluated with an INSTRON test machine. The test results showed that the prototype had fulfilled the basic requirements of the desired MR ankle physiotherapy.

NiTi shape memory thin films are potentially desirable for MEMS actuators. Traditionally, there are two approaches to obtain NiTi shape memory thin films. One is to anneal amorphous NiTi films in a vacuum chamber and the other is to deposit NiTi on a high temperature substrate (about 500 °C). Both approaches have difficulty in terms of compatibility with traditional IC techniques, and are not applicable for annealing a prescribed local area of a NiTi film at the micron scale. In this paper, a new approach, CO2 laser annealing, which can overcome both problems mentioned above, is presented. Results of optical microscopy, x-ray diffraction (XRD) and atomic force microscopy (AFM) reveal the crystalline structures and phase transformation in annealed NiTi films. Furthermore, a CO2 laser annealed line, about 100 µm in width, demonstrates the capability of a CO2 laser for local annealing of NiTi thin film.

TiNi thin films have attracted much attention in recent years as intelligent and functional materials because of their unique properties. TiNi thin film based micro-actuators will become the actuator of choice in many aspects in the rapidly growing field of micro-electro-mechanical systems (MEMSs). In this review paper, some critical issues and problems in the development of TiNi thin films are discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue and stability, modeling of behavior as well as functionally graded or composite thin films. Comparison is made of TiNi SMA micro-actuation with other micro-actuation methods. Different types of TiNi thin film based microdevices, such as microgrippers, microswitches, microvalves and pumps, microsensors, etc. are also described and discussed.

In many proposed applications, magnetorheological (MR) fluids are subjected to a dynamic stimulus with finite deformation. Dynamic behavior of reduced iron based MR suspensions under oscillatory shear is experimentally investigated using a parallel-plate rheometer. The effects of strain amplitude, oscillation frequency, and magnetic field strength on the dynamic behavior are studied. MR fluids behave as linear viscoelastic materials for only sufficiently small strain amplitudes. At large strain amplitudes, MR fluids are nonlinear viscoelastic or viscoplastic, where the storage modulus shows a decreasing trend with the strain amplitude. At large enough strain rate amplitudes, the yield stress contribution is negligible and the suspension response is Newtonian. The dependence of the dynamic behavior on the strain amplitude and oscillation frequency is qualitatively summarized in the form of a Pipkin diagram.

Hydrogen-free diamond-like carbon coatings of thickness 1.5 μm were deposited on 440C stainless steel substrates and silicon wafers via DC magnetron sputtering of graphite target at power density of 10.5 W/cm2. RF bias voltage was applied in the range of −20 to −150 V in two configurations: constant bias and bias-graded. The structure, surface topography, hardness and tribological behavior of these coatings were investigated. The surface roughness (Ra) of the coating decreased from 5.8 to 3.4 nm as bias voltage increased. Results from nanoindentation showed that the hardness of the coatings deposited at high bias voltage reached at 30 GPa and toughness (plasticity during indentation deformation) from approximately 50 to 60%. The hardness of the coating deposited with bias-graded configuration was comparable to the coatings deposited at high bias voltage but the toughness and adhesion strength were significantly improved. Ball-on-disc tribotests were carried out under dry, water- and oil-lubrication conditions. The result showed that the bias-graded coating had a very low coefficient of friction (down to 0.07 in oil). Furthermore, after 2.5 km sliding against alumina and steel (6 mm in diameter) at a high load of 10 N with and without lubrication, no sign of damage was observed on the wear track. Bias-graded sputtering deposition is an appropriate technique to combine the hardness, toughness and adhesion strength into one coating for demanding tribological applications.

TiNiCu films with different Cu contents (up to 15 at.%) were prepared by co-sputtering of TiNi and Cu targets using a magnetron sputtering system. Film crystalline structure, phase transformation and shape memory behaviors were characterized by X-ray diffraction, differential scanning calorimeters (DSCs) and curvature method. The substitution of Ni by Cu in TiNi based films resulted in a dramatic change in martensite structure, film orientation and phase transformation behavior. With the increase of Cu content in the films, both the transformation temperatures and hysteresis decreased significantly. From DSC and curvature measurement results, the specific heat and the maximum recovery stress (corresponding to actuation force) generated during martensite transformation decreased with Cu contents, indicating the weak performance of phase transformation, especially at high Cu contents above 9 at.%. There was a maximum value for the stress increase rate (corresponding to actuation speed) at a Cu content of 9 at.%.

A typical microelectrode structure, interdigitated bar electrodes, has been developed for the selective manipulation and separation of bioparticles using traveling field dielectrophoresis effects under AC electrokinetics. This paper presents meshless numerical solutions of traveling wave dielectrophoresis for such interdigitated electrode array energized with 4-phase signal. This meshless method is based on a truncated 2D Taylor series expansion with the first three orders together with a weighted least-square approximation procedure. Dielectrophoretic forces and traveling wave forces are calculated and their applications for bioparticle manipulation and separation are discussed.

In this paper we present a bulk micromachined check valve with very high frequency and extremely low leak rates. The valve is designed to have a hexagonal orifice, a hexagonal membrane flap and three flexible tethers. The three elbow-shaped flexible tethers are used to secure the membrane flap to the valve seat and to obtain large flap displacement in the forward flow direction. A silicon-on-insulator wafer and deep reactive ion etching technology are used to implement this microvalve. A very simple fabrication process has been developed, and only two photolithographic masks are required. Preliminary fluidics testing on a 1.44 mm size check valve was performed. A maximum flow rate (deionized water) of 35.6 ml min−1 was obtained at a forward pressure of 65.5 kPa, and only negligible leakage rate was observed at a reverse pressure of up to 600 kPa. The frequency response of the valve in air was also measured and its first resonance frequency was found at 17.7 kHz.

Shape memory alloy TiNi films were prepared on Si and SiySiO by co-sputtering of TiNi target (Ti 50 at.% and Ni 50 at.%) 2 and Ti target (99.999 at.%).When comparing Si yTiNi with SiySiO yTiNi, the addition of SiO sandwich layer did not result in 22 significant change in the crystalline structures and shape memory properties.The SiO sandwich layer served as an effective 2 diffusion barrier in preventing formation of interfacial titanium silicide at the expense of film adhesion.As revealed by X-ray photoelectron spectroscopy, under the same conditions, the interfacial diffusion zone in Si yTiNi system was approximately 120 nm while in SiySiO yTiNi system the diffusion zone was only approximately 30 nm—a four-fold reduction in inter diffusion. 2 Meanwhile, the scratch adhesion testing registered a sharp drop in adhesion of the film from 170 mN in SiyTiNi system to 60 mN in SiySiO yTiNi system. 2

TiNi films with different Ti/Ni ratios were prepared by co-sputtering Ti50Ni50 (at%) target with Ti target at temperature of 723 K. The stress values in the deposited films changed significantly with Ti contents and post-annealing temperatures due to the differences in phase transformation behaviors and intrinsic stress. Post-annealing of these films at 923 K for 1 hour could modify the intrinsic stress and martensite transformation behavior thus cause the significant decrease in residual stress. For all three types of film annealed at 1023 K for 1 hour, the large stress in the thin films could damage the shape memory effect or result in the peeling-off of film from Si substrate.

We demonstrate a novel rotary micromirror for fiber-optic switching. A very simple fabrication process which uses SOI wafer and DRIE technology has been employed to micromachine this electrotastically actuated vertical mirror. Based on this one-mask process, 2N-switch-architecture crossconnects with all the components, inlcuding optic fiber couplers electrostatic comb drives and reflective vertical mirrors, has been integrally fabricated on a monolithic silicon substrate.

This paper presents a bulk micromachined check valve with very high frequency and extremely low leak rates. The valve is designed to have a hexagonal orifice, a hexagonal membrane flap and three flexible tethers. The three elbow-shaped flexible tethers are used both to secure the membrane flap to the valve seat and to abtain a large flap displacement in the forward flow direction. SOI wafer and DRIE technology are used to implement this micro valve. A very simple farbication process has been developed, and only two photolithographic masks are employed. Preliminary testing on a 1.5 milimeters size check valve shows that a maximum flow rate (DI water) of 35.6ml/min was obtained at pressure drop of 65.5kPa and negligible leakage rate in the reverse flow direction observed at pressure up to 600kPa.

This paper presents the design, fabrication and testing of a Magnetorheological (MR) steering damper for motorcycles. After exploring many possible configurations of the MR valve, the proposed design makes sure that the damper is test- and research- friendly in that the damper can be easily assembled and disassembled with simple tools and procedures. The structural and functional integrity of the damper was maintained even with the simple layout of the damper. The dimensions of the MR valve are optimally determined by using finite element analysis. The damper performance under steady shear is experimentally evaluated with an INSTRON test machine. The test results showed that the prototype had fulfilled the basic requirements of the desired MR fluid steering damper.

The presence of an adherent and hard TiN layer (200 nm) on TiNi-based shape memory alloy (SMA) film (3.5 μm) formed a passivation layer, improved hardness and tribological properties, without sacrificing the phase transformation and shape memory effect of the TiNi film.

Some critical issues and problems for the development of TiNi thin films and their MEMS applications were discussed in this paper. New types of TiNi thin film based microactuators, such as microgrippers, microvalves, micromirror, etc. were designed and fabricated using MEMS techniques.

In this paper we present knowledge of an intensive approach and system for selecting suitable manufacturing processes and materials for microelectromechanical systems (MEMS) devices in concurrent collaborative design environment. In the paper, fundamental issues on MEMS manufacturing process and material selection such as concurrent design framework, manufacturing process and material hierarchies, and selection strategy are first addressed. Then, a fuzzy decision support scheme for a multi-criteria decision-making problem is proposed for estimating, ranking and selecting possible manufacturing processes, materials and their combinations. A Web-based prototype advisory system for the MEMS manufacturing process and material selection, WebMEMS-MASS, is developed based on the client–knowledge server architecture and framework to help the designer find good processes and materials for MEMS devices. The system, as one of the important parts of an advanced simulation and modeling tool for MEMS design, is a concept level process and material selection tool, which can be used as a standalone application or a Java applet via the Web. The running sessions of the system are inter-linked with webpages of tutorials and reference pages to explain the facets, fabrication processes and material choices, and calculations and reasoning in selection are performed using process capability and material property data from a remote Web-based database and interactive knowledge base that can be maintained and updated via the Internet. The use of the developed system including operation scenario, use support, and integration with an MEMS collaborative design system is presented. Finally, an illustration example is provided.

A new magnetorheological (MR) brake prototype was designed, fabricated and tested. Firstly, the rheological properties of MR fluids, in particular the dynamic yield stress, were experimentally investigated based on a Bingham plastic model. The working principles of the MR brake were then analysed and discussed. The equations for transmitted torque were derived and used to evaluate the disc-shaped MR brake. This was followed by an analysis of an electromagnet using the finite element method. Following the manufacturing and fabrication of a brake prototype, the mechanical performance of the MR brake was experimentally evaluated with a specially designed test rig. The effects of magnetic field and rotary speed on the transmitted torque were addressed, and an amplifying factor was introduced to evaluate the brake performance. It was found that brake torque increased steadily with the increment of magnetic field or rotary speed. The amplifying factor showed an increasing trend with the magnetic field but a decreasing trend with rotary speed.

TiNi films were prepared by co-sputtering a Ti50Ni50 target and a Ti target under different process parameters. Stress in TiNi film on silicon substrate were evaluated using curvature method. A wide range of residual stress levels (either tensile or compressive) were found in the deposited films, depending significantly on Ti/Ni ratio, gas pressure, deposition temperature and/or annealing conditions. Stress evolution for as-deposited amorphous films during annealing process were systematically studied with the consideration of residual stress in as-deposited films; thermal stress; tensile stress due to densification crystallization; stress relaxation due to martensite transformation, etc. Upon heating, the crystallized TiNi films generated large tensile stresses when transforming from martensite to austenite, whereas during cooling, the stress relaxed significantly when austenite transformed back to the ductile martensite. The stress generation and relaxation behavior was significantly affected by film composition, deposition temperature and/or annealing temperature.

Simultaneous structural-control optimization of a coupled structural-acoustic enclosure is investigated in this paper. The whole system has a rectangular parallelepiped sound field of which the entire bottom face and the partial top face are covered with two elastic plates while the other boundaries are enclosed with rigid walls. Two point forces applied on the two plates are used as disturbance and control inputs respectively. In the sound field, one sound sensor is placed to measure the sound pressure output. Feedback H 1 control is used to generate the control input signal to reduce the noise at the sensor spot induced by the disturbance. The coupled structural-acoustic enclosure is modeled by the finite element method. The element thickness parameters of the top elastic plate along with the controller parameters are adopted as design variables for the simultaneous optimization in which the closed-loop H 1 norm is minimized. To solve the simultaneous design problem, a nested approach is used in which the controller syntheses are considered as subprocesses included in the main optimization process dealing with the structural design variables. Moreover, since the matrices are unsymmetrical for structural-acoustic coupling problems, indirect modal analysis is used to reduce the computational cost instead of the direct method. Numerical example shows that the system performance is improved significantly by the simultaneous optimization. The effectiveness and potentiality of the design approach presented in this paper are also demonstrated by the results.

In this paper, a review of the present status of the research and technological development in the field of superhard nanocomposite coatings is attempted. Various deposition techniques have been used to prepare nanocomposite coatings. Among them, reactive magnetron sputtering is most commonly used. Nanocomposite coating design methodology and synthesis are described with emphasis on the magnetron sputtering deposition technique. Also discussed are the hardness and fracture toughness measurements of the coatings and the size effect. Superhard nanocomposite thin films are obtainable through optimal design of microstructure. So far, much attention is paid to increasing hardness, but not enough to toughness. The development of next generation superhard coatings should base on appropriate material design to achieve high hardness and at the same time high toughness.

TiNi based shape memory alloy (SMA) thin films have been widely used in biomedical and microelectromechanical systems. However, there are still some concerns for their wide applications because of their unsatisfactory mechanical and tribological performances, chemical resistance and biological reliability. This paper explored the deposition and effects of TiN protective layer on TiNi thin films to improve their surface properties while retaining the shape memory effects. Results indicated that the presence of an adherent and hard TiN layer (300 nm) on TiNi based SMA film (3.5 μm) formed a passivation layer, improved hardness and tribological properties, without sacrificing the phase transformation and shape memory effect of the TiNi film.

This paper presents an optimised design of a high-efficiency magnetorheological (MR) valve using finite element analysis. The MR valve is composed of a core, a wound coil, and a cylinder-shaped flux return. The core and flux return form the annulus through which the MR fluid flows. The effects of magnetic field formation mechanism and MR effect formation mechanism on the MR valve performance are investigated. Analytical results of the magnetic flux density in the valve indicate that the saturation in the magnetic flux may be in the core, the flux return, or the valve length. To prevent the saturation as well as to minimise the valve weight, the dimensions of the valve are optimally determined using finite element analysis. In addition, this analysis is coupled with the typical Bingham plastic analysis to predict the MR valve performance.

Currently ultrasonic wire bonders with precision capillary tips are widely used for bonding wires to integrated circuit (IC) chips and circuits. However, the quality and strength of a bond may be affected significantly by the change of vibration during the bonding process. It is therefore important to understand the dynamics of the bonding process as well as the vibration characteristics of the bonding system, so bonding quality may be monitored. This paper reports the study on the dynamic characteristics of the stacked piezoelectric transducers used in the ultrasonic wire bonding system. The vibration characteristics are first analysed using the finite element method with resonant frequency and vibration modes. The predicted impedance response is compared with the measurement using a high-pressure (HP) impedance analyser. The displacement profile along the transducer assembly, which includes a piezoelectric stack, clamping and horn sections, are also analysed. The effects of multilayer and polarization on the response of the transducer are discussed. It was found there is good agreement between the prediction and measurement, and bending and extension modes may be excited differently according to the polarization configuration used in the multilayer stack.

TiNi films with different Ni/Ti ratios were prepared by co-sputtering of a Ti50Ni50 (at.%) target with a separated Ti target at a temperature of 723 K. The stress values in the deposited films changed significantly with Ti contents and post-annealing temperatures due to the differences in phase transformation behaviors and intrinsic stress. For the film with Ti content of 51.3%, a two-step transformation was observed among martensite, R-phase and austenite, and residual stress was quite low at room temperature. After post-annealing the above film at 923 K, only one-stage transformation was observed. For the films with Ti contents of 47.3 and 53%, residual stress was quite high due to the high intrinsic stress and partial relaxation of stress caused by the R-phase transformation. When the films with Ti contents of 47.3 and 53% were annealed at 923 K, residual stress in films decreased significantly, because post-annealing could probably modify the film structure, reduce the intrinsic stress, increase the transformation temperatures, and cause martensite transformation above room temperature. For all the three types of films annealed at 1023 K for 1 h, the high thermal stress in the thin films could cause non-recoverable deformation during phase transformation, damage the shape memory effect, and result in the peeling-off of film from Si substrate.

A new type of functionally graded (FG) piezoelectric bending actuator was proposed by the present authors in their former study and the advantage of the new actuator over the traditional bimorph and unimorph actuators in internal stress distribution was illustrated by simulation results. In this study, the fabrication process of FG piezoelectric bending actuators is developed and the characteristics of the fabricated actuators are investigated. The material compositions with different dielectric and piezoelectric constants were selected from the Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 family and used as the four layers in the new FG piezoelectric actuator. The piezoelectric constant and dielectric constant were graded oppositely in the thickness direction. The durability of the fabricated FG piezoelectric actuators was measured in a vibration test and compared with that of the traditional bimorph actuator to evaluate the improvement of performance. The results show that the durability of the FG piezoelectric actuators is much higher than that of the bimorph actuator.

Superhard nanocrystalline (Ti, Cr)CN/DLC coatings were prepared through co-sputtering of Ti, Cr and graphite targets in an argon/nitrogen atmosphere. Results from both transmission electron microscopy (TEM) and grazing incident X-ray diffraction (GIXRD) indicated that the grain size of (TiCr)CxNy crystals was approximately 10–20 nm. X-ray photoelectron spectroscopic studies confirmed that an increase in the sputtering power at the Ti target not only increased the Ti composition in the film but also brought about an increase in sp3 bonding in DLC matrix, in agreement with the raising hardness with Ti sputtering power. Film hardness and elastic modulus were measured with a nano-indenter, and film hardness reached 40 GPa. Tribological behaviors of the films were evaluated using a ball-on-disk tribometer, and the films demonstrated properties of low-friction and good wear resistance.

In this paper, diamond microstructures were patterned over silicon/silicon dioxide substrate using the processes combined with bulk or surface micromachining, selective growth of diamond and plasma etching technique. Polycrystalline diamond films were prepared using microwave plasma enhanced chemical vapour deposition (MW-PECVD) and a gas mixture of hydrogen and methane. Two types of techniques for precise patterning of diamond microstructures were investigated in this paper. The first one was to selectively grow diamond films in the desired region by pre-depositing a Pt interlayer on silicon dioxide layer. The second one was to selectively etch the deposited diamond film in oxygen/argon plasma under an Al mask. Different microstructures, e.g., microgear, microrotor, comb drive structure, etc. were successfully fabricated.

Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(t, γ), shows a decreasing trend with step strain. The experimental results indicate that G(t, γ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(t, γ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(t, γ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior.

The interfacial structures of diamond coatings deposited on pure titanium substrate were analyzed using scanning electron microscopy and grazing incidence X-ray diffraction. Results showed that beneath the diamond coating, there was one titanium carbide and hydride interlayer, followed by a heat-affected and carbon/hydrogen diffused Ti layer. Residual stress in the diamond coating and TiC interlayer under different process parameters were measured using Raman and X-ray diffraction (XRD) methods. Diamond coatings showed large compressive stress on the order of a few giga Pascal. XRD analysis also showed the presence of compressive stress in the TiC interlayer and tensile stress in the Ti substrate. With increasing deposition duration, or decreasing plasma power and concentration of CH 4 in gas mixture, the compressive residual stress in the diamond coating decreased. The large residual stress in the diamond coating resulted in poor adhesion of the coatings to substrate, but adhesion was also related to other factors, such as the thickness and nature of the TiC interlayer, etc. A graded interlayer design was proposed to lower the thermal stress, modify the interfacial structure and improve the adhesion strength.

Shape memory alloys (SMAs) offer a unique combination of novel properties, such as shape memory effect, super-elasticity, biocompatibility and high damping capacity, and thin film SMAs have the potential to become a primary actuating mechanism for micro-actuators. In this study, TiNiCu films were successfully prepared by mix sputtering of a Ti55Ni45 target with a separated Cu target. Crystalline structure, residual stress and phase transformation properties of the TiNiCu films were investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and curvature measurement methods. Effects of the processing parameters on the film composition, phase transformation and shape-memory effects were analyzed. Results showed that films prepared at a high Ar gas pressure exhibited a columnar structure, while films deposited at a low Ar gas pressure showed smooth and featureless structure. Chemical composition of TiNiCu thin films was dependent on the DC power of copper target. DSC, XRD and curvature measurement revealed clearly the martensitic transformation of the deposited TiNiCu films. When the free-standing film was heated and cooled, a ‘two-way’ shape-memory effect can be clearly observed.

The complete mitochondrial genome of Ictiobus cyprinellus was first determined by a polymerase chain reaction-based sequencing method in this study. The mitochondria was 16,611 bp in length, including 13 protein genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and 1 control region. All genes were encoded on the heavy strain except for ND6 and eight tRNA genes. The gene arrangement of I. cyprinellus was similar to those found in the other Catostomidae species. Base composition of the heavy strain was A (29.40%), T (24.86%), C (27.96%), G (17.78%) and with A + T bias of 54.26%.

The complete mitochondrial genome of Megalobrama pellegrini was determined by using a PCR-based sequencing method. The mitochondrial was 16,620 bp in length, including 13 protein genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and one control region. All genes were encoded on the heavy strain except for ND6 and eight tRNA genes. The gene arrangement of M. pellegrini was similar to those found in the other Megalobrama species. Base composition of the heavy strain was A (31.19%), T (24.69%), C (46.37%), G (16.22%) and with A + T bias of 55.88%.

Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s2. By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration. Published version

Nonlinear viscoelastic properties of the MR fluid, MRF-132LD, under large-amplitude oscillatory shear were investigated. This was accomplished by carrying out the experiments under the amplitude sweep mode and the frequency sweep mode, using a rheometer with parallel-plate geometry. Investigations under the influence of various magnetic field strength and temperatures were also conducted. MR fluids behave as nonlinear viscoelastic or viscoplastic materials when they are subjected to large-amplitude shear, where the storage modulus decreases rapidly with increasing strain amplitude. Hence, MR fluid behaviour ranges from predominantly elastic at small strain amplitudes to viscous at high strain amplitudes. Large-amplitude oscillatory shear measurements with frequency sweep mode reveal that the storage modulus is independent of oscillation frequency and approaches plateau values at low frequencies. With increasing frequency, the storage modulus shows a decreasing trend before increasing again. This trend may be explained by micro-structural variation. In addition, the storage modulus increases gradually with increasing field strength but it shows a slightly decreasing trend with temperature.