Lubrication of the head disk interface (HDI) of a hard disk drive is achieved by coating a magnetic disk with a liquid lubricant film of monolayer thickness. It is important to clarify the tribological properties of the lubricant film for optimal lubrication of the HDI. In our previous study, we developed a highly sensitive method to measure shear force, which we called the "fiber wobbling method (FWM)." This method enables us to measure the viscoelastic properties of molecularly thin lubricant films. However, the shearing speeds were less than a few hundred µm/s, which is much slower than expected for the HDI. In this study, we developed a novel technique to measure displacement with a wide measuring range and high sensitivity, which will be essential for high speed tribological measurement using FWM.
It has been postulated that the higher the lubricant diffusion coefficient, the higher the hard disk drive (HDD) reliability. However, it has been reported that head wear increased in higher temperature environment even though the diffusion coefficient became larger. To understand this contradiction, we studied the effects of environmental conditions on pin wear using a transparent pin-on-disk seek wear test. The results showed large scattering in data points especially in low temperature or low humidity conditions but the reason of the scattering was not clear. Judging from the averaged data, we considered that the higher the temperature or the relative humidity, the lower the pin wear. These results followed our expectation, though the reason for the difference between prior head wear and present pin wear tests were not clear. However, the behavior of lubricant picked up on pin surface was not the same under the two high diffusion coefficient / low wear conditions. In high temperature conditions, lubricant pick-up became large. On the other hand, the amount of picked up lubricant became less in higher humidity environments. We consider more detailed studies are necessary to understand the effects of environmental conditions on head disk interface tribology.
A 2-D dynamic model was proposed to describe the dynamic behavior of the ramp/lift-tab interface of a one-inch hard disk drive with consideration of the air bearing force and contact stages during the unloading process. The contribution of the geometric parameters of the ramp/lift-tab interface on the dynamic performance of the suspension lift-tab was studied through simulation. A modified Reynolds equation and an iterative formulation for numerical scheme were presented considering continuum Poiseuille flows. The dynamic model developed for the lift-tab motion was extended to simulate the contact and separation stages of head-disk interface. The contact forces and deformation at the ramp/lift-tab contact interface were calculated. The effect of the horizontal velocity of the suspension lift-tab on the dynamic performance of the slider was analyzed. The results show that the dynamic characteristics of slider were independent on the geometric parameters of the ramp and the velocity of the suspension lift-tab. The calculation method to solve the Reynolds Equation proposed in the paper is with enough precision and high efficiency.
Clearance change between a magnetic head with a thermal flying-height control (TFC) function and a magnetic disk at high altitude was investigated. To clarify the change of head-disk clearance in the case of TFC actuation at high altitude, head-disk clearance change was experimentally evaluated as a function of altitude and head-disk clearance by using a TFC function. The evaluation results show that the head-disk clearance change is larger in the case with TFC actuation at high altitude than that in the case without TFC actuation.
This investigation presents a finite element simulation of contact between a magnetic recording slider and patterned media. The stress distribution due to contact in patterned media is evaluated. The effects of pad radius and filling materials on the stress distribution are studied.
This work presents numerical simulation results of head/disk interface for bit patterned media using the direct simulation Monte Carlo method. The effects of geometry of the bit pattern and of temperature on the air bearing force are studied.
The lubricant, perfluoropolyethers (PFPEs), has been modeled and analyzed using molecular dynamics simulations based on a coarse-grained bead-spring model. An ultrathin lubricant film with a thickness of 1-2 nm is coated on a disk to lubricate the head disk interface (HDI) of hard disk drives (HDDs). The retention performance of the lubricant film is studied, which is important to avoid a direct contact between the head and disk. The replenishment performance is also studied, which is essential to repair the lubricant film ruptured by a contact of the head. Finally, the typical phenomenon of touch down-take off hysteresis during the contact between head and disk is confirmed and analyzed because of the nanoscopic interactions in the HDI.
A numerical scheme by which to analyze the dynamic behavior of an ultra-thin liquid (lubricant) surface in the frequency domain resulting from repetitively applied pressure and shear stress was established. Numerical results for the dynamic behavior of an ultra-thin liquid (lubricant) surface produced by sinusoidally applied pressure and shear stress were obtained. The dependence of the liquid surface deformation on the frequency of the stresses and the disk speed were clarified.
This paper describes the application of geometry optimization method proposed by Hashimoto to the design of air lubricated thrust bearings used for HDD spindle motors. The optimization is carried out to maximize the dynamic stiffness of air films because the low stiffness is a serious problem of thrust air bearings in the actual application to HDD spindle motor. The optimized dynamic stiffnesses are obtained by changing the allowable film thickness, which is corresponding to the tolerance of bearings. The results obtained show that the optimized thrust air bearings have the comparable stiffness to the oil lubricated thrust bearings and it is verified theoretically that this type of thrust air bearing can be used for HDD spindle motors.
Some hard disk drives (HDDs) have fewer than the maximum number of magnetic heads. Such HDDs need to be re-designed to keep their position accuracy. We focused on adding dummy heads instead of re-designing the whole actuator. A dummy head is put on the edge of an arm model, and it influences the vibration characteristics of the model. Because the vibration characteristics of the arm model are related to those of the whole actuator, we optimized the dummy head design by focusing on the vibration characteristics of a local arm model instead of focusing on the whole actuator. We created a dummy head that would enable HDDs to keep the gain of their vibration characteristics around the sampling frequency as low as those of an HDD with the maximum number of mountable magnetic heads.
Swaging process is studied through a 2-D axisymmetric finite element model with non-linear material models and allowing large deformation. The effects of major baseplate hub geometrical parameters are studied for the case of a single actuator arm with two suspensions. Linear regression model is established to quantify the important output variables. The linear regression model provides a clear understanding of the effects of hub dimensions.
Energy harvesters with battery charging circuitry, which collect wasted kinetic energy from a magnetic disk drive's rotary actuator seek operations and flexible cable vibrations, are proposed, prototyped and presented in this paper. Depending on a disk drive's form factor and seek format, it is suggested by the present study that the harvested energy can be optimized by tuning the harvester's natural frequencies to major frequency content in the rotary actuator's excitation. It is demonstrated in this study that with prototype energy harvester systems, one can easily light up a regular LED. The work presented in this paper has implications in energy saving and recycling wasted mechanical energy for other low-power electronic applications in magnetic disk drive storage devices.
A data-based approach is presented for modeling and controller design of a dual-stage servo actuator in a hard disk drive. The servo actuator in this hard disk drive consists of a conventional voice coil motor and a piezo-electrically actuated suspension. A weighted Hankel matrix based realization algorithm that uses frequency domain data is applied to estimate a discrete-time model of the voice coil motor and the piezoelectric actuator. Based on the discrete-time models, different dual-stage track-following controllers were designed using classic and H∞ loop shaping techniques. The controllers were implemented in real-time in the investigated hard disk drive. A stable feed-back control and good agreement between measurements and simulations show the promising result of data based modeling and control.
In this paper, novel solutions are provided for designing the disturbance filter when there are significant plant dynamics within the bandwidth of the filter. The filter zero is designed appropriately so that the root loci originating from both the filter poles and the lightly damped plant poles go to the stable region under certain low gain condition. By providing compromised departure angles from filter poles and plant poles, the stability margin especially the gain margin is dramatically increased. The resulting closed-loop systems can provide large gain attenuation at the resonance frequency, and thus have more disturbance rejection capability.
For most servo systems, servo performance is quantified by the variance of a system dependent or user defined Servo Performance Signal (SPS). The smaller the variance of the SPS, the better is the performance of the servo control system. However, the variance of the SPS may be determined by both period and non-repeatable disturbances for which the characteristics are often not known a-priori during the servo algorithm design. Moreover, the servo control algorithm is often limited to a standard Proportional, Integral and Derivative (PID) controller as more complicated algorithms are viewed to be less robust. In this paper it is shown how a standard (PID) servo control algorithm can be augmented with an additional feedback loop that can be tuned automatically by estimating the actual disturbance spectra seen in a system dependent or user defined SPS. Adaptation to the disturbance spectra is done in lieu of possible model uncertainties in the servo actuator, guaranteeing stability robustness. As such, the control algorithm provides a Robust Estimation and Adaptive Controller Tuning (REACT) to disturbance spectra to maximize servo performance by minimizing SPS variance in high performance servo systems.
We present a self-sensing control method of piezoelectric actuators that compensate the hysteresis characteristics by using the linear relationship between the permittivity change and the piezoelectric displacement. In this article, improvement of this method is described. Increasing the frequency of the voltage for a permittivity detecting, the sensitivity of the permittivity detection was improved and the accuracy of the displacement sensing could be enhanced. In addition, by applying this self-sensing method, we tried to overcome the creep phenomenon that is a peculiar problem of piezoelectric actuators.
Methods for enhancing the gripping ability of microtweezers are examined in terms of friction force. Two aspects are investigated experimentally. One is a method for increasing the coefficient of friction of the handling part of the microtweezers. We examined the effect of the etching time on the surface roughness of surfaces processed by the Bosch process and the coefficient of friction. The coefficient of friction increased with increasing etching time. The other aspect we investigated is the optimum handling force. In tweezers-based handling, it is not clear whether the friction force is proportional to the handling force in accordance with Coulomb's law of friction. We performed measurements and found that the friction force is approximately proportional to the handling force. Using this knowledge, the optimum handling force can easily be determined.
Continuous monitoring of eating habits could be useful in preventing lifestyle diseases such as metabolic syndrome. Conventional methods consist of self-reporting and calculating mastication frequency based on the myoelectric potential of the masseter muscle. Both these methods are significant burdens for the user. We developed a non-invasive, wearable sensing system that can record eating habits over a long period of time in daily life. Our sensing system is composed of two bone conduction microphones placed in the ears that send internal body sound data to a portable IC recorder. Applying frequency spectrum analysis on the collected sound data, we could not only count the number of mastications during eating, but also accurately differentiate between eating, drinking, and speaking activities. This information can be used to evaluate the regularity of meals. Moreover, we were able to analyze sound features to classify the types of foods eaten by food texture.
The aim of this study is to propose the measurement method of three-dimensional (3D) movement of forearm and upper arm during pitching motion of baseball using inertial sensors without serious consideration of sensor installation. Although high accuracy measurement of sports motion is achieved by using optical motion capture system at present, it has some disadvantages such as the calibration of cameras and limitation of measurement place. Whereas the proposed method for 3D measurement of pitching motion using body mounted sensors provides trajectory and orientation of upper arm by the integration of acceleration and angular velocity measured on upper limb. The trajectory of forearm is derived so that the elbow joint axis of forearm corresponds to that of upper arm. Spatial relation between upper limb and sensor system is obtained by performing predetermined movements of upper limb and utilizing angular velocity and gravitational acceleration. The integration error is modified so that the estimated final position, velocity and posture of upper limb agree with the actual ones. The experimental results of the measurement of pitching motion show that trajectories of shoulder, elbow and wrist estimated by the proposed method are highly correlated to those from the motion capture system within the estimation error of about 10 [%].
Continuous monitoring of blood pressure in daily life could improve early detection of cardiovascular disorders, as well as promoting healthcare. Conventional ambulatory blood pressure monitoring (ABPM) equipment can measure blood pressure at regular intervals for 24 hours, but is limited by long measuring time, low sampling rate, and constrained measuring posture. In this paper, we demonstrate a new method for continuous real-time measurement of blood pressure during daily activities. Our method is based on blood pressure estimation from pulse wave velocity (PWV) calculation, which formula we improved to take into account changes in the inner diameter of blood vessels. Blood pressure estimation results using our new method showed a greater precision of measured data during exercise, and a better accuracy than the conventional PWV method.
Focusing on the Personal Handy-phone System (PHS) positioning service used in physical distribution logistics, a positioning error offset method for improving positioning accuracy is invented. A disadvantage of PHS positioning is that measurement errors caused by the fluctuation of radio waves due to buildings around the terminal are large, ranging from several tens to several hundreds of meters. In this study, an error offset method is developed, which learns patterns of positioning results (latitude and longitude) containing errors and the highest signal strength at major logistic points in advance, and matches them with new data measured in actual distribution processes according to the Mahalanobis distance. Then the matching resolution is improved to 1/40 that of the conventional error offset method.
A conceptual Guide-Dog Robot prototype to lead and to recognize a visually-handicapped person is developed and discussed in this paper. Key design features of the robot include a movable platform, human-machine interface, and capability of avoiding obstacles. A novel algorithm enabling the robot to recognize its follower's locomotion as well to detect the center of corridor is proposed and implemented in the robot's human-machine interface. It is demonstrated that using the proposed novel leading and detecting algorithm along with a rapid scanning laser range finder (LRF) sensor, the robot is able to successfully and effectively lead a human walking in corridor without running into obstacles such as trash boxes or adjacent walking persons. Position and trajectory of the robot leading a human maneuvering in common corridor environment are measured by an independent LRF observer. The measured data suggest that the proposed algorithms are effective to enable the robot to detect center of the corridor and position of its follower correctly.
To recognize human behavior in unlimited environments, sensing shoes for measuring foot pressure distribution were developed. Seven pressure sensors were installed on an insole, and a measurement module was embedded in the shoe. An analysis for discriminating the user's movements from the foot pressure distribution was examined, considering the movements, walking, running, standing, sitting, going upstairs and downstairs, and cycling. These seven actions were discriminated using feature quantities such as the average, standard deviation, maximum, and difference deviation extracted from the data of three sensors by discriminant analysis. The evaluation results showed highly accurate behavior recognition based on foot pressure at some points. In addition, by canonical discriminant analysis, six discriminant functions which classify the seven actions with an accuracy of 100% were derived by using feature quantities extracted from five sensors. The results confirmed that discriminant analysis can be used for automatically recognizing human behaviors based on foot pressure data.
This paper describes the novel optimization method of wind-up tension to prevent wound roll defects, mainly star defect (wrinkling) and telescoping (slippage), based on the optimum design technique. Modified Hakiel model with air entrainment effects is applied to analyze in-roll stress distributions in the radial and tangential directions. In the present optimization method, the wind-up tension is gradually changed in the radial direction to minimize the tangential stresses under the constraint of nonnegative tangential stresses. At the same time, we consider the friction conditions to prevent the slippage between web layers due to a decrease of radial stresses and friction force. Successive quadratic programming, which is a typical mathematical programming method, is used as the optimization technique. The optimized wind-up tensions are obtained for various winding conditions, and we confirmed theoretically and experimentally that the in-roll stress distributions are very much improved for preventing both wrinkling and slippage simultaneously by the optimization method being proposed.
We describe an entirely new method of improving the slippage between web and roller. First, the concept of a micro-grooved roller is introduced, and then a theoretical model for estimating the slip onset velocity under the transport of web by the micro-grooved roller is formulated. The predicted results are compared with the experimental data to verify the applicability of the prediction model of slippage. Moreover, the web-wrinkling condition, which is in a trade-off relationship with the slippage condition, is also considered in the model. From the theoretical and experimental results, it is confirmed that the optimized micro-grooved roller is very effective in improving the slippage and wrinkling of thin web under the high-speed transport with low tension at the actual production line.
In the transport processes of plastic-films, wrinkling is sometimes generated due to misalignment of roller. To avoid the wrinkling, it is effective to reduce the web tension. However, under the low web tension, the traction inevitably falls as transport velocity increases due to air entrainment and is accompanied by the onset of slip. This paper examined such a trade-off relation between the wrinkling generation due to roller misalignment and onset of slip. At first, the prediction models for slippage and wrinkling are formulated based on the contact mechanics. Moreover, the observation method of wrinkling generation and slip was presented and the critical misalignment angle, critical web tension to generate wrinkling and slip onset velocity were measured for various operation conditions. Five types of PET (polyethylene terephthalate) films were used for measurements. From the experimental and theoretical results, the effects of roller velocity, anisotropic Young's modulii and film thickness on the relation between the roller misalignment and web tension were made clear. As a summary of experimental and theoretical works, the stable transportation map was newly introduced for protecting both wrinkling and slip.
The overlap separation mechanism is widely used to separate paper sheets from each other in automatic teller machines. In this study, we first derived a formula used for expressing the normal separation condition of paper sheets. Then we analyzed the deformation force acting on the paper sheet surfaces by treating the paper sheet as an elastic beam and using Clapeyron's theorem of three moments. Furthermore, by using the finite element analysis software LS-DYNA, we developed a three-dimensional simulation method that can accurately reproduce normal separation, misfeeding, and double feeding behaviors. Finally, the effects of the main parameters on deformation force will be discussed. The results show that the deformation force is proportional to the overlap; the bigger the width of gate-roller or the distance of roller edges, the bigger the deformation force. Moreover, the width of the feed-roller has hardly any effect on deformation force. It is shown that separation defects obtained by the elastic beam model agree well with those obtained by the FE model.
This paper deals with a theoretical stability analysis of an unstable wave generated on a thin film subjected to a fluid flow in a narrow gap. In stability analysis, the basic equations of fluid flow around the thin film are based on the Navier-Stokes equations integrated over a gap width between the thin film surface and side wall, assuming that the gap width is enough small compared with a length of the passage. The structural equation of the thin film in the transverse motion is based on the Kirchhoff-Love's thin-plate model. From these basic equations, the governing equations of the thin film coupled with the fluid flow are obtained, employing the moving boundary conditions of the surface of the thin film. These equations are linearized around the equilibrium position, and the dispersion relation of the wave motion is derived as a function of the flow velocity. As a result, the analytical results show that traveling-wave type unstable wave occurs to the thin film due to the fluid flow in the narrow gap and clarify the dispersion relation of the wave motion, phase velocity (traveling-wave velocity) and growth rate of the wave. Moreover, the analytical results are verified by experiments on the most unstable wave number and critical flow velocity.
This paper develops a non-contact active feedback control of web flutter in a narrow passage by using movable plates set at inlet and outlet of the passage. The strategy of this active feedback control is based on the flow-control which cancels the exciting fluid force acting on the web, i.e., cancels the self-excited feedback mechanism. In this paper, suppression of the web flutter by the active feedback control is demonstrated experimentally. In the experiments, a web (film), as a controlled object, is subjected to air flow in a narrow passage. The web flutter occurs to the web in the translational motion over the critical flow velocity. And the web flutter is actively controlled and suppressed by the movable plate motion which changes the air flow in the passage. The critical flow velocity under controlled condition is examined with changing the controller gain and phase-shift between the web motion and the movable plate motion. As a result, it is indicated that the active feedback control increases the critical flow velocity, and suppress the web flutter effectively. Moreover, the control performance is examined experimentally, and stabilization mechanism by the active feedback control is discussed.
A method for simulating a web winding process and for predicting wound roll stresses is proposed. The simulation model is two-dimensional and is composed of a web and a core. The simulation was carried out on a FEM software to investigate effects of a slip between web layers, a core rigidity, and a leading edge of a wound web on the wound roll stress distributions. The results show that both the radial and circumferential stresses of the wound roll become extremely larger when the web layer slip is considered. While they decrease when the core rigidity becomes lower. The simulated stresses for no slip cases are compared with the results obtained by Hakiel model.
A modern high-density magnetic tape drive is an ideal solution for archival storage in terms of its storage capacity and reliability among other available data storage products such as hard disk drives and optical drives. Following similar trend as hard disk drives, tracking density for modern tape drives is projected to be doubled every five years. For higher recording density, thinner magnetic tape is desirable. Since flanged rollers are currently widely used in modern tape drive to reduce tape lateral motion, reducing thickness of the tape can significantly decrease its stiffness and increase like-hood of damaging tape edges by adjacent mechanical components in a tape drive as well as in manufacturing, shipping and handling processes. To avoid this, alternative tape guiding and actuation method are required. Among all methods, good contact between tape and actuator is required for local motion generation. In this paper a novel air-breathing mechanism in an ultrasonic plate-like actuator to actively guide the tape is proposed and validated through experiments. Significant enhancement of surface contact between traveling tape and guider is demonstrated. A perfect parallel contact can be easily reached by the proposed method. It is found that pattern of air-breathing holes plays significant role in reducing proximity between traveling tape and guider plate which has implications in actuator vibration for local motion and assembly tolerance designs.
The authors proposed a new actuator for track following on a spin-stand that evaluated magnetic heads and media for high density magnetic recording with high speed. The new actuator was named “Nano-Motion Actuator (NMA)” by the authors. At the present time, effect of azimuth angle which causes between a center line of a head slider and a tangential direction of the track is increasingly actualized as a track pitch of the head becomes narrow. Therefore, if a discrete track media (DTM) will be put to practical use, the effect of the azimuth angle will be actualized more clearly. Because, DTM will have large RRO (Repeatable Run-Out) that is caused by eccentricity error between a medium and a hub of an air-spindle. Furthermore, NRRO (Non-Repeatable Run-Out) which is caused by mechanical vibration of the air-spindle, flutter of the medium, turbulence around a HGA (Head gimbals Assembly) and so on is overlapped with the RRO. Especially in case of the large NRRO, since the azimuth angle will rapidly change, compensations of the azimuth angle should be absolutely necessary. Therefore, precision positioning actuator with high speed on an X-Y plane which is coplanar will be required the evaluation of the high density magnetic recording. We proposed a new actuator which was consisted of a NMA mechanism and a translation mechanism. The translation mechanism was composed of a stacked piezoelectric that was supported by two elastic springs. The new actuator that was called “2D Nano-Motion Actuator (2D NMA)” could move within 10 square micrometer and be positioned by nanometer resolution with high speed.
We have developed a traveling small capsule, which has a smooth outer surface and is driven by inertia force and friction force. Measuring only 7 mm in diameter and 12 mm in length, it is sufficiently small to be placed in the human gullet or intestines. The capsule contains a small magnet and a coil, and an electric pulse drives the magnet to move the capsule. We performed an experimental investigation on making our capsule travel on a plastic material, which has similar elasticity characteristics to the living body. We also showed that it can travel on the surface of a pig's intestine. Our capsule may be useful for medical treatments such as inspection, drug delivery and operation.
As hard disk drive (HDD) areal density increases, its track width becomes smaller and smaller and so is non-repeatable runout. HDD industry needs more accurate and better resolution runout measurements of spinning spindle motors and media platters in both axial and radial directions. This paper introduces a new system how to precisely measure the runout of HDD spinning disks and motors through synchronously acquiring the rotor position signal and the displacements in axial or radial directions. In order to minimize the synchronizing error between the rotor position and the displacement signal, a high resolution counter is adopted instead of the conventional phase-lock loop method. With Laser Doppler Vibrometer and proper signal processing, the proposed runout system can precisely measure the runout of the HDD spinning disks and motors with 1 nm resolution and 0.2% accuracy with a proper sampling rate. It can provide an effective and accurate means to measure the runout of high areal density HDDs, in particular the next generation HDDs, such as, pattern media HDDs and HAMR HDDs.
Superhydrophobic double roughening structure of DLC film was prepared by 2.45 GHz surface wave-excited plasma CVD with the mixture of methane (CH4) and tetramethylsilane (TMS: Si(CH3)4) gases on the undulated DLC film by a series of plasma Ar etching, coating process and plasma Ar etching. Static wetting angle of water was observed that double roughening structure of DLC was superhydrophobicity such as wetting angle 161°. This approach also increased in air pockets easily trap among the needle-like posts. For the low friction at nanoscale, the surface wettability of the solid lubrication played a significant role, when the DLC film modified from flat to double roughening structure, the friction was constantly inner humidity conditions. Results generally showed that humidity had insignificant effect on the nanoscale friction at superhydrophobic DLC surface. The effect of the superhydrophobic double roughening DLC and friction were discussed with the following factors; the surface morphology affinity to needle-like shape, a reduction of the real area of contact, graphitization and easily occur to slip at small contact interface due to superhydrophobicity.
An electrohydrodynamic (EHD) micropump to generate oscillating flow is newly developed and experimentally tested using an arrangement of thin stainless steel wires. A working fluid is accelerated from the charged electrode to the ground electrode by a high electric field. The electric body force responsible for this acceleration is primarily the Coulomb force. To increase the electric filed, the distance between the charged and ground electrodes is 0.2 mm. The size of the present EHD pump is 24×30×7.8 mm. Since the pressure increases with the increase in the number of the electrode pairs, a pumping channel fabricated in this EHD pump is bent in parallel so as to increase the number of electrode pairs. This channel has the dimensions of 24×48×0.9 mm, in which ten pairs of electrodes are fabricated. The maximum static pressure generated by the present EHD pump is approximately 550 Pa at an input of DC 1 kV, and the maximum flow rate is 4.3 ml/min at the unloaded condition. In order to generate symmetric oscillating flows, alternating voltage is applied. The present EHD pump is demonstrated to successfully generate symmetric oscillating flows at low frequencies (0.01 Hz ∼ 0.05 Hz)
There is an issue of the fish adhering to the metal grids of grill strongly after grilling fish. Recently, the temperature in a grill equipment is over 500 °C, Fluorine resin coating which has low adhesion property can not endurant at 500 °C. In order to overcome this issue, we proposed a new grill not to adhere a fish with Ultra-Hydrophobic Diamond-like Carbon coating named as UH-DLC coating. UH-DLC coating has high hydrophobicity. We expected this coating to decrease wettability of water including fish protein and contact area, because fish protein includes about 90% water. Contact angle of water on UH-DLC was over 120° at room temperature. After heating at 500 °C for 54 minutes, UH-DLC kept ultra-hydrophobic property. On the other hand, Fluorine resin coating desappeared hydrophobic properties after heating at 500 °C for 54 minutes. It was conducted adhesion test for UH-DLC coating, Fluorine resin coating and no coating grilling rods after the grilling of real fish in a grill equipment by gas. The adhesion force between UH-DLC coating grill rods and real fish was as half as that of no coating grill rods and as much as that of Fluorine resin grill rods. So, we believe that Ultra Hydrophobic Diamond-like Carbon coating has a possibility for the usage as new grilling grids at high temperature.
This paper describes the electrowetting-on-dielectric (EWOD) actuation of liquid droplets for transportation of micromechanical parts. As dimensions of mechanical parts decrease, surface tension and electrostatic force become dominant compared to gravity force. Recent studies show that these forces can be utilized for actuation of liquid droplets and transportation of micromechanical elements. In this study, behavior of liquid droplet actuated by EWOD on a single substrate is analyzed using a high speed camera. Effects of applied voltage, switching frequency, and volume of the droplet are investigated experimentally. Furthermore, application of EWOD actuation to micro transportation systems is proposed. Surface properties for the conveyer pad are discussed.
This paper shows the wear characteristics of carbon nanotube films made by surface decomposition of SiC. By this method, one can obtain remarkably high density of CNTs with well vertical alignment. For the purpose of measuring the wear characteristics of CNT films with submicrometer thickness, we carried out nanoscratch and nanoindentation tests by using an atomic force microscope (AFM). And we used 2 kinds of AFM cantilever tips with tip radii of about 20 nm and 150 nm. The experimental results showed wear behaviors of CNT films dependent on CNT length and normal load. And CNT films were worn gradually as the number of wear cycles increased. The effect of CNT length on wear of CNT films appeared as different behaviors of CNT films under normal load. That was originated from bending stiffness of each CNTs with different length as measured by nanoindentation. Shorter-CNT films had less wear because of higher deformation resistance than longer ones. Under the normal load, the SCD tip penetrated to several tens of nanometers in depth, but the CNT films showed only wear depth on the order of angstrom for each scratch cycle. Thus we confirmed that CNT films have both strength and flexibility, which reflects remarkable mechanical properties of CNTs. These results are important for machine designs using CNT films as friction materials.
This paper describes insect-inspired wall-climbing robot that is capable of walking on a smooth vertical surface utilizing surface tension forces. The adhesion mechanism of the robot is inspired from the attachment system of ants, which is responsible for a thin film of secreted liquid between the adhesive organs and the surface. Two kinds of adhesive pads made of PDMS and glass were fabricated using MEMS techniques and adhesive properties were measured. Furthermore, a hexapod robot with the adhesive pads installed on its feet was developed. The robot weighs 9.5g and walks in the alternating tripod gait. It successfully walked on vertical and inverted glass surfaces.
The dependences of surface energy on ultra-thin film thickness are investigated experimentally and theoretically. Langmuir-Blodgett (LB) film and perfluoropolyether (PFPE) lubricant on solid substrates are used as ultra-thin film samples. Surface energies as a function of film thickness are experimentally obtained from contact angle measurements. The theoretical equation of the dispersive component of the surface energy of ultra-thin film is derived from the corrected van der Waals pressure equation for a multilayered system proposed by the authors. The theoretical values are found to agree with the experimental values. The theoretical equation presented in this study is considered to be useful in predicting the surface energy of an ultra-thin film on a solid substrate.
The influence of an electric field on the dip-coating process was studied by using the lubricants Z-tetraol, D-4OH, TA-30, and QA-40. The electric field facilitated the adsorption of lubricant molecules onto the disk surface. It also resulted in an increase in the lubricant film thickness. The surface free energy and molecular height of the Z-tetraol lubricant film were not affected by the electric field; however, they decreased in the case of other lubricant films. To elucidate these results, we estimated that the molecular conformation of the lubricants changed due to the electric field and that the OH end-groups aligned to the carbon surface. These results suggest the possibility of resistance to outgas contamination and humidity through electric field assisted dip (EFAD) coating.
Inelastic deformation of gold (Au) atomic cluster is investigated by using molecular dynamics (MD) simulations. We performed compression and unloading tests in which silicon (Si) plates approach each other and push single Au cluster of 4 nm diameter in between. Possibility of super-elastic (hyper-elastic) behavior is first discussed in the present study. The potential function of embedded atom method is adopted inside Au cluster, whereas other interactions are formulated by simplified Lennard-Jones interaction. The cluster in MD simulation shows large recovery strain which is reversible in unloading process after compression. The recovery strain is estimated on average from 5 to 10%. It is found that there are deformation mechanisms depending on temperature of the cluster. Mechanism for low temperature is based on slip motion and that for high temperature is dominated by surface reconstruction. The strength of interaction energy between Si plate and the Au cluster which may cause pulling force and produce tensile state is investigated, referring to our AFM experiment.
In near-field optical recording, the combination of a triangular aperture and a polarized illuminating light is thought to be one of the most promising breakthroughs for improving both spatial resolution and signal-to-noise ratio. In light of this, we have already fabricated a triangular-aperture mounted optical head slider and demonstrated its superior performance while clarifying the influence of the polarization direction on the spatial resolution in the circumferential direction. When the polarization direction was perpendicular to the bottom side (which is parallel to the slider trailing edge) of the aperture, the highest spatial resolution and signal contrast were obtained, in spite of the usage of a fairly large aperture, indicating the presence of clear readout signal waveforms corresponding down to 100 nm line-and-space (L/S) patterns. In this study, we tried to experimentally clarify the influence of the polarization direction of the illuminating light on an aperture's field spread in the radial direction. In order to concretely evaluate the field spread, we prepared 1-mm-long linearly arranged (in the circumferential direction) L/S patterns on a metal-layered medium, and a piezo-electric actuator combined positioner. Intersecting the aperture at two portions of the tracks, directly acquired signal waveforms could be successfully transformed into the waveforms that would be obtained if the aperture had crossed the track at right angles. The field spreads in the radial direction were estimated to be approximately 250 nm when the polarization direction was perpendicular to the bottom side. In contrast, when the polarization direction was 45 degrees, the stationary field spread in the radial direction was estimated to be approximately 350 - 370 nm. It could be confirmed experimentally that both the highest spatial resolution in the circumferential direction and the smallest field spread in the radial direction were realized with the combination of the triangular aperture and the illuminating polarized light whose direction was perpendicular to the bottom side. Based on these results, the signal-to-noise ratio will be evaluated and discussed in the future with respect to the above-mentioned optimum aperture structure and conditions.