Recording Disks Research Articles

Patterned gold electrode prepared from optical discs display largely enhanced electrochemical sensitivity as exemplified in a sensor for hydrogen peroxide

Gold film electrodes (Au-FE) with distinct nanostructured patterns were prepared from polycarbonate (PC) substrates and investigated with respect to their analytical sensitivity. The recordable (R) and read-only memory (ROM) discs, respectively, yield PC substrates with grooves (stripe pattern) or pits (indented pattern). The Au-FEs were characterized in terms of surface morphology and surface patterns, and it was found that the surface area of all Au-FEs does not significantly differ (by 0.2 to 7.4 %) compared to electrode with flat surfaces. However, the electrical signal of indented patterns is larger by 32 to 213 % when directly compared to stripe-patterned Au-FEs (at the same scale of groove and pit). An Au-FE prepared from a polycarbonate sheet from a Blu-ray disc read only memory (BD-ROM) as substrate displayed the best electrochemical performance towards reductive sensing of H2O2. The respective calibration plot, acquired at a working potential of −0.1 V vs. Ag/AgCl, covers the 0 to 10 mM hydrogen peroxide concentration range. The sensitivity is as high as 3.11 μA∙mM−1∙cm−2 which is larger by a factor of 28 compared to flat gold electrodes, and the detection limit (at a signal-to-noise ratio of 3) is 6 μM. Therefore, the results confirm that the indented nanopattern on the Au-FE significantly increases the efficiency of electrochemical detection. Conceivably, the surface patterns and structures may be designed in order to tune sensitivity with respect to future applications of Au-FEs in diagnostics, agriculture, and environmental monitoring.

A Low-Cost Label-Free AFB1 Impedimetric Immunosensor Based on Functionalized CD-Trodes

This work describes the investigation of a label-free immunosensor for the detection of aflatoxin B1 (AFB1). CD-trodes (electrodes obtained from recordable compact disks) were used as low-cost and disposable transducers after modification with a self-assembled monolayer (SAM) of lipoic acid. The anti-aflatoxin B1 antibody was immobilized via EDC/NHS activation, followed by blocking with bovine serum albumin and immunoassays with AFB1. The optimization of analytical parameters and the detection were carried out using electrochemical impedance measurements. Using chemometric tools, the best conditions for the immunosensor development were defined as: anti-AFB1 antibody at 1:2000 dilution and surface blocking with 0.5% bovine serum albumin, both incubated for 1 h, and antibody–antigen immunoreaction for 30 min. The impedimetric immunosensor showed a linear range from 5 × 10−9 to 1 × 10−7 mol·L−1 (1.56–31.2 ng·mL−1), limit of detection and limit of quantification, respectively, 3.6 × 10−10 and 1.1 × 10−9mol·L−1 (0.11 and 0.34 ng·mL−1). The proposed immunosensor was applied to analyze peanut samples.

Fast analysis of terbutaline in pharmaceuticals using multi-walled nanotubes modified electrodes from recordable compact disc

In this study, homemade disposable gold electrodes made from recordable compact disks were modified with carbon nanotubes for amperometric quantification of terbutaline sulfate in pharmaceutical products. A flow cell using an impingent jet of solution on the electrode surface was build and used for amperometric detection, and a series of experiments were carried out to find the best experimental conditions for the new electrode in a specially designed cell. A linear response for terbutaline was obtained in the range from 3.0 × 10−6 to 5.0 × 10−4 mol L−1 (at 0.63 V vs. Ag/AgCl). The limits of detection and quantification were calculated as 5.8 × 10−7 mol L−1 (S/N = 3) and 1.9 × 10−6 mol L−1 (S/N = 10), respectively. A frequency of 30 injections h−1 was attained. The proposed method was successfully applied to the analyses of commercial syrup samples, and all results were in good agreement with those obtained by using high performance liquid chromatography and capillary electrophoresis-tandem mass spectrometry.

Gold-sputtered Blu-ray discs: simple and inexpensive SERS substrates for sensitive detection of melamine.

Nanostructured gold substrates provide chemically stable, signal-enhancing substrates for the sensitive detection of a variety of compounds through surface-enhanced Raman spectroscopy (SERS). Recent developments in advanced fabrication methods have enabled the manufacture of SERS substrates with repeatable surface nanostructures that provide reproducible quantitative analysis, historically a weakness of the SERS technique. Here, we describe the novel use of gold-sputtered Blu-ray disc surfaces as SERS substrates. The unique surface features and composition of the Blu-ray disc recording surface lead to the formation of gold nano-islands and nanogaps following simple gold sputtering, without any background peaks from the substrate. The SERS performance of this substrate is strong and reproducible with an enhancement factor (EF) of 10(3) for melamine. A limit of detection (LOD) for this compound of 70ppb and average reproducibility of ±12% were achieved. Gold-sputtered Blu-ray discs thus offer an excellent alternative to more exotic gold SERS substrates prepared by advanced, time-consuming and expensive methods. Graphical abstract AFM 3D images of 1-μm(2) sections of uncoated and gold-sputtered recordable Blu-ray disc (BD-R) surfaces and the SERS signal obtained on the gold-sputtered surface for a 1000ppm aqueous solution of melamine.

Design and Implementation of a Hybrid Shingled Write Disk System

Disk data density improvement will eventually be limited by the super-paramagnetic effect for perpendicular recording. While various approaches to this problem have been proposed, Shingled Magnetic Recording (SMR) holds great promise to mitigate the problem of density scaling cost-effectively by overlapping data tracks. However, the inherent properties of SMR limit Shingled Write Disk (SWD) applicability since writing data to one track destroys the data previously-stored on the overlapping tracks. As a result, various data layout management designs have been proposed. In this paper, we present a hybrid wave-like shingled recording (HWSR) disk system, which can improve both the performance and the capacity of a shingled write disk. We propose a novel segment-based data layout management and a new wave-like shingled recording that overlaps adjacent tracks from two opposite radial directions. This new scheme can not only efficiently reduce the write amplification, but also double the areal density of conventional circular log-based shingled recording. A new replacement policy based on least write amplification is also devised to manage the hybrid system to effectively eliminate the performance degradation. Our measurements on HWSR implemented in Linux kernel 2.6.35.6 show that it provides superb performance. For example, HWSR reduces the average I/O response time by an order of magnitude compared to S-block for Financial1 trace, and provides up to 3.7 speedup over standard hard disks without using shingled magnetic recording technology.

液体ナノ薄膜の変形流動特性

In the head-disk interface (HDI) of a hard disk drive (HDD), the effects of lubricant deformation on the flying characteristics of a head slider increase as the flying height decreases. Therefore, it is very important to investigate the deformation and flow characteristics of lubricant on a recording disk. In particular, in heat-assisted magnetic recording (HAMR), laser heating of the lubricant induces surface tension distribution and evaporation of lubricant, which may cause deformation of the lubricant film. In this paper, deformation and flow characteristics of liquid nano-film of perfluoropolyether (PFPE) film on solid substrate is investigated numerically and experimentally. Calculation results are compared with experimental results, and validity of the analytical model is investigated.

Progress and Prospect of Tribology in Magnetic Recording Disk Storage

Progress and Prospect of Tribology in Magnetic Recording Disk Storage

Multihead Multitrack Detection With Reduced-State Sequence Estimation

To achieve ultra-high storage capacity, the data tracks are squeezed more and more on the magnetic recording disks, causing severe intertrack interference (ITI). The multihead multitrack (MHMT) detector is proposed to better combat ITI. Such a detector, however, has prohibitive implementation complexity. In this paper we propose to use the reduced-state sequence estimation (RSSE) algorithm to significantly reduce the complexity, and render MHMT practical. We first consider a commonly used symmetric two-head two-track (2H2T) channel model. The effective distance between two input symbols is redefined. It provides a better distance measure and naturally leads to an unbalanced set partition tree. Different trellis configurations are obtained based on the desired performance/complexity tradeoff. Simulation results show that the reduced MHMT detector can achieve near maximum-likelihood (ML) performance with a small fraction of the original number of trellis states. Error event analysis is given to explain the behavior of RSSE algorithm on 2H2T channel. Search results of dominant RSSE error events for different channel targets are presented. We also study an asymmetric 2H2T system. The simulation results and error event analysis show that RSSE is applicable to the asymmetric channel.

Digital versatile disc bipolar electrode: A fast and low-cost approach for visual sensing of analytes and electrocatalysts screening

This work represents a new, extremely low cost and easy method for fabrication of bipolar electrode (BPE) for rapid and simultaneous screening of potential candidates for electrocatalytic reactions and sensing applications. Our method takes advantage of the silver reflective layer deposited on already available recordable digital versatile disc (DVD-R) polycarbonate substrate which acts as BPE. Oxidation of the reflective layer of the DVD-R in anodic pole of the BPE results in a permanent and visually measurable dissolute length. Therefore, one could correlate the electrocatalytic activity of the catalyst at the cathodic pole of the BPE, as well as the concentration of analyte in the solution, to the dissolution length of the BPE. To illustrate the promising applications of this new substrate as BPE, p-benzoquinone (BQ) and hydrogen peroxide were tested as model targets for the sensing application. Moreover, in order to show the feasibility of using DVD BPEs for screening applications, the electrocatalytic activity of Pt, Pd, Au, and pristine DVD substrate toward hydrogen evolution reaction (HER) were compared using an array of BPEs prepared on DVD substrate.

Laser-Induced Thermo-Desorption of Perfluoropolyether Lubricant from the Surface of a Heat-Assisted Magnetic Recording Disk: Lubricant Evaporation and Diffusion

Heat-assisted magnetic recording (HAMR) storage technology will thermally stress the lubricant film typically applied to the storage disk surface. Different lubricant loss and morphology change mechanisms have been hypothesized to occur during information writing. A loss to of the lubricant film will dramatically affect its overall mechanical and chemical performance of the head–disk interface, decreasing its reliability and its durability. Thus an all optical pump–probe method was used to study the effect of fast thermal transients (106 K/s) on a lubricant film on HAMR media. Thermal transients (Bhushan and Cheng in J Appl Phys 81:5390, 1997) with peak temperatures above the HAMR media Curie temperature (T c) were found to remove by evaporation the lubricant within the heated region creating a lubricant depression in the otherwise continuous film. No accumulation of lubricant volume was observed to take place in the cooler regions of the thermal spot, indicating that thermocapillary shear stress is not an important mechanism of lubricant thickness change with the optical spot size used (65 μm). The onset of lubricant loss was observed to begin at approximately 610 K and was totally removed at 823 K. The change in depth of the lubricant depression with time showed that no structural terms contributed to the disjoining pressure for the lubricant thickness range studied. From this change, the diffusion coefficient of the lubricant on the carbon overcoat surface was determined to be 1 × 10−13 m2/s by fitting Fick’s second law to the normalized lubricant thickness. The importance of these observations on the operating HAMR head–disk interface is discussed.

Amperometric Determination of Hydrogen Peroxide at a Silver Electrode Fabricated from a Recycled Compact Disc

This present study investigates the utilisation of Ag electrodes fabricated from recycled recordable compact discs (CD-R) for the amperometric determination of hydrogen peroxide. The analytical curve was linear up to at least 30 mM hydrogen peroxide with a sensitivity of 21.89 µA/mM over this range. A corresponding detection limit of 17.7 µM, based on a signal-to-noise ratio of three was recorded. The developed electrode represents a simple, inexpensive, reliable method for the determination of hydrogen peroxide, avoiding extended and complex multi-step fabrication as it is readily fabricated from recycled materials. It has a number of potential applications, including environmental, industrial, physiological and home security, especially where single use and disposability could be beneficial.

Comparison of Gold CD-R Types as Electrochemical Device and as Platform for Biosensors

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.

Japanese 2011 nationwide survey on complications from spine surgery.

BackgroundThe Japanese Society for Spine Surgery and Related Research (JSSR) previously carried out two nationwide surveys in 1994 and 2001 on complications from spine and spinal cord surgery. More than 10 years have now elapsed since 2001. Rapidly ageing populations have major impacts on society, particularly in the medical field. The purpose of this study was therefore to examine the present situation for spine surgery in Japan.MethodsThe JSSR research team prepared a computerized questionnaire made up of two categories in order to capture clinicopathological information and surgical information. A recordable optical disc for data storage was sent to surgeons who were certified for spine surgery by JSSR. The data was analyzed.ResultsThe JSSR carried out a nationwide survey of complications of 31,380 patients. Patients aged 60 years or older comprised 63.1 % of the overall cohort. This was considerably higher than observed in previous surveys. Degenerative spinal diseases increased 79.7 %. With regard to surgical approach, the incidence of anterior surgery has decreased, while that of posterior surgery has increased compared to the earlier surveys (both p < 0.05). Spinal instrumentation was applied in 30.2 % cases, compared to 27.0 and 34.0 % cases in the 1994 and 2001 surveys, respectively. Intraoperative and postoperative complications were reported in 10.4 % and were slightly increased compared to 8.6 % in the earlier surveys (both p < 0.05). Diseases associated with a high incidence of complication included intramedullary tumor (29.3 %) and primary malignant tumor (22.0 %). The highest incidence of complication was dural tear (2.1 %), followed by neurological complication (1.4 %).

Investigation of localized surface plasmon/grating-coupled surface plasmon enhanced photocurrent in TiO2 thin films.

We fabricated plasmonic gold nanoparticle (AuNP)-TiO2 nanocomposite films and measured the photocurrent that originates from the water-splitting reaction catalyzed by the AuNP-TiO2 nanocomposite photoelectrocatalytic (PEC) electrode. The localized surface plasmon resonance (LSPR) of the gold nanoparticles affected the generation of photocurrent by TiO2 upon illumination with visible light. Electrochemical impedance spectroscopy (EIS) revealed that the improvement in the photocurrent generation originates from an enhancement in electron-hole pair generation induced by the SPR of the plasmonic gold nanoparticles rather than the extension of the electron lifetime. Moreover, we introduced a novel method to enhance the photocurrent of TiO2 by a multiple plasmonic effect, i.e., LSPR of plasmonic gold nanoparticles and the grating-coupled propagating SP on a gold grating. We fabricated the AuNP-TiO2 nanocomposites on a gold-coated Blu-ray disc recordable (BD-R). The enhancement of the photocurrent due to the combination of LSPR and the grating-coupled SP was investigated.

Laser irradiation effect on carbon overcoat for HAMR application

Heat‐assisted magnetic recording (HAMR) applies a laser beam to heat the disk magnetic recording unit in a hard drive. It lowers the coercivity of the recording material temporarily before data writing and thus overcomes the superparamagnetic limit. This approach can largely increase the storage density of hard disk drives. To apply it to current hard disk drive, all data recording component including carbon overcoats on hard disk surfaces should have high thermal stability because any degradation or film diffusion may affect the drive performance. To explore HAMR application suitable carbon overcoats, this paper studies the HAMR laser effect on different hard disk carbon overcoats and discusses the related material property change mechanism. Copyright © 2014 John Wiley &amp; Sons, Ltd.

HAMR HDD shock responses

Heat assisted magnetic recording (HAMR) and slim mobile hard disk drives (HDD) are being developed parallelly to maintain cost advantage over the solid state drive. Operational shock and non-operational shock capabilities are seriously challenged for the slim HDDs due to reduced stiffness (thickness). It is worse for slim HAMR drives due to additional laser diode (LD) and other necessities being added on slider. Shock tests are part of the key performance matrices that must be passed in HDD reliability tests, and the concerns for HAMR mobile drives are, (1) slider lift-off G-level degradation during op-shock, and (2) LD back-to-back hitting during non-operational shock. We studied a few potential HAMR HGA designs, also analyzed a design that improves drive op-shock performances.

BD-R 장기보존 특성 평가를 위한 가속 열화 실험 조건과 안정성 평가 기준에 관한 연구

The Blu-ray Disc Recordable(BD-R) is one of strong candidates for archival application among optical media formats, because of its large capability. However, the well-defined accelerated aging test conditions and evaluation criteria have not yet been fully confirmed for BD-R. In this study, the data stability and degradation aspect of BD-R were analyzed by the random-symbol error rate(R-SER) measurement after the accelerated aging test. And a reasonable test condition of accelerated aging for BD-R and the appropriate evaluation criterion using R-SER measurement were discussed.

Contact Stress-Induced Micromagnetic Behavior in Magnetic Recording Disk

Stress plays an important role in the magnetic properties of ferromagnetic materials. Sliding contact in hard disk drives can lead to tribological failures of the disk in terms of data loss and demagnetization. However, the relationship between contact stress-induced magnetization changes and tribological failures of magnetic recording disk is rarely discussed. In this study, the contact stress-induced micromagnetic behavior in magnetic recording disk was investigated using micromagnetic simulation. A micromagnetic model including the magnetostriction effect into the Landau–Lifshitz–Gilbert equation was developed to simulate the stress effect on the magnetization changes. Then finite element analysis was used to calculate the critical stresses for the occurrence of data loss and demagnetization of perpendicular magnetic recording disk under sliding contact according to our previous experimental results. Based on these simulation results, it was found that the magnetic moment decreased by 8.9 % under the critical stress for data loss, and it rotated 55.7° under the critical stress for demagnetization. In addition, the simulated static domain structures when data loss and demagnetization occur were in agreement with the previously reported experimental results. Finally, the relationship between the contact stress-induced tribological failures and micromagnetic behavior of the magnetic disk was illustrated. It was proposed that data loss is caused by the magnetization reduction, while demagnetization is caused by the magnetization rotation.

Thermomechanical Contact Between Magnetic Recording Head and Disk Defect Accounting for Heat Partition Factor

The formation of defects on a magnetic recording disk is one of the critical issues in the reliability of a hard disk drive. When a magnetic recording head comes into contact with a disk defect, the resulting surface damage can cause significant degradation on read/write performance. Considering the carbon atoms in diamond like carbon (DLC) coating can experience phase change and oxidation under high temperature (i.e., mechanical softening process due to the thermal stability), the frictional heat generated by the sliding contact between a head slider and a disk defect can lead to severe damage on the head DLC film. In addition to the mechanical degradation of the head DLC film, the magnetic properties of underlying read/write elements and shield materials can also be deteriorated due to the mechanical stress and high temperature rise. In this paper, the thermomechanical contact between a head slider and a disk defect was systematically examined through analytical modeling and simulations. For the three different disk defects (i.e., Al2O3, SiO2, and AlTiC), the temperature rise and distribution on the contact area were determined from a theory of contact mechanics and heat transfer with the modified Francis heat partition factor. To obtain more physical insight into the thermomechanical head disk contact, parametric study was performed using a modified control parameter (ψ*), which was made of material properties of a disk defect and system operating conditions. According to the simulation results, it was observed that Al2O3 showed the worst thermomechanical contact performance among the three defects as it generated the highest flash temperature of 439.0°C on the head DLC film. The increased surface temperature was high enough to degrade the head DLC film as well as the underlying magnetic materials. Moreover, it was found that the surface temperature rise on a head slider was proportional to the values of ψ*.

A-P-1 液体ナノ薄膜の流動特性に関する実験的研究

In the head-disk interface (HDI) of a hard disk drive (HDD), the effects of lubricant deformation on the flying characteristics of a head slider increase as the flying height decreases. Therefore, it is very important to investigate the deformation and flow characteristics of lubricant on a recording disk. In particular, in heat-assisted magnetic recording (HAMR), laser heating of the lubricant induces surface tension distribution and evaporation of lubricant, which may cause deformation of the lubricant film. In this paper, flow characteristics of liquid nano-film of perfluoropolyether (PFPE) film on solid substrate is investigated experimentally. Using the modified Boltzmann-Matano method, diffusion coefficients of liquid nano-step are calculated. In addition, thicknesses of mobile layer and bonded layer of PFPE are measured.