Siridech Boonsang

A numerical model for ultrasonic measurements of swelling and mechanical properties of a swollen PVA hydrogel

This paper presents a numerical model for the evaluation of mechanical properties of a relatively thin hydrogel. The model utilizes a system identification method to evaluate the acoustical parameters from ultrasonic measurement data. The model involves the calculation of the forward model based on an ultrasonic wave propagation incorporating diffraction effect. Ultrasonic measurements of a hydrogel are also performed in a reflection mode. A Nonlinear Least Square (NLS) algorithm is employed to minimize difference between the results from the model and the experimental data. The acoustical parameters associated with the model are effectively modified to achieve the minimum error. As a result, the parameters of PVA hydrogels namely thickness, density, an ultrasonic attenuation coefficient and dispersion velocity are effectively determined. In order to validate the model, the conventional density measurements of hydrogels were also performed.

A Computational Model of Magnetic Drug Targeting in Blood Vessel using Finite Element Method

This paper purposes a numerical model of drug targeting using wedge-like magnetic device. The magnetic liquids play a crucial role as drug carriers in the human body. The wedgelike magnetic is also utilized to focus magnetic liquids. The finite element method, FEM, is applied to solve two important sets of partial differential equation. Electromagnetic field is described by Maxwell equation and velocity field is expressed by Navier-Stoke equation. The result shows the potential to target drug in the tumor cell locally.

An interferometric back focal plane microellipsometry for the determination of optical properties of a slider's air bearing surface

This paper presents a back focal plane microellipsometer combined with a polarized shifting interferometer. This system is used for the determination of optical phase shift on reflection of a sliders air bearing surface. These optical properties are essential parameters for the flying height measurements in a HDD manufacturing process. The resulting phase shifting images were processed by using Windowed Fourier filters and phase unwrapping techniques, in order to precisely determine the phase of a back focal plane image. The phase images were then used to determine the optical phase shift on reflection values. The results from an aluminum sample show that the measured optical phase shift on reflection values are comparable to the standard values.

The rework study and simulation on solder bridging of TuMR magnetic head

The Hard Disk Drive is the important storage component in computer. The high volume of Hard Disk Drive manufacturing is required. The cost improvements are strictly focused on yield, direct material, indirect material, and operation cost. The defect reduction is a important key to improve cost. The small percentage of defect reduction will contribute the huge profit for manufacturing due to the high volume manufacturing. The defect rework is a good idea to bring back profit from the scrap cost and the waste eliminate cost. This paper will show a alternative rework area on solder bridging defect which is a major defect in Head Gimbals Assembly process. The reworking process considers the product function and critical parameters.

Cloud-based Optical Characterization of Hard Disk Drive Recording Heads

1Department of Electrical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, 1, Soi Chalong Krung 1, Chalong Krung Road, Ladkrabang, Bangkok 10520, Thailand 2Center of Industrial Robots and Automation (CiRA), College of Advanced Manufacturing Innovation (AMI), King Mongkut’s Institute of Technology Ladkrabang, 1, Soi Chalong Krung 1, Chalong Krung Road, Ladkrabang, Bangkok 10520, Thailand

Highly-transparent multi-layered spin-coated silk fibroin film

In this study, the silk fibroin films with different numbers of layers were fabricated by the spin-coating method and their optical transmittances were observed. The process to synthesise the silk fibroin solution was explained – starting from the silk cocoon until the silk-fibroin solution, approximately 7.5% concentration wt/vol, was obtained. The solution was spin-coated onto clean glass substrates to fabricate samples. Totally 10 samples with different numbers of layers, from 1 to 5 layers, were obtained. All samples can be separated into two groups: those left dried at room temperature after spin-coating and those heated at 60°C. They were then measured for their transmittance over the visible-to-near-infrared region. All samples exhibited the high transmittance where the values were at 95% and 98%, for the samples at room temperature and those at 60°C, respectively. This was believed to be due to the heating effect that caused the silk fibroin to arrange itself after being heated, hence the higher transmittance. These high transmittances were maintained regardless of the number of layers and length of heating time. Results from this study could be used to fabricate a silk fibroin film with high optical transmittance and adjustable other properties.

An image-based visual servo control system based on an eye-in-hand monocular camera for autonomous robotic grasping

This paper presents an image-based visual servo control system incorporating with an eye-in-hand monocular camera without using the interaction matrix as traditional method. Instead, we propose the modified image-based visual servo control system for monocular from point error and area error. By using the method derived from the point error and area error of features and one value of the simple depth estimation, we can find camera velocity whereas a traditional method we need to know every depth values for each feature for determining the camera velocity. In addition, a physical eye-in-hand robot system is developed and implemented in order to validate the proposed algorithm. The experimental results obtained from the systems show significant improvement in control performances.

A micro-ellipsometry method based on polarization shifting interferometry for determining complex reflective index

In hard disk drive (HDD) industry, the flying height measurement is one of the key processes for validating the recording head production. In order to assure the reliability of the HDD, the flying performance of recording heads has to be measured and compared with the original design. However, as the capacity of HDD increases exponentially, the design of the flying height of a recording head has to be as low as about 10 nanometer. Thus, the precision of flying height measurement is of critical importance. One important input parameter of the flying height measurement is the complex refractive index of the surface of recording heads. In this paper, we present a novel technique for measuring complex reflective index of a relatively small spot size (0.1 micron) using a combined micro-ellipsometry and phase shifting interferometer. This paper shows that the measurement of the complex reflective index can be done for each recording head and that improved precision of the flying height measurement can be obtained.

Uncertainty analysis of polarization interferometric measurements of hard disk drive recording head-media dynamic spacing

In this paper the numerical method based on Monte Carlo techniques is utilized for the analysis of the flying height measurement uncertainty. In the current flying height tester, the prediction of error is the main concern in order to assure the attainable precision. In previous study, a simplified analytical method is normally used and it may not provide the accurate results of the error prediction especially when the amount of the flying height values becoming as low as sub-5 nm. In this paper, instead of using the analytical method for error analysis, the numerical method based on Monte-Carlo techniques is utilized. Our simulation results show that the measurement uncertainty is mainly from the variation in the optical constants of the DLC layer. They also show that the increasing of standard deviation of the optical constants of DLC layer causes the higher measurement uncertainty.

A solder bridging rework study and an experimental investigation of the TuMR magnetic head

The TuMR reader was designed with high sensitivity for high areal density magnetic recording in the hard disk drive. The assembly process requires the use of solder jet welding on small connectors in the head circuit. The solder bridging problem is the cause of the major mechanical yield loss. This work considers how to resolve the bridging problem without degrading the TuMR sensor by examining the use of Nd:YAG laser reheating. The use of double laser pulses yields better results than the use of single pulses. The critical parameters of the TuMR sensor are monitored with the Quasi tester.