Sunkil Park

A novel microactuator for microbiopsy in capsular endoscopes

This paper presents a LiGA (a German acronym for lithographie, galvanoformung, abformung) process based microactuator to be used for microbiopsy in capsular endoscopes. This microactuator is designed to be integrated into a capsular endoscope and to extract tissue samples inside the small gastrointestine which a conventional endoscope cannot reach. The proposed microactuator was fabricated as a cylindrical shape of diameter 10 mm and length 1.8 mm. This actuator consists of three parts: a microbiopsy part with a microspike, an actuating part with a torsion spring and a triggering part with a shape memory alloy (SMA) heating wire and polymer string. In order to extract sample tissue, a microspike in the developed actuator moves forward and backward using the slider-crank mechanism. For low power consumption triggering, a polymer-melting scheme was applied. The SMA heating wire consumed approximately 1.5 V × 160 mA × 1 second (66.67 µWH) for triggering. The precise components of the microactuator were fabricated using the LiGA process in order to overcome the limitations in accuracy of conventional precision machining. The developed microactuator was evaluated by extracting tissue samples from the small intestine of a pig ex vivo, and examining the tissue with hematoxylin and eosin (H&E) staining protocol. The experimental tests demonstrated that the developed microactuator with microspike successfully extracted tissue samples from the pigs small intestines.

Barbed micro-spikes for micro-scale biopsy

Single-crystal silicon planar micro-spikes with protruding barbs are developed for micro-scale biopsy and the feasibility of using the micro-spike as a micro-scale biopsy tool is evaluated for the first time. The fabrication process utilizes a deep silicon etch to define the micro-spike outline, resulting in protruding barbs of various shapes. Shanks of the fabricated micro-spikes are 3 mm long, 100 ?m thick and 250 ?m wide. Barbs protruding from micro-spike shanks facilitate the biopsy procedure by tearing off and retaining samples from target tissues. Micro-spikes with barbs successfully extracted tissue samples from the small intestines of the anesthetized pig, whereas micro-spikes without barbs failed to obtain a biopsy sample. Parylene coating can be applied to improve the biocompatibility of the micro-spike without deteriorating the biopsy function of the micro-spike. In addition, to show that the biopsy with the micro-spike can be applied to tissue analysis, samples obtained by micro-spikes were examined using immunofluorescent staining. Nuclei and F-actin of cells which are extracted by the micro-spike from a transwell were clearly visualized by immunofluorescent staining.

Sensing behaviour of semconducting metal oxides for the detection of organophosphorus compounds

Abstract Sensing behaviours of doped SnO 2 and ZnO elements have been investigated for the detection of organophosphorus compounds. Among the elements examined, SnO 2 − or ZnO-based elements doped with basic oxides such as CaO and MgO exhibit a promising sensing property to DMMP (dimethyl methylphosphonate). Reasonable sensitivity can be obtained at concentrations of DMMP down to 44 ppb. The test gas was oxidized upon exposure to the oxides. It has been suggested that the basic oxide additives are effective in aiding dissociative adsorption of DMMP on the oxide surface, thus facilitating the oxidation reaction of the test gas.

Optimal Clustering of Kinetic Patterns on Malignant Breast Lesions: Comparison between K-means Clustering and Three-time-points Method in Dynamic Contrast-enhanced MRI

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is useful for breast cancer diagnosis and treatment planning. Nevertheless, due to the multi-temporal nature of DCE-MRI data, the assessment of early stage breast cancer is a challenging task. In this study, we applied an unsupervised clustering approach and cluster validation technique to the analysis of malignant intral-tumoral kinetic curves in DCE-MRI. K-means cluster analysis was performed from real world malignant tumor cases and the data were transformed into an optimal number of reference patterns representative each cluster. The optimal number of clusters was estimated by a cluster validation index, which was calculated with the ratio of inter-class scatter to intra-class scatter. This technique then classifies tumor specific patterns from a given MRI data by measuring the vector distances from the reference pattern set, and compared the result from the k- means clustering with that from three-time-points (3TP) method, which represents a clinical standard protocol for analysis of tumor kinetics. The evaluation of twenty five cases indicates that optimal k-means clustering reflects partitioning intra-tumoral kinetic patterns better than the 3TP technique. This method will greatly enhance the capability of radiologists to identify and characterize internal kinetic heterogeneity and vascular change of a tumor in breast DCE-MRI.

Robust SOI process without footing for ultra high-performance microgyroscopes

A microgyroscope with flat bottom surfaces is fabricated by combining the SOI (silicon on insulator) method with the SBM (sacrificial bulk micromachining) process [1/spl sim/3]. Roughened bottom surfaces and loose silicon fragments are common problems in deep silicon RIE (Reactive Ion Etching) using SOI wafers. In this paper, the silicon fragments are removed and the roughened bottom surfaces are smoothed by the SBM process to achieve robust performance. A gyroscope is fabricated by the proposed method. The measured noise equivalent resolution is 0.0044/spl deg//sec, and the measured bandwidth is 12.8 Hz. The linearity of output is within 7.4% for /spl plusmn/50/spl deg//sec range.

A disposable MEMS-based micro-biopsy catheter for the minimally invasive tissue sampling

This paper presents a novel minimally invasive MEMS (micro-electromechanical system)-based micro-biopsy catheter for the diagnosis of gastrointestinal tissue samples. Conventional macro-scale biopsy tools such as biopsy forceps often cause a significant discomfort, infectious risk, and injury to the patients. In this study, a disposable micro-scale biopsy tool is proposed for the first time and MEMS technology is implemented for the fabrication process. Micro-biopsy catheter successfully extracts tissue samples from the small intestines of the anesthetized rabbit and pig. The proposed micro biopsy catheter is found to be useful in minimally invasive diagnosis.

A Novel Micro-Biopsy Actuator for Capsular Endoscope using LIGA Process

This paper presents the LiGA (a German acronym for lithographie, galvanoformung, abformung) process based microactuator to be used for microbiopsy in capsular endoscopes. This microactuator is designed to be integrated into a capsular endoscope and to extract tissue samples inside small gastrointestine which a conventional endoscope cannot reach. The proposed microactuator was fabricated as a cylindrical shape of diameter 10 mm and length 1.8 mm. This actuator consists of 3 parts: microbiopsy part with microspike, actuating part with torsion spring, and triggering part with shape memory alloy (SMA) heating wire and polymer string. In order to extract sample tissue, a micro-spike in the developed actuator moves forward and backward using slider-crank mechanism. For the low power consumption triggering, polymer-melting scheme was applied. The SMA heating wire consumed approximately 1.5 V times 160 mA times 1 sec (66.67 muWH) for triggering. The precise components of the microactuator were fabricated using the LiGA process in order to overcome the limitations in accuracy of conventional precision machining. The developed microactuator was evaluated by extracting tissue samples from small intestine of a pig ex vivo, and examining the tissue with the Hematoxylin and Eosin (H&E) staining protocol. The experimental tests demonstrated that developed microactuator with microspike successfully extracted tissue samples from the pigs small intestines.

Novel Valveless Micro Suction Pump Using a Solid Chemical Propellant

Recently, various micro injection pumps with different driving forces have been reported. However, attributed to the poor performance and reliability of valves in the micro scale, no micro suction pump has found a successful application thus far. In this paper, a valveless micro suction pump, using a solid chemical propellant, azobisisobutyronitrile (AIBN), is developed for the first time. This novel pump is designed based on the Bernoulli Principle applied to a Venturi tube. That is, for an incompressible fluid, a negative pressure is generated as the fluid is accelerated through a vena contracta section. In the designed pump, the width of the vena contracta section is 350 µm, and the width ratio of the input fluid inlet and the vena contracta section is approximately 8.5:1. The core of this pump is a propellant chamber with an AIBN matrix, which generates biologically inert N2 gas as it is heated by an underlying micro heater. The generated gas passes through the Venturi tube producing a negative pressure at the front section of the vena contracta in the Venturi tube. The pump and channels are fabricated by curing polydimethylsiloxane (PDMS) on a silicon mold which was patterned using the deep RIE process. The micro pump is tested for sampling porcine gastric juice. Heating the AIBN core for 3 seconds successfully pumped approximately 20 µl of gastric juice, showing the pump’s potential applicability to various lab-on-a-chip devices and systems.

A Hub-protein based Visualization of Large Protein-Protein Interaction Networks

According as the protein-protein interaction (PPI) data more increase, we need to optimally visualize them as network, in that describing the relationship among proteins is able to easily analyze biological processes happened in a cell. In this paper, to fast layout large-scale PPI networks, we proposed a method taking hub-proteins into consideration, which have more interactions than any other proteins in a network. In other words, it enforces two core parts of Walshaws multilevel force-directed placement algorithm (MLFDP) to be modified. The modification is achieved by coarsening and expanding all neighboring proteins of hub-protein just once, whereas only two proteins in Walshaws method. Our experiments show that the quality of layout is better optimal and time cost is reduced up to 63% in comparison with other methods.

Nickel Micro‐spike for Micro‐scale Biopsy using LiGA Process

In this paper, biopsy tools are developed for minimally invasive tissue sampling using the LiGA (Lithographie Galvanoformung Abformung) process. The micro‐spike is composed of two barbed‐shanks and a body. The shank of the micro‐spike is between 2 mm ∼ 3 mm and the opening gap is approximately 350 μm between the shanks. The micro‐spike is integrated with the conventional catheter, for medical diagnostics. Tissue samples were extracted from the anesthetized pigs using biopsy catheters in vivo, and observed with hematoxylin and eosin (H&E) staining. The amount of extracted sample is sufficient to diagnose abnormal cells.