• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1998-2003
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• 2007

A flexible but implantable polyimide-based neural implant was fabricated for reliable and stable long-term monitoring of neural activities from brain. The developed neural implant provides 3-dimensional (3D) $3{\times}3$ structure, avoids any hand handling, and makes the insertion more efficient and reliable. Any film curvature caused by residual stress was not observed in the electrode. The 3D flexible polyimide electrode penetrated a dense gel whose stiffness is close to live brain tissue, because a ${\sim}1{\mu}m$ thick nickel was electroplated along the edge of the shank in order to improve the stiffness. The recording sites were positioned at both side of the shank to increase the probability of recording neural signals from a target volume of tissue. Impedance remained stable over 72 hours because of extremely low moisture uptake in the polyimide dielectric layers. At electrical recording test in vitro, the fabricated electrode showed excellent recording performance, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• The Korean Journal of Pain
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• v.29 no.1
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• pp.23-28
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• 2016

Background: Sacral nerve stimulation is a therapeutic option with demonstrated efficacy for conditions presenting with perineal pain caused by different etiologies. We aimed to assess whether a sacral electrode ($Interstim^{(R)}$, Medtronic, Minneapolis, MN, USA) inserted through the caudal pathway is able to offer an acceptable level of sacral stimulation and rate of catheter migration. Methods: We present 12 patients with pelvic pain who received sacral neuromodulation via the sacral hiatus with the InterStim electrode. We evaluated patient satisfaction as well as migration and removal of the electrode, if necessary. Results: Our experience included 12 patients, 10 women and two men, with a mean age of 60 years. In eight of the 12 patients, the initial therapy was effective, and the final system implantation was performed. During subsequent follow-up, patient satisfaction was good. To date, there have been no cases of electrode displacement or migration. Conclusions: The caudal insertion of the InterStim electrode, with its own fixation system, and initially designed for transsacral insertion, appears in our experience to be a satisfactory option which can minimize electrode displacements, achieving similar results in therapeutic efficacy and causing no difficulties in removal.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.278.1-278.1
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• 2013

Among the prerequisites for stable neural interfacing are the long-term stability of electrical performance of and the excellent biocompatibility of conducting materials in implantable neural electrodes. Reduced graphene oxide offers a great potential for a variety of biomedical applications including biosensors and, particularly, neural interfaces due to its superb material properties such as high electrical conductivity, decent optical transparency, facile processibility, and etc. Nonetheless, there have been few systematic studies on the graphene-based neural interfaces in terms of biocompatibility of electrode materials and long term stability in electrical characteristics. In this research, we prepared the primary culture of rat hippocampal neurons directly on reduced graphene oxide films which is chosen as a model electrode material for the neural electrode. We observed that the viability of primary neuronal culture on the present structure is minimally affected by nanoscale graphene flakes below. These results implicate that the multilayer films of reduced graphene oxides can be utilized for the next-generation neural interfaces with decent biocompatibility and outstanding electrical performance.

• Journal of Biomedical Engineering Research
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• v.34 no.1
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• pp.34-39
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• 2013

For the biocompatibility test of implantable devices or for the sensitivity evaluation of biomedical sensors, it is required to understand the mechanism of the protein adsorption and the interaction between the adsorbed proteins and cells. In this study, the adsorption of proteins in a cell culture medium with fetal bovine serum onto an indium tin-oxide electrode was characterized by using linear sweep voltammetry and impedance spectroscopy. We immersed the fabricated ITO electrodes in the culture medium for 30, 60, or 90 min, and then measured the electrochemical properties of electrodes with 10 mM $Fe(CN){_6}^{3-/4-}$ and 0.1 M KCl electrolyte. With an increase of contacting time, the anodic peak current was decreased and the charge transfer resistance was increased. However, both parameters were recovered to the values before contact with the medium after the treatment of Trypsin/Ethylenediaminetetraacetic acid hydrolyzing proteins.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.72-73
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• 1998

A new method for enzyme immobilization has been developed to remove interference by potential interferents in body fluids. Instead of using electron mediators, we chose direct hydrogen peroxide measurement route. Extremely hydrogen peroxide-selective polymer was coated as an inner membrane to exclude interferents and then glucose oxidase(GOx) was entrapped by electropolymerization of inert monomers. There was no solvent casting step throughout the whole fabrication procedure but all membranes on Pt-Ir electrode were formed by electropolymerization. Thus, membrane thickness, quantity of enzyme loaded and can be controlled by electrochemical parameters. As a result, reproducibility of biosensor characteristics becomes remarkably improved in terms of mass production.

• Journal of Chest Surgery
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• v.16 no.2
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• pp.190-198
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• 1983

The management of cardiac arrhythmias by cardiac pacing has increased greatly since the treatment of complete heart block with an external transcutaneous pacemaker in 1952, followed by the use of myocardial wires connected to an external pulse generation, by external transvenous pacing, and then by transvenous pacing with implantable components in thoracic wall.By now, the three bases of modern cardiac pacing for bradyarrhythmias had been established [1] an implantable device [2] the transvenous approach [3] the ability of the pacemaker to sense cardiac activity and modify its own function accordingly. In transvenous implantation of a pacemaker, any one of four vessels at the root of the neck is suitable for passage of the electrode - cephalic vein, external jugular vein, internal jugular vein, costo-axillary branch of the axillary vein. The new technique of direct puncture of the subclavian vein, either percutaneously or after skin incision only has been made, is invaluable & is used routinely. We have experienced one 25 years old patient who had rheumatic mitral stenosis & minimum aortic regurgitation with sinus bradycardia associated with premature atrial tachycardia & another 54 years old female patient who was suffered from sick sinus syndrome with sinus bradycardia & sinus arrest. The 1st patient was taken open mitral commissurotomy & aortic valvuloplasty and then was taken atrlal pace-maker implantation through If subclavian puncture method in post-op 14 days, and the second patient was taken atrial pacemaker implantation through If subclavian puncture method. Their postop course was in uneventful & were discharged, without complication. Their condition have been good to now.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.45-49
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• 2010

$Li_2PtO_3$ thin film electrodes, which might be possible candidate for the cathode materials for implantable batteries, were synthesized using an electrostatic spray deposition (ESD) technique onto a platinum foil substrate. Single phase $Li_2PtO_3$with a structure similar to layered $LiCoO_2$ structure were synthesized by spraying a precursor solution of $CH_3CO_2Li2H_2O$ in ethanol onto a Pt substrate at temperatures ranging from 200 to $400^{\circ}C$ followed by annealing at above $600^{\circ}C$. Lithium carbonate was the only major phase at temperatures up to $500^{\circ}C$. The X-ray diffraction (XRD) peaks of the Pt foil substrate and lithium carbonate disappeared at temperatures >$600^{\circ}C$. The volumetric capacity of the $Li_2PtO_3$ thin film synthesized using the ESD technique was approximately 817 mAh/$cm^3$, which exceeded that of $LiCoO_2$ (711 mAh/$cm^3$).

• Journal of Biomedical Engineering Research
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• v.38 no.6
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• pp.277-284
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• 2017

This paper presents an implantable pH measurement electrode for wireless gastroesophageal reflux measurement. Usually, gastroesophageal reflux is diagnosed by a catheter-type wire connection between the esophagus and the diagnostic device which brings many side effects such as restriction of daily living, pain, and discomfort in the nasal cavity and pharynx of patients. In order to solve these issues, researchers have been studied a wireless measurement method and a micro-sized pH electrode for human body insertion is necessary. Commercial glass packaged pH meter is formed by a sensing and a reference electrodes in a KCl solution. However, if the glass meter is inserted into the human body, there are risks of leakage of the solution, breakage of the glass package, injury of the body elements. Therefore, the solution should be solidified on the micro-sized noble metal wire which has a characteristic of biocompatible. After solidified wire fabrication, the designed meter was tested for feasibility of measurement and the result was well agreed with pH values of commercial pH meter. Potentials in pH 1 to 12 solution was measured to obtain the sensitivity of the sensor with linearity. And we have designed a simulation of gastroesophageal reflux with symptom frequency, interval, and duration time in pH 2 solution. The proposed sensor has capable to get the same potential for 24 measurements in 3 days, and it has sensed same pH values of 2 for one hour with every 10 minutes. Furthermore, the sensor was survived for 48 hours with reasonable potentials in the acid solution.

• Journal of Chest Surgery
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• v.32 no.5
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• pp.428-432
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• 1999

Background: It has been shown that low-grade electrical stimulus can transform fatigue resistant muscles which then can be used to protect the heart. The bulky and cumbersome power sources of the artificial heart or implantable ventricular assist devices are still in need of solution; however, on the other hand, the implantable ventricular assist devices using the resistant muscles as the power source have the advantages of using its own muscle contractions. The purpose of this study was to determine the possibility of a clinical application of the skeletal muscle ventricle. Material and Method: Latissimus dorsi muscles (LDM) of 8 canines were used for skeletal muscle ventricle. A latex chamber was wrapped one and a half times with LDM. The chamber was attached to a pressure transducer via Tygon tube. An electrode stimulator was placed around the thoracodorsal nerve and LDM was stimulated in cyclic bursts of 0.31 sec on time and 6.0 sec off time using 3.0 volt Itrel stimulator. The preload volume was added to the system in 25cc increments. Ejection volumes, pressures, and peak power outputs were measured. Result: Ejection volume was 76.3cc with 0cc of preload. Ejection volumes were less than 70ml with increments of preload over 75cc Pressures were more than 107 mmHg when the preloads were less than 75cc and less than 100 mmHg when the preloads were more than 100cc. Peak power output of 16.6 W/kg was observed at 50cc preload. Conclusion: Depending on the changes of preload, the volumes ejected from skeletal muscle ventricle and pressures from the skeletal muscle contraction surpassed those of the normal heart. These data suggest that there are clinical applications for skeletal muscle ventricular assist system.