Medical System Laboratory

A new process for the fabrication of high current and very low profile micromachined inductors has been developed. This process involves the combination of mechanical lamination and electrodeposition of copper windings by means of LIGA-like lithography through thick epoxy photoresists. The dimension of the fabricated inductor is 16 mm/spl times/19 mm/spl times/1 mm. The fabricated inductor has an inductance value of 1.2 /spl mu/H with DC saturation current of 3 A and an electrical resistance of less than 30 m/spl Omega/ at 10 kHz.

Integrated inductors are typically formed either on a chip or embedded in a package or board. In this work, we explore the possibility of forming inductors in the chip-to-board interconnect layer. The solderless technique of copper (Cu) electroplating bonding is used to simultaneously form inductor structures as well as chip-to-board interconnect. The use of the gap between the chip and substrate for inductors not only increases integration density, but also allows large magnetic cross-sectional areas to be achieved. To demonstrate the technology, a plating-through-mold method has been used in the establishment of tall interconnect or solenoid inductors. For demonstration of the electroplating bonded micro solenoid structures, three- and seven-turn (500mum in height) inductors have been realized with measured inductances of 3.6 and 10.4nH, and Q-factors of 71 and 55, respectively. As an alternative approach, a polymer-core-conductor method in which polymer posts coated with metal are electroplating bonded, has been developed. This approach reduces processing time in the fabrication of the tall metal structures. For the polymer core RF structures, three-, five-, seven-, and 10-turn inductors have been fabricated. These inductors have inductances of 4.2, 7.0, 9.6, and 13.6nH, and Q-factors of 72, 64, 56, and 61, respectively

This paper explores the technological capabilities as well as theoretical limitations of electroplating bonding technology (EBT). EBT is of particular interest for the fabrication of complex three-dimensional electrical components (e.g. inductors, high frequency antennae, etc) as well as high aspect ratio mechanical structures with exotic geometrical features. Two separate substrates, each containing identical arrays of 150 µm tall copper microstructures, are aligned and then joined together using electrodeposition of copper under forced convection conditions to form 300 µm long structures that mechanically and electrically link the two substrates. Theoretical and experimental approaches are used to develop this bonding system. Mass transfer calculations of diffusion and convection are performed to predict optimal fabrication conditions. To demonstrate the ability to predict optimal plating conditions, a test coupon mimicking a chip-scaled interconnect system with 256 chip interconnects is designed, fabricated and characterized. The mechanical and electrical connectivity are verified by formation of daisy-chained test beds. The electrical testing of the bonded system shows an excellent conductivity of 0.097 Ohm/test row. Thermal-cycling-accelerated aging tests are performed over a temperature range from −55 to +125 °C. Electroplating bonded structures show excellent mechanical stability as well as electrical performance.

We demonstrate a micromachined flexible chip-to-board chip interconnect structure for a chip scale package. Micromachined flexible interconnects enable robust operation in high thermal cycling environments, even for high pinout chips due to the flexible interconnect ability to absorb thermal expansion strain. The interconnects on the chip-side and printed wiring board (PWB)-side are united by electroplating bonding technology, a direct bonding technology resulting in solder-free, underfill-free, low temperature joining by means of copper (Cu) electroplating. Over 200 surface micromachined interconnects, which have a thermal relief geometry, are radially arranged on 11 cm substrates. A chip surrogate consisting of glass with integrated platinum (Pt) microheaters mimics a real electronic device under varying thermal loads. The integrated microheaters can simultaneously test mechanical and electrical performance of the interconnects by generation of on-chip temperatures up to 150 C. Lateral and vertical displacement of the interconnects in the thermal environment are measured and simulated. A mechanical reliability test of the chip scale package is successfully performed for 5000 cycles with thermal cycles of 5 min between 40 C to 147 C. No failures were observed during this period.

In multilevel inverter development for 3-phase applications, total number of transformer in the circuit can be reduced by using of cascaded 3-phase transformer circuit instead of single-phase transformer circuit. In the scheme, total number of switching components in the circuit is still a drawback to achieve lower cost and smaller size of the inverter compared with conventional multilevel inverter. This paper includes a challenging method to reduce total switching components in the multilevel inverter by adopting common-arm structure. The proposed inverter has been operated by two control schemes, Newton–Raphson and Equal-area method. After theoretical and experimental comparison of the methods, we found that Newton–Raphson method is useful to eliminate a specific harmonic order. However, the method has a shortcoming in real time operation which is performed by iterative calculation of the nonlinear equations. With Equal-area method, we can easily find the switching angles by calculating a trigonometric function. It can sufficiently minimize Total Harmonic Distortion (THD) of output voltage in real time operation of Digital Signal Processor (DSP).

This paper describes amorphous silicon carbide (a-SiC) film as an alternative material to silicon nitride (SiN) and silicon oxide (SiO2) for the passivation layer of solar cells. We deposited the film on p-type silicon (100) wafers and glass substrates by RF magnetron sputtering using a SiC (99%) target. Structural and optical properties of the films were investigated according to the process temperature (room temperature, 300 °C, 400 °C, 500 °C and 600 °C). The structural properties were analyzed by Raman microscopy and XPS (X-ray Photoelectron Spectroscopy). The XPS showed that the content of SiC in the film is increased when the substrate temperature is higher. The optical properties of the films were examined by UV–visible spectroscopy and Ellipsometer. The optical characteristic measurement showed that the lowest refractive index of the film is 2.65. Also, using carrier lifetime measurement, we investigated the performance of SiC as the passivation layer. At the substrate temperature of 600 °C, we obtained a highest carrier lifetime of 7.5 μs.

In this paper, we describe a method of amorphous silicon carbide film formation for a solar cell passivation layer. The film was deposited on p-type silicon (100) and glass substrates by an RF magnetron co-sputtering system using a Si target and a C target at a room-temperature condition. Several different SiC [Si1-xCx] film compositions were achieved by controlling the Si target power with a fixed C target power at 150 W. Then, structural, optical, and electrical properties of the Si1-xCx films were studied. The structural properties were investigated by transmission electron microscopy and secondary ion mass spectrometry. The optical properties were achieved by UV-visible spectroscopy and ellipsometry. The performance of Si1-xCx passivation was explored by carrier lifetime measurement.

This study introduces optical properties of a columnar structured zinc oxide [ZnO] antireflection coating for solar cells. We obtained ZnO films of columnar structure on glass substrates using a specially designed radio frequency magnetron sputtering system with different growth angles. Field-emission scanning electron microscopy was utilized to check the growth angles of the ZnO films which were controlled at 0°, 15°, and 30°. The film thickness was fixed at 100 nm to get a constant experiment condition. Grain sizes of the ZnO films were measured by X-ray diffraction. A UV-visible spectrometer was used to measure the transmittance and reflectance of the ZnO film columnar structures as a function of the growth angles.

In this paper we introduce mechanical and structural characteristics of diamond-like carbon (DLC) films which were prepared on silicon substrates by radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) method using methane (CH4) and hydrogen (H2) gas. The films were annealed at various temperatures ranging from 300 to 900 °C in steps of 200 °C using rapid thermal processor (RTP) in nitrogen ambient. Tribological properties of the DLC films were investigated by atomic force microscopy (AFM) in friction force microscopy (FFM) mode. The structural properties of the films were obtained by high resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The wettability of the films was obtained using contact angle measurement. XPS analysis showed that the sp3 content is decreased from 75.2% to 24.1% while the sp2 content is increased from 24.8% to 75.9% when the temperature is changed from 300 to 900 °C. The contact angles of DLC films were higher than 70°. The FFM measurement results show that the highest friction coefficient value was achieved at 900 °C annealing temperature.

One of the major trends in traction power electronics is increasing the switching frequencies. The advances in the frequency elevation have made it possible to reduce the total size and weight of the passive components such as capacitors, inductors and transformers in the DC/DC converter and hence to increase the power density. The traction dynamic performance is also improved. This paper describes several aspects relating to the design of resonant DC/DC converter operating at high frequency (10 kHz) and the converter topologies and the control method of maglev, which result in soft switching, are discussed.

Abstract – This paper presents a multilevel inverter configuration which is designed by insertion of a bidirectional switch between capacitive voltage sources and a conventional H-bridge module. The modified inverter can produce a better sinusoidal waveform by increasing the number of output voltage levels. By serial connection of two modified H-bridge modules, it is possible to produce 9 output voltage levels including zero. There are 24 basic switching patterns with the 9 output voltage levels. Among the patterns, we select the 2 most efficient switching patterns to get a lower switching loss and minimum dv/dt stress. We then analyze characteristics of Total Harmonic Distortion (THD) of the output voltage with variation of input voltage by computer-aided simulations and experiments.

From the first pacemaker implant in 1958, numerous engineering and medical activities for implantable medical device development have faced challenges in materials, battery power, functionality, electrical power consumption, size shrinkage, system delivery, and wireless communication. With explosive advances in scientific and engineering technology, many implantable medical devices such as the pacemaker, cochlear implant, and real-time blood pressure sensors have been developed and improved. This trend of progress in medical devices will continue because of the coming super-aged society, which will result in more consumers for the devices. The inner body is a special space filled with electrical, chemical, mechanical, and marine-salted reactions. Therefore, electrical connectivity and communication, corrosion, robustness, and hermeticity are key factors to be considered during the development stage. The main participants in the development stage are the user, the medical staff, and the engineer or technician. Thus, there are three different viewpoints in the development of implantable devices. In this review paper, considerations in the development of implantable medical devices will be presented from the viewpoint of an engineering mind.

In this study, we investigated the low-temperature growth process of carbon nanowalls (CNWs). A microwave plasma-enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on Si and glass substrates using methane (CH4) and hydrogen (H2) gases. CNWs were synthesized at a substrate temperature of 500 °C, and their growth properties depending on their growth time were examined. The vertical and surficial conditions of the grown CNWs depending on the growth temperature were characterized via field-emission scanning electron microscopy (FE-SEM), and the Raman spectroscopy measurements showed structural variations. The optical properties of the CNWs that were synthesized on the glass substrate were analyzed using UV–vis spectroscopy, and it was found that the light transmittance was affected by the form and shape of the CNWs. Energy dispersive spectroscopy (EDS) showed that the CNWs consisted solely of carbon.

The microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow a carbon nanowall (CNW) on a silicon (Si) substrate with hydrogen (H2) and methane (CH4) gases. To find the growth mechanism of CNW, we increased the growth time of CNW from 5 to 30 min. The vertical and surficial conditions of the grown CNWs according to growth time were characterized by field emission scanning electron microscopy (FE-SEM). Energy dispersive spectroscopy (EDS) measurements showed that the CNWs consisted solely of carbon.

The amorphous silicon carbide (a-SiC) film has been considered a good candidate for the rear passivation layer of the high-efficiency silicon solar cell. We describe the results of the post-annealing of an amorphous silicon carbide (a-SiC) film deposited using the radio frequency magnetron sputtering method. The post-annealing was performed with rapid thermal annealing process in three different chamber environments: nitrogen (N2), oxygen (O2), and hydrogen (H2). After the annealing process, the characteristic properties of the films were investigated in several categories. The transmittance of the film was measured with Scinco s-3100 at the 400–800 nm wavelength. The average transmittance increased after the annealing treatment, and the highest transmittance was achieved with the H2 ambient. Using a silicon wafer lifetime tester, we measured the carrier lifetime of the films. We found that the carrier lifetime was highest in the N2 ambient annealing process. Also, the refractive index was determined using an ellipsometer. The measurement indicated that the refractive index of the film decreased in the annealing process, unlike that of the as-deposited film.

A wearable sensing ECG T-shirt for ubiquitous vital signs sensing is proposed. The sensor system consists of a signalprocessing board and capacitive sensing electrodes which together enable measurement of an electrocardiogram(ECG) on the human chest with minimal discomfort. The capacitive sensing method was employed to prevent directECG measurement on the skin and also to provide maximum convenience to the user. Also, low power integratedcircuits (ICs) and passive electrodes were employed in this research to reduce the power consumption of the entiresystem. Small flexible electrodes were placed into cotton pockets and affixed to the interior of a worn tight NIKEPro combat T-shirt. Appropriate signal conditioning and processing were implemented to remove motion artifacts. The entire system was portable and consumed low power compared to conventional ECG devices. The ECG signalobtained from a 24 yr. old male was comparable to that of an ECG simulator.

The ability to take electrocardiographic measurements while performing our daily activities has become the peoplechoicefor modern age vital sign sensing. Currently, wet and dry ECG electrodes are known to pose threats likeinflammations, allergic reactions, and metal poisoning due to their direct skin interaction. Therefore, the maingoal in this work is to implement a very small ECG sensor system with a capacitive coupling, which is able to detectelectrical signals of heart at a distance without the conductive gel. The aim of this paper is to design, implement, andcharacterize the contactless ECG electrodes. Under a careful consideration of factors that affect a capacitive electrodefunctional integrity, several different sizes of ECG electrodes were designed and tested with a pilot ECG device. Avery small cotton-insulated copper tape electrode (2.324 cm2) was finally attained that could detect and measurebioelectric signal at about 500 um of distance from the subject’s chest.

The amorphous silicon carbide (a-SiC) film has been considered a good candidate for the rear passivation layer of the high-efficiency silicon solar cell. We describe the results of the post-annealing of an amorphous silicon carbide (a-SiC) film deposited using the radio frequency magnetron sputtering method. The post-annealing was performed with rapid thermal annealing process in three different chamber environments: nitrogen (N2), oxygen (O2), and hydrogen (H2). After the annealing process, the characteristic properties of the films were investigated in several categories. The transmittance of the film was measured with Scinco s-3100 at the 400–800 nm wavelength. The average transmittance increased after the annealing treatment, and the highest transmittance was achieved with the H2 ambient. Using a silicon wafer lifetime tester, we measured the carrier lifetime of the films. We found that the carrier lifetime was highest in the N2 ambient annealing process. Also, the refractive index was determined using an ellipsometer. The measurement indicated that the refractive index of the film decreased in the annealing process, unlike that of the as-deposited film.

The loss of urinary bladder control/sensation, also known as urinary incontinence (UI), is a common clinical problem in autistic children, diabetics, and the elderly. UI not only causes discomfort for patients but may also lead to kidney failure, infections, and even death. The increase of bladder urine volume/pressure above normal ranges without sensation of UI patients necessitates the need for bladder sensors. Currently, a catheter-based sensor is introduced directly through the urethra into the bladder to measure pressure variations. Unfortunately, this method is inaccurate because measurement is affected by disturbances in catheter lines as well as delays in response time owing to the inertia of urine inside the bladder. Moreover, this technique can cause infection during prolonged use; hence, it is only suitable for short-term measurement. Development of discrete wireless implantable sensors to measure bladder volume/pressure would allow for long-term monitoring within the bladder, while maintaining the patient's quality of life. With the recent advances in microfabrication, the size of implantable bladder sensors has been significantly reduced. However, microfabricated sensors face hostility from the bladder environment and require surgical intervention for implantation inside the bladder. Here, we explore the various types of implantable bladder sensors and current efforts to solve issues like hermeticity, biocompatibility, drift, telemetry, power, and compatibility issues with popular imaging tools such as computed tomography and magnetic resonance imaging. We also discuss some possible improvements/emerging trends in the design of an implantable bladder sensor.

This research investigates plasma-treated and metal-coated carbon nanowalls (CNWs) for use as counter electrodes of dye-sensitized solar cells (DSSCs). The CNWs were synthesized on a fluorine-tin-oxide (FTO) glass substrate using the microwave plasma-enhanced chemical vapor deposition (PECVD) system with methane (CH4) gas. The post-plasma treatment was performed on the CNWs with hydrogen (H2) plasma using PECVD, and the CNWs were sputter-coated with metal films using the RF magnetron sputtering system with a four-inch tungsten (W) target. Then the post-plasma-treated and metal-coated CNWs were used as counter electrodes for the fabrication of the DSSCs. Field-emission scanning electron microscopy (FE-SEM) was performed to obtain cross-sectional and planar images of the grown CNWs. The energy conversion efficiencies of the DSSCs manufactured using the post-plasma-treated and metal-layer-coated CNWs as the counter electrodes were measured.

In this study, diamond films were prepared using the microwave plasma-enhanced chemical vapor deposition (PECVD) system, which included a DC bias system to enhance the nucleation of the films. The films were synthesized on Si wafers with different ratios of methane (CH4) and hydrogen (H2) gases. We have studied the effects of the CH4-to-H2 ratio on the structural and optical properties of diamond films. The thickness and surface profile of the films were characterized via field emission scanning electron microscopy (FE-SEM). Raman was used to investigate the structural properties of the diamond films. The refractive indexes as functions of the CH4-to-H2 ratio were measured using an ellipsometer. The FE-SEM analysis showed that the 3 and 5 sccm CH4 created diamond films. The Raman analysis indicated that a nanocrystalline diamond film was formed at 3 sccm; a general diamond film, at 5 sccm; and films similar to the a-C:H film, at 7 sccm. The ellipsometer measurement showed that the refractive index of the synthesized diamond film was around 2.42 at 3 sccm. This value decreased as the CH4 volume increased.

In this study, the effects of post-plasma treatment on synthesized carbon nanowalls (CNWs) grown with a microwave were investigated. CNWs were synthesized by microwave plasma enhanced chemical vapor deposition (PECVD), employing a mixture of CH4 and H2 gases. The plasma treatment was done in different plasma environments (O2 and H2) but under the same condition of synthesized CNWs. Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and fourier transform infrared spectroscopy (FT-IR) were used to analyze the effects of the post-plasma treatment on the synthesized CNWs. After the H2 post-plasma treatment, no significant changes in the appearance and characteristics of the CNWs were observed. After the O2 post-plasma treatment, on the other hand, the CNWs were etched at a rate of 18.05 nm/sec. The Raman analysis confirmed, however, that the structural changes in the CNWs caused by the O2 post-plasma treatment were insignificant.

Contact electrodes pose threats like inflammation, metal poisoning, and allergic reaction to the user during long term ECG procedure. Therefore, we present a novel noncontact electrocardiographic electrode designed through microelectromechanical systems (MEMS) process. The proposed ECG electrode consists of small inner and large outer circular copper plates separated by thin insulator. The inner plate enables capacitive transduction of bio-potential variations on a subject’s chest into a voltage that can be processed by a signal processing board, whereas the outer plate shields the inner plate from environmental electromagnetic noise. The electrode lead wires are also coaxially designed to prevent cables from coupling to ground or electronic devices. A prototype ECG electrode has an area of about 2.324 cm2, is very flexible and does not require power to operate. The prototype ECG electrode could measure ECG at about 500 um distance from the subject’s chest.

In this paper, we investigated the effect of microwave power, during the plasma-etching of grown carbon nanowalls (CNWs), on the properties of the CNWs. A microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on a glass substrate using a mixture of CH4 and H2 gases. The grown CNWs were plasma-treated under the oxygen ambient (O2) with different degrees of microwave power (500∼1000 W, in steps of 100 W). After the post-plasma treatment, the cross-sectional and planar images of the CNWs were examined via field-emission scanning electron microscopy (FE-SEM) according to the microwave power of the plasma treatment. Then the structural characteristics of the CNWs were analyzed via Raman spectroscopy, and the changes in the light transmittance according to the degrees of the O2 plasma treatment power were analyzed using UV-visible spectroscopy.

The optical and mechanical characteristics of a novel hydrophilic coating material are introduced according to the annealing temperature. As a water-based SiO2-abundant material has perfect transparency, as does glass, and a hydrophilic property, it can be applied to the protective glass for a PV module. After the coating process on the glass substrate, the film was cured at different annealing temperatures of 200–500 °C in 100 °C increments. A UV-visible spectrometer was utilized to measure the optical transmittance of the film. To verify the mechanical properties, the hardness and adhesion of the film were tested using ASTM standard methods. 9H hardness and 5B adhesion were achieved. Self-cleaning characterization was performed with artificial pollutants and with simple watering of the samples. Moreover, the self-cleaning experiment was conducted on a real-sized 40 × 40 cm2 solar panel cover glass with successful results.

The insulation resistance of a ceramic insulator substrate decreases when contaminants are attached to its surface, and this can result in a spark flashover that can trigger accidents involving power transmission or power supply systems. To prevent such accidents, ceramic insulators have to be continually maintained and cleaned regularly. However, removing contaminants attached to ceramic insulators requires the use of much water and entails a high cost. Thus, the maximum washing efficacy with a minimum amount of water should be secured. The surface features of the object that will be washed are an important determinant of the washing capacity. In this study, ceramic insulators are coated with a nano-sized functional thin film by using the spray coating method. The coated ceramic insulators were annealed with an increase in temperature from 100 °C to 400 °C. Then, the surface features of the annealed ceramic insulators were analyzed, and the results of the experiment are presented.

In this paper, a novel anti-pollution coating film developed to enhance the self-cleaning property of glass for the photovoltaic (PV) module is introduced. In the PV system, modules are exposed to pollutants like dust and bird excrement. The coating material was applied to a substrate using different coating methods: spraying, dipping, and brush/fabric coating. The mechanical, optical, and self-cleaning properties of the thin coating layer applied using these three different methods were characterized through surface profile measurement; hardness, adhesion, and contact angle measurement; light transmittance measurement; and a water cleaning test. 9H hardness and 5B adhesion were achieved. Among the coating methods, the bar coating method showed the thinnest film layer, the lowest contact angle (10.6°), and the best water self-cleaning result. Also, the bar-coated film had more than 90% average light transmittance.

Background/aims: Bile acid is an important luminal factor that affects gastrointestinal motility and secretion. We investigated the effect of bile acid on secretion in the proximal and distal rat colon and coordination of bowel movements in the guinea pig colon. Methods: The short-circuit current from the mucosal strip of the proximal and distal rat colon was compared under control conditions after induction of secretion with deoxycholic acid (DCA) as well as after inhibition of secretion with indomethacin, 1,2-bis (o-aminophenoxy) ethane-N,N,N',N'-tetra-acetic acid (an intracellular calcium chelator; BAPTA), and tetrodotoxin (TTX) using an Ussing chamber. Colonic pressure patterns were also evaluated in the extracted guinea pig colon during resting, DCA stimulation, and inhibition by TTX using a newly developed pressure-sensing artificial stool. Results: The secretory response in the distal colon was proportionate to the concentration of DCA. Also, indomethacin, BAPTA, and TTX inhibited chloride secretion in response to DCA significantly (P < 0.05). However, these changes were not detected in the proximal colon. When we evaluated motility, we found that DCA induced an increase in luminal pressure at the proximal, middle, and distal sensors of an artificial stool simultaneously during the non-peristaltic period (P < 0.05). In contrast, during peristalsis, DCA induced an increase in luminal pressure at the proximal sensor and a decrease in pressure at the middle and distal sensors of the artificial stool (P < 0.05). Conclusions: DCA induced a clear segmental difference in electrogenic secretion. Also, DCA induced a more powerful peristaltic contraction only during the peristaltic period.

Introduced herein is a novel hydrophilic coating material designed to increase the self-cleaning of ceramic substrates. This material can be applied to various other materials, such as metal, glass, and polymer films. In this study, a thin coating was applied to each of several ceramic substrates to demonstrate its use as a ceramic insulator in electrical railway systems. Many of these insulators are exposed to polluting environments, such as in tunnels and subterranean sites, leading to electrical power failure. Application of a water-based, self-cleaning coating material would offer an advantage over methods such as photocatalysis, the application of which requires extra energy. Ceramic substrates were coated with the hydrophilic material by means of brushing and spraying, after which the coated layers were cured using different firing methods: natural, microwave, and electrical oven firing. The mechanical and self-cleaning properties of the films were then characterized in terms of their hardness, adhesion, and contact-angle measurements, and the samples were subjected to a water cleaning test. Hardness was measured using the ASTM D3363 test method, and adhesion was tested using the ASTM D3359 method, resulting in 9H hardness and 5B adhesion. To check the wettability of the films, a contact angle analyzer was used. The brush-coated film fired in a microwave environment at 11.2 °C had the smallest contact angle. To measure the film's self-cleaning property, a permanent-marker cleaning test was performed.

We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was applied for local melting of the glass interface in the vicinity of the microchannels. To pattern channels, a pulse energy of 10 μJ was used with a scanning speed of 100 mm/s at a pulse repetition rate of 500 kHz. After 20–30 min of etching in hydrofluoric acid (HF), the glass was welded with a pulse energy of 2.7 μJ and a speed of 20 mm/s. The developed process was as simple as drawing, but powerful enough to reduce the entire production time to an hour. To investigate the welding strength of the fabricated glass device, we increased the hydraulic pressure inside the microchannel of the glass device integrated into a custom-built pressure measurement system and monitored the internal pressure. The glass device showed extremely reliable bonding by enduring internal pressure up to at least 1.4 MPa without any leakage or breakage. The measured pressure is 3.5-fold higher than the maximum internal pressure of the conventional polydimethylsiloxane (PDMS)–glass or PDMS–PDMS bonding. The demonstrated laser process can be applied to produce a new class of glass devices with reliability in a high pressure environment, which cannot be achieved by PDMS devices or ultraviolet (UV) glued glass devices.

We propose a new packaging process for an implantable blood pressure sensor using ultrafast laser micro-welding. The sensor is a membrane type, passive device that uses the change in the capacitance caused by the membrane deformation due to applied pressure. Components of the sensor such as inductors and capacitors were fabricated on two glass (quartz) wafers and the two wafers were bonded into a single package. Conventional bonding methods such as adhesive bonding, thermal bonding, and anodic bonding require considerable effort and cost. Therefore CO2 laser cutting was used due to its fast and easy operation providing melting and bonding of the interface at the same time. However, a severe heat process leading to a large temperature gradient by rapid heating and quenching at the interface causes microcracks in brittle glass and results in low durability and production yield. In this paper, we introduce an ultrafast laser process for glass bonding because it can optimize the heat accumulation inside the glass by a short pulse width within a few picoseconds and a high pulse repetition rate. As a result, the ultrafast laser welding provides microscale bonding for glass pressure sensor packaging. The packaging process was performed with a minimized welding seam width of 100 μm with a minute. The minimized welding seam allows a drastic reduction of the sensor size, which is a significant benefit for implantable sensors. The fabricated pressure sensor was operated with resonance frequencies corresponding to applied pressures and there was no air leakage through the welded interface. In addition, in vitro cytotoxicity tests with the sensor showed that there was no elution of inner components and the ultrafast laser packaged sensor is non-toxic. The ultrafast laser welding provides a fast and robust glass chip packaging, which has advantages in hermeticity, bio-compatibility, and cost-effectiveness in the manufacturing of compact implantable sensors.

We present the selective laser-induced etching (SLE) process and design guidelines for the fabrication of three-dimensional (3D) microfluidic channels in a glass. The SLE process consisting of laser direct patterning and wet chemical etching uses different etch rates between the laser modified area and the unmodified area. The etch selectivity is an important factor for the processing speed and the fabrication resolution of the 3D structures. In order to obtain the maximum etching selectivity, we investigated the process window of the SLE process: the laser pulse energy, pulse repetition rate, and scan speed. When using potassium hydroxide (KOH) as a wet etchant, the maximum etch rate of the laser-modified glass was obtained to be 166 μm/h, exhibiting the highest selectivity about 333 respect to the pristine glass. Based on the optimized process window, a 3D microfluidic channel branching to three multilayered channels was successfully fabricated in a 4 mm-thick glass. In addition, appropriate design guidelines for preventing cracks in a glass and calibrating the position of the dimension of the hollow channels were studied.

In this study, the characteristics of functional films were investigated according to the number of coatings and their heat treatment times. The functional coating films were deposited on glass substrates made of the same material as the cover glass of photovoltaic (PV) modules. Each film was coated once by brushing with a special silica-based solution, and each heat treatment was done using a hot-air fan for 2 min at 300 °C. The substrates were coated once, twice, and thrice, respectively, and were annealed once, twice, and thrice by drying and cooling alternately. The specimens were then analyzed for their anti-pollution properties, contact angles, light transmittance, and mechanical properties. The anti-pollution function was confirmed through a self-cleaning test, while the contact angle and light transmittance were examined using special equipment. Mechanical properties, including hardness and adhesion, were confirmed using the standard hardness testing method (ASTM D3363) such as those using an H-9H, F, HB, or B-6B pencil (Mitsubishi, Japan) and a standard adhesion testing method (ASTM D3359). It was confirmed that the film coated once yielded a very low contact angle of 8.9° and very good anti-pollution properties. Its adhesion and strength also showed high values of 5B and 9H, respectively.

In this study, the characteristics of functional coating films were investigated to improve the anti-pollution properties and efficiency of PV (Photovoltaic) module according to the variation of coating film thickness. Functional coating was applied of a glass substrate, which was composed with the same material as PV module. Brush coating method was used for the coating process. We coated the functional film on the glass substrate 1, 2 and 3 times alternately in the horizontal and vertical directions to change the film thickness, and a hot air fan equipment was used as a heat treatment process for easy application to existing PV modules. The heat treatment process was performed for 2 minutes after the coating process using a hot air fan equipment. After coating and heat treatment, glass substrates were analyzed for the anti-pollution properties, contact angle, optical properties and the mechanical properties such as hardness and adhesion. The anti-pollution properties were identified through self-cleaning test. The contact angle of the functional coating film was measured by a contact angle analyzer, and the optical properties were measured via UV-visible spectroscopy, which can be used as an integrating sphere. The hardness of the functional film was measured by the standard hardness testing method using H-9H, F, HB and B-6B pencil. Also, the adhesion of the functional film was measured by the standard adhesion testing method.

In this study, the optical and electrical properties of a transparent conductive oxide (TCO) film synthesized via the radio frequency (RF) magnetron co-sputtering of Al-doped ZnO (AZO) and ZnO targets on a glass substrate were investigated. In the visible region, the resistivity, transmittance, and carrier concentration of the TCO film are influenced by the ratio of Al doping. The samples were prepared using two targets with the same deposition condition, except several different power levels on an AZO target to obtain different Al compositions in the film. The power range was 100-160 W in 20 W steps on the AZO target with a constant 50 W power level on the ZnO target. The electrical and optical characteristics of the film were measured using several apparatuses. The cross-section of the films was measured with via field emission scanning electron microscopy (FESEM) to determine the thickness of the film. The electrical and optical properties of the AZO films were measured via Hall measurement and UV-visible spectroscopy. The structural characteristics of the AZO films were confirmed by Raman spectroscopy.

The performance of micromixers, namely their mixing efficiency and throughput, is a critical component in increasing the overall efficiency of microfluidic systems (e.g., lab-on-a-chip and μ-TAS). Most previously reported high-performance micromixers use active elements with some external power to induce turbulence, or contain long and complex fluidic channels with obstacles to increase diffusion. In this paper, we introduce a new type of 3D impeller micromixer built within a single fused silica substrate. The proposed device is composed of microchannels with three inlets and a tank, with a mixing impeller passively rotated by axial flow. The passive micromixer is directly fabricated inside a glass plate using a selective laser-induced etching technique. The mixing tank, with its rotating shaft and 3D pitched blade impeller, exists within a micro-cavity with a volume of only 0.28 mm3. A mixing efficiency of 99% is achieved in mixing experiments involving three dye colours over flow rates ranging from 1.5–30 mL min−1, with the same flow rates also applied to a sodium hydroxide-based bromothymol blue indicator and a hydrochloric acid chemical solution. To verify the reliable performance of the proposed device, we compare the mixing index with a general self-circulation-type chamber mixer to demonstrate the improved mixing efficiency achieved by rotating the impeller. No cracking or breakage of the device is observed under high inner pressures or when the maximum flow rate is applied to the mixer. The proposed microfluidic system based on a compact built-in 3D micromixer with an impeller opens the door to robust, highly efficient, and high-throughput glass-based platforms for micro-centrifuges, cell sorters, micro-turbines, and micro-pumps.

In this study, the characteristics of functional films were investigated according to the number of coatings and their heat treatment times. The functional coating films were deposited on glass substrates made of the same material as the cover glass of photovoltaic (PV) modules. Each film was coated once by brushing with a special silica-based solution, and each heat treatment was done using a hot-air fan for 2 min at 300 °C. The substrates were coated once, twice, and thrice, respectively, and were annealed once, twice, and thrice by drying and cooling alternately. The specimens were then analyzed for their anti-pollution properties, contact angles, light transmittance, and mechanical properties. The anti-pollution function was confirmed through a self-cleaning test, while the contact angle and light transmittance were examined using special equipment. Mechanical properties, including hardness and adhesion, were confirmed using the standard hardness testing method (ASTM D3363) such as those using an H-9H, F, HB, or B-6B pencil (Mitsubishi, Japan) and a standard adhesion testing method (ASTM D3359). It was confirmed that the film coated once yielded a very low contact angle of 8.9° and very good anti-pollution properties. Its adhesion and strength also showed high values of 5B and 9H, respectively.

We demonstrate a two-step hybrid process for fabricating movable parts inside glass substrate using the selective laser-induced etching (SLE) process that is consisted of laser-direct writing and wet chemical etching. To obtain an influence by the optical characteristics of a glass substrate when fabricating a 3D microstructure using the SLE, we analyzed the relationship of their dimensions between the designed and the fabricated devices. Two 3D microfluidic devices are designed and fabricated on glass substrates as the demonstrations of the hybrid process: a 3D microfluidic valve device with a movable plug and a 3D microfluidic mixer with a rotatable impeller and multilayer microchannels. The valving plug and the impeller of each device are successfully moved and rotated. The smallest structure is a pillar of the impeller device, and its size is 29 μm (diameter) × 277 μm (height). We expect this study to be extended to potential applications in 3D glass microfabrication and microfluidic systems.

In this study, a four-inch zinc oxide (ZnO) nanostructure was synthesized using radio frequency (RF) magnetron sputtering to maximize the electrochemical performance of the anode material of a lithium-ion battery. All materials were grown on cleaned p-type silicon (100) wafers with a deposited copper layer inserted at the stage. The chamber of the RF magnetron sputtering system was injected with argon and oxygen gas for the growth of the ZnO films. A hydrogen (H2) reduction process was performed in a plasma enhanced chemical vapor deposition (PECVD) chamber to synthesize the ZnO nanostructure (ZnO NS) through modification of the surface structure of a ZnO film. Field emission scanning electron microscopy and atomic force microscopy were performed to confirm the surface and structural properties of the synthesized ZnO NS, and cyclic voltammetry was used to examine the electrochemical characteristics of the ZnO NS. Based on the Hall measurement, the ZnO NS subjected to H2 reduction had a higher electron mobility and lower resistivity than the ZnO film. The ZnO NS that was subjected to H2 reduction for 5 min and 10 min had average roughness of 3.117 nm and 3.418 nm, respectively.

This study focused on glass-based functional coating fi lms to achieve anti-pollution characteristics and photovoltaic (PV) modules effi ciency improvement. Anti-pollution functional coating fi lm was applied on glass substrate made of the same material as the cover glass for PV modules. The fi lm was applied to the PV module’s surface by spray coating method and was subsequently annealed by torching to demonstrate real fi eld application. The number of coating application varied from 1 to 3 times to obtain diff erent thickness of fi lms. Natural drying of the sprayed fi lm was done by 10 min dwelling. In sequence, fi ring process was performed by torch for 2 min to solidify the sprayed fi lms. For the specimens that completed both coating and annealing processes, characteristics including anti-pollution ability, contact angle, and light transmittance were analyzed. Contact angle was analyzed using a contact-angle analyzer, while light transmittance was analyzed using UV–visible capable of utilizing the integrating sphere. Based on the characteristics analyzed, the manufacturing process of the functional coating fi lm was optimized. If the coating process proposed in this study is applied to PV modules, improvement in anti-pollution characteristics as well as effi ciency can be expected.

This paper presents a silicon-dioxide-coated capacitive electrode system for an ambulatory electrocardiogram (ECG). The electrode was coated with a nano-leveled (287 nm) silicon dioxide layer which has a very high resistance of over 200 MΩ. Due to this high resistance, the electrode can be defined as only a capacitor without a resistive characteristic. This distinct capacitive characteristic of the electrode brings a simplified circuit analysis to achieve the development of a high-quality ambulatory ECG system. The 240 um thickness electrode was composed of a stainless-steel sheet layer for sensing, a polyimide electrical insulation layer, and a copper sheet connected with the ground to block any electrical noises generated from the back side of the structure. Six different diameter electrodes were prepared to optimize ECG signals in ambulatory environment, such as the amplitude of the QRS complex, amplitude of electromagnetic interference (EMI), and baseline wandering of the ECG signals. By combining the experimental results, optimal ambulatory ECG signals were obtained with electrodes that have a diameter from 1 to 3 cm. Moreover, we achieved high-quality ECG signals in a sweating simulation environment with 2 cm electrodes.

Research has shown that pulse transit time (PTT), which is the time delay between the electrocardiogram (ECG) signal and the signal from a photoplethysmogram (PPG) sensor, can be used to estimate systolic blood pressure (SBP) and diastolic blood pressure (DBP) without the need for a cuff. However, the LED of the PPG sensor requires the precise adjustment of both light intensity and light absorption rates according to the contact status of the light-receiving element. This results in the need for regular calibration. In this study, we propose a cuffless blood pressure monitor that measures real-time blood pressure using a microphone instead of a PPG sensor. The blood pulse wave is measured in the radial artery of the wrist using a microphone that can directly measure the sound generated by a body rather than sending energy inside the body and receiving a returning signal. Our blood pressure monitor uses the PTT between the R-peak of the ECG signal and two feature points of the blood pulse wave in the radial artery of the wrist. ECG electrodes and circuits were fabricated, and a commercial microelectromechanical system (MEMS) microphone was used as the microphone to measure blood pulses. The peak points of the blood pulse from the microphone were clear, so the estimated SBP and DBP could be obtained from each ECG pulse in real time, and the resulting estimations were similar to those made by a commercial cuff blood pressure monitor. Since neither the ECG electrodes nor the microphone requires calibration over time, the real-time cuffless blood pressure monitor does not require calibration. Using the developed device, blood pressure was measured three times daily for five days, and the mean absolute error (MAE) and standard deviation (SD) of the SBP and DBP were found to be 2.72 ± 3.42 mmHg and 2.29 ± 3.53 mmHg, respectively. As a preliminary study for proof-of-concept, these results were obtained from one subject. The next step will be a pilot study on a large number of subjects.

SAW filter has been used in mobile communication device, bandpass filter and resonator for merits )f miniaturization and high reliability. Materials for substrate mainly used single crystal such as LiNbO$_{3}$, LiTaO$_{3}$, ZnO. In this study, it was attempted that LiNbO$_{3}$ was substituted for piezoelectric ceramics(PZT4, PZT5A and PZT8) which had simple fabrication process because fabrication of crystal is difficult and it's cost is high. SAW filters were fabricated by the photolithography on piezoelectric ceramics substrates in order to compare their characteristics with LiNbO$_{3}$'s. The experimental value of center frequency was compared with theoretical one. The average difference of center frequency was 3.7%. PZT8 showed the best bandwidth properties among them. It is considered that PZT8 has higher mechanical quality factor and propagation velocity than others.

심혈관계의 실시간 혈압 측정을 위하여 생체 이식형 무선 혈압 센서를 개발하였다. 센서는 MEMS (micro-electro-mechanical system) 기술을 바탕으로 개발되었다. 센서 구조는 포토리소그래피를 이용, 위 아래기판에 형성된 두 개의 인덕터와 두 인덕터 사이 형성된 갭에 의해 만들어진 커패시터로 구성되어진다. 제작된 센서들은 740 mmHg의 기준 압력에서 269∼284 MHz 범위의 공진 주파수를 나타내었다. 혈관내의 혈압 변화를 무선으로 측정하기 위해 network analyzer 원리를 이용, 센서 공진 주파수 변화를 측정할 수 있는 시스템을 자체 개발하였다. 개발된 센서들 중 하나의 센서를 선택, 일반 돼지의 대퇴부 혈관에 삽입, 무선으로 혈관의 혈압 변화를 측정하였다. 측정된 혈압 값은 79/41 (55)이었다 (팽창기 혈압/ 수축기 혈압 (중간 값)). 최초 측정 45일 후 센서의 전기적 생체 호환적 특성을 측정하였다. 생체 동물의 움직임에 의해 혈관으로부터 센서의 이탈이 발견되었으나 센서의 생체 호환성은 우수한 특성을 보였다.

논문에서는 마이크로스트립 안테나 제작에 상용화되어 있는 에폭시계 FR-4 기판과 압전물질인 LiNbO3와 PVDF를 기판으로 사용하여 마이크로스트립 패치 안테나를 제작하였다. 제작된 마이크로스트립 안테나에 DC 전계를 인가하였을 때 압전기판인 LiNbO3와PVDF의 경우 실시간으로 주파수 이동을 구현하여 안테나 제작 후에도 물리적 변형을 가하지 않고 공진주파수와 대역폭을 이동및 조정할 수 있는 단일형 마이크로스트립 패치 안테나를 제작하고 특성을 분석하였다. 압전 특성을 갖는 LiNbO3, PVDF 압전기판과 에폭시계 FR-4 기판을 사용하여 마이크로스트립 패치 안테나를 제작한 후 DC 전계를인가함으로써 공진주파수의 이동을 확인하였다. 실험을 통하여 PVDF 압전기판에 400V/mm까지 DC 전계를 인가하였을 경우 최대각각 17 MHz의 변화 값을 보였고 LiNbO3는 29 MHz의 변화를 보였지만 FR-4 기판에서는 아무런 변화가 없었다. 이러한 결과들로부터 압전기판을 사용한 마이크로스트립 안테나는 안테나 제작 후에도 물리적 변형을 가하지 않고 공진주파수와 대역폭을 이동 및조정할 수 있는 특성을 이용하여 최근 이동통신 분야에 많이 쓰이고 있는 마이크로스트립 안테나에 응용 가능하리라 사료된다.

외부에 노출된 형태로 장착되거나 사용되는 전기전자부품들의 경우 오염에 의한 내구성과 안정성에 문제가 발생한다. 오염 방지의 대표적인 방법인 자기세정(self-cleaning) 효과는 친수성(hydrophilic) 또는 소수성(hydrophobic) 코팅을 통해 구현이 가능하다. 이러한 두 가지 코팅은 물과의 반응을 통해 자기세정이 가능하며, 친수성 코팅의 경우 이물질과 코팅면 사이에 물이 흡수되어 이물질을 분리하고, 소수성 코팅의 경우 이물질이 물방울에 흡수되어 코팅면에서 분리된다. 또한 일부 자기세정 코팅의 경우 빛에 조사되면 화학적으로 이물질을 제거하는 방식도 있다. 본 연구에서는 친수성 무기 코팅을 활용, 박막의 자기세정 효과를 살펴보았고, 합성된 박막의 폭넓은 활용을 위해 강도 및 접촉성과 같은 기계적 특성을 살펴보았다. 박막은 실리콘 기판위에 스핀 코팅 방식으로 도포하였으며 박막의 두께 제어를 위해 스핀 코팅의 회전 속도를 달리하여 (700∼2,500 rpm) 제작하였다. 제작된 박막의 크린성(clean properties)을 테스트하였고, 접촉각 분석과 기계적 특성 분석을 수행하였다.

다이아몬드와 흑연은 탄소 원자로만 이루어져 있다. 그러나 이 둘은 원자의 종류는 하나이지만 성질이 다른 동소체이다. 이는 결합방식의 차이로 인한 것으로, 다이아몬드는 강한 충격을 받아도 원자의 결합이 떨어지지 않지만 흑연은 적은 충격을 받아도 분자단위로 결합이 떨어진다. 흑연의 결합력이 약한 특성으로 인해 많은 연구가 진행되었고, 이로 인하여 새로운 물질들이 발견되었다. 그 중에서 탄소나노월 (Carbon nanowall, CNW)은 화학적으로 매우 안정적이고 기계적 강도가 우수하다. 또한 촉매 없이 기판 위에 직접 성장이 가능하여 공정시간이 짧아 대량생산이 가능하다. 탄소원자들을 겹겹이 세워놓은 형태의 구조이기에 반응 면적이 매우 넓은 장점을 가진다. CNW의 합성에는 화학기상증착 (Chemical Vapor Deposition, CVD) 방식이 주로 사용되며 이 중 마이크로웨이브 방식과 RF (Radio Frequency) inductively coupled plasma 방식이 대표적이며 공정조건에 따라 CNW의 성장 특성이 바뀌기에 활용분야에 따른 공정조건 확보가 요구된다. 본 연구에서는 마이크로웨이브 PECVD (Plasma Enhanced Vapor Deposition) 방법을 사용하여 CNW을 합성하였다. 반응가스로는 메탄 (CH4)을 주가스로 사용하고, 보조가스로 수소 (H2)와 아르곤 (Ar) 그리고 질소 (N2)를 별도로 주입하여 실리콘(Si) 기판 위에 CNW를 합성하였다. 또한 수소와 아르곤을 메탄가스와 함께 반응가스로 사용하여 CNW의 성장 변화 및 저항 특성을 관찰하였다.

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway toincreased the reaction area of graphite electrodes used carbon nanotube (CNT) and porous carbon. CNT is limited todevice utilization in order to used a metal catalyst by lack of surface area to improve. In contrast carbon nanowall(CNW) is chemically very stable. So this paper, microwave plasma enhanced chemical vapor deposition (PECVD) systemwas used to grow carbon nanowall (CNW) on Si substrate with methane (CH4) and hydrogen (H2) gases. To find thegrowth properties of CNW according to the reaction gas ratio, we have changed the methane to hydrogen gas ratios(4:1, 2:1, 1:2, and 1:4). The vertical and surficial conditions of the grown CNW according to the gas ratios werecharacterized by a field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy measurementsshowed structure variations.

We investigated that effects of annealing ambient on the characteristics of functional nano thin film synthesized on glass substrate. The functional nano thin films were annealed by using rapid thermal annealing (RTA) equipment in vacuum, oxygen and nitrogen ambient, respectively. The hardness of the functional nano thin films were measured by a standard hardness testing method (ASTM D3363) such as a H-9H, F, HB and B-6B pencil (Mitsubishi, Japan). Also, the adhesion of the functional nano thin films were measured by a standard adhesion testing method (ASTM D3359) using scotch tape (3M, Korea). The contact angle of the functional nano thin films was measured by a contact angle analyzer (Phoenix 300 Touch, S.E.O.). The optical property of functional nano thin films was measured via UV-visible spectroscopy (S-3100, Scinco).

본 논문은 Micro-Electro-Mechanical System (MEMS) 공정으로 제작된 초소형 압력센서를 이용하여 절취된 기니피그 대장에서 발생하는 연동운동을 압력으로 실시간 측정, 이를 데이터화하였다. 기니피그 대장의 기계적 메커니즘 및 생체 호환성을 고려하여 근위부, 중앙부, 원위부로 나누어진 대장의 압력을 측정할 수 있도록 폴리이미드 기판 위에 air-gap 커패시터를 제작하였다. 제작된 센서는 절취된 대장 내에서 대변이 배변되는 상황을 정확히 구현하기 위해 실제 기니피그 대변과 크기, 모양이 동일한 폴리머 재질의 artificial pellet을 제작하여 압력센서 표면에 부착한 후 대장의 연동운동 시 압력센서가 대변과 같은 움직임을 보이도록 제작하였다. 제작된 센서의 커패시턴스는 impedance analyzer로 측정한 결과 대기압에서 2.5∼3 pF의 커패시턴스 값을 보였으며 자체 제작한 성능평가 시스템과 데이터 측정 장치를 이용하여 센서의 커패시턴스 값을 카운터 값으로 변화하였다. 측정된 커패시턴스는 15,000의 카운트 값으로 변환되었으며 센서의 민감도는 1 mmHg 이하로 나타났다. 대장의 연동 운동을 일으키는 약물인 chenodeoxycholic acid (CDCA)와 deoxycholic acid (DCA)에 의한 인위적인 연동 운동을 측정하기 위해 기니피그에서 절취한 직경 5 mm, 길이 10 cm의 대장 내부에 제작된 압력센서를 삽입한 후 labview와 연동된 측정시스템을 통해 실시간적인 대장의 연동 운동에 의해 발생하는 압력 값을 영상화 및 데이터화 하였다. 실험 결과 기니피그의 대장은 약물의 투여량에 비례하여 압력이 상승하는 것을 확인하였으며, 초소형 압력센서를 통해 대장연동운동에 따른 각 대장근육의 압력 변화를 관찰하였다.

본 논문은 빛을 일정한 방향으로 전달하는 광가이드 특성을 이용하여 디지털 사이니지 베젤에서의 광학적 불연속성을 개선하고자한다. 광학적 성능이 우수한 Polycarbonate에 Light guide film을 부착, 필름 내부에 존재하는 마이크로 사이즈의 구조에 의한 빛의굴절, 반사, 산란의 효과를 발생하였다. 아크(arc) 모양의 polycarbonate 광가이드 필름을 각기 다른 색의 LED source (적색, 녹색)에기계적으로 밀착하여 광학적 전달효과를 관찰하였다. 아크 형태의 광가이드 필름에 빛의 반사 및 산란이 발생하여 녹색과 붉은색의혼합색인 주황색이 발생하는 것을 확인하였다. 이는 일반적으로 베젤이 존재하는 멀티 디지털 사이니지 시스템의 약점인 디스플레이의 광학적 불연속성을 해결할 수 있을 것으로 판단된다.

For the improvement of the anti-pollution properties of porcelain electrical insulators, in this study, we have applied the functional film to the surface of insulator. The functional films were coated on the ceramic substrates which components were like the porcelain electrical insulator. The coating material was applied to ceramic substrate by spray coating method and then the film was cured at around 300oC for 10 minutes with different gas ambient, such as O2, N2, and only vacuum. We have measured the contact angle of the coated surface, and obtained the lowest angle (8.9o) and a strong hydrophilic property at vacuum condition. The anti-pollution properties were measured, revealing that as the contact angle decreased, the anti-pollution properties improved. The mechanical hardness and adhesion were both excellent regardless of the annealing ambient.

다양한 인체 정보 중에서 맥박은 신체의 활력 징후를 확인할 수 있는 가장 기본적인 방법 중의 하나이다. PPG (Photoplethysography )는 하드웨어 구조의 단순함, 저비용 등의 장점으로 많은 웨어러블용 헬스케어 장치에 적용되고 있다. 그러나 PPG방식을 이용한 웨어러블용 헬스케어 장치는 맥박 측정 시 동잡음(motion artifacts) 및 외부 잡음 광에 민감하여 실시간 맥박 측정에 어려움을 갖는다. 외부잡음에 덜 민감한 맥박 측정 장치를 개발하기 위하여 본 연구에서는 MEMS 공정에 의한 초소형 LC 공진형 무선 압력센서를 제작하고, 이를 이용하여 실시간의 맥박을 측정할 수 있는 시스템을 개발하였다. 제작된 무전원 초소형 압력센서의 선형성 및 반복성에 대한 성능 평가 후 공진주파수-압력 변환 방식을 이용하여 요골 동맥 위에서의 맥박 및 맥파를 측정하였다. 측정된 맥박 수는 실제 상용 제품과 비교, 측정함으로써 충분히 유효한 데이터를 얻을 수 있음을 확인하였다. 실시간 측정된 맥박 및 맥파는 블루투스 통신에 의해 단말기에 전송된다.

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of 3 mm × 15 mm × 0.5 mm. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure

본 논문은 프리즘 구조물의 집광효과를 이용하여 옥외용 사이니지 이산형 LED 패널의 광학적 불연속성을 개선할 수 있는 방법적접근에 관한 것이다. 광투과성이 우수한 Polycarbonate에 MEMS(Microelectromechanical systems) 공정 및 극초단파(Femto-second) 레이저를 이용하여 프리즘 형태를 패터닝을 하였다. 패터닝된 polycarbonate는 light guide film의 역할을 하여 서로다른 디스플레이 패널에서 발생하는 빛을 프리즘 구조에 의해 한 곳으로 모이게 함을 확인하였다. Polycarbonate와 디스플레이 패널의 간격에 따라 디스플레이 패널간의 거리를 조절할 수 있었으며 한 곳으로 모인 빛은 마치 두 디스플레이 패널이 연결된 것과 같은효과를 나타내었다. 이는 아웃도어 사이니지용 디스플레이 패널에서 발생하는 문제점인 광학적 불연속성을 개선할 수 있을 것으로보인다.

본 논문에서 심전도 검사에 있어 전도성 연고 사용으로 인한 피부발진과 장시간 측정시 몸의 움직임에 따라 발생하는 동잡음을 감쇄하기 위한 dry-contact 방식의 회로와 전극 구조에 대하여 연구하였다. Dry-contact 전극을 사용할 경우 피부와 전극 사이에 임피던스가 매우 높아 생체 입력 신호를 전기적 회로 전달하기 위해서는 반드시 임피던스 매칭이 필요하다. 또한 생체 동작시 발생할 수 있는 동잡음을 제거하기 위해 전극의 구조는 동잡을 제거할 수 있도록 설계 되어야 한다. 이를 위해 본 연구에서는 피부와 전극 사이의 임피던스를 직접 측정하여 이를 회로에 반영하였고 노이즈 제거를 위해 전극과 의복 사이에 발생하는 전기 마찰력을 제거하기 위해 접지 전극 추가하였다. 이러한 임피던스 매칭 회로와 전극 구조를 이용하여 실제 인가의 피부에 부착하여 발생하는 심전도 신호를 측정하였고 측정된 신호는 제자리 걸음과 안정 상태에서는 노이즈가 완전 제거된 신호를 발생하였다. 이와 더불어 전극의 크기를 변화시켜 크기에 따른 신호의 발생을 실험하였고 전극의 크기가 50 mm일 때 최상의 심전도 신호를 획득할 수 있었다.

본 논문에서는 인체 삽입형 의료기기의 유해성분과 생체 조직의 물리적, 화학적 완전분리를 위해 무선통신 및 무선충전이 용이하며, 인체 조직과 접촉해도 물리적·화학적 반응이 발생하지 않는 생체 적합성 소재인 quartz를 이용한 의료기기 패키징을 개발에 대한 것이다. 패키징의 밀폐성을 평가하기 위해 패키징 내부에 micro-electro-mechanical system (MEMS) 공정을 이용하여 제작된 압력센서와 외부 신호 측정 리더기가 무선으로 통신 가능한 압력센서 시스템을 내장하여 외부 압력변화에 따른 패키징 내부의 압력변화를 측정하였다. 패키징은 압력측정 시스템의 크기를 고려하여 폭 6 cm × 길이 10 cm × 높이 3 cm로 제작되었으며, CO2 레이저 가공을 통해 최종 완성되었다. 제작된 패키징의 밀폐성 평가를 위해 미세 압력조절기와 압력챔버로 구성된 성능평가 시스템을 자체적으로 구성하였으며, 실험은 인체 내에서 발생할 수 있는 압력을 고려하여 대기압과 900 mmHg의 높은 공기압의 환경에서 실시되었다. 그 결과 패키징은 대기압과 900 mmHg의 공기압에서 모두 동일한 count 값 (sensor1 - 25500, sensor2 - 26000, sensor3 – 20800)을 나타냈으며, 이를 통해 패키징의 내부 압력환경이 인체에서 외부 압력변화에 영향을 받지 않는 완전밀폐 되었음을 확인할 수 있었다.

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.

In this paper, we proposed a portable electronic cardiogram and stethoscope (ECGS) that can simulta- neously perform the electrocardiogram (ECG) and auscultation tests to increase the reliability of diagnosis of heart disease. To measure the ECG and heart sound (HS) at the same time, three ECG electrodes and a microphone sensor were combined into a triangular shape with a width of 90 mm and a height of 97 mm that can be held in one hand. In order to prevent skin problems when they contact the patient’s skin, a capacitive coupled electrode was selected as the ECG electrode and a silicone material was used in a chest piece with the microphone sensor. For the signals measured from the electrodes and the chest piece, filters were respectively configured to pass only the signals of 0.01-100 Hz and 20-250 Hz, which are frequency bands for ECG and HS. The filtered ECG and HS analog signals were converted into digital signals and transmitted to a PC using wireless communication for monitoring them. The HS could be auscultated simultaneously using an earphone. The monitored ECG had an SNR of about 34 dB and a P-QRS-T waveform is clearly visible. In addition, the HS had an SNR of about 28 dB and both S1 and S2 are clearly visible. It is expected that it can aid doctors’ inexperience in analyzing the ECG and HS.

In this paper, we present a QRS-complex detection algorithm to calculate an accurate heartbeat and clearly recognize irregular rhythm from ECG signals. The conventional Pan-Tompkins algorithm brings false QRS detection in the derivative when QRS and noise signals have similar instant variation. The proposed algorithm uses amplitude differences in 7 adjacent samples to detect QRS-complex which has the highest amplitude variation. The calculated amplitude is cubed to dominate QRS-complex and the moving average method is applied to diminish the noise signal’s amplitude. Finally, a decision rule with a threshold value is applied to detect accurate QRS-complex. The calculated signals with Pan-Tompkins and proposed algorithms were compared by signal-to-noise ratio to evaluate the noise reduction degree. QRS-complex detection performance was confirmed by sensitivity and the positive predictive value(PPV). Normal ECG, muscle noise ECG, PVC, and atrial fibrillation signals were achieved which were measured from an ECG simulator. The signal-to-noise ratio difference between Pan-Tompkins and the proposed algorithm were 8.1, 8.5, 9.6, and 4.7, respectively. All ratio of the proposed algorithm is higher than the Pan-Tompkins values. It indi- cates that the proposed algorithm is more robust to noise than the Pan-Tompkins algorithm. The Pan-Tompkins algo- rithm and the proposed algorithm showed similar sensitivity and PPV at most waveforms. However, with a noisy atrial fibrillation signal, the PPV for QRS-complex has different values, 42% for the Pan-Tompkins algorithm and 100% for the proposed algorithm. It means that the proposed algorithm has superiority for QRS-complex detection in a noisy environment.