• Journal of the Semiconductor & Display Technology
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• v.2 no.4
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• pp.37-40
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• 2003

We have studied micro-machining technologies to fabricate parts and sensors used in the semiconductor equipment. The studies were based on the silicon integrated circuit processes, and composed of the anisotropic etching of single crystal silicon to fabricate a membrane structure for hot and cold junctions in the infrared absorber. KOH and TMAH were used as etching solutions for the anisotropic wet etching for membrane structure formation. The etching characteristic was observed for the each solution, and etching rate was measured depending upon the temperature and concentration of the etching solution. The different characteristics were observed according to pattern directions and etchant concentration. The pattern was made to incline $45^{\circ}$ on the primary flat, and optimum etching property was obtained in the case of 30 wt% and $90^{\circ}C$ of KOH etching solution for the formation of the membrane structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.18-26
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• 2001

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in 1~2 GHz frequency region are analyzed by it's input impedance which was calculated by three dimensional finite element method formulated as eigenvalue problem using electro-mechanical wave equation and boundary condition. It was extracted that the resonant and the spurious characteristics considering the effects of electrode area and shape variation and unsymmetry of upper and lower electrode. Those effects couldn't be analyzed by on dimensional analysis, e.g. Mason equivalent model. The simulation result was confirmed by comparing with the simulation data from Mason model analysis and the measured data of the ZnO FBAR fabricated using micro-machining technique. Also, through the simulation of the area variations of FBAR, it was obtained that the optimum ratio of length and thickness is 20:1 and the minimum ratio is 5:1 to operate thickness vibration mode.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.3
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• pp.173-179
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• 2004

In this study, the influence of heat treatment and Ca contents on the electrochemical behavior was investigated. Mg-Ca alloys, i.e., Mg-0.22wt%Ca, Mg-0.56wt%Ca, Mg-1.31wt%Ca are prepared by ingot metallurgy. As-cast Mg-Ca alloys exhibited better electrochemical properties than pure Mg. Especially, Mg-0.22wt%Ca alloy improves its anode efficiency up to 62% and lowers the OCP up to -1.72VSCE. Microstructure and XRD patterns of Mg-Ca alloys show that additive Ca element is mainly solid-solutioned. While, the others show the microstructure and XRD pattern with large $Mg_2Ca$ at grain boundary. To assess the effect of heat treatment on the as-cast Mg-alloy, the specimens were heat treated at $200^{\circ}C$ for 2 hours under $CO_2$ gas atmosphere. Although corrosion properties of Mg-Ca alloys are somewhat deteriorated by heat treatment at $200^{\circ}C$ Mg-0.22wt%Ca alloy with uniformly distributed nano-sized $Mg_2Ca$ phase in ${\alpha}$-Mg matrix show still better corrosion properties than pure Mg specimen.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.871-876
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• 2019

We fabricated concave optical fiber tips using hydrofluoric acid solution and photothermal effect induced by $1.55{\mu}m$ wavelength laser applied to an optical fiber. The radius of curvature of the concave optical fiber tips fabricated with different applied laser power, etching time, and concentration of hydrofluoric acid was measured with an optical microscope. Then, we analyzed how the radius of curvature changes for those three variables. In addition, the reliability of the measurement method using a microscope was verified through a free spectral range(FSR) and a scanning electron microscope(SEM). Through this paper, the radius of curvature can be adjusted by the variables of the fabrication process of concave optical fiber tips; thus, it is overcoming the limitations of conventional optical fiber etching methods using hydrofluoric acid solutions.

• Design & Manufacturing
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• v.17 no.3
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• pp.48-54
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• 2023

In this study, an injection mold with ultra-small surface properties was manufactured using nanosecond laser processing. A superhydrophobic characteristic analysis was performed on the PET specimen manufactured through this. To this end, a hydrophobic pattern was defined using the Cassie-Baxter model. The defined features were selected with a spot diameter of 25um and pitch spacing of 30um and 35um. As a result of the basic experiment, it was confirmed that the fine pattern shape had an aspect ratio of 1:1 when the pitch interval was 35um and 20 iterations. Through the determined processing conditions, a hydrophobic pattern was implemented on the core surface of KP4. A specimen with a hydrophobic pattern was produced through injection molding. The height of the molded hydrophobic pattern is 20 ㎛ less than the depth of the core and the contact angle measurement results are 92.1°. This is a contact angle smaller than the superhydrophobic criterion. Molding analysis was performed to analyze the cause of this, and it was analyzed that the molding was not molded due to the lack of pressure in the injection machine.

• Restorative Dentistry and Endodontics
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• v.32 no.2
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• pp.130-137
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• 2007

This in vitro study examined the effect of surface defects on cutting blades on the extent of the cyclic fatigue fracture of HEROShaper Ni-Ti rotary files using fractographic analysis of the fractured surfaces. A total of 45 HEROShaper (MicroMega) Ni-Ti rotary flies with a #30/.04 taper were divided into three groups of 15 each. Group 1 contained new HEROShapers without any surface defects. Group 2 contained HEROShapers with manufacturing defects such as metal rollover and machining marks. Croup 3 contained HEROShapers that had been clinically used for the canal preparation of 4-6 molars A fatigue-testing device was designed to allow cyclic tension and compressive stress on the tip of the instrument whilst maintaining similar conditions to those experienced in a clinic. The level of fatigue fracture time was measured using a computer connected the system. Statistical analysis was performed using a Tukey's test. Scanning electron microscopy (SEM) was used for fractographic analysis of the fractured surfaces. The fatigue fracture time between groups 1 and 2, and between groups 1 and 3 was significantly different (p<0.05) but there was no significant difference between groups 2 and 3 (p>0.05). A low magnification SEM views show brittle fracture as the main initial failure mode At higher magnification, the brittle fracture region showed clusters of fatigue striations and a large number of secondary cracks. These fractures typically led to a central region of catastrophic ductile failure. Qualitatively, the ductile fracture region was characterized by the formation of microvoids and dimpling. The fractured surfaces of the HEROShapers in groups 2 and 3 were always associated with pre-existing surface defects. Typically, the fractured surface in the brittle fracture region showed evidence of cleavage (transgranular) facets across the grains, as well as intergranular facets along the grain boundaries. These results show that surface defects on cutting blades of Ni-Ti rotary files might be the preferred sites for the origin of fatigue fracture under experimental conditions. Furthermore this work demonstrates the utility of fractography in evaluating the failure of Ni-Ti rotary flies.

• Journal of Periodontal and Implant Science
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• v.32 no.3
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• pp.523-537
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• 2002

The present study was performed to evaluate the effect of tetracycline - HCl on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, SLA surface and $TiO_2blasted$ surface were used. Implant surface was rubbed with 5Omg/ml tetracycline - HCl solution for ${\frac}{1}{2}$ min., 1 min., $1{\frac}{1}{2}$ min., 2 min., and 3min. respectively in the test group and with no conditioning in the control group. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. In the pure titanium machined surfaces, the control specimen showed a more or less rough machined surface composed of alternating positive and negative lines corresponding to grooves and ridges. After treatment, machining line was more pronounced for the control specimens. but in general, test specimens were similar to control. 2. In the SLA surfaces, the control specimen showed that the macro roughness was achieved by large-grit sandblasting. subsequently, the acid-etching process crated the micro roughness, which thus was superimposed on the macro roughness. 3. In the SLA surfaces, irrespective of the application time of 50mg/ml tetracycline-HCl solution, in general, test specimens were similar to control. 4. In the $TiO_2blasted$ surfaces the control specimen showed the rough surface with small pits. The irregularity of the $TiO_2blasted$ surfaces with 50mg/ml tetracycline-HCl solution was lessened and the flattened areas were wider relative to the application time of tetracycline - HCl solution. In conclusion, pure titanium machined surfaces and SLA surfaces weren't changed irrespective of the application time of tetracycline-HCl solution. And the $TiO_2blasted$ surfaces conditioned with tetracycline - HCl solution began to be changed from $1{\frac}{1}{2}$ min. This results are expected to be applied to the regenerative procedures for peri-implantitis treatment.

• Journal of Biomedical Engineering Research
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• v.23 no.3
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• pp.217-225
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• 2002

The implantable middle ear(IME) system, which has good sound quality. superior sound intelligibility and wide frequency characteristics. can resolve the sound distortion and ringing effect by sound feedback at high gain operation those are the major problems of conventional hearing aid. In this paper, we have manufactured the IME system using differential electromagnetic transducer(DET) and verified the performance of the system by carrying out vibration and animal implanting experiment. The DET was manufactured using micro-machining technology and vibration experiment of the transducer was performed to inspect whether the transducer could vibrate in accordance with the applied sound signal or not. And the result of the loaded experiment using temporal bone sampled from cadaver showed that the transducer can drive the middle ear bone and transmit the signal to inner ear After the internal unit of IME system was implanted in a dog. the auditory brainstem response (ABR) test was carried out. The result of the test indicated the Proper behavior of the IME system in the living body From the results of the experiments, it is verified that the manufactured system ewll work well when it is applied to human and a basis of clinical experiment of IME system to real human hearing impaired was be arranged.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.921-937
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• 2005

Mechanical and chemical methods are the two ways to treat the implant surfaces. By using mechanical method, it is difficult to eliminate bacteria and by-products from the rough implant surface and it can also cause the structural change to the implant surface. Therefore, chemical method is widely used in order to preserve and detoxicate the implant surface more effectively. The purpose of this study is to evaluate the effect of tetracylcline- HCl on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, SLA surface and $TiO_2blasted$ surface were used in this study. Implant surface was rubbed with sponge soaked in 50mg/ml tetracycline - HCl solution for $\frac{1}{2}$ min., 1min., $1\frac{1}{2}$ min., 2 min., and $2\frac{1}{2}min.$ respectively in the test group and with no treatment in the control group. The sponge was soaked in every 30 seconds. Then, the specimens were processed for scanning electron microscopic observation. Based upon the analysis of photographs by three dentists who are not related with this study, the results were obtained as follows; 1. In the pure titanium machined surfaces, the control specimen showed a more or less rough machined surface composed of alternating positive and negative lines corresponding to grooves and ridges. After treatment, machining line was more pronounced for the control specimens. but in general, test specimens were similar to control. 2. In the SLA surfaces, the control specimen showed that the macro roughness was achieved by large-grit sandblasting. Subsequently, the acid-etching process created the micro roughness, which thus was superimposed on the macro roughness. Irrespective of the application time of 50mg/ml tetracycline - HCl solution, in general, test specimens were similar to control. 3. In the $TiO_2blasted$ surfaces, the control specimen showed the rough surface With small pits. The irregularity of the $TiO_2blasted$ surfaces with 50mg/ml tetracycline - HCl solution was lessened and the flattened areas got wider after 1 minute.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.390-397
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• 2022

Parylene-C which was mainly used for industries such as electronics, machinery and semiconductors has recently been in the spotlight in the medical field due to its properties such as corrosion resistance and biocompatibility. In this study we intend to derive a plan to improve the bonding strength of Parylene-C coating with the SUS304 base material for medical use which can be applied to various medical fields such as needles, micro needles and in vitro diagnostic device sensors. Through plasma pretreatment the bonding strength between Parylene-C and metal materials was improved. It was confirmed that the coated surface was hydrophobic by measuring the contact angle and the improvement of the surface roughness of the sample manufactured through CNC machining was confirmed by measuring the surface roughness with SEM. Through the above results, it is thought that it will be effective in increasing usability and reducing pain in patients by minimizing friction when inserting medical devices and in contact with skin. In addition it can be applied to various application fields such as human implantable stents and catheters, and is expected to improve the performance and lifespan of medical parts.