• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.115-116
• /
• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• 대한환경공학회지
• /
• 제31권11호
• /
• pp.965-974
• /
• 2009

본 연구는 가시광선 조건에서 질소 및 황 도핑 $TiO_2$를 활용하여 악취유발 황화유기화합물질의 분해능을 평가하고, 광촉매 분해시 발생하는 촉매 비활성화와 비활성화된 촉매의 재생에 대해 조사하였다. 적외선 분광법을 이용하여 촉매 표면의 특성을 조사하였다. 가시광선을 이용한 광촉매 기술이 낮은 농도의 황화 이메틸(0.039 ppm)과 이황화 이메틸 (0.027 ppm)은 97% 이상의 높은 효율로 처리할 수 있으나, 촉매 비활성으로 인해 높은 농도(황화 이메틸, 7.8 ppm 및 이황화 이메틸, 5.4 ppm)에 대해서는 광촉매 공정 시간 5시간만에 처리 효율이 황화 이메틸은 84% 그리고 이황화 이메틸은 23%까지 매우 낮게 나타났다. 황화 이메틸에 비하여 황 원소가 하나 더 결합된 이황화 이메틸의 광촉매 분해시 촉매가 빠르게 비활성화되었다. 높은 유입 농도 조건에서 이황화 이메틸 또는 황화 이메틸의 광촉매 반응기의 출구 농도가 유 입농도와 비슷하거나, $CO_2$의 생성률이 제로에 가깝거나, FTIR 스펙트럼 상에서 촉매 표면의 비활성을 유발하는 황 이온 화합물의 피크들이 강하게 나타나, 촉매의 비활성화를 확인하였다. 광촉매 반응기의 유출구에서의 최대 $CO_2$ 농도인 8 ppm에 대해서 황화 이메틸의 광물화 효율을 계산한 결과 144%로서 100%를 초과한 것으로 나타났다. 건조-공기 및 습윤-공기 재생 방법에 비해 고온 소성에 의한 촉매의 재생효율이 높게(이황화 이메틸, 53% 그리고 황화 이메틸, 58%) 나타났으나, 이 또한 촉매 비활성을 유발시키는 황 이온 화합물과 같은 부산물들을 완전히 제거되지는 못하는 것으로 확인되었다.

• Journal of Periodontal and Implant Science
• /
• 제44권5호
• /
• pp.242-250
• /
• 2014

Purpose: This study aimed to evaluate the effects of fibronectin and oxysterol immobilized on machined-surface dental implants for the enhancement of cell attachment and osteogenic differentiation, on peri-implant bone healing in the early healing phase using an experimental model in dogs. Methods: Five types of dental implants were installed at a healed alveolar ridge in five dogs: a machined-surface implant (MI), apatite-coated MI (AMI), fibronectin-loaded AMI (FAMI), oxysterol-loaded AMI (OAMI), and sand-blasted, large-grit, acid-etched surface implant (SLAI). A randomly selected unilateral ridge was observed for 2 weeks, and the contralateral ridge for a 4-week period. Histologic and histometric analyses were performed for the bone-to-implant contact proportion (BIC) and bone density around the dental implant surface. Results: Different bone healing patterns were observed according to the type of implant surface 2 weeks after installation; newly formed bone continuously lined the entire surfaces in specimens of the FAMI and SLAI groups, whereas bony trabecula from adjacent bone tissue appeared with minimal new bone lining onto the surface in the MI, AMI, and OAMI groups. Histometric results revealed a significant reduction in the BIC in MI, AMI, and OAMI compared to SLAI, but FAMI demonstrated a comparable BIC with SLAI. Although both the BIC and bone density increased from a 2- to 4-week healing period, bone density showed no significant difference among any of the experimental and control groups. Conclusions: A fibronectin-coated implant surface designed for cell adhesion could increase contact osteogenesis in the early bone healing phase, but an oxysterol-coated implant surface designed for osteoinductivity could not modify early bone healing around implants in normal bone physiology.

• Journal of Periodontal and Implant Science
• /
• 제49권6호
• /
• pp.366-381
• /
• 2019

Purpose: The purpose of this study was to evaluate the effectiveness of conventional sandblasted, large-grit, acid-etched (SLA) surface coated with a pH buffering solution based on surface wettability, blood protein adhesion, osteoblast affinity, and platelet adhesion and activation. Methods: Titanium discs and implants with conventional SLA surface (SA), SLA surface in an aqueous calcium chloride solution (CA), and SLA surface with a pH buffering agent (SOI) were prepared. The wetting velocity was measured by the number of threads wetted by blood over an interval of time. Serum albumin adsorption was tested using the bicinchoninic acid assay and by measuring fluorescence intensity. Osteoblast activity assays (osteoblast adhesion, proliferation, differentiation, mineralization, and migration) were also performed, and platelet adhesion and activation assays were conducted. Results: In both the wetting velocity test and the serum albumin adsorption assay, the SOI surface displayed a significantly higher wetting velocity than the SA surface (P=0.000 and P=0.000, respectively). In the osteoblast adhesion, proliferation, differentiation, and mineralization tests, the mean values for SOI were all higher than those for SA and CA. On the osteoblast migration, platelet adhesion, and activation tests, SOI also showed significantly higher values than SA (P=0.040, P=0.000, and P=0.000, respectively). Conclusions: SOI exhibited higher hydrophilicity and affinity for proteins, cells, and platelets than SA. Within the limits of this study, it may be concluded that coating an implant with a pH buffering agent can induce the attachment of platelets, proteins, and cells to the implant surface. Further studies should be conducted to directly compare SOI with other conventional surfaces with regard to its safety and effectiveness in clinical settings.

• The Journal of Advanced Prosthodontics
• /
• 제10권5호
• /
• pp.374-380
• /
• 2018

PURPOSE. The effect of silica-based glass-ceramic liners on the tensile bond strength between zirconia and resin-based luting agent was evaluated and compared with the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers. MATERIALS AND METHODS. Titanium abutments and zirconia crowns (n = 60) were fabricated, and the adhesive surfaces of the specimens were treated by airborne-particle abrasion. The specimens were divided into 5 groups based on surface treatment: a control group, 2 primer groups (MP: Monobond Plus; ZP: Z Prime Plus), and 2 liner groups (PL: P-containing Liner; PFL: P-free Liner). All specimens were cemented with self-adhesive resin-based luting agent. After 24-hour water storage and thermocycling (5,000 cycles, $5^{\circ}C/55^{\circ}C$), the tensile bond strength was measured using a universal testing machine. Failure mode analysis and elemental analysis on the bonding interface were performed. The data were analyzed using Kruskal-Wallis test, Dunn's post hoc test, and Fisher's exact test. RESULTS. The liner groups and primer groups showed significantly higher tensile bond strengths than that of the control group (P<.05). PFL showed a significantly higher tensile bond strength than the primer groups (P<.05). The percentage of mixed failure was higher in the primer groups than in the control group (P<.001), and all the specimens showed mixed failure in the liner groups (P<.001). A chemical reaction area was observed at the bonding interface between zirconia and liner. CONCLUSION. The application of liner significantly increased the tensile bond strength between zirconia and resin-based luting agent. PFL was more effective than MDP-containing primers in improving the tensile bond strength with the resin-based luting agent.

• 한국산학기술학회논문지
• /
• 제20권12호
• /
• pp.94-101
• /
• 2019

본 연구에서는 초음파 용접기의 진동에너지를 모재에 전달하는 금속 용접용 혼의 형상설계를 위해 해석적 기법을 적용하였으며, 20kHz 영역에서 사용되는 한파장 바 형상을 갖는 용접용 혼의 형상설계를 위해 FEM(Finite Element Method)을 사용하였다. 봉의 종진동 이론을 Ansys APDL(Ansys Parametric Design Language)에 적용하여 혼의 형상을 최적화하였다. 적절한 혼의 형상을 도출하기 위해 진동의 입력면과 출력면의 면적비와 혼의 축방향 길이비를 이용하여 총 25가지의 모델을 설계하였으며, Modal 해석과 Harmonic 해석을 통해 균일한 진동특성을 확보하고자 하였다. 스텝 바혼의 끝단부(팁)의 균일도 90%이상을 확보하기 위해 Harmonic 해석을 통해 길이비, 면적비를 결정하였고 이에 따라 혼의 총길이 130mm, 스텝 길이 65mm, 출력단 면적 28.79mm의 혼을 설계하였다. 설계치수를 바탕으로 Titanium (Ti-6Al-4V)-GR5 재료를 이용하여 혼을 제작하였다. 또한, 별도로 구성된 초음파 용접시스템을 이용하여 혼의 끝단부의 진동 진폭률 및 변위특성을 평가하였다. 최적화된 혼의 진폭률은 51%까지 향상됨을 확인하였다. 최종적으로 균일한 종방향 스텝 바혼을 설계하였으며, 끝단부(팁)의 균일도 97.4%이상을 확보하였다.

• 한국재료학회지
• /
• 제4권3호
• /
• pp.319-328
• /
• 1994

솔-제법에 의한 고분자솔 제조를 위하여 금속 알콕사이드에 $\beta$-diketonate(DKT)기의 유기 리간드를 치환시켜 만든 전구체를 합성한 결과, 가수분해와 축합 반응의 속도 조절이 가능하였고, 이를 이용하여 코팅에 적합한 nm단위의 입자 크기를 갖는 알루미나, 티타니아 솔을 제조하고 그 물성을 파악하였다. 코팅에 적합한 알루미나 솔의 최적조건은 알콕사이드 1몰당 물 1몰, 산 0.3-0.4몰이었다. 티타니아 솔의 제조시는 물/알콕사이드의 몰비가 1이고, 산의 양은 치환수에 따라 달라 1개와 2개 치환된 전구체의 경우 1목의 알콕사이드당 각각 0.25, 0.20몰 이하였다. Dynamic light scattering 장치를 이용하여 제조한 솔의 평균 입자 크기를 측정한 결과 수 nm단위의 미세한 입자를 갖고 있었다. 슬라이드 글라스 위에 코팅하여 $450^{\circ}C$에서 소결한 막을 SEM으로 관찰한 결과 알루미나와 타타니아의 경우 각각 4-4.5$\mu \textrm{m}$, 2-2.5$\mu \textrm{m}$두께의 매끄럽고 균열이 없는 막이 형성되었음을 알 수 있었다. 이때의 입자 크기는 TEM사진을 통하여 알 수 있었으며 티타니아의 경우 수 nm에서 최대 30nm, 알루미나는 1-2nm이하 심지어 수 $\AA$정도의 입자들로 이루어졌음을 관찰하였다. 또한 회절무늬 분석 결과 알루미나는 $\gamma$구조, 티타니아는 anastase결정임을 알 수 있었다.

• 자원환경지질
• /
• 제40권5호
• /
• pp.661-673
• /
• 2007

안성 청룡사삼층석탑의 구성암석은 대부분 편마상 복운모 화강암과 세립질 화강암으로 이루어져 있다. 이 석탑은 거의 전면에 걸쳐 나타나는 부재의 균열과 결실이 탑의 구조안정성을 위협한다. 또한 표면의 무기오염물과 다양한 서식형태를 갖는 생물침해는 석재표면의 손상을 가중시키고 있다. 따라서 이 연구에서는 석탑에 대한 종합적인 비파괴훼손도 진단을 수행하고 이를 근거로 풍화를 저감시키기 위해 최소한의 보존처리를 수행하였다. 보존처리에서는 석탑의 전면에 걸쳐 자생하는 지의류 및 생물오염물을 건식 및 습식 세정하였으며, 과거 이 석탑의 보수에 사용되었던 노화된 콘크리트를 제거하고 합성수지를 이용하여 복원하였다. 부재사이에 삽입된 부식된 철편은 티타늄 강철 합금으로 교체하였으며, 모든 공정이 완료된 후에 석질 강화처리를 실시하였다. 또한 석탑의 지반과 주위환경을 보강하고 정비하였으며 관람객에 의한 손상을 제어하기 위한 보호시설을 설치하였다.

• 구강회복응용과학지
• /
• 제32권3호
• /
• pp.194-201
• /
• 2016

목적: 본 연구는 Co-Cr, Ti-6Al-4V 합금에 Zirconium Nitride (이하 ZrN) 적용 시, 의치상 레진과의 접착력을 비교하는 것이다. 연구 재료 및 방법: Co-Cr, Ti-6Al-4V 디스크(직경 10 mm, 두께 2.5 mm)를 각각 14개씩 제작하였고, ZrN 코팅에 따라 2개의 그룹으로 나누었다. Primer로 시편 전처리 후, 의치상 레진(직경 6 mm, 두께 5 mm)을 부착하였다. 표면 측정기를 이용하여 시편의 거칠기를 측정한 후, 만능 시험기를 이용하여 전단결합강도를 측정하였으며, 이원분산분석으로 통계 분석하였다. 시편 표면과 파절 양상을 주사전자현미경을 이용하여 관찰하였다. 결과: ZrN을 코팅한 시편에서 유의하게 높은 표면 거칠기를 나타내었고(P < 0.05), 전단결합강도는 낮았다(P < 0.001). ZrN 코팅 시편에서는 혼합성 파절과 부착성 파절이 함께 나타났다. 결론: Co-Cr, Ti-6Al-4V 합금에서 ZrN 코팅 처리는 의치상 레진과의 결합력을 약화시켰다.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제31권1호
• /
• pp.41-45
• /
• 2009

Background: Reduced bone height is one of the major problems faced in restoring tooth loss with implants. By the use of short implants, it is possible to reduce complicated and invasive treatment such as bone graft, allowing more simple surgery. But short implants are generally considered to have lower success rates than that of standard implants. Purpose: To assess the results of short Straumann implants by a retrospective study of short Straumann implants with TPS(titanium plasma-sprayed) and SLA(sandblasted, large grit, acid etched) surfaces. Materials and methods: 173 implants in 106 patients who received short Straumann implant surgery(${\le}8\;mm$) in the department of oral and maxillofacial surgery, Kyunghee Dental Hospital, from February 1996 to October 2006 were selected and studied. All of the implants were followed up after prosthetic rehabilitation. The average follow-up period was 34 months with 119 months as the longest follow up period. The average follow-up period after prosthetic rehabilitation was 31 months. 64 females(60.4%) and 42 males(39.6%) participated in the research with the age range of 19 to 85(mean age 47). 20 patients(18.9%) were under 40, 85 patients(80.2%) were over 40 and under 70, and only one patient(0.9%) was over 70 years old. Results: 27 implants(15.6%) had TPS surface while 146 implants(84.4%) had SLA surface. 9 implants(5.2%) were 3.3, 108 implans(62.4%) were 4.1mm and 56 implants(32.4%) were 4.8mm in diameter. 167 implants(96.5%) were 8mm and 6 implants(3.5%) were 6mm in length. There were 24 implants(13.9%) on the maxillas and 149 implants(68.8%) on the mandibles. 119 implants(68.8%) were rehabilitated with FPD(fixed partial denture), 47 implants(27.2%) with single crowns and 4 implants(2.3%) with overdentures. Among the fixed partial dentures, 30 of them were splinted with short implants only. After over an year of follow-up period, 139 implants(96.5%) out of 144 implants showed marginal bone loss of less than 1mm. 3 out of 173 implants failed showing 98.27% survival rate. Conclusions: The use of short Straumann implants(${\le}8mm$) can be a simple and reliable treatment method in minimal residual bone height.