필렛효과에 따른 미세혈관 문합커플러(AnaFix<SUP>Ⓡ</SUP>) 마이크로핀의 응력재분포

지대원(Dae-Won Jee),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

Automated anastomosis using the Microvascular Anastomotic Coupler System (MAC) have lately increased by overcoming disadvantages of conventional suturing technique. In this study, we also developed a new automated anastomotic coupler system, AnaFix<SUP>ⓡ</SUP>, with improvement of the predicate device. We found that the micro-sized pins, which could lead to optimal end-to-end anastomoses, were critical in designing the ring-pin system of the AnaFix<SUP>ⓡ</SUP>. Materials for micro-sized pins can be chosen among 316 Stainless Steel, Ti-6Al-7Nb, Ti-6Al-4V ELI, and Unalloyed Titanium which are biocompatible and equivalent with those of the predicate device. The pinheads are usually shaped like arrows to prevent failures of anastomosis as vessels are manually inserted into the pins and can easily fall out. In this study, the most ideal materials and shapes for the micro pins were suggested using the Finite Element Analysis (FEA) based on the conditions mentioned above. In particular, we evaluated stress redistribution with the effect of fillets and further observed damaged hardness or portion of the pins. The detailed projects performed in the study were as follows. 1) Effect of variations in pinheads' shape and diameter. 2) Deformation behavior of micro-pins produced by four different materials, 316 Stainless Steel, Ti-6Al-7Nb, Ti-6Al-4V ELI and Unalloyed Titanium. 3) Evaluation of stress concentration behavior and maximum load from the effects of fillets with four different conditions. As a result, we found the optimal condition in order to effectively redistribute stress concentration, which occurred on the notch of the rings during anastomosis, and increase allowable load by 2.3 times.

고온과 고압축하중에서 압전 세라믹의 비선형 거동 관찰

지대원(Dae Won Jee),김상주(Sang-Joo Kim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-2

필렛효과에 따른 미세혈관 문합커플러(AnaFix<SUP>Ⓡ</SUP>) 마이크로핀의 응력분포

지대원(Dae-Won Jee),김철웅(Cheol-Woong Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.11

기존 봉합사를 이용한 미세혈관수술의 단점을 개선한 기계식 미세혈관 문합시스템은 크게 문합링-핀 시스템 및 디바이스로 구분된다. 유한요소해석을 이용한 본 연구에서 문합링파트는 생체적합성과 사출성형 가공성이 우수한 High Density Polyethylene(HDPE)가 적용되었고, 마이크로핀은 SUS316, Ti-6Al-4Nb, Ti-6Al-4V, unalloyed titanium 이상 4가지 재료가 적용되었다. 미세혈관 문합링 마이크로핀의 fillet radius, neck length가 von Mises stress 변화에 미치는 영향을 평가하기 위해 Short Neck(SN)과 Long Neck(LN)으로 구분하고, 필렛이 존재하지 않는 경우(SN-1, LN-1)와 존재하는 경우(SN-2, SN-3, LN-2, LN-3)로 구분하였다. 필렛 유무와 형상에 대한 von Mises stress의 변화비인 Fillet Radius Rate(FRR)와 동일 필렛형상 내에서 neck 길이변화에 따른 von Mises stress의 변화비인 Neck Length Rate(NLR)의 결과를 종합해본 결과 SN-3의 마이크로핀 neck 형상이 가장 안전한 설계 형상임을 파악할 수 있었다. An automated anastomotic ring-pin system consisting of both the anastomotic ring-pin system and the coupler device has eliminated the drawbacks of the suture method. High density polyethylene (HDPE), a material with outstanding biocompatibility and injection molding capability, was used in the ring. SUS316 stainless steel, Ti-6Al-4Nb, Ti-6Al-4V, and unalloyed titanium were used in FEM simulations of the micropin. The authors categorized the microvascular anastomotic ring micropins into short neck (SN) and long neck (LN) groups in order to evaluate the effect of the micropin's fillet radius and neck length on the von Mises stress. The micropins were further divided into those with and without fillet. On the basis of the fillet radius rate (FRR), which represents the rate of change in the von Mises stress with respect to the availability and shape of the fillet, and the neck length rate (NLR), which represents the rate of change in the von Mises stress with respect to changes in the length of the neck within the fillet shape, it can be concluded that the SN-3 neck design is the most stable.

하지강성 가변 인공건 액추에이터(Leg Stiffness controllable Artificial Tendon Actuator, LeSATA™)의 개발

한기봉(Gi-Bong Han),어은경(Eun-Kyung Eo),지대원(Dae-Won Jee),양영규(Young-Gyu Yang),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

If we can design a knee actuating mechanism as a primary actuator for supporting knee extension, it might be possible to revolutionarily store or release elastic strain energy, which is consumed during the gait cycle, and as a result leg stiffness is expected to increase. In this case, it is necessary to design an ankle actuating mechanism as a secondary actuator which will adjusted excessive artificial leg stiffness from the primary actuator by reserving or releasing the elastic strain energy, because the energy, which is a part of kinetic and potential energy generated by human walking and is temporarily reserved in collision phase, will be discharged in rebound phase of elastic recoil. Dissimilar to previous study, we assumed that the leg stiffness could be increased by controlling walking speed with relative angular velocity of two segments and accordingly we are currently developing a knee-ankle two actuator system. As mentioned above, however, the artificial knee actuating will generate a new compensatory mechanism in the ankle part. It suggests that excessive leg stiffness caused by the artificial knee actuating will lead to a stumbling gait in abnormal collision phase accompanied by foot touch-down. Therefore, in designing the actuators we also considered the increase in walking speed and stumbling from repetitive acceleration in swing phase of previous gait cycles, satisfying the conditions with regard to relative angular velocity of two segments, thigh and shank, in order to raise leg stiffness. Furthermore, it might be difficult to confirm the effectiveness of the actuators if kinematic energy from unnecessary human walking is released under artificial deceleration control, which was designed to prevent an increase in walking speed. Therefore, we believed that the solution for the compensatory mechanism in ankle joint would be conversely derived by confirming the effect of changes in metatarsophalangeal joint tilt angle and walking speed on knee movement. Accordingly, we invented a new generation leg stiffness actuator in order to avoid the stumbling gait from the ankle joint compensatory mechanism caused by leg stiffness. The trademark of the device is called Leg Stiffness Artificial Tendon Actuator (LeSATA™). The stiffness between two springs could be variably controlled by adding eccentric mass inside the actuator, LeSATA. We also verify the functionality of the actuator which will automatically transfer between walking and running mode by actively monitoring any changes in gait pattern of LeSATA™ and in relative angular velocity between thigh and shank.

와전류탐상에 의한 미세혈관 문합용 마이크로링-핀시스템(AnaFix<SUP>®</SUP>)의 자기장민감성 및 전기전도도 평가

박천웅(Cheon-Woong Park),서용범(Yong-Beom Seo),지대원(Dae-Won Jee),양영규(Young-Gyu Yang),김철웅(Cheol-Woong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

Automated devices for microvascular anastomoses are more frequently used lately and the Microvascular Anastomotic Coupler (MAC) System is widely known for its clinically proven ring-pin system. In this study, we also developed a new anastomotic coupler system, AnaFix<SUP>®</SUP>, for secure end-to-end anastomoses. The coupler system consists of two rings and six pins inserted for each ring. Titanium Ti-6Al-4V and HDPE (High Density Polyethylene) are commonly used for micro-sized rings and pins, respectively, due to its bio-compatibility as well as accurate and consistent anastomoses. However, the pins produced by Ti-6Al-4V, which would be permanently implemented, can cause non-uniformity in MRI images by interfering them as artifacts. Therefore, it is necessary to evaluate electric current density, magnetic field sensitivity and electrical conductivity of the Ti-6Al-4V pins in human body to prevent the image distortions created by them. For the study, we performed the following simulations. 1) Calculation of electric current density from the pins in a 1T~4T(Telsa) magnetic field. 2) Evaluation of electrical conductivity of the electric current density. 3) Verification of magnetic susceptibility with comparative displacement of the pins.