• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.19-26
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• 2022

In droplet microfluidics, precise droplet manipulation is required in numerous applications. This study presents ultrasonic surface acoustic wave (USAW)-based microfluidic device for label-free droplet separation based on size. The proposed device is composed of a slanted-finger interdigital transducer on a piezoelectric substrate and a polydimethylsiloxane microchannel placed on the substrate. The microchannel is aligned in the cross-type configuration where the USAWs propagate in a perpendicular direction to the flow in the microchannel. When droplets are exposed to an acoustic field, they experience the USAW-induced acoustic radiation force (ARF), whose magnitude varies depending on the droplet size. We modeled the USAW-induced ARF based on ray acoustics and conducted a series of experiments to separate different-sized droplets. We found that the experimental results were in good agreement with the theoretical estimation. We believe that the proposed method will serve as a promising tool for size-based droplet separation in a label-free manner.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.97-101
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• 2009

STATEMENT OF PROBLEM. Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink. PURPOSE. In this study, Bicon$^{(R)}$ Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured. MATERIAL AND METHODS. 10 Bicon$^{(R)}$ implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length. RESULTS. It was evident, that the amount of abutment sinking in Bicon$^{(R)}$ Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at $0.45{\pm}0.09\;mm$. CONCLUSION. Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location.

• Physical Therapy Rehabilitation Science
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• v.5 no.3
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• pp.138-142
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• 2016

Objective: The purpose of this study was to investigate how light touch with a finger affects balance ability when a posture is maintained in the condition of visual information blockage and to provide a fundamental material for developing balance ability in the process of rehabilitation treatment. Design: Cross-sectional study. Methods: The study subjects were 17 healthy men and women in their twenties and thirties who were studying at S University in Seoul. The system was comprised of an equilateral triangular force platform. Subjects were asked to step on the foot position of the force platform (Good Balance, Finland) barefooted for 30 seconds, with eyes closed, hands hanging down loosely, and feet comfortably apart. It was connected to a laptop by using Bluetooth technology. An experiment was conducted in the following three circumstances: 1) no-touch trial, 2) light touch to the back (T7 area), and 3) light touch to the middle finger of the left hand. Each subject was given a 10-minute break between consecutive measurements. The experimental circumstances were performed randomly. Anteroposterior sway (APSV), mediolateral sway velocity (MLSV), and velocity moment (VM) were measured. Results: The APSVs (mm/s) were $9.32{\pm}3.37$ and $5.45{\pm}2.98$; the MLSVs (mm/s), $6.39{\pm}3.35$ and $3.31{\pm}2.48$; and VM ($mm^2/s$), $17.13{\pm}11.75$ and $6.76{\pm}8.31$ in the first and second experimental circumstances, respectively. APSV, MLSV, and VM values were significantly improved with the 1) no-touch trial and 2) light touch to the back trail conditions compared with the 3) light touch to the middle finger of the left hand condition (p<0.05). Conclusions: This study revealed that the balance ability for maintaining a body posture was influenced more by light touch to the back (T7) than by light touch with the sensitive fingertip and body sway diminished after visual information was blocked.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.4
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• pp.101-109
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• 2020

PURPOSE: This study investigates the therapeutic effect of a prototype of a hand rehabilitation device based on magnetic forces. METHODS: Using an electromagnet and permanent magnets, we developed an end effector type device that induces various movements of the finger in accordance with the magnetic field direction. A total of 26 subacute stroke patients were enrolled and assigned to two groups in this randomized controlled trial. The intervention group received 30 minutes hand rehabilitation therapy per day for 4 weeks, using the device developed by us. Conventional physical therapies were conducted equally twice a day, 30 minutes per session, during the same period in both groups. RESULTS: After 4 weeks, rate of the Wolf Motor Function Test as a primary outcome measure showed significant improvement in the intervention group as compared to control group(p = .036). Scores of the Manual Function Test and Fugl-Meyer Assessment of upper limb were also significantly increased in the intervention group as compared to control group(p = .038 and p = .042, respectively). Moreover, the Korean version of Modified Barthel Index tended to improve after subjecting to physical therapy in both groups. CONCLUSION: Our results indicate that the novel hand rehabilitation device developed using a magnetic force, improves the hand motor functions and activities of daily life in subacute stroke patients.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.6
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• pp.594-599
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• 2006

In this paper an anthropomorphic robot hand called SKKU Hand IIl is presented, which has a miniaturized fingertip tactile sensor. The thumb is designed as one part of the palm and multiplies the mobility of the palm. The fingertip tactile sensor, based on polyvinylidene fluoride (PVDF) and pressure variable resistor ink, is physically flexible enough to be deformed into any three-dimensional geometry. In order to detect incipient slip, a PVDF strip is arranged along the direction normal to the surface of the finger of the robot hand. Also, a thin flexible sensor to sense the static force as well as the contact location is fabricated into an arrayed type using pressure variable resistor ink. The driving circuits and the tactile sensing systems for the SKKU Hand II are embedded in the hand. Each driving circuit communicates with others using CAN protocol. SKKU Hand II is manufactured and its feasibility is validated through preliminary experiments.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.2
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• pp.9-16
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• 2002

The machinability of Ti-6Al-4V titanium alloy and tool wear behavior in machining of Ti-6Al-4V titanium alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials in present and future aerospace or medical applications. Recently, their usage has already been broaden to everybody's commercial applications such as golf heads, finger rings and many decorative items. To anticipate the general use of this material and development of the titanium alloys in domestic facilities, the review and the study of the machining parameters for those alloys are necessary. This study is concentrated to the machining parameters of the Ti-6A1-4V alloy due to their dominant position in the production of titanium alloys.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.8
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• pp.825-835
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• 1991

This paper deals with a case for robotic hands to grasp the objects using inner link contact as well as fingertip contact. And the case is proved to be more efficient than the case of using only fingertip contact in terms of stability and uniform distribution of the contact forces. The general algorithm for the determination of the optimal ocntact force is developed for the soft finger contact as well as the point contact with friction. To show the validity of the proposed algorithm a numerical example is illustated by employing a robotic hand with three fingers each of which has four joints.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.818-822
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• 2000

The low density, sustained high temperature strength and excellent resistivity to acid materials have made them strong candidate materials for future aerospace or medical applications. Nowadays their usage has already been broaden to everyday's commercial applications such as golf club heads, finger rings and many decorative items, Anticipating the general use of this material and development of the titanium alloys in domestic furnaces, the review and the study of the machining parameters for those alloys are deemed necessary. The present studies are concentrated to the machining parameters of the Ti-6Al-4V alloys due to their dominant position in the production of titanium alloys.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.985-989
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• 1990

This paper presents a fundamental study of a millimeter-sized master-slave robot driven by conduit-guided wires, which is expected to be applied to the delicate surgical operations, the assembling precise and small parts and so on. This system consists of a millimeter-sized slave robot and a master manipulator of which the size is adapted to a human finger. Displacement and torque of the master side can be reduced and transferred to the slave robot by controlling the motor torque against the master torque by feeding back tension signals. The master can feel the tensions by the motor torque. In this paper, the design method and making process of the master-slave system and the dynamical characteristic of displacement and torque control are proposed.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.20-28
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• 2003

The machinability of Ti-6Al-4V titanium alloy and tool wear behavior in machining of Ti-6Al-4V titanium alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials in present and future aerospace or medical applications. Recently, their usage has already been broaden to everyday's commercial applications such as golf club heads, finger rings and many decorative items. To anticipate the general use of this material and development of the titanium alloys in domestic facilities, the review and the study of the machining parameters for those alloys are necessary. This study is concentrated to the machining parameters of the Ti-6Al-4V alloy due to their dominant position in the production of titanium alloys.