• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.99-104
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• 2018

A micro electromagnetic actuator with high vibration efficiency is proposed for use in an implantable hearing device. The actuator, which can be implanted in the middle ear, consists of membranes based on the stainless steel 304 (SUS-304), and other components. In conventional actuators, in which a thick membrane and a silicone elastomer are used, the size reduction was difficult. In order to miniaturize the size of the actuator, it is necessary to reduce the size of the actuation potion that generates the driving force, resulting in reduction of the electromagnetic force. In this paper, the electromagnetic actuator is further miniaturized by the metal membrane and the vibration amplitude is also optimized. The actuator designed according to the simulation results was fabricated by using micro-electro-mechanical systems (MEMS) technology. In particular, a $20{\mu}m$ thick metal membrane was fabricated using the erosion process, which reduced the length of the actuator by more than $400{\mu}m$. In the experiments, the vibration displacement characteristics of the optimized actuator were above 400 nm within the range of 0.1 to 1 kHz when a current of $1mA_{rms}$ was applied to the coil.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.72-77
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• 2008

In this study, we propose and develop PDMS-based modular actuators. The microactuator which looks like a small insect uses thermal expansion power of the PDMS (polydimethylsiloxane; $sylgar^{(R)}$ 184 silicone elastomer). The PDMS-based microactuator provides a large displacement due to a high thermal expansion coefficient (approximately 310ppm). The microacruator with 1mm length $350{\mu}m$ width is optimized by using a numerical analysis. The shape of the PDMS actuatoris variously designed. They are placed at several positions to find the optimal position that provides a high transformation ratio. The PDMS-based microactuators are fabricated using a conventional micromaching technique. The fabricated microactuator is heated using a hot-plate. The actuator displacement is measured as a function of temperature from $27^{\circ}C$ to $300^{\circ}C$. The experimental results are compared to the simulation result. When heating temperature up to $300^{\circ}C$ is applied to the PDMS actuator, each V-groove-shaped joint is actuated $30{\mu}$ mat $300^{\circ}C$. Anotherdesign of the microactuator has a maximum displacement of about 656mm.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.413-418
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• 2001

We developed shunt valves used to treat patients with hydrocephalus. The valves under development were constant Pressure type ventriculoperitoneal (VP) calves made of silicone elastomer. In vitro experiments showed that our valves had similar Pressure-flow control characteristics to the valved currently available in the market. Our valves also showed competent performance in the 28 days of continuous pumping tests acording to the IS07197 specifications. We artificially inducted hydrocephalus to a 10kg beagle do9. The size of the ventricles of the dog was substantially increased and the dog showed abnormal behavior. After our valve being implanted, the ventricles recovered regular size with the normal behavior observed in the dog. The flow orifice of the shunt valve diaphragm was in the older of 10$\mu$m during calve operation and hence the pressure-flow control characteristics tended to change by a small chance in the valve dimension. Therefore, precision design and manufacturing techniques were necessary for successful operations of the shunt valves .

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.498-504
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• 2011

In this research, hollow fiber membranes were used in order to investigate to permeation and selectivity of the $CH_4$ and $N_2$. Polyimide and polyethersulfone hollow fiber membrane were prepared by the dry-wet phase inversion method and the module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy (SEM) studies showed that the produced fibers typically had an asymmetric structure. The permeance of $CH_4$ and $N_2$ were increased with pressure and temperature. However, the selectivity was decreased with increasing temperature. The permeances of $CH_4$ and $N_2$ were decreased with increasing the air gap and the effect of post-treatment on membrane showed the increase in permeance up to 3.2~7.0 times.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.660-667
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• 2010

In this research polyimide, Matrimid 5218, hollow fiber membrane was used to recover sulfur hexafluoride($SF_6$) which is one of the six greenhouse gases from $N_2/SF_6$ mixture gas. Fibers were spun from using dry-wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a sponge-like substructure. The developed module had a permeance of 0.78-1.36 GPU for $N_2$ with $N_2/SF_6$ selectivity of 2.44-5.08 at various pressure and temperature. For recovery of $SF_6$, a membrane module and 10 vol.% $SF_6$ from $N_2/SF_6$ mixture gas was used. The effects of various operating condition such as pressure, temperature, and retentate side flow rate were tested. When pressure and temperature were increased and retentate flow rate was decreased, the $SF_6$ purity in recovered gas was increased up to 37.5 vol.% with decreasing recovery ratio. When retentate flow rate was increased pressure and temperature was decreased, the $SF_6$ recovery ratio in retentate side was increased up to 89% with decreasing the $SF_6$ purity in retentate side.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.250-255
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• 2011

In this study, by using the polymeric membrane separation process, the $CO_{2}/CH_{4}$ separation and $H_{2}S$ removal from biogas were performed in order to $CH_{4}$ purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of $CO_{2}$ and $CO_{2}/CH_{4}$ selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the $CO_{2}$ and $H_{2}S$ were decreased while concentration of $CH_{4}$ was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the $CH_{4}$ recovery ratio in retentate side was increased while the $CH_{4}$ purity in retentate side was decreased.