• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.68-71
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• 2008

Transdermal and topical drug delivery with minimal tissue damage has been an area of vigorous research for a number of years. Our research team has initiated the development of an effective method for delivering drug particles across the skin (transdermal) for systemic circulation, and to localized (topical) areas. The device consists of a micro particle acceleration system based on laser ablation that can be integrated with endoscopic surgical techniques. A layer of micro particles is deposited on the surface of a thin metal foil. The rear side of the foil is irradiated with a laser beam, which generates a shockwave that travels through the foil. When the shockwave reaches the end of the foil, it is reflected as an expansion wave and causes instantaneous deformation of the foil in the opposite direction. Due to this sudden deformation, the microparticles are ejected from the foil at very high speeds, and therefore have sufficient momentum to penetrate soft body tissues. We have demonstrated this by successfully delivering cobalt particles $3\;{\mu}m$ in diameter into gelatin models that represent soft tissue with remarkable penetration depth.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.521-528
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• 2017

In this paper, the numerical analysis for heat conduction of silica/phenolic composite material, which is used for solid rocket nozzle liner or insulator, was conducted. 1-D Finite Difference Method for the analysis of silica/phenolic during the firing of solid rocket motor was used to calculate the heat conduction considering the surface ablation and the thermal decomposition. The boundary condition at the nozzle wall took into account the convective heat transfer, which was obtained by integration equation. The numerical results of the surface ablation and char depth were compared with the results of test motor that is TPEM-10. It was found that the result of calculation is favorably agreed with the thermal response of test motor.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.76-84
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• 2018

In this paper, the numerical analysis for heat conduction of silica/phenolic composite material, used for solid rocket nozzle liners or insulators, is conducted. A 1-dimensional finite difference method for the analysis of silica/phenolic during the firing of a solid rocket motor is used to calculate heat conduction, considering surface ablation and thermal decomposition. The boundary condition at the nozzle wall, considering the convective heat transfer, is obtained via integration equations. The numerical results of the surface ablation and char depth are compared with the results of a TPEM-10 test motor, finding that the result of calculation agrees with the thermal response of the test motor.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.17-23
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• 2002

A new 3D micromachining method called Hole Area Modulation(HAM), has been introduced to enhance the current micromachining technology. In this method, information on the depth of machining is converted to the sizes of small holes in the mask. The machining is carried out with a simple 2D movement of the workpiece. This method can be applied for machining various kinds of microcavities in various materials. In this paper, a machematical model for excimer laser micromachining based on HAM and also determination of optimal laser ablation conditions(width hole radius, step size, path, etc.) is performed by Genetic Algorithm(GA).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.587-593
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• 2008

Transdermal and topical drug delivery with minimal tissue damage has been an area of vigorous research for years. Our research team has initiated the development of an effective method for delivering drug particles across the skin (transdermal) for systemic circulation, and to localized (topical) areas. The device consists of a laser ablation based micro-particle acceleration system that can be integrated with endoscopic surgical techniques. We have successfully delivered 3μm size cobalt particles into gelatin models that represent soft tissue with remarkable penetration depth.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.224-225
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• 2000

Transparent and hard materials such as sapphire are used for many industrial applications as optical windows, hard materials on mechanical contact against abrasion, and substrate materials for opto-electronic semiconductor devices such as blue LED and blue LD etc. The materials should be cut along the proper shapes possible to be used for each application. In case of blue LED, the blue LED wafer should be cut to thousands of blue LED pieces at the final stage of the manufacturing process. The process of cutting the wafer is usually divided into two steps. The wafer is scribed along the proper shapes in the first step. It is inserted between transparent flexible sheets for easy handling. And then, it is broken and split in the next step. Harder materials such as diamonds are usually used to scribe the wafer, while it has a problem of low depth of scribing and abrasion of the harder material itself. The low depth of scribing can induce failure in breaking the wafer along the scribed line. It was also known that the expensive diamond tip should be replaced frequently for the abrasion. (omitted)

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.247-252
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• 2008

A laser glass cutting system using a femto-second laser was evaluated for Flat Panel Display (FPD) glass. A theoretical analysis of the ablation threshold and depth is described using an explicit analytic form. Experiments for clean and deep grooves were performed using a 3W femto-second laser, and the relationships between the input energy and the scribing depth as well as the threshold energy are presented. Mechanical breaking after the scribing process was carried out and the results are compared with a theoretical method. It was found that a two-sided LCD panel glass can be cut clearly using the laser cutting method. The methodology was found to be very effective as a mass-production cutting system.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.68-74
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• 2014

This computational study features the transient compressible and inviscid flow analysis on a metallic plasma discharge from the opposing composite electrodes which is subjected to pulsed electric power. The computations have been performed using the flux corrected transport algorithm on the axisymmetric two-dimensional domain of electrode gap and outer space along with the calculation of plasma compositions and thermophysical properties such as plasma electrical conductivity. The mass ablation from aluminum electrode surfaces are modeled with radiative flux from plasma column experiencing intense Joule heating. The computational results shows the highly ionized and highly under-expanded supersonic plasma discharge with strong shock structure of Mach disk and blast wave propagation, which is very similar to muzzle blast or axial plasma jet flows. Also, the geometrical effects of composite electrodes are investigated to compare the amount of mass ablation and penetration depth of plasma discharge.

• Laser Solutions
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• v.17 no.3
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• pp.19-23
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• 2014

To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

• Journal of the Optical Society of Korea
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• v.12 no.1
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• pp.38-41
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• 2008

Precise micropatterning of polypropylene film, which is highly transparent in the wavelength range over 250 nm has been demonstrated by 355 nm nano/picosecond laser and 785 nm femtosecond laser. Increments of both the pulse energy and the shot number of pulses lead to cooccurrence of photochemical and thermal effects, demonstrated by the spatial expansion of rim on the surface of PP. The shapes of the laser-ablated polypropylene films were imaged by optical microscope and measured by a 3D optical measurement system. And, the ablation depth and width of polypropylene film ablated by femtosecond laser at various pulse energy and pulse number were characterized. Our results demonstrate that a femtosecond pulsed laser is an efficient tool for fabricating micropatterns of polypropylene films, where the micropatterns are specifically tailored in size, location and number easily controlled by laser processing conditions.