Geunyoung Kim

Atmospheric-Pressure Plasma Jet Induces Apoptosis Involving Mitochondria via Generation of Free Radicals

The plasma jet has been proposed as a novel therapeutic method for anticancer treatment. However, its biological effects and mechanism of action remain elusive. Here, we investigated its cell death effects and underlying molecular mechanisms, using air and N2 plasma jets from a micro nozzle array. Treatment with air or N2 plasma jets caused apoptotic death in human cervical cancer HeLa cells, simultaneously with depolarization of mitochondrial membrane potential. In addition, the plasma jets were able to generate reactive oxygen species (ROS), which function as surrogate apoptotic signals by targeting the mitochondrial membrane potential. Antioxidants or caspase inhibitors ameliorated the apoptotic cell death induced by the air and N2 plasma jets, suggesting that the plasma jet may generate ROS as a proapoptotic cue, thus initiating mitochondria-mediated apoptosis. Taken together, our data suggest the potential employment of plasma jets as a novel therapy for cancer.

Atmospheric-pressure plasma-jet from micronozzle array and its biological effects on living cells for cancer therapy

We propose a plasma-jet device with a micrometer-sized nozzle array for use in a cancer therapy. Also, we show the biological effects of atmospheric-pressure plasma on living cells. Nitrogen-plasma activated a surrogate DNA damage signal transduction pathway, called the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 pathway, suggesting that the nitrogen-plasma generates DNA double-strand breaks. Phosphorylation of H2AX and p53 was detected in the plasma-treated cells, leading to apoptotic cell death. Thus, an effect for the nitrogen plasma in the control of apoptotic cell death provides insight into the how biological effects of the nitrogen-plasma can be applied to the control of cell survival, a finding with potential therapeutic implications.

Surface Acoustic Wave Based Pressure Sensor with Ground Shielding over Cavity on 41° YX LiNbO3

A surface acoustic wave (SAW)-based pressure sensor was fabricated for stable mechanical compression force measurement. A single phase unidirectional transducer (SPUDT) and two acoustic tracks were employed to minimize inherent insertion loss and improve reflectivity from the reflectors. The coupling of modes (COM) theory and finite element methods (FEMs) were used to determine optimal design parameters. A LiNbO3 diaphragm was bonded to a heavily doped silicon substrate with a cavity of ~250 µm deep, in which gold was lined all over the inner cavity to reduce the coupling loss of SAW energy to the surrounding atmosphere. As a mechanical compression force was applied to the diaphragm, the diaphragm bent, resulting in phase shifts of the reflected peaks. The phase shifts were modulated depending on the amount of mechanical compression applied. The measured reflection coefficient S11 showed good agreement with simulated results.

Simple Atmospheric-Pressure Nonthermal Plasma-Jet System for Poly(dimethylsiloxane) Bonding Process

In this paper, we propose a simple nonthermal plasma-jet system operated at atmospheric pressure. To evaluate the capability of surface modification, we performed an experimental study on the surface modification of poly(dimethylsiloxane) (PDMS) using Ar, He, and N2 plasma jets. The contact angles of a water droplet were measured after the surface modification by the proposed system. Among the three types of plasma used, the nitrogen plasma is the most efficient for surface modification. The N2 plasma-jet treatment for 60 s decreased the contact angle of PDMS to about 30°. The hydrophilic property of the modified surface lasted for at least 3 days. The PDMS modified with the nitrogen plasma is bonded well with glass. The bonding strength is equivalent to the yield strength of PDMS.

Atmospheric plasma jet from micro nozzle array and its biological effects on living cells for cancer therapy

In this paper, we propose a miniature plasma-jet device for new cancer therapy and report the biological effects of atmospheric plasma on living cells found by investigating the DNA damage signal pathway. The micro plasma-jet device proposed in this paper has an array of 100 µm-size holes so that we can treat a large area with a cheap power system. After plasma treatment, we observed apoptotic cell death. In order to find underlying mechanism, we investigated the possibility of DNA double-strand breaks formation and ATM-mediated DNA damage signaling activation. The result illustrate that the nitrogen plasma induced DNA double-strand breaks activate ATM-mediated DNA damage signaling cascade, and also activate tumor suppressor p53 protein, and lead apoptotic cell death.

Novel Fabrication Method of a Round Microtip Based on Aluminum Spike Phenomenon

In this paper, we present a new method of fabricating microtips based on the aluminum spike phenomenon. Silicon dissolves in aluminum at high temperatures above 400 C, and normally this is an undesirable effect in integrated circuit (IC) processing. However, in this study, this phenomenon is exploited, with which a round tip is fabricated by a simple process involving the annealing of aluminum at 800 C; a major advantage of the method is that the apex of the fabricated tip is round. The penetration depth of aluminum increases with annealing time, and the height of the fabricated tip can be controlled by adjusting annealing time. The height and width of the tip, annealed for 25min using (100) silicon wafer, are 40 and 80m, respectively. # 2011 The Japan Society of Applied Physics

A Micromachined Flexible Hollow Cathode Discharge Device

This paper presents the fabrication and test of a flexible hollow cathode discharge device. The discharge device consists of three layers; a thin anode layer, an insulation layer and a hollow cathode layer. The hollow cathode discharge is characterized by its high current density. The discharge device is fabricated by micromachining technology. The anode and cathode are made of aluminum and nickel, respectively. Polyimide is chosen as an insulating material because of its excellent dielectric properties and good mechanical stability. The device has an array of 10 ×10 holes for the discharge. The hole diameter and depth are 70 and 110 µm, respectively. The size of the flexible discharge device is 9 ×9 ×0.13 mm3. The discharge test was performed in an argon gas chamber at room temperature. The current is measured during the discharge at various applied voltages. At a pressure of 510 Torr, the discharge appears at an operating voltage of 270 V. The discharge is also observed at atmospheric pressure.

Optimized Surface Acoustic Wave-based Pressure Sensor Using Equivalent Circuit Model

This paper presents an optimized design on surface acoustic wave (SAW)-based pressure sensor, which is composed of a broadband reflective delay line and a bond substrate underneath the diaphragm. Using the equivalent circuit model (ECM), the SAW device was simulated, and the effect of inter-digital transducer structure, acoustic aperture and number of finger pairs on the performance of the system was studied. To determine the geometry and configuration of the sensor, Finite Element Method (FEM) was used to calculate the diaphragm bending and stress/strain distribution. From the ECM simulation and FEM analysis, the optimal design parameters were determined, and a new 440 MHz reflective delay line on 41deg YX LiNbO3 was developed, the measured reflection coefficient S11 results in time domain shows a good agreement with simulated one, low loss, sharp reflected peaks and high dynamic separation between the peaks were observed. The SAW device was successfully applied to pressure measurement, and the experiment results approve it is working satisfactorily

Spherical and non-spherical high fill-factor microlens arrays fabricated by polymer coating on isotropically etched quartz

Various shapes of microlens arrays (MLAs) were developed by utilizing polymer coating on etched quartz substrates. Spherical and non-spherical plano-concave curvatures were realized via isotropic wet etching of quartz in buffered oxide etchant (BOE), based on diverse design parameters and calculated etching times. The fabricated curvatures showed a high fill-factor and uniform elements in the array. By coating a higher refractive index polymer on the etched quartz, the illuminated light was well focused at the focal plane forming a micronscale light spot array. The experimental focal length was increased from 39.8 to 49.6 μm, as the shape of microlens was flattened. These results well correspond to those obtained from an optical simulation.

Development of a microlens array (MLA) for maskless photolithography application

A microlens array (MLA) was developed based on isotropic wet etching of quartz and coating of polymer on the etched substrate for maskless lithography application. Through the optimized manufacturing procedures, uniform elements, excellent light focusing ability, and dense fill factor were obtained. The fabricated MLA has the focal length ranging from 32.2 to 45.4 μm depending on the etching time and the thickness of the coated polymer. The collimated light was uniformly focused on the whole focal plane after passing through the fabricated array of microlenses and the size of the each focused beam was ~1.5 μm. By using the compact imaging ability of the miniaturized lenses, the MLA was applied to UV photolithography process. The illuminated UV passing the MLA focused on the photoresist, producing micron scale pattern array. Various sizes and shapes of micropattern arrays were realized onto the PR via controlling the experimental variables. Even at high temperature, the MLA performances were not changed indicating thermal stability of the developed MLA.