Hyouk Kwon

Contact materials and reliability for high power RF-MEMS switches

This paper presents test and characterization of various thin film contact materials for reliable high power RF- MEMS switches. We selected Au, Pt, Ir, and AuPt alloys for contact materials and fundamentally studied on contact phenomena and reliability of similar or dissimilar contacts using a contact measurement apparatus at high current condition. We also investigated the electrical contact behavior of the MEMS switches. From these studies, Au-to-Pt, Pt-to-Pt and Au-to-Ir contact showed reliable characteristics for the high power RF-MEMS switches.

Correlation between the Korean Version of Asthma Control Test and Health-Related Quality of Life in Adult Asthmatics

The Asthma Control Test (ACT) is a patient-completed questionnaire developed to assess asthma control. Health-related quality of life (HRQL) in asthmatics has shown relatively low correlations with parameters of asthma control and the relationship between the ACT and HRQL in asthmatics is yet unclear. Because revalidations of translated versions of questionnaires are critical for its utilization, we first sought to validate the Korean version of ACT and then to evaluate the relationship between the ACT and HRQL. Patients (n=117) completed the ACT and asthma-related quality of life questionnaire (AQLQ) at 3 physician visits. Pulmonary function was measured and an asthma specialist rated asthma control. The Korean version of ACT was found to be reliable, valid, and responsive to changes in asthma control over time up to three consecutive visits. ACT scores correlated significantly (p=0.001) with symptoms domain (r=0.72), activity domain (r=0.65), emotional domain (r=0.69), and environmental domain (r=0.67) of AQLQ. In conclusion, the Korean version of the ACT was found to be a reliable and valid tool for measuring asthma control, and to correlate well with AQLQ scores. Moreover, the ACT was responsive to changes in AQLQ scores over time.

Investigation of the electrical contact behaviors in Au-to-Au thin-film contacts for RF MEMS switches

This paper presents the electrical contact behaviors of gold-to-gold thin-film contacts under high current conditions and describes the major factors that influence these contact behaviors for radio frequency microelectromechanical system switches. The fundamental phenomena in the contact resistance versus contact force curve were investigated with a contact measurement setup, which we devised. Based on the experimental results, the contact resistance behavior with increasing contact force can be divided into three regions: first, an unstable contact regime before the minimum contact force is reached; second, a stable contact regime where the plastic deformation of the asperities explains the behavior and, finally, a saturated regime where the thickness effect of the film on a hard substrate becomes evident. The minimum contact force required for a stable contact depended on the roughness of the surface and the current flow through the contact. The smooth surface of the Au film and the metal softening caused by a high current flow of 100 mA had the effect of lowering the minimum contact force. After the minimum contact force is exceeded, the contact resistance initially follows the asperity plastic deformation behavior, where the contact resistance is related to the resistivity and hardness of the contact material. In the higher contact force regime, the decrease in the contact resistance becomes almost negligible. With increasing contact force, the effective contact area is limited by the effect of the film thickness on a hard substrate. From these results, we found the principal factors influencing the contact behaviors of the Au-to-Au contacts to be the resistivity, hardness and softening temperature of the contact materials and the design factors such as the surface roughness, the film thickness and the substrate.

A Case of Hypersensitivity Syndrome to Both Vancomycin and Teicoplanin

Drug hypersensitivity syndrome to both vancomycin and teicoplanin has not been previously reported. We describe here a 50-yr-old male patient with vertebral osteomyelitis and epidural abscess who developed hypersensitivity syndrome to both vancomycin and teicoplanin. Skin rash, fever, eosinophilia, interstitial pneumonitis, and interstitial nephritis developed following the administration of each drug, and resolved after withdrawing the drugs and treating with high dose corticosteroids. The vertebral osteomyelitis was successfully treated with 6-week course of linezolid without further complications. Skin patch tests for vancomycin and teicoplanin was done 2 months after the recovery; a weak positive result for vancomycin (10% aq.,+at D2 and +at D4 with erythema and vesicles; ICDRG scale), and a doubtful result for teicoplanin (4% aq.-at D2 and±at D4 with macular erythema; ICDRG scale). We present this case to alert clinicians to the hypersensitivity syndrome that can result from vancomycin and teicoplanin, with possible cross-reactivity, which could potentially be life-threatening.

A high-sag microlens array film with a full fill factor and its application to organic light emitting diodes

This paper reports a novel high-sag microlens array (MLA) film with a full fill factor and presents its application to organic light emitting diodes (OLEDs) for the purpose of improving their outcoupling efficiency. A gapless hexagonal MLA film having a high sag ratio is proposed and fabricated by a simple micromachining process including trench formation and the conformal vapor phase deposition of a polymer. By applying the MLA films to OLED panels, the outcoupling efficiency was increased by a maximum of 48% without any apparent color shift. A high-sag MLA film with a full fill factor is expected to impart remarkable optical efficiency to various display or lighting applications with flat panel light sources including OLEDs.

Investigation of Similar and Dissimilar Metal Contacts for Reliable Radio Frequency Micorelectromechanical Switches

The evaluation test of various thin film contact materials for reliable radio frequency (RF) microelectromechanical systems (MEMS) switches is presented. Given that two of the most important performance criteria of RF MEMS switches are a low contact resistance and high reliability, the purpose of this study is to search for feasible contact materials and combinations by measuring the contact resistance and hot switching reliability under high current condition. We selected gold, platinum, and iridium for the contact materials and compared the contact resistance and failure point for various similar or dissimilar contacts; Au/Au, Pt/Pt, Ir/Ir, Au/Pt, and Au/Ir using a contact measurement apparatus. Also, we investigated the insertion loss and power handling capability of Au/Au and Au/Ir in the RF MEMS switches. From these studies, it was found that dissimilar contacts such as Au/Pt or Au/Ir are an effective means of enhancing the reliability for high power RF MEMS switches. This evaluation method represents an important step toward the development of reliable metal contacts.

A case of chlorpheniramine maleate-induced hypersensitivity with aspirin intolerance.

Antihistamines are commonly used to treat allergic disease, such as allergic rhinitis, urticaria, and angioedema. Although several previous reports describe hypersensitivity to antihistamines such as cetirizine and hydroxyzine, documented cases of chlorpheniramine hypersensitivity are extremely rare. Here, we report the case of a 45-year-old Korean woman who presented with urticaria after ingesting a cold medication. Over the previous 5 years, she had also experienced a food allergy to crab and shrimp, allergic rhinitis, and repeated urticaria after ingesting cold medication. Provocation with aspirin elicited generalized urticaria. Intravenous chlorpheniramine and methylprednisolone was injected for symptom control, but in fact appeared to aggravate urticaria. A second round of skin and provocation tests for chlorpheniramine and methylprednisolone showed positive results only for chlorpheniramine. She was diagnosed with aspirin intolerance and chlorpheniramine hypersensitivity, and was instructed to avoid these drugs. To date, this is the second of only two cases of chlorpheniramine-induced type I hypersensitivity with aspirin intolerance. Although the relationship between aspirin intolerance and chlorpheniramine-induced type I hypersensitivity is unclear, physicians should be aware of the possibility of urticaria or other allergic reactions in response to antihistamines.

Microlens Array Film with Full Fill Factor for Enhancing Outcoupling Efficiency from OLED Lighting

This paper reports a microlens array (MLA) film with full fill factor and presents its application to organic light emitting diode (OLED) for improving outcoupling efficiency. Gapless MLA film having high sag ratio is proposed and fabricated by simple micromachining process including trench formation and conformal vapor phase deposition of polymer. As applying MLA film to OLED panel, the outcoupling efficiency increased by maximum 48%. High-sag MLA optical film with full fill factor is expected to give remarkable optical efficiency to various display or lighting applications of the flat panel light sources including OLED.