Yeolho Lee

Sensitive and simultaneous detection of cardiac markers in human serum using surface acoustic wave immunosensor.

We present a rapid and sensitive surface acoustic wave (SAW) immunosensor that utilizes gold staining as a signal enhancement method. A sandwich immunoassay was performed on sensing area of the SAW sensor, which could specifically capture and detect cardiac markers (cardiac troponin I (cTnI), creatine kinase (CK)-MB, and myoglobin). The analytes in human serum were captured on gold nanoparticles (AuNPs) that were conjugated in advance with detection antibodies. Introduction of these complexes to the capture antibody-immobilized sensor surface resulted in a classic AuNP-based sandwich immunoassay format that has been used for signal amplification. In order to achieve further signal enhancement, a gold staining method was performed, which demonstrated that it is possible to obtain gold staining-mediated signal augmentation on a mass-sensitive device. The sensor response due to gold staining varied as a function of cardiac marker concentration. We also investigated effects of increasing operating frequency on sensor responses. Results showed that detection limit of the SAW sensor could be further improved by increasing the operating frequency.

22.2: The First 9-inch Carbon-Nanotube Based Field-Emission Displays for Large Area and Color Applications

The first 9-inch carbon nanotube based color field emission displays (FEDs) are integrated using a paste squeeze technique. The panel is composed of 576 × 242 lines with implementation of low voltage phosphors. The uniform and moving images are achieved only at 2 V/μm. This demonstrates a turning point of nanotube for large area and full color applications.

P‐43: A Simple Structure and Fabrication of Carbon‐Nanotube Field Emission Display

A triode structure of field emission displays based upon carbon nanotube emitters is presented. In this structure, gate electrodes are located underneath cathode electrodes with an in-between insulating layer, so called an under-gate type triode structure. The modulation of electron emission by changing gate voltages is confirmed. The advantage of simple structure and fabrication processes may lead the under-gate triode type structure to the practical applications.

Improvements in electrical properties of piezoelectric microcantilever sensors by reducing parasitic effects

Piezoelectric microcantilever sensors (PEMSs) are very highly sensitive label-free sensors, and silicon-based PEMSs have parasitic elements such as parasitic capacitances and resistances between the electrodes through their substrate; they affect the coupling coefficient and leakage current and thereby the accuracy of the sensor. In this study, we have experimentally analyzed the parasitic effects that affect these PEMSs. Further, we have developed a method to reduce the parasitic effects and fabricated a PEMS on this basis; we have successfully demonstrated that its electrical properties improved. The parasitic effects were reduced by employing a deep trench structure near the electrodes and a highly resistive (>10 kΩ cm) silicon-on-insulator (SOI) wafer and by reducing the electrode pad areas. The coupling coefficient and leakage current were analyzed from the experimental data of admittance spectra and velocity spectra. The coupling coefficient increased by approximately 42%, the leakage current at resonance decreased by approximately 76%, the parasitic conductance decreased and the transformation factor increased. Moreover, the electrical power loss decreased as the leakage current decreased, whereas the motional conductance increased with the coupling coefficient. In this manner, we could enable more accurate electrical readouts of the PEMS by reducing the parasitic effects.

Under-Gate Triode Type Field Emission Displays with Carbon Nanotube Emitters

A new structure of triode type field emission displays based on single-walled carbon nanotube emitters is demonstrated. In this structure, gate electrodes are situated under cathode electrodes with an in-between insulating layer, so called under-gate type triode. Electron emission from the carbon nanotube emitters is modulated by changing gate voltages. A threshold voltage is approximately 70 V at the anode bias of 275 V.

Increase in detection sensitivity of surface acoustic wave biosensor using triple transit echo wave

Here, we present a surface acoustic wave (SAW) biosensor for the highly sensitive detection of cardiac troponin I, a gold standard biomarker for the diagnosis of myocardial infarction, using a triple transit echo (TTE) wave of a SAW rather than a conventional main wave. Compared with the main wave, the TTE wave is caused by reflections from output and input interdigitized transducers (IDTs) after traversing the propagation path three times between input and output IDTs. The SAW biosensor using a TTE wave signal showed enhanced sensitivity for measuring the viscosity of glycerol solution and the mass loading effect of immunoassay reaction due to much bigger modulation induced in the amplitude, phase, frequency, and time-delay of the TTE wave. Our results showed that the proposed SAW biosensor could quantitatively analyze cardiac troponin I. Detection limit values using the main wave and the TTE wave were 766 pg/ml and 24.3 pg/ml, respectively. Therefore, one can say that the sensitivity of the SAW biosensor substantially improved when the TTE wave is used.Here, we present a surface acoustic wave (SAW) biosensor for the highly sensitive detection of cardiac troponin I, a gold standard biomarker for the diagnosis of myocardial infarction, using a triple transit echo (TTE) wave of a SAW rather than a conventional main wave. Compared with the main wave, the TTE wave is caused by reflections from output and input interdigitized transducers (IDTs) after traversing the propagation path three times between input and output IDTs. The SAW biosensor using a TTE wave signal showed enhanced sensitivity for measuring the viscosity of glycerol solution and the mass loading effect of immunoassay reaction due to much bigger modulation induced in the amplitude, phase, frequency, and time-delay of the TTE wave. Our results showed that the proposed SAW biosensor could quantitatively analyze cardiac troponin I. Detection limit values using the main wave and the TTE wave were 766 pg/ml and 24.3 pg/ml, respectively. Therefore, one can say that the sensitivity of the SAW biosenso...

Wrist-wearable bioelectrical impedance analyzer with contact resistance compensation function

Bioelectrical impedance analysis (BIA) is used to calculate the body fat percentage of a human by applying a small amount of alternating current through a human body and measuring the impedance. As the electrode size of a BIA device becomes small, the measurement error of impedance becomes large due to the contact resistance between the electrode and human skin. Most commercial BIA devices, therefore, utilize electrodes large enough to ignore the effect of contact resistance, e.g. 35×40 mm2 × 4EA. We propose a novel method for compensating the contact resistance by performing a 4-point and a 2-point measurement alternately such that body impedance can be accurately estimated even with a considerably smaller size of electrode (8×8 mm2 × 4EA). Also, we report a wrist-wearable BIA device with single-finger contact measurement and analysis results of user data acquired from 148 volunteers: the correlation coefficient of body fat percentage was 0.903 and the SEE (Standard Error of Estimate) of body fat percentage was 3.07% when compared with InBody 720 (whole-body composition analyzer), which was found to be at the same level of performance as commercial portable upper-body BIA device.