Browsing by Author "Su, Yi-Jr"

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Comparison of backward-scattered detection and forward-scattered detection for measuring optical force in optical tweezers
(2010)
Su, Yi-Jr
;
Hsu, Long
;
電子物理學系
;
Department of Electrophysics
Optical tweezers have become an important tool to measure forces in biology. The trapped particle displacements acquired from the position detection system are applied to calibrate trapping stiffness using power spectrum method. The near infrared light is typically used as a laser source to reduce the damage to a cell or cellular organelles and the biological objects can be held and moved by exerting piconewton forces. In force measurement, optical force strength is calculated by multiplying trapping stiffness and trapped bead displacement. Optical tweezers perform a wider range of experiments through the integration of a quadrant photodiode for position detection. Both forward-scattered detection and backward-scattered detection are the typical position detection. This study discussed both backward-scattered detection and forward-scattered detection that add a probing beam and their linear detection ranges that describe the precise position of the trapped bead. This work also discussed their linear detection ranges related to the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicated that the linear detection range of backward-scattered detection is longer than the forward-scattered detection. Hence, backward-scattered detection measures the longer displacement of the trapped bead in optical force measurement.
Measurement of Macrophage Adhesion at Various pH Values by Optical Tweezers with Backward-Scattered Detection
(2010)
Su, Yi-Jr
;
Hsu, Long
;
電子物理學系
;
Department of Electrophysics
Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 mm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 mm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection. (C) 2010 The Japan Society of Applied Physics
Measurement of macrophage adhesion by optical tweezers with backward-scattered detection
(2010)
Wei, Sung-Yang
;
Su, Yi-Jr
;
Shih, Po-Chen
;
Yang, Shih-Mo
;
Hsu, Long
Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 mu m diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.
Recovery Based Nanowire Field-Effect Transistor Detection of Pathogenic Avian Influenza DNA
(2012-02-01)
Lin, Chih-Heng
;
Chu, Chia-Jung
;
Teng, Kang-Ning
;
Su, Yi-Jr
;
Chen, Chii-Dong
Fast and accurate diagnosis is critical in infectious disease surveillance and management. We proposed a DNA recovery system that can easily be adapted to DNA chip or DNA biosensor for fast identification and confirmation of target DNA. This method was based on the re-hybridization of DNA target with a recovery DNA to free the DNA probe. Functionalized silicon nanowire field-effect transistor (SiNW FET) was demonstrated to monitor such specific DNA-DNA interaction using high pathogenic strain virus hemagglutinin 1 (H1) DNA of avian influenza (AI) as target. Specific electric changes were observed in real-time for AI virus DNA sensing and device recovery when nanowire surface of SiNW FET was modified with complementary captured DNA probe. The recovery based SiNW FET biosensor can be further developed for fast identification and further confirmation of a variety of influenza virus strains and other infectious diseases. (C) 2012 The Japan Society of Applied Physics
Sloped-Gate Voltage Method for Improving Measurement of Poly-Si Nanowire FET in Aqueous Environment
(2013-05-02)
Chen, Chien-Hung
;
Su, Yi-Jr
;
Lin, Chih-Heng
;
Liao, Tai-Shan
;
Yang, Yuh-Shyong
Nanowire field-effect transistors are suited to. study the activity of biomolecules in bionanotechnology. The changes of biomolecules process are efficiently affected the charge at the nanowire surface; thus, the electrical characterization of NW-FET is Changed. Although NW-FET is a well-known device in bioapplications, however, the intrinsic electrical characterization of NW-FET effect, on real electrical measurement is not well studied. We present herein a novel measurement method to avoid errors in electrical characteristic of nanowire field-effect transistors. A physical model is developed to explore the effect of the leakage current, which is influenced by the charging effect of an equivalent capacitor in a NW-FET. We also present a sloped-gate voltage method to reduce the effect, of equivalent capacitor in air, liquid, and phosphate buffered solution. The application of the sloped gate voltage Method significantly increases the stability of electrical characterization measurements. This method can also be easily applied to biosensing experiments.