Browsing by Author "Chou, CK"

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Critical length of nanowires for hydrophobic behavior
(2004-10-11)
Cheng, YH
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Chou, CK
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Chih, C
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Cheng, SY
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材料科學與工程學系
This Letter investigates the wetting behavior on surface with well-controlled nanoscale structure. Water and water-alcohol droplets were brought to contact the surface electroplated by Ag nanowires. It is found that hydrophobic behavior becomes more pronounced as the length of the nanowires increases. A critical length of approximately 100 nm is observed, beyond which the contact angle approaches a steady value of 130degrees. In addition, the contact angle of water levels off around 160degrees when the length of the fluorine-coated Ag nanowires exceeds the critical value of 100 nm. The mechanism of the hydrophobic behavior on surface with nanoscale structure is proposed. (C) 2004 Elsevier B.V. All rights reserved.
Effects of glucose concentration on in vitro fertilization in BALB/c mice
(2003-12-01)
Wu, HT
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Chou, CK
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Lin, CS
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Huang, MC
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生物科技學系
BALB/c mice are widely used in genetic, tumour and immunological studies. However, the mice demonstrate a lower reproduction rate, low fertility and small litters, because of their highly genetic homozygoisty. Based on in vitro fertilization (IVF), a routine technique for biomedical studies, it is worth to evaluate the effects to BALB/c mice on IVF efficiency. In order to test the genetic factor affecting the IVF efficiency of BALB/c, four reciprocal IVF tests of BALB/cByJ and FVB/NCrl mice were performed. The results showed that the average fertility of IVF sponsored by FVB/NCrl spermatozoa was 69.6%, but only 12.1% was obtained from BALB/cByJ strain. Effect of glucose contained in the culture medium to the IVF efficiency of BALB/cByJ was also evaluated. The results showed that the fertility of BALB/cByJ spermatozoa incubated with 0, 2.7, 5.5, 11.1 and 22.2 mM of glucose in the TYH medium were 6.8, 9.9, 13.9, 32.7 and 22.2%, respectively. It is showed that IVF efficiency of BALB/cByJ spermatozoa could be improved depending on the concentration of glucose in the IVF medium. According to the results, it is beleived that lower IVF of BALB/cByJ mice might be due to the genetic defect in spermatozoa and increasing glucose in the IVF medium which significantly affect the IVF efficiency of BALB/cByl via activating the spermatozoa.
Electromigration in pb-free SnAg3.8Cu0.7 solder stripes
(2005-08-01)
Hsu, YC
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Chou, CK
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Liu, PC
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Chen, C
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Yao, DJ
Electromigration behavior in the eutectic SnAg3.8Cu0.7 solder stripes was investigated in the vicinity of the device operation temperature of 100 degrees C by using the edge displacement technique. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ(*)). The threshold current densities were estimated to be 4.3x10(4) A/cm(2) at 80 degrees C, 3.2x10(4) A/cm(2) at 100 degrees C, and 1.4x10(4) A/cm(2) at 120 degrees C. These values represent the maximum current densities that the SnAg3.8Cu0.7 solder can carry without electromigration damage at the three stressing temperatures. The electromigration activation energy was determined to be 0.45 eV in the temperature range of 80-120 degrees C. The measured products of diffusivity and the effective charge number, DZ(*), were -1.8x10(-10) cm(2)/s at 80 degrees C, -5.0x10(-10) cm(2)/s at 100 degrees C, and -7.2x10(-10) cm(2)/s at 120 degrees C. (c) 2005 American Institute of Physics.
Identification of V23RalA-Ser(194) as a critical mediator for aurora-A-induced cellular motility and transformation by small pool expression screening
(2005-03-11)
Wu, JC
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Chen, TY
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Yu, CTR
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Tsai, SJ
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Hsu, JM
Human Aurora kinases have three gene family members: Aurora-A, Aurora-B, and Aurora-C. It is not yet established what the specificity of these kinases are and what signals relayed by their reactions. Therefore, we employed small pool expression screening to search for downstream substrates of Aurora-A. Interestingly, all of the identified Aurora-A substrates were resistant to serve as substrates for Aurora-B or Aurora-C, suggesting that these Aurora family members may have distinct substrate specificity for propagation of diverse signaling pathways, even though they share a conserved catalytic kinase domain. Of the candidate substrates, Aurora-A could increase the functional activity of RalA. Mutational analysis revealed that RalA-Ser(194) was the phosphorylation site for Aurora-A. Ectopic expression of V23RalA-WT could enhance collagen I-induced cell migration and anchorage-independent growth in Madin-Darby canine kidney (MDCK) Aurora-A stable cell lines. In contrast, overexpression of V23RalA-S194A in MDCK Aurora-Astable cell lines abolished the intrinsic migration and transformation abilities of Aurora-A. To our knowledge, this is the first systematic search for the downstream substrates of Aurora-A kinase. Moreover, these results support the notion that Aurora-A may act in concert with V23RalA through protein phosphorylation on Ser(194) to promote collagen I-induced cell motility and anchorage-independent growth in MDCK epithelial cells.
Redistribution of Pb-rich phase during electromigration in eutectic SnPb solder stripes
(2006-03-01)
Chou, CK
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Chen, CA
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Liang, SW
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Chen, C
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材料科學與工程學系
The microstructural evolution occurring within the eutectic SnPb solder during electromigration is investigated utilizing Blech specimens. Solder stripes of about 3 mu m in thickness were fabricated on Cu/Ti metallization. It was found that the Pb-rich phase ripened and aligned along the direction of the electron flow following the current stressing of 9.7x10(3) A/cm(2) at 80 degrees C for 24 h. As the stressing time or current density increased, the redistribution of the Pb-rich phase became more significant. Three-dimensional simulation was performed to examine the change in resistance and current-density distribution during electromigration. It was found that when the Pb-rich phase aligned along the direction of the electron flow, the total resistance of the solder stripe decreased. This reduction in total resistance may provide the driving force for the redistribution of the Pb-rich phase during electromigration. In addition, current crowding occurred in the vicinity of the interface of the Pb-rich and Sn-rich phases, creating a gradient of current density. This gradient might trigger the resistive Pb atoms to align along the direction of the electron flow.
Threshold current density of electromigration in eutectic SnPb solder
(2005-05-16)
Yeh, YT
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Chou, CK
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Hsu, YC
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Chen, C
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Tu, KN
Electromigration has emerged as an important reliability issue in the microelectronics packaging industry since the dimension of solder joints has continued to shrink. In this letter, we report a technique that enables the precise measurement of the important parameters of solder electromigration, such as activation energy, critical length, threshold current density, effective charge numbers, and electromigration rate. Patterned Cu/Ti films in a Si trench were employed for eutectic SnPb solder to be reflowed on, and thus solder Blech specimens were fabricated. Atomic force microscope was used to measure the depletion volume caused by electromigration on the cathode end. The threshold current density is estimated to be 8.5x10(3) A/cm(2) at 100 degrees C, which relates directly to the maximum allowable current that a solder joint can carry without electromigration damage. This technique facilitates the scientifically systematic investigation of electromigration in solders. (c) American Institute of Physics.