Browsing by Author "Ko, Wen-Ching"

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Conductive films based on sandwich structures of carbon nanotubes/silver nanowires for stretchable interconnects
(2019-06-07)
Jheng, Li-Cheng
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Hsiao, Chi-Hui
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Ko, Wen-Ching
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Hsu, Steve Lien-Chung
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Huang, Yu-Lun
A variety of conductive films made of a hybrid of two conductive nanomaterials have been used as stretchable electrodes or interconnectors, desirable for stretchable electronic devices. Their intrinsic stretchability of electrical conductivity allows for accommodating mechanical strain to a certain extent under various deformations. However, few efforts have been made to enhance the interactions between two conductive components in a hybrid system. Herein, we reported new conductive films with tri-layer sandwich structures based on carbon nanotubes (CNTs) and Ag nanowires (NWs), encapsulated in silicone rubber, exhibited high stretchability along with insignificant piezoresistivity. They are suitable to be stretchable interconnectors. A successive vacuum filtration method was used to stack the conductive components layer by layer. The effects of the stacking sequence and the interactions between layers on the stretchability and stability of the electrical properties under mechanical deformations were studied. In the case of a tri-layer conductive film comprising two CNT outer layers and one AgNW central layer in the presence of enhanced interfacial interactions, it showed exceptionally durability in withstanding repetitive deformations.
Using in-situ synchrotron x-ray diffraction to investigate phase transformation and lattice relaxation of a three-way piezo-phototronic soft material
(2017-07-01)
Ko, Wen-Ching
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Hsu, Yu-Hsiang
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Weng, Shih-Chang
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Chang, Chung-Kai
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Lee, Ming-Tao
A poly(vinylidene fluoride-co-trifluoro-ethylene) piezoelectric polymer is blended with nano particles of titanium oxide phthalocyanine to bridge photoconductive and piezoelectric effects. In this study, a system is examined by in situ synchrotron x-ray to test a three-way piezo-phototronic soft-material design. The sample is heated for in situ phase transformation characterization. The semi-crystalline poly (vinylidene fluoride-co-trifluoro-ethylene) polymer gradually transforms to an amorphous structure. A complementary piezoelectric experiment before and after the heating experiment shows that the piezoelectric performance is proportional to the phase ratio. Secondly, the system is examined to test its phototronic effect. Piezoelectric responses are measured by controlling the light illumination. The positive and negative controls of light illumination which validate this newly-designed system can be modulated by a three-way piezo-phototronic effect. In-situ synchrotron x-ray diffraction experiments are employed to measure the microstructure evolution as a function of applied voltage up to 800 V. We then turned off both the light and the applied voltage to examine the kinetic behavior of the system. There is orientation-dependent anisotropic relaxation. We compared the lattice-strain evolutions. Piezo-phototronic creep is found in the (110), but not the (310) planes.
Visible-Light Modulation on Lattice Dielectric Responses of a Piezo-Phototronic Soft Material
(2015-12-16)
Huang, E-Wen
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Hsu, Yu-Hsiang
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Chuang, Wei-Tsung
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Ko, Wen-Ching
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Chang, Chung-Kai