Surface Modification of Polyimide Films for Inkjet-Printing of Flexible Electronic Devices

Kapton polyimide films are one of the most commonly used flexible and robust substrates for flexible electronic devices due to their excellent thermal, chemical, mechanical, and electrical properties. However, such films feature an inert and highly hydrophobic surface that inhibits the deposition of functional materials with water-based fluids (solutions, suspensions, inkjet inks, etc.), which raise the need for their surface modification to reduce their inherent surface inertness and/or hydrophobicity in order to allow for the fabrication of electronic devices on the substrates. Traditional Kapton surface modification approaches use harsh conditions that not only cause environmental and safety problems but also compromise the structural integrity and the properties of the substrates. This chapter focuses on two recently-developed mild and environmentally friendly wet chemical approaches for surface modification of Kapton HN films. Unlike the traditional methods that target the polyimide matrix of Kapton films, these two methods target the slip additive embedded in the polyimide matrix. The surface modified Kapton films resulted from these two methods allowed for not only great printability of both water- and organic solvent-based inks (thus facilitating the full-inkjet-printing of entire flexible electronic devices) but also strong adhesion between the inkjet-printed traces and the substrate films

Converting Silver Electrodes into Porous Gold Counterparts: A Strategy to Enhance Gas Sensor Sensitivity and Chemical Stability <em>via</em> Electrode Engineering

This chapter describes a strategy for sensitivity and chemical stability enhancement of chemiresistive gas sensors via electrode engineering. In this strategy, flexible chemiresistive gas sensors were fabricated by uniformly depositing functionalized semiconducting carbon nanotubes (CNTs) on a polyimide substrate via a novel layer-by-layer wet chemical method, followed by inkjet printing fine-featured silver interdigitated electrodes (IDEs) on the substrate. The electrode engineering was realized by converting the inkjet-printed IDEs into their highly porous and chemically stable gold counterparts via a mild and facile two-step process, with the substrate-IDE adhesion retained. As a proof-of-concept demonstration, a diethyl ethylphosphonate (DEEP, a simulant of the nerve agent sarin) sensor equipped with inkjet-printed dense silver IDEs was converted into its counterpart equipped with highly porous gold IDEs. The resulting gold-electrode gas sensor exhibited sensitivity to DEEP of at least fivefold higher than a similar sensor electrode with the dense silver IDEs. The sensitivity enhancement was probably due to the catalytic activity of the resulting gold IDEs, as well as the creation of the nano−/micro-scale pores in the gold IDEs that increased the Schottky contacts between the gold IDEs and the semiconducting CNTs

Assessing the disease burden of Yi people by years of life lost in Shilin county of Yunnan province, China

<p>Abstract</p> <p>Background</p> <p>Years of Life Lost (YLL) is one of the methods used to estimate the duration of time lost due to premature death. While previous studies of disease burden have been reported using YLL, there have been no studies investigating YLL of Yi people in rural China. Yunnan Province ranks first in terms of Yi people in China. This paper uses YLL to estimate the disease burden of Yi people in Shilin county of Yunnan Province. This study aims to address the differentials about YLL between Yi people and Han people for providing useful information for health planning.</p> <p>Methods</p> <p>We applied the Global Burden of Disease (GBD) method created by WHO. YLL rate per 1,000 were calculated from medical death certificates in 2003 in Shilin Yi Nationality Autonomous County (Shilin county).</p> <p>Results</p> <p>The male had greater YLL rate per 1,000 than did the female almost in each age group. It demonstrated a higher premature mortality burden due to injuries in Shilin county. Among the top non-communicable diseases, respiratory diseases are the most common mortality burden. Yi people are still suffering from maternal conditions, with two times the burden rates of Han people. For Yi people, while malignant neoplasm was one of the least burden of disease for male, it was the greatest for female, which is the opposite to Han people.</p> <p>Conclusion</p> <p>Strategies of economic development should be reviewed to enhance the prevention and treatment of injuries, maternal conditions and respiratory diseases for Yi people.</p

Contrasting rift and subduction-related plagiogranites in the Jinshajiang ophiolitic mélange, southwest China, and implications for the Paleo-Tethys

The Jinshajiang ophiolitic mélange zone in southwest China represents a remnant of the eastern Paleo-Tethys Ocean. Field, geochronological and geochemical studies have identified two distinct suites of plagiogranites within the mélange, the Dongzhulin trondhjemite and Jiyidu tonalite, which represent rift and subduction settings, respectively, related to opening and closing of the ocean. SHRIMP U-Pb analysis on zircons extracted from the Dongzhulin trondhjemite yields a mean 206Pb/238U age of 347 ± 7 Ma. REE and isotopic characteristics suggest an origin from low pressure partial melting of an amphibolitic protolith. Highly variable Hf isotopic compositions for zircons from this body may indicate a heterogenous source involving both depleted mantle and enriched continental components. This, together with geologic relations, suggests formation near an embryonic spreading center in a continent-ocean transition setting. The Jiyidu tonalite has a U-Pb zircon age of 283 ± 3 Ma, and geochemical data indicates high Sr/Y, (La/Yb)N, Nb/Ta and low Y, and marked heavy REE depletion. These signatures suggest derivation from low degree partial melting of subducted slab at pressure high enough to stabilize garnet and rutile. A slab-melt origin is also supported by in situ Hf and O data for zircon that show isotopic compositions comparable with typical altered oceanic crust. Thus, the crystallization age of the Jiyidu high Sr/Y tonalite provides a constraint for the subduction of the Jinshajiang ocean floor. The rift-related Dongzhulin trondhjemite and subduction-related Jiyidu high-Sr/Y tonalite constrain the timing and setting of opening and closing of this segment of the Paleo-Tethys Ocean

Sensitivity enhancement of flexible gas sensors via conversion of inkjet-printed silver electrodes into porous gold counterparts

This work describes a facile, mild and general wet chemical method to change the material and the geometry of inkjet-printed interdigitated electrodes (IDEs) thus drastically enhancing the sensitivity of chemiresistive sensors. A novel layer-by-layer chemical method was developed and used to uniformly deposit semiconducting single-wall carbon nanotube (SWCNT)-based sensing elements on a Kapton® substrate. Flexible chemiresistive sensors were then fabricated by inkjet-printing fine-featured silver IDEs on top of the sensing elements. A mild and facile two-step process was employed to convert the inkjet-printed dense silver IDEs into their highly porous gold counterparts under ambient conditions without losing the IDE-substrate adhesion. A proof-of-concept gas sensor equipped with the resulting porous gold IDEs featured a sensitivity to diethyl ethylphosphonate (DEEP, a simulant of the nerve agent sarin) of at least 5 times higher than a similar sensor equipped with the original dense silver IDEs, which suggested that the electrode material and/or the Schottky contacts between the electrodes and the SWCNTs might have played an important role in the gas sensing process.publishedVersionPeer reviewe

Inverted polymer solar cells with amorphous indium zinc oxide as the electron-collecting electrode

© 2010 Optical Society of AmericaThe definitive version of this paper is available at: http://dx.doi.org/10.1364/OE.18.00A506DOI: 10.1364/OE.18.00A506We report on the fabrication and performance of polymer-based inverted solar cells utilizing amorphous indium zinc oxide (a-IZO) as the electron-collecting electrode. Amorphous IZO films of 200 nm thickness were deposited by room temperature sputtering in a high-purity argon atmosphere. The films possessed a high optical transmittance in the visible region (≥ 80%), a low resistivity (3.3 × 10⁻⁴ Ωcm), a low surface roughness (root mean square = 0.68 nm), and a low work function (4.46 ± 0.02 eV). Inverted solar cells with the structure a-IZO/P3HT: PCBM/PEDOT:PSS/Ag exhibited a power conversion efficiency of 3% estimated for AM 1.5G, 100 mW/cm² illumination