Konstantinos A. Sierros

Transparent conductive carbon‐nanotube films directly coated onto flexible and rigid polycarbonate

— Carbon nanotubes have quickly emerged over the last several years as a potential candidate material to replace metal oxides in devices which require transparent and conductive electrodes. Typically, these materials are coated onto substrates such as PET and PEN for flexible electrodes and glass for rigid electrodes. Recently, there has been interest in more durable and lightweight substrates to replace glass, one such substrate being polycarbonate. Sputter coating of indium tin oxide onto polycarbonate leads to low conductivity and inconsistent results, due to out-gassing and materials mismatch issues. In this work, it is shown that direct coating of carbon nanotubes onto polycarbonate leads to high-performance films with facile manufacturing.

Robotic Deposition of TiO2 Films on Flexible Substrates from Hybrid Inks: Investigation of Synthesis–Processing–Microstructure–Photocatalytic Relationships

TiO2 is an important material widely used in optoelectronic devices due to its semiconducting and photocatalytic properties, nontoxicity, and chemically inert nature. Some indicative applications include water purification systems and energy harvesting. The use of solution, water-based inks for the direct writing of TiO2 on flexible substrates is of paramount importance since it enables low-cost and low-energy intensive large-area manufacturing, compatible with roll-to-roll processing. In this work we study the effect of crystalline TiO2 and polymer addition on the rheological and direct writing properties of Ti-organic/TiO2 inks. We also report on the bridging crystallite formation from the Ti-organic precursor into the TiO2 crystalline phase, under ultraviolet (UV) exposure or mild heat treatments up to 150 °C. Such crystallite formation is found to be enhanced by polymers with strong polarity and pKα such as polyacrylic acid (PAA). X-ray diffraction (XRD) coupled with Raman and X-ray photoelectron (XPS) spectroscopy are used to investigate the crystalline-phase transformation dependence based on the initial TiO2 crystalline-phase concentration and polymer addition. Transmission electron microscopy imaging and selected area electron diffraction patterns confirm the crystalline nature of such bridging printed structures. The obtained inks are patterned on flexible substrates using nozzle-based robotic deposition, a lithography-free, additive manufacturing technique that allows the direct writing of material in specific, digitally predefined, substrate locations. Photocatalytic degradation of methylene blue solutions highlights the potential of the studied films for chemical degradation applications, from low-cost environmentally friendly materials systems.

Mechanical integrity of touch‐screen components

— Despite efforts to replace them, ceramic-coated polymer electrodes are still enjoying an extensive use in touch-screen applications. Their mechanical behavior is of importance and can have an effect on the structural integrity of the touch system. In this paper, the mechanical and tribological response of such electrodes, under cyclic loading conditions, is investigated. Controlled buckling experiments and reciprocating wear studies are performed. Buckling experimental results suggest that the residual stresses present in the film can play an important role in the overall mechanical integrity of the device. Also, tribological studies show that an irreversible damage of the ITO functionality, above 1000 reciprocating cycles, takes place. Understanding and improving the mechanical and tribological reliability of touch-screen electrodes will result in designing touch-screen devices with enhanced structural integrity.

Toxicity evaluations of nanoclays and thermally degraded byproducts through spectroscopical and microscopical approaches.

BACKGROUNDnMontmorillonite is a type of nanoclay that originates from the clay fraction of the soil and is incorporated into polymers to form nanocomposites with enhanced mechanical strength, barrier, and flammability properties used for food packaging, automotive, and medical devices. However, with implementation in such consumer applications, the interaction of montmorillonite-based composites or derived byproducts with biological systems needs to be investigated.nnnMETHODSnHerein we examined the potential of Cloisite Na+ (pristine) and Cloisite 30B (organically modified montmorillonite nanoclay) and their thermally degraded byproducts to induce toxicity in model human lung epithelial cells. The experimental set-up mimicked biological exposure in manufacturing and disposal areas and employed cellular treatments with occupationally relevant doses of nanoclays previously characterized using spectroscopical and microscopical approaches. For nanoclay-cellular interactions and for cellular analyses respectively, biosensorial-based analytical platforms were used, with induced cellular changes being confirmed via live cell counts, viability assays, and cell imaging.nnnRESULTSnOur analysis of byproducts chemical and physical properties revealed both structural and functional changes. Real-time high throughput analyses of exposed cellular systems confirmed that nanoclay induced significant toxic effects, with Cloisite 30B showing time-dependent decreases in live cell count and cellular viability relative to control and pristine nanoclay, respectively. Byproducts produced less toxic effects; all treatments caused alterations in the cell morphology upon exposure.nnnCONCLUSIONSnOur morphological, behavioral, and viability cellular changes show that nanoclays have the potential to produce toxic effects when used both in manufacturing or disposal environments.nnnGENERAL SIGNIFICANCEnThe reported toxicological mechanisms prove the extensibility of a biosensorial-based platform for cellular behavior analysis upon treatment with a variety of nanomaterials.

P‐73: Mechanical Assisted Corrosion: An Investigation of Thin Film Components used in Flexible Optoelectronic Applications

During flexible optoelectronic device packaging, acid containing layers initiate the functional failure of the underlying indium tin oxide film. We experimentally investigate the stressassisted corrosion cracking of thin conductive optoelectronic components. It is essential to understand the stress corrosion mechanisms in order to design highly durable flexible electronic structures.

Short-Term Pulmonary Toxicity Assessment of Pre- and Post-incinerated Organomodified Nanoclay in Mice

Organomodified nanoclays (ONCs) are increasingly used as filler materials to improve nanocomposite strength, wettability, flammability, and durability. However, pulmonary risks associated with exposure along their chemical lifecycle are unknown. This studys objective was to compare pre- and post-incinerated forms of uncoated and organomodified nanoclays for potential pulmonary inflammation, toxicity, and systemic blood response. Mice were exposed via aspiration to low (30 μg) and high (300 μg) doses of preincinerated uncoated montmorillonite nanoclay (CloisNa), ONC (Clois30B), their respective incinerated forms (I-CloisNa and I-Clois30B), and crystalline silica (CS). Lung and blood tissues were collected at days 1, 7, and 28 to compare toxicity and inflammation indices. Well-dispersed CloisNa caused a robust inflammatory response characterized by neutrophils, macrophages, and particle-laden granulomas. Alternatively, Clois30B, I-Clois30B, and CS high-dose exposures elicited a low grade, persistent inflammatory response. High-dose Clois30B exposure exhibited moderate increases in lung damage markers and a delayed macrophage recruitment cytokine signature peaking at day 7 followed by a fibrotic tissue signature at day 28, similar to CloisNa. I-CloisNa exhibited acute, transient inflammation with quick recovery. Conversely, high-dose I-Clois30B caused a weak initial inflammatory signal but showed comparable pro-inflammatory signaling to CS at day 28. The data demonstrate that ONC pulmonary toxicity and inflammatory potential relies on coating presence and incineration status in that coated and incinerated nanoclay exhibited less inflammation and granuloma formation than pristine montmorillonite. High doses of both pre- and post-incinerated ONC, with different surface morphologies, may harbor potential pulmonary health hazards over long-term occupational exposures.

Early assessment and correlations of nanoclay’s toxicity to their physical and chemical properties

Nanoclays functionalization with organic modifiers increases their individual barrier properties, thermal stability, and mechanical properties and allows for ease of implementation in food packaging materials or medical devices. Previous reports have shown that, while organic modifiers integration between the layered mineral silicates leads to nanoclays with different degrees of hydrophobicity that become easily miscible in polymers, they could also pose possible effects at inhalation or ingestion routes of exposure. Through a systematic analysis of three organically modified and one pristine nanoclay, we aimed to relate for the first time the physical and chemical characteristics, determined via microscopical and spectroscopical techniques, with the potential of these nanoclays to induce deleterious effects in in vitro cellular systems, i.e. in immortalized and primary human lung epithelial cell lines. To derive information on how functionalization could lead to toxicological profiles throughout nanoclays life cycle, both as-received and thermally degraded nanoclays were evaluated. Our analysis showed that the organic modifiers chemical composition influenced both the physical and chemical characteristics of the nanoclays as well as their toxicity. Overall, when cells were exposed to nanoclays with organic modifiers containing bioreactive groups, they displayed lower cellular numbers as well more elongated cellular morphologies relative to the pristine nanoclay and the nanoclay containing a modifier with long carbon chains. Additionally, thermal degradation caused loss of the organic modifiers as well as changes in size and shape of the nanoclays, which led to changes in toxicity upon exposure to our model cellular systems. Our study provides insight into the synergistic effects of chemical composition, size, and shape of the nanoclays and their toxicological profiles in conditions that mimic exposure in manufacturing and disposal environments, respectively, and can help aid in safe-by-design manufacturing of nanoclays with user-controlled functionalization and lower toxicity levels when food packaging applications are considered.

P‐184: Highly Durable Transparent Carbon Nanotube Films for Flexible Displays and Touch ‐ Screens

This paper describes a durable carbon nanotube (CNT) film, used in flexible displays and touch-screens, and its mechanical properties. CNT films as thin as 10 nm thick have properties approaching those of existing electrodes based on indium tin oxide (ITO) but with significantly improved mechanical properties. These durable CNT-based electrodes hold the key to developing robust, large-area, lightweight, optoelectronic devices such as lighting, displays, electronic-paper, and printable solar cells. Such devices could hold the key to producing inexpensive green energy, providing reliable solid-state lighting, and significantly reducing our dependence on paper.

59.2: Durable Solid State Flexible LED Devices

Energy efficient solid state lighting flexible and lightweight devices can offer an attractive alternative to bulky traditional rigid lighting solutions. We demonstrate a highly durable solid state flexible light emitting diode device and we report on critical factors during device manufacturing and use. We also propose alternative materials in order to further enhance the operational lifetime of the device.

Electrically Switchable Liquid Crystal Polymer Rod Actuators

Stimulus responsive liquid crystal nanorods, 60 μm in length and 200 nm in diameter, were fabricated by a template synthesis technique. The liquid crystal, RM 257, is a reactive monomer which polymerizes with the application of UV light. After polymerization the liquid crystals orientational order is permanently “frozen”. Therefore, the subsequent structures are temperature independent after curing. In this study the liquid crystal was confined in the pores of Anopore membranes before curing, which results in rod structures after photo-polymerization. After fabrication, the rods were observed under the application of both AC and DC electric fields. DC fields were noted by either up and down or translational movement of the rods. Application of AC fields resulted in random movement of the rods.