Transparent, Stretchable, and Conductive SWNT Films Using Supramolecular Functionalization and Layer-by-Layer Self-Assembly

We demonstrate films of single-walled carbon nanotubes (SWNTs) on the elastomer polydimethylsiloxane (PDMS) that are stretchable, conductive, and transparent. Our fabrication method uses the supramolecular functionalization of SWNTs with conjugated polyelectrolytes to generate aqueous dispersions of positively- and negatively-charged SWNTs, followed by layer-by-layer self-assembly onto a PDMS substrate. Adding bilayers of positively- and negatively-charged SWNTs to the surface causes the sheet resistance and the % transmittance of the film to both progressively decrease. The sheet resistance decreases sharply in the first five bilayers as the layer-by-layer process efficiently establishes the percolation network, whereas the % transmittance declines more gradually. Films with 25 bilayers are transparent (75% at 550 nm) and conductive (560 ± 90 ohms/sq). The combination of electrostatic and pi-stacking forces very effectively bind the SWNTs within the film, producing smooth film surfaces (root-mean-square roughness of 18 nm) and enabling the films to remain conductive up to 80% elongation. We demonstrate the use of the SWNT films as transparent conductive electrodes in light-emitting devices and as soft strain sensors that are both wearable and transparent

Fabrication of elastomeric wires by selective electroless metallization of poly(dimethylsiloxane)

The study was conducted for fabrication of elastomeric wires by selective electroless metallization of poly(dimethylsiloxane) (PDMS). The microcontact printing method was used to define a chemical pattern on an elastomeric substrate PDMS. The pattern directs the deposition of metal on the PDMS surface from an electroless deposition. Integrating metals with elastomers in an effective way to create flexible conductors. The high conductivity and mechanical flexibility result from microfabricating metal wires on the surface of PDMS or enclosing electroplated wires in PDMS. The selective electroless metallization of PDMS is a rapid an inexpensive way to fabricate flexible conductive pathways. The method is particularly well-suited to the fabrication of electrodes,which can be laminated on organic devices based on fragile or ultrathin organic materials. The preparation of the flexible electronic circuitry has provided the reliable, inexpensive fabrication approach that needed for future lightweight and flexible devices

Silver Nanowire/Optical Adhesive Coatings as Transparent Electrodes for Flexible Electronics

We present new flexible, transparent, and conductive coatings composed of an annealed silver nanowire network embedded in a polyurethane optical adhesive. These coatings can be applied to rigid glass substrates as well as to flexible polyethylene terephthalate (PET) plastic and elastomeric polydimethylsiloxane (PDMS) substrates to produce highly flexible transparent conductive electrodes. The coatings are as conductive and transparent as indium tin oxide (ITO) films on glass, but they remain conductive at high bending strains and are more durable to marring and scratching than ITO. Coatings on PDMS withstand up to 76% tensile strain and 250 bending cycles of 15% strain with a negligible increase in electrical resistance. Since the silver nanowire network is embedded at the surface of the optical adhesive, these coatings also provide a smooth surface (root mean squared surface roughness \u3c10 nm), making them suitable as transparent conducting electrodes in flexible light-emitting electrochemical cells. These devices continue to emit light even while being bent to radii as low as 1.5 mm and perform as well as unstrained devices after 20 bending cycles of 25% tensile strain. © 2013 American Chemical Society

New Dihexadecyldithiophosphate SAMs on Gold Provide Insight into the Unusual Dependence of Adsorbate Chelation on Substrate Morphology in SAMs of Dialkyldithiophosphinic Acids

We report the formation and characterization of new self-assembled monolayers (SAMs) formed from dihexadecyldithiophosphate (C16) 2DDP and compare their properties with those of SAMs formed from the structurally similar adsorbate dihexadecyldithiophosphinic acid (C 16)2DTPA. The new (C16)2DDP SAMs were characterized using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact angle measurements, and electrochemical impedance spectroscopy. The data indicate that (C16)2DDP forms SAMs on gold films formed by e-beam evaporation in which all adsorbates chelate to gold, in contrast to (C16)2DTPA SAMs, in which 40% of the adsorbates are monodentate. The alkyl chains of the (C 16)2DDP SAM are also less densely packed and ordered than those of the (C16)2DTPA SAM. To understand these differences, we present density functional theory calculations that show that there are only minimal differences between the geometric and electronic structures of the two adsorbates and that the energetic difference between monodentate and bidentate binding of a gold(I) ion are surprisingly small for both adsorbates. This study leads to the conclusion that differences in intermolecular interactions within the SAM are the driving force for the difference in chelation between the two adsorbates. © 2013 American Chemical Society