Printing technology can be used for manufacturing stretchable electrodes, which represent essential parts of wearable devices requiring relatively high degrees of stretchability and conductivity. In this work, a strategy for fabricating printable and highly stretchable conductors are proposed by transferring printed Ag ink onto stretchable substrates comprising Ecoflex elastomer and tough hydrogel layers using a water-soluble tape. The elastic modulus of the produced hybrid film is close to that of the hydrogel layer, since the thickness of Ecoflex elastomer film coated on hydrogel is very thin (30 µm). Moreover, the fabricated conductor on hybrid film is stretched up to 1780% strain. The described transfer method is simpler than other techniques utilizing elastomer stamps or sacrificial layers and enables application of printable electronics to the substrates with low elastic moduli (such as hydrogels). The integration of printed electronics with skin-like low-modulus substrates can be applied to make wearable devices more comfortable for human skin.

Thin (0.5 to 1 microm) layers of nonaligned or quasi-aligned hollow ZnO fibers were prepared by sputtering ZnO onto sacrificial templates comprising polyvinyl-acetate (PVAc) fibers deposited by electrospinning on silicon or alumina substrates. Subsequently, the ZnO/PVAc composite fibers were calcined to remove the organic components and crystallize the ZnO overlayer, resulting in hollow fibers comprising nanocrystalline ZnO shells with an average grain size of 23 nm. The inner diameter of the hollow fibers ranged between 100 and 400 nm and their wall thickness varied from 100 to 40 nm from top to bottom. The electronic transport and gas sensing properties were examined using DC conductivity and AC impedance spectroscopy measurements under exposure to residual concentrations (2-10 ppm) of NO(2) in air at elevated temperatures (200-400 degrees C). The inner and outer surface regions of the hollow ZnO fibers were depleted of mobile charge carriers, presumably due to electron localization at O(-) adions, constricting the current to flow through their less resistive cores. The overall impedance comprised interfacial and bulk contributions. Both contributions increased upon exposure to electronegative gases such as NO(2) but the bulk contribution was more sensitive than the interfacial one. The hollow ZnO fibers were much more sensitive compared to reference ZnO thin film specimens, displaying even larger sensitivity enhancement than the 2-fold increase in their surface to volume ratio. The quasi-aligned fibers were more sensitive than their nonaligned counterparts.

Significant progress has been achieved recently in developing dye-sensitized solar cells (DSSCs) [1] for low-cost solarpower devices using typical thick (∼ 12 lm) films of TiO 2 nanoparticles. [1][2][3] However, in TiO 2 nanoparticle-based DSSCs, the photoconverison efficiency is often limited by the disordered electrode morphology, which gives rise to interfacial interferences for electron transport. [4][5][6][7] To overcome this limitation, wide bandgap semiconducting oxides comprising 1D and 2D nanostructures have been proposed as promising solutions. [8][9][10][11][12][13][14] These include oriented single-crystalline ZnO nanowires, [8] quasi-ordered arrays of TiO 2 nanotubes, [15][16][17][18] core/shell nanostructures, [19][20][21][22] and 2D hollow structures assembled by colloidal templates.[23]In conjunction with these efforts, growing attention has also been paid to the importance of thin-film devices for use in DSSCs.[24] The key challenge here has been to enhance the surface area of thin-film electrodes. A TiO 2 electrode with a high surface area is necessary to effectively adsorb the dye and achieve a high photocurrent.[1] So far, however, there have been only a few reports on processing strategies designed to provide markedly enhanced surface activities and photocurrent efficiency for thin-film photoelectrodes (≤ 1-2 lm).[15] In particular, there are very few studies on TiO 2 electrodes prepared by physical vapor deposition (PVD), i.e., sputtering, which is a conventional method used in preparing thin films. [25,26] The sputtered film shows a dense columnar microstructure that provides efficient electron paths, a large internal surface area, and mitigates recombination processes. [25,27] Even though sputtered films give rise to a faster electron diffusion coefficient, the amount of dye they adsorbs is still small compared to nanoparticle-based TiO 2 electrodes because the sputtered films typically exhibit densely packed or pore-free morphologies. [25,26] In order to satisfy the requirements for fast electron transport and high surface area in thin-film photoelectrodes, we have combined colloidal templates and rf-sputtering to deposit quasi-ordered hollow TiO 2 hemispheres [28] on conducting glass substrates. This fabrication route produced monolayer-dispersed colloidal templates, providing flexible dimensional control over such features as colloidal diameter (hemisphere size) and shell thickness. Enhanced photoconversion efficiency was obtained due to the predominant role of the hollow structure in promoting electron transport [29] as well as a large surface area for enhanced dye loading. Moreover, the macroporous structure with hollow hemispheres allowed even viscous electrolytes to easily penetrate up to the glass substrate. In this work, the suitability of ordered hollow TiO 2 hemisphere films for highefficiency photoelectrodes in DSSCs was examined further. The scheme in Figure 1 illustrates the procedure used to fabricate the DSSCs used in this study. Detailed processing procedures are described...

A hierarchical nanostructure of PS‐b‐PEO is demonstrated (see figure) with a novel approach by solvent vapor annealing of a micropatterned block copolymer thin film selectively spun cast on microcontact printed surface of SAMs. Dewetting of the thin film, inevitable during the ordering of block copolymer microdomains upon solvent annealing, is strictly confined to the patterned regions, leading to the controlled micropatttern with nearly perfect ordering of PEO microdomains.