The formation of 3D objects composed of shape memory polymers for flexible electronics is described. Layer-by-layer photopolymerization of methacrylated semicrystalline molten macromonomers by a 3D digital light processing printer enables rapid fabrication of complex objects and imparts shape memory functionality for electrical circuits.

Stretchable UV-curable (SUV) elastomers can be stretched by up to 1100% and are suitable for digital-light-processing (DLP)-based 3D-printing technology. DLP printing of these SUV elastomers enables the direct creation of highly deformable complex 3D hollow structures such as balloons, soft actuators, grippers, and buckyball electronical switches.

We report here a concept for utilization of the "coffee ring effect" and inkjet printing to obtain transparent conductive patterns, which can replace the widely used transparent conductive oxides, such as ITO. The transparent conductive coating is achieved by forming a 2-D array of interconnected metallic rings. The rim of the individual rings is less than 10 microm in width and less than 300 nm in height, surrounding a "hole" with a diameter of about 150 microm; therefore the whole array of the interconnected rings is almost invisible to the naked eye. The rims of the rings are composed of self-assembled, closely packed silver nanoparticles, which make the individual rings and the resulting array electrically conductive. The resulting arrays of rings have a transparency of 95%; resistivity of 0.5 cm(2) was 4 +/- 0.5 Omega/, which is better than conventional ITO transparent thin films. The silver rings and arrays are fabricated by a very simple, low cost process, based on inkjet printing of a dispersion of 0.5 wt % silver nanoparticles (approximately 20 nm diameter) on plastic substrates. The performance of this transparent conductive coating was demonstrated by using it as an electrode for a plastic electroluminescent device, demonstrating the applicability of this concept in plastics electronics. It is expected that such transparent conductive coatings can be used in a wide range of applications such as displays (LCD, plasma, touch screens, e-paper), lighting devices (electroluminescence, OLED), and solar cells.

The field of 3D printing, also known as additive manufacturing (AM), is developing rapidly in both academic and industrial research environments. New materials and printing technologies, which enable rapid and multimaterial printing, have given rise to new applications and utilizations. However, the main bottleneck for achieving many more applications is the lack of materials with new physical properties. Here, some of the recent reports on novel materials in this field, such as ceramics, glass, shape-memory polymers, and electronics, are reviewed. Although new materials have been reported for all three main printing approaches-fused deposition modeling, binder jetting or laser sintering/melting, and photopolymerization-based approaches, apparently, most of the novel physicochemical properties are associated with materials printed by photopolymerization approaches. Furthermore, the high resolution that can be achieved using this type of 3D printing, together with the new properties, has resulted in new implementations such as microfluidic, biomedical devices, and soft robotics. Therefore, the focus here is on photopolymerization-based additive manufacturing including the recent development of new methods, novel monomers, and photoinitiators, which result in previously inaccessible applications such as complex ceramic structures, embedded electronics, and responsive 3D objects.

This is a review on recent developments in the field of transparent conductive coatings (TCCs) for ITO replacement. The review describes the basic properties of conductive nanomaterials suitable for fabrication of such TCCs (metallic nanoparticles and nanowires, carbon nanotubes and graphene sheets), various methods of patterning the metal nanoparticles with formation of conductive transparent metallic grids, honeycomb structures and 2D arrays of interconnected rings as well as fabrication of TCCs based on graphene and carbon nanotubes. Applications of TCCs in electronic and optoelectronic devices, such as solar cells, electroluminescent and electrochromic devices, touch screens and displays, and transparent EMI shielders, are discussed.

Ink-jet printing of thermoelectric nanomaterials is successfully used to fabricate flexible thin film TE devices for power generation and cooling.

Printed electrochromic flexible films were obtained by combining transparent silver grid electrodes formed by self-assembly and inkjet printed WO3 nanoparticles. Concentrated dispersions of WO3 nanoparticles were inkjet printed on transparent plastic silver grid electrodes with a high transparency of 83% in the spectral range of 400-800 nm, and a low sheet resistance in the range of 1-5 Ω sq(-1). These electrodes were used for electrochromic applications for the first time. The resultant patterned nanostructured electrochromic films maintained their coloring and bleaching performance after bending of the flexible films.

Transparent conductive coatings are essential for fabrication of a variety of printed electronic devices such as flexible displays and solar cells. We report on a simple method to obtain such coatings by using aqueous dispersions of silver nanoparticles in an evaporative lithography process which is performed directly onto plastic substrates. In essence, a droplet containing silver nanoparticles is placed on top of a metallic mesh, instantaneously spreading over the mesh and the plastic substrate, and after the flow of the dispersion towards the wires of the mesh and drying, a transparent grid composed of the nanoparticles is formed. The silver nanoparticles are tailored to self-sinter upon short exposure to HCl vapors, due to the presence of polyacrylic acid salt on the surface of the particles. Therefore, immediate sintering of the silver nanoparticles in the thin lines of the grid occurs even at room temperature, enabling formation of transparent, flexible conductive grid on heat-sensitive substrates. The process yielded a conductive array having a very low sheet resistance, 9 AE 0.8 U/,, and a transparency above 75%. The application of the flexible conductive grid, which can replace conventional and expensive ITO, is demonstrated in an electroluminescent (EL) device.