Patterned deposition of highly flexible transparent conducting materials is essential to realize stretchable optoelectronic devices. Silver nanowires (NWs) are suitable for these applications because they possess high electrical conductivity and good optical transparency. However, NWs have poor surface adhesion and large roughness. Embedding them in a conducting polymer, such as poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PE-DOT:PSS), is one way to overcome these disadvantages without affecting the optoelectronic properties. However, this is normally a two-step deposition process and difficult to pattern directly. In this work, we have formulated a stable and printable nanocomposite ink consisting of Ag NWs and PEDOT:PSS. This ink can be directly used for patterned deposition in a single-step process. The printed film shows 86% transparency and 23 Ω/sq sheet resistance, which is suitable for flexible transparent electrode applications. The printed film shows good adhesion and excellent stability to mechanical deformation, with less than 20% resistance variation after 10,000 bending cycles. The nanocomposite also exhibits improved thermal stability, planarity, reduced contact resistance, and good optical transparency when compared to pure Ag NWs. We demonstrate suitability of this nanocomposite using two applications −a printed transparent flexible antenna radiating at Wi-Fi frequencies and a printed transparent flexible heater suitable for antifogging applications. The nanocomposite properties make it suitable as a transparent electrode in flexible optoelectronic devices such as photovoltaics and light-emitting diodes.

Printed electronics is an emerging field involving the fabrication of electronic devices by the patterned deposition of material inks. For many systems, producing stable printable inks is the key challenge. In this work, the formulation of a silver nanowire-based ink for printed transparent electrode applications is described. The nanowire length and rheology of the ink are adjusted for printing, with a single layer printed film having a sheet resistance of approximately 30 Ω/, and a transmittance of 94% at 550 nm. The number of printed layers and volume per layer are optimized to get maximum transparency with good electrical conduction. A transparent capacitive touch pad, in the form of a 2×2 matrix is implemented, using this ink and with PDMS as the dielectric. The touch pad has a high degree of flexibility with a resistance variation less than 2% after 10 000 bending cycles. The formulated nanowire ink can be extended for other flexible and stretchable transparent sensing applications.

Silver nanowires (Ag NWs) have become a ubiquitous part of flexible electronic devices. The good electrical conductivity of silver, coupled with the excellent ductility and bendability exhibited by the wires make them ideal for flexible devices. Additionally, deposited films of Ag NWs are also found to be transparent due to the incomplete areal coverage of the wires. Thus, Ag NWs are widely used as transparent conducting electrodes (TCEs) for flexible and wearable electronics, replacing the traditionally used metal oxide based TCEs. The properties and functionality of NWs can be further improved by forming composites with other materials. Composites have been synthesized by combining Ag NWs with metals, metal oxides, and polymers. Both dry and wet- techniques have been used to synthesize and deposit these composites, which have unique structural, chemical, and functional properties leading to myriad applications. This review focuses on recent developments in the field of Ag NW-based composites. An overview of the various fabrication techniques is provided, with a particular focus on coating and printing techniques, which are widely used for depositing Ag NWs. The application of the composites in diverse fields is also discussed. While the most common application for these composites is as TCEs, they are also used in sensors (physical, chemical, and biological), displays, and energy-related applications. The structural and environmental stability of the composites is also discussed. Given the wide interest in the development of printed flexible electronic devices, new Ag NW-based composites and application areas can be expected to be developed going forward.

In this work, we describe the preparation of a zinc oxide-ethylene glycol nanoparticle ink and the parameters that control the printing using a custom-built direct writer system. The ink (nanoparticle dispersion) was prepared using a two-step wet synthesis method, without using any surfactant. Its viscosity was found to be in the suitable range for printing and straight lines were printed on cleaned glass substrates. The influence of various printing parameters, such as total dispersed volume, number of printed layers, substrate temperature, drying temperature and time, and particle loading, on the morphology of the printed patterns was investigated. In-situ and post-printing drying of the printed pattern, at the same temperature, produced different morphologies, which can be attributed to the direction of heat transfer and solvent removal. Optimization of these printing parameters enabled us to obtain a continuous printed pattern with uniform morphology using a direct writing system, which can be extended to a variety of nanoparticle based inks.

Flexible, lightweight, low-power, and low-cost displays are an active area of interest in the electronics community. In this work, we have developed a composite electrothermochromic material consisting of silver nanowires (Ag NWs) and thermochromic powders, which exhibits reversible color (phase) change during biasing due to Joule heating. A wide variety of color combinations are possible with suitable thermochromic material selection. We have formulated this composite material as a printable ink so that patterned deposition can be achieved in a single step. A low processing temperature of 100 °C makes the composite compatible with a wide range of flexible substrates such as paper and polyethylene terephthalate (PET). The material (encapsulated with polydimethylsiloxane (PDMS)) exhibits good flexibility and is observed to be functional after 10 000 bending cycles with <7% resistance change. We have fabricated a low-power seven-segment color display to show the material’s suitability for practical display applications. We have also demonstrated that the same layer can function as a display and as a touch sensor because of its conducting and chromatic properties without additional active layers on top. The material is suitable for the fabrication of low-cost, flexible touch color displays for interactive electronic readers, digital posters, and flexible digital signboards.