Plasmonic color generation offers several advantages but is also limited by the cost and availability of noble metals like gold. In this work, we present color-tunable metasurfaces with high chromaticity and reflectivity consisting of an aluminum mirror, a dielectric spacer, and a plasmonic nanohole array in copper. Copper is shown to be an excellent alternative to gold when properly protected from oxidation and makes it possible to generate a wide RGB gamut covering 27% of the standard RGB. By patterning the metasurfaces into microscale pixel triplets, color photos can be well reproduced with high resolution over wafer-sized areas. Further, we demonstrate active modulation of the reflected intensity using an electrochromic conductive polymer deposited on top of the nanostructures by screen printing. This technology opens up for ultrathin and flexible reflective displays in full color, that is, plasmonic electronic paper, compatible with large-scale sustainable production.

Organic electronic ion pumps (OEIPs) are a versatile tool for electrophoretic delivery of substances with high spatiotemporal resolution. To date, OEIPs and similar iontronic components have been fabricated using thin-film techniques, and often rely on laborious, multistep photolithographic processes. OEIPs have been demonstrated in a variety of in vitro and in vivo settings for controlling biological systems, but the thin-film form factor and limited repertoire of polyelectrolyte materials and device fabrication techniques unnecessarily constrain the possibilities for miniaturization and extremely localized substance delivery, e.g., the greater range of pharmaceutical compounds, on the scale of a single cell. Here, we demonstrate an entirely new OEIP form factor based on capillary fibers that include hyperbranched polyglycerols (dPGs) as the selective electrophoretic membrane. The dPGs enable electrophoretic channels with high concentration of fixed charges, well-controlled cross-linking, and can be realized using a simple "one-pot" fluidic manufacturing protocol. Selective electrophoretic transport of cations and anions of various sizes is demonstrated, including "large" substances difficult to transport with other OEIP technologies. We present a method for tailoring and characterizing the electrophoretic channels' fixed charge concentration in the operational state. Subsequently, we compare the experimental performance of these capillary-OEIPs to a computational model and are able to explain unexpected features in the ionic current for the transport and delivery of larger, lower mobility ionic compounds. From the model, we are able to elucidate several operational and design principles relevant for miniaturized electrophoretic drug delivery technologies in general. Overall, the compactness of the capillary-OEIP enables electrophoretic delivery devices with probe-like geometries, suitable for a variety of ionic compounds, paving the way for less-invasive implantation into biological systems and for healthcare applications.

The advent of the Internet of Things and the growing interest in continuous monitoring by wearables have created a need for conformable and stretchable displays. Electrochromic displays (ECDs) are receiving attention as a cost-effective solution for many simple applications. However, stretchable ECDs have yet to be produced in a robust, large scale and cost-efficient manner. Here we develop a process for making fully screen printed stretchable ECDs. By evaluating commercially available inks with respect to electromechanical properties, including electrochromic PEDOT:PSS inks, our process can be directly applied in the manufacturing of stretchable organic electronic devices. The manufactured ECDs retained colour contrast with useful switching times at static strains up to 50 % and strain cycling up to 30 % strain. To further demonstrate the applicability of the technology, double-digit 7-segment ECDs were produced, which could conform to curved surfaces and be mounted onto stretchable fabrics while remaining fully functional. Based on their simplicity, robustness and processability, we believe that low cost printed stretchable ECDs can be easily scaled up and will find many applications within the rapidly growing markets of wearable electronics and the Internet of Things.

Biological systems use a large variety of ions and molecules of different sizes for signaling. Precise electronic regulation of biological systems therefore requires an interface which translates the electronic signals into chemically specific biological signals. One technology for this purpose that has been developed during the last decade is the organic electronic ion pump (OEIP). To date, OEIPs have been fabricated by micropatterning and labor-intensive manual techniques, hindering the potential application areas of this promising technology. Here we show, for the first time, fully screen-printed OEIPs. We demonstrate a large-area printed design with manufacturing yield >90%. Screen-printed cation- and anion-exchange membranes are both demonstrated with promising ion selectivity and performance, with transport verified for both small ions (Na+, K+, Cl–) and biologically-relevant molecules (the cationic neurotransmitter acetylcholine, and the anionic anti-inflammatory salicylic acid). These advances open the ‘iontronics’ toolbox to the world of printed electronics, paving the way for a broader arena for applications.