Inkjet-Printed Polyelectrolyte Seed Layer-Based, Customizable, Transparent, Ultrathin Gold Electrodes and Facile Implementation of Photothermal Effect.

Recently, interest in transparent electrodes has been increasing in biomedical engineering applications for such as electro-optical hybrid neuro-technologies. However, conventional photolithography-based electrode fabrication methods have limited design customization and large-area applicability. For biomedical engineering applications, it is crucial that we can easily customize the electrode design for different patients over a large body area. In this paper, we propose a novel method to fabricate customization-friendly, transparent, ultrathin, gold microelectrodes using inkjet printing technology. Unlike with typical direct printing of conductive inks, we inkjet-printed a polymer nucleation-inducing seed layer, followed by mask-less vacuum deposition of ultrathin gold (<6 nm) to produce selectively, high-transparency electrodes in the predefined shapes of the inkjet-printed polymer. Owing to the design flexibility of inkjet printing, the transparent ultrathin gold electrodes can be highly efficient in design customization over a large area. Simultaneously, a layer of nonconductive gold islands is formed in the nonprinted region, and this nanostructured layer can implement a photothermal effect that offers versatility for novel biomedical applications. As a demonstration of the effectiveness of these transparent electrodes, and the facile implementation of the photothermal effect for biomedical applications, we successfully fabricated transparent resistive temperature detectors. We used these to directly sense the photothermal effect and to demonstrate their bioimaging capabilities.

Designing a Bimodal BaTiO3 Artificial Layer to Boost the Dielectric Effect toward Highly Reversible Dendrite-Free Zn Metal Anodes.

With the growing interest in suppressing greenhouse gas emissions from fossil fuel combustion, the implementation of electrical energy storage devices for efficiently utilizing renewable energy is expanding worldwide. Zn-ion batteries are attractive for energy storage because of their safety, eco-friendliness, high energy density, and low cost. However, their commercialization is hindered by the poor rechargeability of the zinc anode because of Zn dendrite growth and hydrogen evolution. Herein, we present the application of an artificial layer composed of bimodal BaTiO3 particles on Zn metal to boost the dielectric properties and thus enhance the reversibility of Zn anodes during long-term cycling. The BaTiO3 layer induces electric polarization under external electric fields, causing the Zn ions to move sequentially toward the Zn anode. Moreover, its mechanical characteristics alleviate the volume changes between the BaTiO3 layer and Zn metal. Consequently, Zn dendrite growth is effectively inhibited, and the electrochemical performance is significantly improved in Zn|Zn symmetric cells, resulting in a low overvoltage (39 mV) and stable cycling (800 h) at 1 mA cm-2. Moreover, the Zn-ion full cell using an α-MnO2 cathode exhibits consistent capacity retention up to 380 cycles. This study demonstrates a new strategy to economically and readily suppress dendrite formation by using bimodal dielectric particles as artificial layers to stabilize metal-based batteries.