Roll-to-roll processed, highly conductive, and flexible aluminum (Al) electrodes based on Al precursor inks.

In this study, a roll-to-roll (R2R) process for the large-scale fabrication of aluminum thin films on flexible polyimide (PI) films is proposed. The R2R machine for Al-film coating assembled in the current work uses a previously reported Al etherate-based precursor ink as the source. After the PI substrate is exposed to a diluted catalyst, the Al precursor ink is coated directly on to the substrate by a slit-die coating method.

Al-Coated Conductive Fiber Filters for High-Efficiency Electrostatic Filtration: Effects of Electrical and Fiber Structural Properties.

Through the direct decomposition of an Al precursor ink AlH{O(CH)}, we fabricated an Al-coated conductive fiber filter for the efficient electrostatic removal of airborne particles (>99%) with a low pressure drop (~several Pascals). The effects of the electrical and structural properties of the filters were investigated in terms of collection efficiency, pressure drop, and particle deposition behavior. The collection efficiency did not show a significant correlation with the extent of electrical conductivity, as the filter is electrostatically charged by the metallic Al layers forming electrical networks throughout the fibers.

Washable antimicrobial polyester/aluminum air filter with a high capture efficiency and low pressure drop.

Here, we introduce a reusable bifunctional polyester/aluminum (PET/Al) air filter for the high efficiency simultaneous capture and inactivation of airborne microorganisms. Both bacteria of Escherichia coli and Staphylococcus epidermidis were collected on the PET/Al filter with a high efficiency rate (∼99.99%) via the electrostatic interactions between the charged bacteria and fibers without sacrificing pressure drop.

Soft Material-Enabled, Flexible Hybrid Electronics for Medicine, Healthcare, and Human-Machine Interfaces.

Flexible hybrid electronics (FHE), designed in wearable and implantable configurations, have enormous applications in advanced healthcare, rapid disease diagnostics, and persistent human-machine interfaces. Soft, contoured geometries and time-dynamic deformation of the targeted tissues require high flexibility and stretchability of the integrated bioelectronics. Recent progress in developing and engineering soft materials has provided a unique opportunity to design various types of mechanically compliant and deformable systems.

Solution-Processed Metal Coating to Nonwoven Fabrics for Wearable Rechargeable Batteries.

Wearable rechargeable batteries require electrode platforms that can withstand various physical motions, such as bending, folding, and twisting. To this end, conductive textiles and paper have been highlighted, as their porous structures can accommodate the stress built during various physical motions. However, fabrics with plain weaves or knit structures have been mostly adopted without exploration of nonwoven counterparts.

Functional Circuitry on Commercial Fabric via Textile-Compatible Nanoscale Film Coating Process for Fibertronics.

Fabric-based electronic textiles (e-textiles) are the fundamental components of wearable electronic systems, which can provide convenient hand-free access to computer and electronics applications. However, e-textile technologies presently face significant technical challenges. These challenges include difficulties of fabrication due to the delicate nature of the materials, and limited operating time, a consequence of the conventional normally on computing architecture, with volatile power-hungry electronic components, and modest battery storage.

Simple Approach to High-Performance Stretchable Heaters Based on Kirigami Patterning of Conductive Paper for Wearable Thermotherapy Applications.

Recent efforts to develop stretchable resistive heaters open up the possibility for their use in wearable thermotherapy applications. Such heaters should have high electrothermal performance and stability to be used practically, and the fabrication must be simple, economic, reproducible, and scalable. Here we present a simple yet highly efficient way of producing high-performance stretchable heaters, which is based on a facile kirigami pattering (the art of cutting and folding paper) of a highly conductive paper for practical wearable thermotherapy.

Al-Coated Conductive Fibrous Filter with Low Pressure Drop for Efficient Electrostatic Capture of Ultrafine Particulate Pollutants.

Here, we demonstrate a new strategy of air filtration based on an Al-coated conductive fibrous filter for high efficient nanoparticulate removals. The conductive fibrous filter was fabricated by a direct decomposition of Al precursor ink, AlH{O(CH)}, onto surfaces of a polyester air filter via a cost-effective and scalable solution-dipping process. The prepared conductive filters showed a low sheet resistance (<1.

Highly Stretchable, Hysteresis-Free Ionic Liquid-Based Strain Sensor for Precise Human Motion Monitoring.

A highly stretchable, low-cost strain sensor was successfully prepared using an extremely cost-effective ionic liquid of ethylene glycol/sodium chloride. The hysteresis performance of the ionic-liquid-based sensor was able to be improved by introducing a wavy-shaped fluidic channel diminishing the hysteresis by the viscoelastic relaxation of elastomers. From the simulations on visco-hyperelastic behavior of the elastomeric channel, we demonstrated that the wavy structure can offer lower energy dissipation compared to a flat structure under a given deformation.

Long-term sustainable aluminum precursor solution for highly conductive thin films on rigid and flexible substrates.

To fabricate the highly conductive Al film via a solution process, AlH3 etherates have been a unique Al source despite their chemical instability in solvents and thus lack of long-term sustainability. Herein, we suggest an innovative solution process to overcome the aforementioned drawbacks in AlH3 etherates; AlH3 aminates powder, which can be stored in low temperature surroundings and redissolved in solvents whenever it is needed. Since refrigeration of AlH3 aminates, AlH3{N(CH3)3}, was very effective to prevent its chemical degradation, Al film with excellence and uniformity in electrical and mechanical properties was successfully fabricated even by the 180-day stored AlH3{N(CH3)3} dissolved in solvents.

Ultrasmooth, extremely deformable and shape recoverable Ag nanowire embedded transparent electrode.

Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens. Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices.

Highly conductive aluminum textile and paper for flexible and wearable electronics.

Light to wear: Aluminum coated fibrous materials with excellent electrical conductivity and mechanical endurance are fabricated at room temperature by a chemical solution process. The resulting aluminum-coated conductive papers and threads can be used in electric circuits for flexible and wearable electronics.

Direct deposition of highly conductive aluminum thin film on substrate by solution-dipping process.

A solution-dipping process consisting of 2 steps, including (i) a catalytic treatment of the substrate and (ii) an immersion of the catalytically treated substrate into an aluminum precursor solution of AlH3{O(C4H9)2}, is suggested for the low-cost and simple preparation of aluminum thin film. This process can be applied to electric devices in the way of not only various film geometry including large area (□ 100 mm (W) × 100 mm (L)) or patterned structure but also the diverse substrate selectivity including rigid or flexible substrate. More interestingly, preparations of aluminum film in this study can be unprecedentedly accomplished at room temperature with the help of chemical catalyst to decompose AlH3{O(C4H9)2} into Al, 1.

Solution processed aluminum paper for flexible electronics.

As an alternative to vacuum deposition, preparation of highly conductive papers with aluminum (Al) features is successfully achieved by the solution process consisting of Al precursor ink (AlH(3){O(C(4)H(9))(2)}) and low temperature stamping process performed at 110 °C without any serious hydroxylation and oxidation problems. Al features formed on several kinds of paper substrates (calendar, magazine, and inkjet printing paper substrates) are less than ~60 nm thick, and their electrical conductivities were found to be as good as thermally evaporated Al film or even better (≤2 Ω/□). Strong adhesion of Al features to paper substrates and their excellent flexibility are also experimentally confirmed by TEM observation and mechanical tests, such as tape and bending tests.

A novel solution-stamping process for preparation of a highly conductive aluminum thin film.

A novel solution-stamping process for the preparation of a highly conductive aluminum thin film on both rigid and flexible substrates is proposed. The superior electrical properties of Al thin films fabricated by the solution-stamping process compared to silver and gold films fabricated from colloidal nanoparticles are experimentally demonstrated, and their applications in electronic circuits on rigid and flexible substrates and to organic light-emitting diodes (OLEDs) are investigated.

Tailoring the morphology of CdSe nanocrystals by incorporation of Pb.

We have investigated the effects of Pb2+ addition on the morphological development of CdSe nanocrystals. We show that the addition of Pb ions in the initial precursor solution changed the morphology of CdSe nanocrystals to branched rods with high aspect ratio. The branched nanocrystals are mainly composed of wurzite phase grown along the [001] direction and the length of rods in each branched nanocrystal can be increased by increasing the amount of Pb2+ addition to accelerate the anisotropic growth of the nanocrystals.

Nanoparticle assembly on patterned "plus/minus" surfaces from electrospray of colloidal dispersion.

Selective deposition of metal (Au) and oxide (SiO2) nanoparticles with a size range of 10-30 nm on patterned silicon-silicon oxide substrate was performed using the electrospray method. Electrical charging characteristics of particles produced by the electrospray and patterned area created by contact charging of the electrical conductor with non- or semi-conductors were investigated. Colloidal droplets were electrosprayed and subsequently dried as individual nanoparticles which then were deposited on substrates, and observed using field emission-scanning electron microscopy.