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Supercapacitor-like Na-ion batteries have attracted much attention due to the high energy density of batteries and power density of capacitors. Titanium dioxide (TiO2), is a promising anode material. Its performance is however seriously hindered by its low electrical conductivity and the sluggish diffusion of sodium ions (Na+) in the TiO2 matrix. Herein, this work combines porous TiO2 nanocubes with carbon nanotubes (CNTs) to enhance the electrical conductivity and accelerate Na+ diffusivity for Na-ion batteries (NIBs). In this composite, an interwoven scaffolded TiO2/CNTs framework is formed to provide abundant channels and shorter diffusion pathways for electrons and ions. The in-situ X-ray diffraction and cyclic voltammetry confirm the low strain and superior transport kinetics in Na+ intercalation/extraction processes. In addition, the chemically bonded TiO2/CNTs hybrid provides a more feasible channel for Na+ insertion/extraction with a much lower energy barrier. Consequently, the TiO2/CNTs composite exhibits excellent electrochemical performance with a capacity of 223.4 mAh g−1 at 1 C and a capacity of 142.8 mAh g−1 at 10 C (3.35 A g−1). The work here reveals that the combination of active materials with CNTs can largely improve the utilization efficiency and enhance their sodium storage.

Flexographic printing is promising for large-area electronics due to high print-speed and roll-to-roll capability. There have been recent attempts in using graphene as an active pigment in inks, most notably for slower techniques such as inkjet and screen printing. However, formulation of graphene-enhanced inks for high-speed printing and its effect on key metrics have never been investigated. Herein, graphene nanoplatelets (GPs) are incorporated to a conductive flexographic ink without compromising the rheological properties. An industrial scale at 100 m min−1 is printed on paper and polyethylene terephthalate (PET) substrates using a commercial flexographic press, and statistical performance variations are investigated across entire print runs. It is shown that GP-incorporation improves sheet-resistance (Rs) and uniformity, with up to 54% improvement in average Rs and 45% improvement in the standard-deviation on PET. The adhesion on both the substrates improves with GP-incorporation, as verified by tape/crosshatch tests. The durability of GP-enhanced samples is probed with a 1000 cyclic bend-test, with 0.31% average variation in resistance in the flat state on PET between the first and last 100 bends, exhibiting a robust print. The statistically scalable results show that GP-incorporation offers a cost-performance advantage for flexographic printing of large-area conductive patterns without modifications to traditional high-speed graphics printing presses. Published version We acknowledge funding from the Engineering and Physical Sciences Research Council (EP/L016087/1) and Alphasense Limited in United Kingdom.

We demonstrate the first fully-printed resistive random access memory (RRAM) on flexible substrate using 2D layered dichalcogenides, exhibiting ultra-low switching voltage down to 0.18 V and an on/off ratio up to 107. The novel switching medium is printed by formulating multilayer molybdenum disulfide (MoS2) into 3D-printable ink. Both volatile and non-volatile resistive switching are achieved within a single device by varying current compliance, which enables the implementation of electronic synapse with neuromorphic functionality including short-term plasticity (STP) and long-term plasticity (LTP).

We report high-energy mid-infrared pulse generation by Q-switching of dysprosium-doped fiber lasers for the first time. Two different modulation techniques are demonstrated. Firstly, using active acousto-optic modulation, pulses are produced with up to 12 {\mu}J energy and durations as short as 270 ns, with variable repetition rates from 100 Hz to 20 kHz and central wavelengths tunable from 2.97 to 3.23 {\mu}m. Experiments are supported by numerical modeling, identifying routes for improved pulse energies and to avoid multi-pulsing by careful choice of modulator parameters. Secondly, we demonstrate passive Q-switching by fabricating an inkjet-printed black phosphorus saturable absorber, simplifying the cavity and generating 1.0 {\mu}J pulses with 740 ns duration. The performance and relative merits of each modulation approach are then critically discussed. These demonstrations highlight the potential of dysprosium as a versatile gain medium for high-performance pulsed sources beyond 3 {\mu}m.

Printing has drawn a lot of attention as a means of low per-unit cost and high throughput patterning of graphene inks for scaled-up thin-form factor device manufacturing. However, traditional printing processes require a flat surface and are incapable of achieving patterning on to 3D objects. Here, we present a conformal printing method to achieve functional graphene-based patterns on to arbitrarily-shaped surfaces. Using experimental design, we formulate a water-insoluble graphene ink with optimum conductivity. We then print single and multi-layered electrically functional structures on to a sacrificial layer using conventional screen printing. The print is then floated on water, allowing the dissolution of the sacrificial layer, while retaining the functional patterns. The single and multilayer patterns can then be directly transferred on to arbitrarily-shaped 3D objects without requiring any post deposition processing. Using this technique, we demonstrate conformal printing of single and multilayer functional devices that include joule heaters, resistive strain sensors and proximity sensors on hard, flexible and soft substrates, such as glass, latex, thermoplastics, textiles, and even candies and marshmallows. Our simple strategy offers great promises to add new device and sensing functionalities to previously inert 3D surfaces., 12 pages, 5 Figures

Solution‐processable thin‐film dielectrics represent an important material family for large‐area, fully‐printed electronics. Yet, in recent years, it has seen only limited development, and has mostly remained confined to pure polymers. Although it is possible to achieve excellent printability, these polymers have low (≈2–5) dielectric constants (εr). There have been recent attempts to use solution‐processed 2D hexagonal boron nitride (h‐BN) as an alternative. However, the deposited h‐BN flakes create porous thin‐films, compromising their mechanical integrity, substrate adhesion, and susceptibility to moisture. These challenges are addressed by developing a “one‐pot” formulation of polyurethane (PU)‐based inks with h‐BN nano‐fillers. The approach enables coating of pinhole‐free, flexible PU+h‐BN dielectric thin‐films. The h‐BN dispersion concentration is optimized with respect to exfoliation yield, optical transparency, and thin‐film uniformity. A maximum εr ≈ 7.57 is achieved, a two‐fold increase over pure PU, with only 0.7 vol% h‐BN in the dielectric thin‐film. A high optical transparency of ≈78.0% (≈0.65% variation) is measured across a 25 cm2 area for a 10 μm thick dielectric. The dielectric property of the composite is also consistent, with a measured areal capacitance variation of, A hexagonal boron nitride‐enhanced, flexible, and optically transparent thin‐film dielectric is reported. The pin‐hole‐free composite is fabricated by K‐bar coating and shows up to a two‐fold increase in dielectric constant. The optical transparency is consistent, with 0.65% variation. The formulation is suitable for large‐area applications such as printed capacitors and transparent capacitive touch surfaces.

EPSRC (EP/L016087/1), A*STAR Science and Engineering Research Council (Grant No. 152-70-00013, and 152-70-00017), Singapore National Research Foundation’s Returning Singapore Scientist Scheme (Grant No. NRF-RSS2015-003), The National Research Foundation, Prime Minister's Office, Singapore.