A general approach to composites containing nonmetallic fillers and liquid gallium.

We report a versatile method to make liquid metal composites by vigorously mixing gallium (Ga) with non-metallic particles of graphene oxide (G-O), graphite, diamond, and silicon carbide that display either paste or putty-like behavior depending on the volume fraction. Unlike Ga, the putty-like mixtures can be kneaded and rolled on any surface without leaving residue. By changing temperature, these materials can be stiffened, softened, and, for the G-O-containing composite, even made porous. The gallium putty (GalP) containing reduced G-O (rG-O) has excellent electromagnetic interference shielding effectiveness. GalP with diamond filler has excellent thermal conductivity and heat transfer superior to a commercial liquid metal-based thermal paste. Composites can also be formed from eutectic alloys of Ga including Ga-In (EGaIn), Ga-Sn (EGaSn), and Ga-In-Sn (EGaInSn or Galinstan). The versatility of our approach allows a variety of fillers to be incorporated in liquid metals, potentially allowing filler-specific "fit for purpose" materials.

Low cost synthesis of reduced graphene oxide using biopolymer for influenza virus sensor.

A biocompatible, cost-effective, and scalable reduced graphene oxide (rGO) film was obtained from shellac using thermal treatment and its structural, chemical, and electrical properties were investigated. This thermally-decomposed rGO (TrGO) film exhibited good crystallinity, low sheet resistance, and high carbon content. TrGO flakes obtained from the film were dispersed and drop cast onto indium tin oxide/glass electrodes to fabricate label-free electrochemical immunosensors for the quantitative detection of the influenza virus H1N1 via electrochemical impedance spectroscopy. These sensors exhibited high stability and reproducibility, both possibly ascribable to the high adhesion of TrGO due to its phenolic-OH moiety; the limits of detection were 26 and 33 plaque-forming units, respectively, in phosphate-buffered saline and diluted saliva. These cost-effective TrGO-based sensors showed great potential as reliable and robust nanomaterial-based biosensors for widespread clinical applications.

Ultrastiff, Strong, and Highly Thermally Conductive Crystalline Graphitic Films with Mixed Stacking Order.

A macroscopic film (2.5 cm × 2.5 cm) made by layer-by-layer assembly of 100 single-layer polycrystalline graphene films is reported. The graphene layers are transferred and stacked one by one using a wet process that leads to layer defects and interstitial contamination. Heat-treatment of the sample up to 2800 °C results in the removal of interstitial contaminants and the healing of graphene layer defects. The resulting stacked graphene sample is a freestanding film with near-perfect in-plane crystallinity but a mixed stacking order through the thickness, which separates it from all existing carbon materials. Macroscale tensile tests yields maximum values of 62 GPa for the Young's modulus and 0.70 GPa for the fracture strength, significantly higher than has been reported for any other macroscale carbon films; microscale tensile tests yield maximum values of 290 GPa for the Young's modulus and 5.8 GPa for the fracture strength. The measured in-plane thermal conductivity is exceptionally high, 2292 ± 159 W m-1 K-1 while in-plane electrical conductivity is 2.2 × 105 S m-1 . The high performance of these films is attributed to the combination of the high in-plane crystalline order and unique stacking configuration through the thickness.