Versatile and low-cost manufacturing processes/materials are essential for the development of paper electronics. Here, a direct-write laser patterning process is developed to make conductive molybdenum carbide-graphene (MCG) composites directly on paper substrates. The hierarchically porous MCG structures are converted from fibrous paper soaked with the gelatin-mediated inks containing molybdenum ions. The resulting Mo C and graphene composites are mechanically stable and electrochemically active for various potential applications, such as electrochemical ion detectors and gas sensors, energy harvesters, and supercapacitors. Experimentally, the electrical conductivity of the composite is resilient to mechanical deformation with less than 5% degradation after 750 cycles of 180° repeated folding tests. As such, the direct laser conversion of MCGs on papers can be applicable for paper-based electronics, including the 3D origami folding structures.

The normal impinging of nanoscale water droplets on the solid surface is investigated through molecular dynamics simulations. A wide regime of impinging from spreading to breakup is studied. The overestimations of dissipation and surface free energy in literature are modified with a more accurate assumption on flow fields. The refined model fits well with the simulation results by introducing the linear distribution of radial velocity gradient. Two modes of breakup are observed during the nanodroplet impinging on the surface: (1) touch-bottom of the surface of the liquid film and (2) propagation of finger-like projections on the flow frontier. The touch-bottom breakup is possibly the dominant mode in cases with large We and small Re. The criterion is proposed to be that the amplitude of the capillary wave is larger than the average height of the droplets at the maximum spreading state. This criterion gives a well prediction comparing to the results obtained in molecular dynamics simulations.

While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min.

Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis. However, large-scale, cost-effective, and precursor-free methods to prepare ultrathin carbides are lacking. Here, we demonstrate a direct pattern method to manufacture ultrathin carbides (MoC x , WC x , and CoC x ) on versatile substrates using a CO 2 laser. The laser-sculptured polycrystalline carbides (macroporous, ~10–20 nm wall thickness, ~10 nm crystallinity) show high energy storage capability, hierarchical porous structure, and higher thermal resilience than MXenes and other laser-ablated carbon materials. A flexible supercapacitor made of MoC x demonstrates a wide temperature range (−50 to 300 °C). Furthermore, the sculptured microstructures endow the carbide network with enhanced visible light absorption, providing high solar energy harvesting efficiency (~72 %) for steam generation. The laser-based, scalable, resilient, and low-cost manufacturing process presents an approach for construction of carbides and their subsequent applications.