Flexible, compact, lightweight and sustainable power sources are indispensable for modern wearable and personal electronics and small-unmanned aerial vehicles (UAVs). Hierarchical honeycomb has the unique merits of compact mesostructures, excellent energy absorption properties and considerable weight to strength ratios. Herein, a honeycomb-inspired triboelectric nanogenerator (h-TENG) is proposed for biomechanical and UAV morphing wing energy harvesting based on contact triboelectrification wavy surface of cellular honeycomb structure. The wavy surface comprises a multilayered thin film structure (combining polyethylene terephthalate, silver nanowires and fluorinated ethylene propylene) fabricated through high-temperature thermoplastic molding and wafer-level bonding process. With superior synchronization of large amounts of energy generation units with honeycomb cells, the manufactured h-TENG prototype produces the maximum instantaneous open-circuit voltage, short-circuit current and output power of 1207 V, 68.5 μA and 12.4 mW, respectively, corresponding to a remarkable peak power density of 0.275 mW cm−3 (or 2.48 mW g−1) under hand pressing excitations. Attributed to the excellent elastic property of self-rebounding honeycomb structure, the flexible and transparent h-TENG can be easily pressed, bent and integrated into shoes for real-time insole plantar pressure mapping. The lightweight and compact h-TENG is further installed into a morphing wing of small UAVs for efficiently converting the flapping energy of ailerons into electricity for the first time. This research demonstrates this new conceptualizing single h-TENG device's versatility and viability for broad-range real-world application scenarios.

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This paper presents a novel process and manufacturing system for the fabrication of Electric Double-Layer Capacitors (EDLCs) as energy storage devices. It shows an approach for printing multilayer EDLC components using 3D printing technology. A dual nozzle deposition system was used based on a fused deposition modelling (FDM) process. This process allows layers of activated carbon (AC) slurry, gel electrolyte and composite solid filaments to be printed with high precision. This paper describes the detailed process of deposition of the AC and gel electrolyte using the dual nozzle system. It describes the energy storage performance of the printed supercapacitors in relation to differences in thickness in the AC printed layers. A supercapacitor based on printed AC and composite materials displays a specific capacitance of 38.5 mF g -1 when measured at a potential rate change of 20 mV s -1 and a current density of 0.136 A g -1 .

To simplify the miniature fuel cell structure and flow mode, we report here a microfluidic fuel cell running on H 2 O 2 as both fuel and oxidant under acidic conditions. Prussian blue coating on carbon paper serves as the cathode side while the anode is made of three-dimensional flow-through Ni foam. The fuel cell achieves a power density in excess of 0.58 ± 0.13 W m −2 at a current density of 3.68 ± 0.1 A m −2 , and an open circuit potential of 0.65 V. Importantly, the Ni foam shows a corrosion in H 2 O 2 -catalyzing after a long-term operation, which is seriously neglected by most of previous H 2 O 2 -running fuel cells. SEM images and XPS spectra demonstrate a gradient corrosion occurs in the three-dimensional flow-through porous Ni-foam electrode. The corrosion degree of Ni foam gradually aggravates along the vertical direction, which is caused by the gradient accumulation of H 2 O in the porous electrode. The protection methods including surface coating a protection layer and doping some more reactive metals have been proposed to improve the system commercialization.

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