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We propose and demonstrate an ultra-sensitive plasmonic fiber-optic hot-wire anemometer. This instrument comprises a highly tilted fiber Bragg grating-assisted surface plasmon resonance (SPR) sensor, which is coated with carbon nanotubes as the photothermal conversion element. The carbon nanotubes on the sensor surface efficiently convert light from the heating laser, of which wavelength matched to the SPR window, into heat, thereby setting the sensor in an elevated temperature state. Air flow draws away surface heat, thus inducing both a strong SPR wavelength shift and power modulation. Using this anemometer, we experimentally achieve a dynamic range of 0.05 to 0.65 m/s for wind speed measurement. Furthermore, we demonstrate real-time monitoring of wind speed by measuring the intensity of the heating laser. This sensor is simple and robust in structure. It has a wide range of potential applications in both scientific research and industrial production. [ABSTRACT FROM AUTHOR]

With the increasing demand for compact storage systems for portable and wearable electronic devices, flexible supercapacitors with high volumetric performance have attracted considerable attention. Here, we report a simple method to fabricate a sandwich-like carbon nanotubes (CNTs)/NiCo2O4 hybrid paper electrode, consisting of a layer of conductive CNT buckypaper coated with honeycomb-like NiCo2O4 nanosheets at both sides. Owing to the high conductivity of the CNT skeleton and vertically aligned structure of NiCo2O4 nanosheets, the free-standing hybrid paper possesses an ultra-high specific capacitance of 1752.3 F g−1 and excellent cycling performance. A flexible all-solid-state symmetrical supercapacitor has been further assembled based on the hybrid paper. The device exhibits excellent volumetric energy and power densities (1.17 mW h cm−3 and 2430 mW cm−3) and deformability, even under bending at an angle of 180°. The hybrid paper can serve as a freestanding and flexible electrode for various energy devices. [ABSTRACT FROM AUTHOR]

Naturally existing materials often acquire unique functions by adopting a gradient structure with gradual change in their microstructure and related properties. Imparting such an elegant structural control into synthetic materials has been a grand challenge in the fi eld. Here, the concept of gradient structure into macroscopic carbon nanotube (CNT) fi lms is employed and the CNT arrangement from well-aligned array to completely random distribution, in a continuous and smooth way, is changed. Gradient films with tailored alignedto- random transition rate or multilevel hierarchical structures with repeated transition have been fabricated. Local deformation and mechanical properties are directly related to the arrangement of CNTs and can be tailored by Herman's orientation factor; in particular, the elastic modulus and stiffness span over several orders of magnitude from aligned to random regions within a single monolithic film. Controlled synthesis of macroscopic CNT gradient structures with tunable mechanical properties opens a potential route toward manufacturing biomimetic functional materials with locally optimized design. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors are of great importance to be applied in artificial intelligence and wearable electronics. However, assembling a simple structure, high-performance capacitive pressure sensor, especially for monitoring the flow of liquids, is still a big challenge. Here, on the basis of a sandwich-like structure, we propose a facile capacitive pressure sensor optimized by a flexible, low-cost nylon netting, showing many merits including a high response sensitivity (0.33 kPa -1 ) in a low-pressure regime (<1 kPa), an ultralow detection limit as 3.3 Pa, excellent working stability after more than 1000 cycles, and synchronous monitoring for human pulses and clicks. More important, this sensor exhibits an ultrafast response speed (<20 ms), which enables its detection for the fast variations of a small applied pressure from the morphological changing processes of a droplet falling onto the sensor. Furthermore, a capacitive pressure sensor array is fabricated for demonstrating the ability to spatial pressure distribution. Our developed pressure sensors show great prospects in practical applications such as health monitoring, flexible tactile devices, and motion detection.

Nature-motivated pressure sensors have been greatly important components integrated into flexible electronics and applied in artificial intelligence. Here, we report a high sensitivity, ultrathin, and transparent pressure sensor based on wrinkled graphene prepared by a facile liquid-phase shrink method. Two pieces of wrinkled graphene are face to face assembled into a pressure sensor, in which a porous anodic aluminum oxide (AAO) membrane with the thickness of only 200 nm was used to insulate the two layers of graphene. The pressure sensor exhibits ultrahigh operating sensitivity (6.92 kPa -1 ), resulting from the insulation in its inactive state and conduction under compression. Formation of current pathways is attributed to the contact of graphene wrinkles through the pores of AAO membrane. In addition, the pressure sensor is also an on/off and energy saving device, due to the complete isolation between the two graphene layers when the sensor is not subjected to any pressure. We believe that our high-performance pressure sensor is an ideal candidate for integration in flexible electronics, but also paves the way for other 2D materials to be involved in the fabrication of pressure sensors.

It is unavoidable to form wrinkles, which are folds or creases in a material, in graphene, whenever the graphene is prepared by micromechanical exfoliation from graphite or chemical vapor deposition (CVD). However, the controllable formation and structures of graphene with nanoscale wrinkles remains a big challenge. Here, we report a liquid-phase shrink method to controllably fabricate large-area wrinkled graphene (WG). The CVD-prepared graphene self-shrinks into a WG on an ethanol solution surface. By modifying the concentration of the ethanol solution, we can easily and efficiently obtain WG with a uniform distribution of wrinkles with different heights. The WG shows high stretchability and can withstand more than 100% tensile strain and up to 720° twist. Furthermore, electromechanical response sensors based on double-layer stacking of WG show ultrahigh sensitivity. This simple, effective, and environmentally friendly liquid-phase shrink method will pave a way for the controllable formation of WG, which is an ideal candidate for application in highly stretchable and highly sensitive electronic devices.