develop new concepts or new technologies to effectively harvest wind energy in various forms around us and further power the smart systems.Recently, triboelectric nanogenerator (TENG) has been invented by Prof. Wang as an effective technology to harvest various forms of mechanical energy from our ambient environment, such as wind, sound, flowing water, and human motion, etc. [3][4][5][6][7][8][9] Compared with traditional wind energy harvesting technology, the TENG has many advantages of simple fabrication, light weight, excellent reliability, low cost, high power density, high energy conver-

The color and/or chromaticity controllability of random lasing is a key factor to promote practical applications of random lasers as high luminance sources for speckle-free imaging. Here, white coherent random lasing with tunable chromaticity is obtained by using broadband enhancement Au-Ag nanowires as scatterers and the resonance energy transfer process between different dyes in the capillary microfluidic channel. Red, green and blue random lasers are separately fabricated with low thresholds, benefiting from the plasmonic resonance of the nanogaps and/or nanotips with random distribution and sizes within Au-Ag nanowires and positive optical feedback provided by the capillary wall. A white random laser system is then designed through reorganizing the three random lasers. And, the chromaticity of the white random laser is flexibly tunable by adjusting pump power density. In addition, the white random laser has anisotropic spectra due to the coupling role between the lasers. This characteristic is then utilized to obtain different random lasing with different chromaticity over a broad visible range. The results may provide a basis for applying random laser in the field of high brightness illumination, biomedical imaging, and sensors.

A color-switchable random laser is designed through directly coupling random laser with a commercial optical fiber. By using a simple approach of selectively coating the random gain layer on the surface of fiber, the red and yellow random lasers are respectively achieved with low threshold and good emission direction due to the guiding role of optical fibers. Moreover, the unique coupling mechanism leads to the random lasing with ring-shape in momentum space, indicating an excellent illuminating source for high-quality imaging with an extremely low speckle noise. More importantly, random lasing with different colors can be flexible obtained by simply moving the pump position. The results may promote random lasers' practical applications in the fields of sensing, in vivo biologic imaging, high brightness full-field illuminating. Experimental MethodsThe fabrication process of the fiber source is illustrated in Fig. 1a. The typical gain materials used in this experiment are: 4-(Dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl) -4H-pyran(DCJTB, Tokyi Chemical Industry) and Pyrromethene567 (PM567, Sigma). The fabricated process of the fiber source is simply supplied as follows. First, polydimethylsiloxane (PDMS, n = 1.41) solution is mixed with cross-linking solution with the ratio of 1:10. Then, TiO 2 nanoparticles are dispersed in the dye-doped acetone solution (DCJTB at 1.5 mg mL -1 or PM567 at 1.25 mg mL -1 ) to obtain TiO 2 dispersion with a concentration of 0.9 mg mL -1 . The dye-doped TiO 2 dispersion and PDMS are mixed at a volume ratio of 1: 5 in an ultrasonic tank for 15 min and then vacuum them for 40 min to remove the air bubble. Finally, the mixture is dipped onto a clean fiber (TAIHAN Fiber Optics) to flow naturally. The length of the fiber is about 60 mm, the core diameter is 50 μm and the diameter of the cladding is 125 μm. The refractive indexes of the core and cladding layer are 1.54 and 1.52, respectively. The sample is placed in a drying oven at 80 °C for 3 hours to complete the cross-linking polymerization and drying. After cooling to room temperature, a fiber source is realized. Random lasers with different colors can be fabricated by coating different dye polymers at different locations on the surface of the fiber. And the polymer film with different thicknesses can be fabricated by controlling the dipping times.Acs Nano, 2017, 11. 36.

Programmable random lasing pulses are highly desired due to their promising applications in information security, flexible encoding systems, and smart imaging. However, the fixed random scattering configuration hinders their realization. Herein, a programmable random laser is designed to dynamically regulate random lasing pulses through introducing an external waveguide structure with random scattering feedback. Liquid and solid film random lasers are thus separately achieved. Most importantly, various pulse time series of random lasing can be flexibly realized by switching the adhesion/separation state between the gain and the destroyed waveguide structure. The Feinam coding system is further realized for encryption and information transmission by combining programmable random pulses. The results may widely expand the application prospects of random lasers in the fields of optical data recording, dynamic security labels, smart sensing, and flexible imaging.

Line width-tunable lasers have wide applications in the fields of high-resolution spectroscopy, optical communications, and other industry and scientific research. Here, manipulating plasmonic scattering of metal particles with plenty of nanogaps is proposed as an effective method to achieve line width-tunable random lasers. Assisted by the nonlinear optical effect of the surrounding medium, the multiscale scattering material demonstrates the transition from local scattering of nanogaps to large-scale profile scattering by increasing the pump power density. Based on these two scattering processes, random lasers can be continuously driven from a narrow-line-width configuration to a broad-line-width regime, demonstrating that line width variation exceeds 2 orders of magnitude. This phenomenon may provide a platform for further studying the conclusive mechanism of random lasing and supply a new approach to tune the line width of random lasers for further applications in high-illumination imaging and biology detection.