commercial polyimide (PI) films with infrared lasers in a protective atmosphere; while subsequent studies showed that LIG can also be processed with a variety of lasers, including infrared and ultraviolet lasers, [6,7] and using both synthetic materials and natural materials (e.g., cork and fruit shells [1,8] ) as the precursor of graphene. The microscopic mechanisms governing the LIG process have been investigated in recent years through reactive molecular dynamics models, [7,9,10] providing a theoretical base for understanding the graphene formation process during LIG.Various applications of LIG have been demonstrated, including supercapacitor, [11] gas sensor, [12] Joule heater, [13,14] and solid-state triboelectric nanogenerator (TENG). [15][16][17] Among these devices, TENG, which exploits the coupling effect of triboelectricity and electrostatic induction [18][19][20] to generate energy, has found applications in many areas. The device can not only collect small-scale environmental mechanical energy, such as kinetic energy of human movement, [21,22] mechanical vibration energy, [23][24][25][26] rotational kinetic energy, [27,28] wind energy, [29][30][31] etc., but also be used as a self-powered sensor for monitoring mechanical motion. [32,33] Laser-induced graphene (LIG) has emerged as a promising and versatile method for high-throughput graphene patterning; however, its full potential in creating complex structures and devices for practical applications is yet to be explored. In this study, an in-situ growing LIG process that enables to pattern superhydrophobic fluorine-doped graphene on fluorinated ethylene propylene (FEP)-coated polyimide (PI) is demonstrated. This method leverages on distinct spectral responses of FEP and PI during laser excitation to generate the environment preferentially for LIG formation, eliminating the need for multistep processes and specific atmospheres. The structured and water-repellant structures rendered by the spectral-tuned interfacial LIG process are suitable as the electrode for the construction of a flexible dropletbased electricity generator (DEG), which exhibits high power conversion efficiency, generating a peak power density of 47.5 W m −2 from the impact of a water droplet 105 µL from a height of 25 cm. Importantly, the device exhibits superior cyclability and operational stability under high humidity and various pH conditions. The facile process developed can be extended to realize various functional devices.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202104290.

In the past decade, graphene has shown great value in both fundamental sciences and practical applications. In spite of the intense research efforts on achieving chemical‐free, low‐temperature processing of high‐quality graphene, cost‐effective synthetic methods to directly fabricate graphene sheets on a substrate are still lacking. Laser‐induced graphene (LIG) is a recently developed method to directly form graphene from carbon‐rich materials. In this work, combined are theoretical and experimental approaches to systematically investigate the light‐material interactions in LIG fabrication processes. First, developed is a molecular dynamics model to disclose the transient formation process of LIG and identified are the critical parameters that govern this process. Following the theoretical prediction, developed is a system to utilize a picosecond UV laser to directly fabricate graphene from polyimide films at room temperature and under atmospheric pressure. After investigating the effects of the laser processing parameters on the LIG quality and subsequent processing optimization, it is experimentally demonstrated that picosecond UV laser processing can be used to prepare high‐quality LIG. With the newly developed LIG, fabricated is a high‐sensitive proximity sensor.

It is a challenge for any optical method to measure objects with a large range of reflectivity variation across the surface. Image saturation results in incorrect intensities in captured fringe pattern images, leading to phase and measurement errors. This paper presents a new adaptive digital fringe projection technique which avoids image saturation and has a high signal to noise ratio (SNR) in the three-dimensional (3-D) shape measurement of objects that has a large range of reflectivity variation across the surface. Compared to previous high dynamic range 3-D scan methods using many exposures and fringe pattern projections, which consumes a lot of time, the proposed technique uses only two preliminary steps of fringe pattern projection and image capture to generate the adapted fringe patterns, by adaptively adjusting the pixel-wise intensity of the projected fringe patterns based on the saturated pixels in the captured images of the surface being measured. For the bright regions due to high surface reflectivity and high illumination by the ambient light and surfaces interreflections, the projected intensity is reduced just to be low enough to avoid image saturation. Simultaneously, the maximum intensity of 255 is used for those dark regions with low surface reflectivity to maintain high SNR. Our experiments demonstrate that the proposed technique can achieve higher 3-D measurement accuracy across a surface with a large range of reflectivity variation.

Kinked silicon (Si) nanowires (NWs) have many special properties that make them attractive for a number of applications, such as microfluidics devices, microelectronic devices, and biosensors. However, fabricating NWs with controlled three-dimensional (3D) geometry has been challenging. In this work, a novel method called alternating metal-assisted chemical etching is reported for the fabrication of kinked Si NWs with controlled 3D geometry. By the use of multiple etchants with carefully selected composition, one can control the number of kinks, their locations, and their angles by controlling the number of etchant alternations and the time in each etchant. The resulting number of kinks equals the number times the etchant is alternated, the length of each segment separated by kinks has a linear relationship with the etching time, and the kinking angle is related to the surface tension and viscosity of the etchants. This facile method may provide a feasible and economical way to fabricate novel silicon nanowires, nanostructures, and devices for broad applications.

Silicon (Si) zigzag nanowires (NWs) have a great potential in many applications because of its high surface/volume ratio. However, fabricating Si zigzag NWs has been challenging. In this work, a diffusion-controlled metal-assisted chemical etching method is developed to fabricate Si zigzag NWs. By tailoring the composition of etchant to change its diffusivity, etching direction, and etching time, various zigzag NWs can be easily fabricated. In addition, it is also found that a critical length of NW (>1 μm) is needed to form zigzag nanowires. Also, the amplitude of zigzag increases as the location approaches the center of the substrate and the length of zigzag nanowire increases. It is also demonstrated that such zigzag NWs can help the silicon substrate for self-cleaning and antireflection. This method may provide a feasible and economical way to fabricate zigzag NWs and novel structures for broad applications.