Green Synthesis of Laser-Induced Graphene with Copper Oxide Nanoparticles for Deicing Based on Photo-Electrothermal Effect.

Homogenously dispersed Cu oxide nanoparticles on laser-induced graphene (LIG) were fabricated using a simple two-step laser irradiation. This work emphasized the synergetic photo-electrothermal effect in Cu oxide particles embedded in LIG. Our flexible hybrid composites exhibited high mechanical durability and excellent thermal properties. Moreover, the Cu oxide nanoparticles in the carbon matrix of LIG enhanced the light trapping and multiple electron internal scattering for the electrothermal effect. The best conditions for deicing devices were also studied by controlling the amount of Cu solution. The deicing performance of the sample was demonstrated, and the results indicate that the developed method could be a promising strategy for maintaining lightness, efficiency, excellent thermal performance, and eco-friendly 3D processing capabilities.

Direct Laser Interference Ink Printing Using Copper Metal-Organic Decomposition Ink for Nanofabrication.

In this study, we developed an effective and rapid process for nanoscale ink printing, direct laser interference ink printing (DLIIP), which involves the photothermal reaction of a copper-based metal-organic decomposition ink. A periodically lined copper pattern with a width of 500 nm was printed on a 240 µm-wide line at a fabrication speed of 17 mm/s under an ambient environment and without any pre- or post-processing steps. This pattern had a resistivity of 3.5 µΩ∙cm, and it was found to exhibit a low oxidation state that was twice as high as that of bulk copper. These results demonstrate the feasibility of DLIIP for nanoscale copper printing with fine electrical characteristics.

Laser-Induced Biochar Formation through 355 nm Pulsed Laser Irradiation of Wood, and Application to Eco-Friendly pH Sensors.

Due to the limited availability of agricultural land, pH sensing is becoming more and more important these days to produce efficient agricultural products. Therefore, to fabricate eco-friendly and disposable sensors, the black carbon, which is called biochar, is formed by irradiation of a UV pulsed laser having a wavelength of 355 nm onto wood and applying the resulting material as a pH sensor. The surfaces of three types of wood (beech, cork oak, and ash) were converted to the graphitic structure after UV laser irradiation; their morphologies were investigated. In addition, since the content of lignin, an organic polymer, is different for each wood, optimal laser irradiation conditions (laser fluence) needed to form these woods into pH sensors were considered. Depending on the degree of oil-like material generated after laser irradiation, a disposable pH sensor that can be used from one to three times is fabricated; due to the environmental characteristics of wood and biochar, the sensor shows high availability in that it can be easily discarded after use on agricultural land. After that, it can be used as filter in soil. Our wood-based pH sensor sensitively measures sequential changes from pH 4 to pH 10 and shows a very linear change of △R/R, indicating its potential for use in agriculture.

Fabrication of UV Laser-Induced Porous Graphene Patterns with Nanospheres and Their Optical and Electrical Characteristics.

Many studies have been conducted to fabricate unique structures on flexible substrates and to apply such structures to a variety of fields. However, it is difficult to produce unique structures such as multilayer, nanospheres and porous patterns on a flexible substrate. We present a facile method of nanospheres based on laser-induced porous graphene (LIPG), by using laser-induced plasma (LIP). We fabricated these patterns from commercial polyimide (PI) film, with a 355 nm pulsed laser. For a simple one-step process, we used laser direct writing (LDW), under ambient conditions. We irradiated the PI film at a defocused plane -4 mm away from the focal plane, for high pulse overlap rate. The effect of the laser scanning speed was investigated by FE-SEM, to observe morphological characterization. Moreover, we confirmed the pattern characteristics by optical microscope, Raman spectroscopy and electrical experiments. The results suggested that we could modulate the conductivity and structural color by controlling the laser scanning speed. In this work, when the speed of the laser is 20 mm/s and the fluence is 5.28 mJ/cm2, the structural color is most outstanding. Furthermore, we applied these unique characteristics to various colorful patterns by controlling focal plane.

Direct Fabrication of Ultra-Sensitive Humidity Sensor Based on Hair-Like Laser-Induced Graphene Patterns.

Three-dimensional (3-D) porous graphitic structures have great potential for sensing applications due to their conductive carbon networks and large surface area. In this work, we present a method for facile fabrication of hair-like laser induced graphene (LIG) patterns using a laser scribing system equipped with a 355 nm pulsed laser. The polyimide (PI) film was positioned on a defocused plane and irradiated at a slow scanning speed using a misaligned laser beam. These patterns have the advantages of a large surface area and abundant oxidation groups. We have applied the hair-like LIG patterns to a humidity sensor. The humidity sensor showed good sensitivity characteristics and a large amount of electronic carriers can be stored.

360 nm Continuous Wave Laser-Based Contact or Non-Contact Laser Interference Nano Lithography.

LIL (laser interference lithography), which does not require a mask, is an effective way to create a wide variety of periodic patterns by exposing two laser beams on a specimen. The LIL method can be used for a wide range of nano-pattern spacing by adjusting the laser intensity, exposure time, and development time. In addition, it has been used in many studies due to its advantage with regard to the forming of nanostructures over a large area in a short period of time. However, the existing LIL technique requires demanding precision levels to align the laser beam. In this paper, we attempt to solve this problem by using a prism laser interferometer to complement the complicated beam alignment of LIL. In this study, ma-p1205 PR-coated silicon wafers were exposed to a CW laser with 360 nm wavelength using a contact-type and a non-contact prism interferometer. A rectangular triangular prism and an equilateral triangular prism of N-BK7 were used, and periods of 300 nm and 260 nm were fabricated, respectively. The MATLAB and COMSOL programs were used to compare the theoretical values and fabricated patterns.

Flexible and Highly Sensitive Strain Sensor Based on Laser-Induced Graphene Pattern Fabricated by 355 nm Pulsed Laser.

A laser-induced-graphene (LIG) pattern fabricated using a 355 nm pulsed laser was applied to a strain sensor. Structural analysis and functional evaluation of the LIG strain sensor were performed by Raman spectroscopy, scanning electron microscopy (SEM) imaging, and electrical-mechanical coupled testing. The electrical characteristics of the sensor with respect to laser fluence and focal length were evaluated. The sensor responded sensitively to small deformations, had a high gauge factor of ~160, and underwent mechanical fracture at 30% tensile strain. In addition, we have applied the LIG sensor, which has high sensitivity, a simple manufacturing process, and good durability, to human finger motion monitoring.