Laser-Marking Mechanism of Thermoplastic Polyurethane/Bi2O3 Composites

Boosting NIR Laser Marking Efficiency of a Transparent Epoxy Using a Layered Double Hydroxide

Efficient near-infrared (NIR) laser marking on transparent polymers like polypropylene, epoxy, and polyethylene has posed a big challenge due to their lack of absorption in the NIR. Currently, inorganic additives are used to improve NIR laser marking efficiency, but they come with issues such as toxicity, high loading requirement, adverse effects on color/opaqueness, and the need for low laser head speeds. Herein, we report a new strategy of incorporating a food-grade, Mg2Al-CO3 LDH as a boosting coadditive alongside the commercial NIR laser marking additive (Iriotech 8815) in an epoxy system. Our findings demonstrate that the incorporation of Mg2Al-CO3 LDH can significantly increase both the darkness and contrast of marking even at high laser head speed (5000 mm/s), while minimizing surface damage. Notably, by replacing 95% of Iriotech 8815 with Mg2Al-CO3 LDH, an epoxy plate can exhibit high transparency, while producing dark, sharply defined markings with excellent readable QR code markings at high laser speeds. This result offers a promising solution for enhancing high-speed NIR laser marking on transparent polymers with additional advantages of lower toxicity and cost and with minimal optical interference from high additive loadings.

Highly Sensitive Fiber Crossbar Sensors Enabled by Second-Order Synergistic Effect of Air Capacitance and Equipotential Body

Fiber crossbars, an emerging electronic device, have become the most promising basic unit for advanced smart textiles. The demand for highly sensitive fiber crossbar sensors (FCSs) in wearable electronics is increased. However, the unique structure of FCSs presents challenges in replicating existing sensitivity enhancement strategies. Aiming at the sensitivity of fiber crossbar sensors, a second-order synergistic strategy is proposed that combines air capacitance and equipotential bodies, resulting in a remarkable sensitivity enhancement of over 20 times for FCSs. This strategy offers a promising avenue for the design and fabrication of FCSs that do not depend on intricate microstructures. Furthermore, the integrative structure of core-sheath fibers ensures a robust interface, leading to a low hysteresis of only 2.33% and exceptional stability. The outstanding capacitive response performance of FCSs allows them to effectively capture weak signals such as pulses and sounds. This capability opens up possibilities for the application of FCSs in personalized health management, as demonstrated by wireless monitoring systems based on pulse signals.

Use of Green Fs Lasers to Generate a Superhydrophobic Behavior in the Surface of Wind Turbine Blades

Ice generation on the surface of wind generator blades can affect the performance of the generator in several aspects. It can deteriorate sensor performance, reduce efficiency, and cause mechanical failures. One of the alternatives to minimize these effects is to include passive solutions based on the modification of the blade surfaces, and in particular to generate superhydrophobic behavior. Ultra-short laser systems enable improved micromachining of polymer surfaces by reducing the heat affected zone (HAZ) and improving the quality of the final surface topography. In this study, a green fs laser is used to micromachine different patterns on the surface of materials with the same structure that can be found in turbine blades. Convenient optimization of surface topography via fs laser micromachining enables the transformation of an initially hydrophilic surface into a superhydrophobic one. Thus, an initial surface finish with a contact angle ca. 69° is transformed via laser treatment into one with contact angle values above 170°. In addition, it is observed that the performance of the surface is maintained or even improved with time. These results open the possibility of using lasers to control turbine blade surface microstructure while avoiding the use of additional chemical coatings. This can be used as a complementary passive treatment to avoid ice formation in these large structures.

Aramid textile with near-infrared laser-induced graphene for efficient adsorption materials

Porous carbon materials show great application potential in the field of adsorption. However, the preparation process of carbon adsorption materials relies on high temperature, high energy consumption, many steps, and long time. Most of them exist in the form of powder or block, and the practical application scenarios are limited and difficult to recycle. In this study, based on in-situ carbonization of polymer precursor, we directly generated laser-induced graphene (LIG) on the surface of commercial aramid textile using a low-energy near-infrared laser in air, and prospected the application prospect of the prepared aramid/graphene textile in the field of adsorption. Under a certain laser energy, the photothermal reaction promotes the breaking of the CO and CN bonds in the surface layer of the aramid fiber, and reorganizes into a graphene structure at an instantaneous high temperature, while the overall flexible structure of the textile was not destroyed. Further, adsorption materials based on the as-prepared aramid/graphene textiles were also designed, including VOC-adsorbing textile in air and dye-adsorbing textile in water. Using low-energy near-infrared laser to directly achieve LIG writing in commercial textiles under air condition will provide an efficient, environmentally friendly, and designable direction for the large-scale fabrication of textile adsorption products.

The Impact of Selected Laser-Marking Parameters and Surface Conditions on White Polypropylene Moldings

Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = 1064 nm). The paper presents the influence of the surface condition of white-colored polypropylene moldings on the efficiency of their marking with a laser beam. In addition, the operation of the commercial laser marking additive (LMA) Lifolas M 117009 UN, intended to support the process of laser marking of polyolefin surfaces, was verified. The study is an attempt to combine laser operating parameters, material, and geometric properties of PP moldings to obtain the expected quality of graphic symbols. The test samples were made by injection molding method with the use of a specially designed modular injection mold. The molding cavities were prepared with various methods of metal processing, thanks to which obtained moldings differed in surface condition. The marking effects were assessed based on colorimetric tests and digital image analysis. The 0.5 wt% LMA content resulted in obtaining a graphic sign with high contrast in comparison to the background. The gradual increase in the modifier content resulted in a further increase in contrast. These values depended on the degree of surface finish of the samples, and therefore on the roughness parameters. Samples with a rough surface finish showed higher contrast compared to surfaces with a high surface finish. It was also found that for the analyzed moldings, the laser-marking process should be performed with the use of a low head velocity (450–750 mm/s) and a high concentration of the laser beam (0.03–0.05 mm).

Pitaya-Structured Microspheres with Dual Laser Wavelength Responses for Polymer Laser Direct Writing

A unique pitaya-structured graphene/TiO₂@PS microsphere with dual laser wavelength responses is designed and prepared via a facile approach of polymer melt blending. The graphene/TiO₂ particles ("pitaya seeds") are homogeneously distributed in the polystyrene ("pitaya pulp") of the microspheres with an average size of 1.5 μm. The graphene in microspheres serves not only as a laser absorber that has responses to both 355 nm UV and 1064 nm NIR lasers but also as a reducing agent of TiO₂ during laser direct writing (LDW). As expected, benefiting from the unique pitaya-structured structure, the graphene/TiO₂@PS microsphere can remarkably improve the performance of both NIR and UV LDW of polymers. The results of characterizations reveal that the black color caused by NIR LDW is due to the generation of the amorphous carbon and the color change after UV LDW is owing to the formation of black sp/sp² carbon compounds. Meanwhile, some TiO₂ in microspheres is reduced into the black/gray titanium oxides of Ti²⁺ and Ti³⁺ after NIR and UV LDW, respectively. The above co-contribution endows the graphene/TiO₂@PS microspheres with an outstanding color-changing ability. This pitaya-structured microsphere will have a profound effect on polymers' laser direct writing.

Preparation and Laser Marking Properties of Poly(propylene)/Molybdenum Sulfide Composite Materials

In this study, using molybdenum sulfide (MoS₂) as laser-sensitive particles and poly(propylene) (PP) as the matrix resin, laser-markable PP/MoS₂ composite materials with different MoS₂ contents ranging from 0.005 to 0.2% were prepared by melt-blending. A comprehensive analysis of the laser marking performance of PP/MoS₂ composites was carried out by controlling the content of laser additives, laser current intensity, and the scanning speed of laser marking. The color difference test shows that the best laser marking performance of the composite can be obtained at the MoS₂ content of 0.02 wt %. The surface morphology of the PP/MoS₂ composite material was observed after laser marking using a metallographic microscope, an optical microscope, and a scanning electron microscope (SEM). During the laser marking process, the laser energy was absorbed and converted into heat energy to cause high-temperature melting, pyrolysis, and carbonization of PP on the surface of the PP/MoS₂ composite material. The black marking from carbonized materials was formed in contrast to the white matrix. Using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy, the composite materials before and after laser marking were tested and characterized. The PP/MoS₂ composite material was pyrolyzed to form amorphous carbonized materials. The effect of the laser-sensitive MoS₂ additive on the mechanical properties of composite materials was investigated. The results show that the PP/MoS₂ composite has the best laser marking property when the MoS₂ loading content is 0.02 wt %, the laser marking current intensity is 11 A, and the laser marking speed is 800 mm/s, leading to a clear and high-contrast marking pattern.

Laser irradiation method to prepare polyethylene porous fiber membrane with ultrahigh xylene gas filtration capacity

In recent years, volatile organic compound (VOC) gases have caused potential harm to people's health. This study reveals the preparation of polyethylene porous fiber membrane with excellent low-concentration VOCs filtration performance via laser irradiation technology. A neodymium-doped yttrium aluminum garnet (Nd:YAG) pulsed laser beam was used to scan the laser-sensitive low-density polyethylene/carbon black (LDPE/CB) fibers prepared by nanolayer coextrusion in the air. The controllable thermal energy generated by laser irradiation makes the surface of the fiber membrane to produce a porous carbon layer in situ. Laser power and scanning speed are important parameters for controlling laser-induced carbonization. The results indicate that the rich "fluffy" carbon structures on the surface of the porous fiber membrane can efficiently adsorb xylene gas. This study can provide a positive reference for the large-scale preparation of polyolefin porous fiber membrane with VOCs filtration by simple and efficient laser irradiation method.

Laser induced porous electrospun fibers for enhanced filtration of xylene gas

With the development of industry, the harm caused by volatile organic compound (VOC) gases to the human body has received much attention. This study reveals as the first attempt to apply laser irradiation technique to the preparation of porous electrospun fibers with excellent low-concentration VOC gases adsorption properties. The laser-sensitive polycarbonate (PC) fibers prepared from electrospinning was treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam to achieve porous structure. During the laser irradiation process, a series of changes such as melting, thermal degradation, and carbonization of the polymer fibers can change the surface structure. The morphology of the porous structure is related to the degree of laser-induced carbonization, and the laser current is an important parameter for determining the degree of laser-induced carbonization of a particular polymer. The results indicate that porous carbon structures can be created on the surface of the fiber membrane by controlling the degree of laser-induced carbonization, and a highly xylene gas adsorption efficiency is exhibited. This study may provide useful insights for developing electrospun porous fibers with VOC adsorption by simple, effective and environmentally friendly laser post-processing process.

Surface Laser-Marking and Mechanical Properties of Acrylonitrile-Butadiene-Styrene Copolymer Composites with Organically Modified Montmorillonite

In this study, organically modified montmorillonite (OMMT) was prepared by modifying MMT with a cationic surfactant cetyltrimethylammonium bromide (CTAB). The obtained OMMT of different loading contents (1, 2, 4, 6, and 8 wt %) was melt-blended with poly(acrylonitrile-co-butadiene-co-styrene) (ABS) to prepare a series of ABS/OMMT composites, which were laser marked using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser beam of 1064 nm under different laser current processes. X-ray diffraction (XRD), color difference spectrometer, optical microscope, water contact angle tests, scanning electron microscope (SEM), and Raman spectroscopy were carried out to characterize the morphology, structure, and properties of the laser-patterned ABS composites. The effects of the addition of OMMT and the laser marking process on the mechanical properties of ABS/OMMT composites were investigated through mechanical property tests. The results show that the obtained ABS/OMMT composites have enhanced laser marking performance, compared to the ABS. When the OMMT content is 2 wt % and the laser current intensity is 9 A, the marking on ABS composites has the highest contrast (ΔE = 36.38) and sharpness, and the quick response (QR) code fabricated can be scanned and identified with a mobile app. SEM and water contact angle tests showed that the holes, narrow cracks, and irregular protrusion are formed on the composite surface after laser marking, resulting in a more hydrophobic surface and an increased water contact angle. Raman spectroscopy and XRD indicate that OMMT can absorb the near-infrared laser energy, undergo photo thermal conversion, and cause the pyrolysis and carbonization of ABS to form black marking, and the crystal structure itself does not change significantly. When the 2 wt % of OMMT is loaded, the tensile strength, elongation at break, and impact strength of ABS/OMMT are increased by 15, 20, and 14%, respectively, compared to ABS. Compared with the unmarked ABS/OMMT, the defects including holes and cracks generated on the surface of the marked one lead to the decreased mechanical property. The desirable combination of high contrast laser marking performance and mechanical properties can be achieved at an OMMT loading content of 2 wt % and a laser current intensity of 9 A. This research work provides a simple, economical, and environmentally friendly method for laser marking of engineering materials such as ABS.

Facile Fabrication of High-Contrast and Light-Colored Marking on Dark Thermoplastic Polyurethane Materials

In this work, using ferroferric oxide (Fe₃O₄) and zirconium oxide (ZrO₂) as laser-sensitive particles and thermoplastic polyurethane (TPU) as the matrix resin, a series of TPU/Fe₃O₄/ZrO₂ composites were prepared by melt blending, and the effect of the laser marking additive content, composition, and laser marking parameters on the laser marking properties of composites was investigated. The laser marking mechanism of Fe₃O₄/ZrO₂ additives and the role of each component in TPU laser marking were studied by metallographic microscopy, color difference test, scanning electron microscopy, and Raman spectroscopy. Fe₃O₄ nanoparticles as a laser sensitizer component, on the one hand, can act as a pigment to make the TPU substrate black and, on the other hand, can absorb laser energy to contribute to the formation of laser markings on TPU composite surfaces. In addition, the introduction of ZrO₂ nanoparticles can help absorb the laser energy, while the contrast can be improved to enhance the laser marking performance of the TPU composite. Through thermogravimetric analysis, the changes in the thermally stable properties of TPU composites before and after laser marking were investigated, and the results indicated that Fe₃O₄/ZrO₂ nanoparticles can absorb the laser energy, causing melting and pyrolysis of the TPU backbone at a high temperature, to produce a gaseous product resulting in foaming. Finally, the high-contrast and light-colored markings were formed on the black TPU composite surface. This work provides a facile method for producing high-contrast and light-colored markings on the dark TPU composite surface.

New Strategy to Achieve Laser Direct Writing of Polymers: Fabrication of the Color-Changing Microcapsule with a Core-Shell Structure

This paper proposed an efficient and environmentally friendly strategy to prepare a new color-changing microcapsule with a core-shell structure for laser direct writing of polymers, and only the physical melt blending of polymers was employed. The laser absorber (SnO₂) and the easily carbonized polymer (PC) were designed as the "core" and the "shell" of the microcapsule, respectively. The microcapsules were in situ formed during melt blending. Scanning electron microscopy, transmission electron microscopy, and energy-dispersive spectrometry confirmed the successful preparation of SnO₂/PC microcapsules with a core-shell structure. Their average diameter was 2.2 μm, and the "shell" thickness was 0.21-0.24 μm. As expected, these SnO₂/PC microcapsules endowed polymers with an outstanding performance of near-infrared (NIR) laser direct writing. Raman spectroscopy and X-ray photoelectron spectroscopy indicated that the color change was ascribed to the polymer carbonization because of the instantaneous high temperature caused by the SnO₂ absorption of NIR laser energy. Optical microscopy observed a thick carbonization layer of 234 μm. Moreover, Raman depth imaging revealed the carbonization distribution, confirming that the amorphous carbon produced by the carbonization of the PC "shell" is the key factor of SnO₂/PC microcapsules to provide polymers an outstanding performance of laser direct writing. This color-changing microcapsule has no selectivity to polymers because of providing a black color source (the carbonization of PC) itself, ensuring the high contrast and precision of patterns or texts after laser direct writing for all general-purpose polymers. We believe that this novel strategy to achieve laser direct writing of polymers will have broad application prospects.

Preparation of near-infrared laser responsive hydrogels with enhanced laser marking performance

Polystyrene modified bismuth oxide particles (PS@Bi2O3) were prepared and characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Using acrylamide (AM) as a monomer, and PS@Bi2O3 as laser sensitive additives, PAM/PS@Bi2O3 hydrogels were fabricated and treated by a 1064 nm near-infrared laser. The laser responsive properties of PAM/PS@Bi2O3 hydrogels were investigated at different current intensities and loading content of PS@Bi2O3 by visual observation, optical microscopy, and SEM, and the mechanism of laser response was analyzed by XRD and Raman spectroscopy. The results indicate that the PAM hydrogel with added PS@Bi2O3 particles showed excellent response to the laser, and high contrast and resolution text and pattern marks on the hydrogel surface can be obtained. The selection of suitable laser current intensity is key to the laser response of the PAM/PS@Bi2O3 composite hydrogel. Through analysis of XRD, Raman spectroscopy, and TGA data, the laser marking of the PAM/PS@Bi2O3 hydrogels originates from the generation of both bismuth metal and amorphous carbonized materials. After adding PS@Bi2O3 with a loading content from 1% to 3%, the mechanical properties of the hydrogels were improved, but the swelling properties were finally decreased.

Intercalation of Bi2O3/Bi2S3 nanoparticles into highly expanded MoS2 nanosheets for greatly enhanced gas sensing performance at room temperature

Synthesizing a gas sensor based on heterostructured nanomaterials (NMs) via a controllable morphology by a facile hydrothermal method is an area of frontier research. In the present work, we designed a facile strategy to synthesize a controllable morphology and composition for three component heterojunctions (MoS₂-Bi₂O₃-Bi₂S₃) NMs using different hydrothermal reaction times. The Bi₂S₃ easily form as an intermediate phase due to the strong interaction of the Bi₂O₃ with MoS₂ nanosheets (NSs). The as fabricated heterojunctions MB-5 NMs exhibited a sensitive response to NO_x gas (R_a/R_g = 10.7 at 50 ppm), with an ultra-fast response time of only 1 s (s) at room temperature (RT) in air. The detection limit was predicted to be as low as 50 ppb. This sensational behaviour of the sensor reveals the outstanding morphological structure and synergistic effect of the MoS₂ NSs with Bi₂O₃ nanoparticles (NPs), which was realized by the flow of electrons across MoS₂-Bi₂O₃-Bi₂S₃ interfaces through band energy alignment.

Local Controllable Laser Patterning of Polymers Induced by Graphene Material

Graphene has been successfully applied to the field of polymer laser patterning. As an efficient 1064 nm near-infrared (NIR) pulsed laser absorber, only 0.005 wt % (50 ppm) of graphene prepared by mechanical exfoliation endowed polymer materials with very good NIR pulsed laser patterning. Optical microscopy observed that the generated black patterns came from the local discoloration of the polymer surface subjected to the laser irradiation, and the depth of the discolored layer was determined to be within 221-348 μm. The X-ray photoelectron spectroscopy confirmed that the polymer surface discoloration was contributed by the local carbonization of polymers caused by graphene due to its high photothermal conversion capacity. Raman depth imaging successfully detected that the generated carbon in the discolored layer was composed of amorphous carbon and complex sp/sp²-carbon compounds containing C≡C or conjugated C═C/C≡C structures. This study also provides a simple guideline to fabricate laser-patterning polymer materials based on graphene. We believe that graphene has broad application prospects in the field of polymer laser patterning. Importantly, this work opens up a valuable, feasible direction for the practical application of this new carbon material.