Thick Glass High-Quality Cutting by Ultrafast Laser Bessel Beam Perforation-Assisted Separation.

The cutting of thick glass is extensively employed in aerospace, optical, and other fields. Although ultrafast laser Bessel beams are heavily used for glass cutting, the cutting thickness and cutting quality need to be further improved. In this research, the high-quality cutting of thick glass was realized for the first time using ultrafast laser perforation assisted by CO2 laser separation. Initially, an infrared picosecond laser Bessel beam was employed to ablate the soda-lime glass and generate a perforated structure. Subsequently, a CO2 laser was employed to induce crack propagation along the path of the perforated structure, resulting in the separation of the glass. This study investigates the influence of hole spacing, pulse energy, and the defocusing distance of the picosecond laser Bessel beam on the average surface roughness of the glass sample cutting surface. The optimal combination of cutting parameters for 6 mm thick glass results in a minimum surface roughness of 343 nm in the cross-section.

Generation of multi-focus shaping with high uniformity based on an improved Gerchberg-Saxton algorithm.

The Gerchberg-Saxton (GS) algorithm has been extensively employed in computational holography and beam shaping with the advantages of quick iteration speed and high energy utilization. However, the GS algorithm is prone to trapping into local optima and not reaching ideal outcomes, leading to poor shaping quality. In this paper, a method of random disturbance superposition (RDS) was proposed to feedback GS amplitude, which could stably and universally achieve over 95% high uniformity shaping of multiple beams without other complex operations. In light of this, this paper also covered how this technique affected energy utilization. It has been discovered that the introduction of perturbation could decrease the energy utilization. By analyzing the mechanism, a phase value replacement (PVR) method was proposed, which could effectively improve energy utilization without reducing uniformity. Finally, the simulation results were experimentally validated and met expectations very well. This method helps to accurately control the energy distribution of multiple beams and has a driving effect on laser precision processing technology.

Revealing the interaction mechanism of pulsed laser processing with the application of acoustic emission.

The mechanisms of interaction between pulsed laser and materials are complex and indistinct, severely influencing the stability and quality of laser processing. This paper proposes an intelligent method based on the acoustic emission (AE) technique to monitor laser processing and explore the interaction mechanisms. The validation experiment is designed to perform nanosecond laser dotting on float glass. Processing parameters are set differently to generate various outcomes: ablated pits and irregular-shaped cracks. In the signal processing stage, we divide the AE signals into two bands, main and tail bands, according to the laser processing duration, to study the laser ablation and crack behavior, respectively. Characteristic parameters extracted by a method that combines framework and frame energy calculation of AE signals can effectively reveal the mechanisms of pulsed laser processing. The main band features evaluate the degree of laser ablation from the time and intensity scales, and the tail band characteristics demonstrate that the cracks occur after laser dotting. In addition, from the analysis of the parameters of the tail band very large cracks can be efficiently distinguished. The intelligent AE monitoring method was successfully applied in exploring the interaction mechanism of nanosecond laser dotting float glass and can be used in other pulsed laser processing fields.

Efficient degradation of norfloxacin using a novel biochar-supported CuO/Fe3O4 combined with peroxydisulfate: Insights into enhanced contribution of nonradical pathway.

Nonradical persulfate oxidation techniques have evolved as a new contaminated water treatment approach due to its great tolerance to water matrixes. The catalysts of CuO-based composites have received much attention in that aside from SO4•-/•OH radicals, the nonradicals of singlet oxygen (1O2) can be also generated during persulfate activation via CuO. However, the issues regarding particles aggregation and metal leaching from the catalysts during the decontamination process remain to be addressed, which could have a remarkable impact on the catalytic degradation of organic pollutants. Accordingly in the present study, a novel biochar-supported bimetallic Fe3O4-CuO catalyst (CuFeBC) was facilely developed to activate peroxodisulfate (PDS) for the degradation of norfloxacin (NOR) in aqueous solution. The results showed CuFeBC has a superior stability against metal ions Cu/Fe leaching, and NOR (30 mg L-1) was degraded at 94.5% within 180 min in the presence of CuFeBC (0.5 g L-1) and PDS (6 mM) in pH 8.5. The scavenging of reactive oxygen species and electron spin resonance analysis revealed that 1O2 dominated the degradation of NOR. Compared with pristine CuO-Fe3O4, the interaction between biochar substrate and metal particles could significantly enhance the contribution of the nonradical pathway to NOR degradation from 49.6% to 84.7%. Biochar substrate could efficiently reduce the leaching of metal species from the catalyst, thereby maintaining excellent catalytic activity and lasting reusability of the catalyst. These findings could enlighten new insights into fine-tuning radical/nonradical processes from CuO-based catalysts for the efficient remediation of organic contaminants in polluted water.

CO2 capture by 1,2,3-triazole-based deep eutectic solvents: the unexpected role of hydrogen bonds.

Herein, tetraethylammonium 1,2,3-triazolide ([Et4N][Tz]), 1,2,3-triazole (Tz), and ethylene glycol (EG) are used to form DESs for CO2 capture. Surprisingly, [Et4N][Tz]-EG DESs can react with CO2, but [Et4N][Tz]-Tz cannot react with CO2, although both of the two systems contain the same anion [Tz]-. Unexpectedly, with the addition of EG to [Et4N][Tz]-Tz, the formed ternary DESs [Et4N][Tz]-Tz-EG can react with CO2, although neither EG nor [Et4N][Tz]-Tz can react with CO2 before the combination of them. NMR, FTIR and theoretical calculation results disclose that the surprise CO2 absorption behavior mainly depends on the strength of hydrogen bonds (H-bonds) between the anion [Tz]- and H-bond donors (EG or Tz). The strength of the H-bond between [Tz]- and Tz is much stronger than that between [Tz]- and EG. The strong H-bond between [Tz]- and Tz in [Et4N][Tz]-Tz greatly reduces the basicity of [Tz]-, rendering the anion [Tz]- unreactive to CO2. In [Et4N][Tz]-Tz-EG ternary DESs, EG competes with Tz to form a H-bond with [Tz]-, which weakens the strength of the H-bond between [Tz]- and Tz. Moreover, H-bonds also impact the desorption behavior. [Et4N][Tz] : EG (1 : 2) is regenerated at 60 °C, whereas the chemisorbed CO2 by [Et4N][Tz] : Tz : EG (1 : 2 : 2) can be released even down to 30 °C.

CO2 Absorption Mechanism by the Deep Eutectic Solvents Formed by Monoethanolamine-Based Protic Ionic Liquid and Ethylene Glycol.

Deep eutectic solvents (DESs) have been widely used to capture CO2 in recent years. Understanding CO2 mechanisms by DESs is crucial to the design of efficient DESs for carbon capture. In this work, we studied the CO2 absorption mechanism by DESs based on ethylene glycol (EG) and protic ionic liquid ([MEAH][Im]), formed by monoethanolamine (MEA) with imidazole (Im). The interactions between CO2 and DESs [MEAH][Im]-EG (1:3) are investigated thoroughly by applying 1H and 13 C nuclear magnetic resonance (NMR), 2-D NMR, and Fourier-transform infrared (FTIR) techniques. Surprisingly, the results indicate that CO2 not only binds to the amine group of MEA but also reacts with the deprotonated EG, yielding carbamate and carbonate species, respectively. The reaction mechanism between CO2 and DESs is proposed, which includes two pathways. One pathway is the deprotonation of the [MEAH]+ cation by the [Im]- anion, resulting in the formation of neutral molecule MEA, which then reacts with CO2 to form a carbamate species. In the other pathway, EG is deprotonated by the [Im]-, and then the deprotonated EG, HO-CH2-CH2-O-, binds with CO2 to form a carbonate species. The absorption mechanism found by this work is different from those of other DESs formed by protic ionic liquids and EG, and we believe the new insights into the interactions between CO2 and DESs will be beneficial to the design and applications of DESs for carbon capture in the future.

Deep eutectic solvents composed of bio-phenol-derived superbase ionic liquids and ethylene glycol for CO2 capture.

Deep eutectic solvents (DESs) formed by bio-phenol-derived superbase ionic liquids (ILs) and ethylene glycol (EG) exhibit a high CO2 capacity, up to 1.0 mol CO2/mol DESs, which is much better than those of the parent ILs. Surprisingly, mechanism results indicate that CO2 reacts with EG, but doesn't react with phenolic anions in the solvent, which is different from other DESs formed by superbase ILs and EG. The reaction pathway between CO2 and DESs used in this work may include two steps. The first step is the acid-base reaction between the phenolic anion and EG, which forms HO-CH2-CH2-O-, and then CO2 is attached to the anion HO-CH2-CH2-O- to form a carbonate species.

Effects of Ambient Temperature on Nanosecond Laser Micro-Drilling of Polydimethylsiloxane (PDMS).

In this research, effects of ambient temperature (-100 °C-200 °C) on nanosecond laser micro-drilling of polydimethylsiloxane (PDMS) was investigated by simulation and experiment. A thermo-mechanical coupled model was established, and it was indicated that the top and bottom diameter of the micro-hole decreased with the decrease of the ambient temperature, and the micro-hole taper increased with the decrease of the ambient temperature. The simulation results showed a good agreement with the experiment results in micro-hole geometry; the maximum prediction errors of the top micro-hole diameter, the bottom micro-hole diameter and micro-hole taper were 2.785%, 6.306% and 9.688%, respectively. The diameter of the heat-affected zone decreased with the decrease of the ambient temperature. The circumferential wrinkles were controlled by radial compressive stress. As the ambient temperature increased from 25 °C to 200 °C, the radial compressive stress gradually decreased, which led to the circumferential wrinkles gradually evolving in the radial direction. This work provides a new idea and method based on ambient temperature control for nanosecond laser processing of PDMS, which provides exciting possibilities for a wider range of engineering applications of PDMS.

The Influence of Hydrogen Bond Donors on the CO2 Absorption Mechanism by the Bio-Phenol-Based Deep Eutectic Solvents.

Recently, deep eutectic solvents (DESs), a new type of solvent, have been studied widely for CO2 capture. In this work, the anion-functionalized deep eutectic solvents composed of phenol-based ionic liquids (ILs) and hydrogen bond donors (HBDs) ethylene glycol (EG) or 4-methylimidazole (4CH3-Im) were synthesized for CO2 capture. The phenol-based ILs used in this study were prepared from bio-derived phenols carvacrol (Car) and thymol (Thy). The CO2 absorption capacities of the DESs were determined. The absorption mechanisms by the DESs were also studied using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and mass spectroscopy. Interestingly, the results indicated that CO2 reacted with both the phenolic anions and EG, generating the phenol-based carbonates and the EG-based carbonates, when CO2 interacted with the DESs formed by the ILs and EG. However, CO2 only reacted with the phenolic anions when the DESs formed by the ILs and 4CH3-Im. The results indicated that the HBDs impacted greatly on the CO2 absorption mechanism, suggesting the mechanism can be tuned by changing the HBDs, and the different reaction pathways may be due to the steric hinderance differences of the functional groups of the HBDs.

Editorial for the Special Issue on Advanced Materials, Structures and Processing Technologies Based on Pulsed Laser.

Pulsed lasers are lasers with a single laser pulse width of less than 0 [...].

Temperature Field-Assisted Ultraviolet Nanosecond Pulse Laser Processing of Polyethylene Terephthalate (PET) Film.

Understanding the mechanism of and how to improve the laser processing of polymer films have been important issues since the advent of the procedure. Due to the important role of a photothermal mechanism in the laser ablation of polymer films, especially in transparent polymer films, it is both important and effective to adjust the evolution of heat and temperature in time and space during laser processing by simply adjusting the ambient environment so as to improve and understand the mechanism of this procedure. In this work, studies on the pyrolysis of PET film and on temperature field-assisted ultraviolet nanosecond (UV-ns) pulse laser processing of polyethylene terephthalate (PET) film were performed to investigate the photothermal ablation mechanism and the effects of temperature on laser processing. The results showed that the UV-ns laser processing of PET film was dominated by the photothermal process, in which PET polymer chains decomposed, melted, recomposed and reacted with the ambient gases. The ambient temperature changed the heat transfer and temperature distribution in the laser processing. Low ambient temperature reduced the thermal effect and an increase in ambient temperature improved its efficiency (kerf width: 39.63 µm at -25 °C; 48.30 µm at 0 °C; 45.81 µm at 25 °C; 100.70 µm at 100 °C) but exacerbated the thermal effect.

PI Film Laser Micro-Cutting for Quantitative Manufacturing of Contact Spacer in Flexible Tactile Sensor.

The contact spacer is the core component of flexible tactile sensors, and the performance of this sensor can be adjusted by adjusting contact spacer micro-hole size. At present, the contact spacer was mainly prepared by non-quantifiable processing technology (electrospinning, etc.), which directly leads to unstable performance of tactile sensors. In this paper, ultrathin polyimide (PI) contact spacer was fabricated using nanosecond ultraviolet (UV) laser. The quality evaluation system of laser micro-cutting was established based on roundness, diameter and heat affected zone (HAZ) of the micro-hole. Taking a three factors, five levels orthogonal experiment, the optimum laser cutting process was obtained (pulse repetition frequency 190 kHz, cutting speed 40 mm/s, and RNC 3). With the optimal process parameters, the minimum diameter was 24.3 ± 2.3 µm, and the minimum HAZ was 1.8 ± 1.1 µm. By analyzing the interaction process between nanosecond UV laser and PI film, the heating-carbonization mechanism was determined, and the influence of process parameters on the quality of micro-hole was discussed in detail in combination with this mechanism. It provides a new approach for the quantitative industrial fabrication of contact spacers in tactile sensors.

CO2 Absorption Mechanism by the Nonaqueous Solvent Consisting of Hindered Amine 2-[(1,1-dimethylethyl)amino]ethanol and Ethylene Glycol.

In this work, we studied the CO2 absorption mechanism by nonaqueous solvent comprising hindered amine 2-[(1,1-dimethylethyl)amino]ethanol (TBAE) and ethylene glycol (EG). The NMR and FTIR results indicated that CO2 reacted with an -OH group of EG rather than the -OH of TBAE by producing hydroxyethyl carbonate species. A possible reaction pathway was suggested, which involves two steps. In the first step, the acid-base reaction between TBAE and EG generated the anion HO-CH2-CH2-O-; in the second step, the O- of HO-CH2-CH2-O- attacked the C atom of CO2, forming carbonate species.

Inverse ZrO2/Cu as a highly efficient methanol synthesis catalyst from CO2 hydrogenation.

Enhancing the intrinsic activity and space time yield of Cu based heterogeneous methanol synthesis catalysts through CO2 hydrogenation is one of the major topics in CO2 conversion into value-added liquid fuels and chemicals. Here we report inverse ZrO2/Cu catalysts with a tunable Zr/Cu ratio have been prepared via an oxalate co-precipitation method, showing excellent performance for CO2 hydrogenation to methanol. Under optimal condition, the catalyst composed by 10% of ZrO2 supported over 90% of Cu exhibits the highest mass-specific methanol formation rate of 524 gMeOHkgcat-1h-1 at 220 °C, 3.3 times higher than the activity of traditional Cu/ZrO2 catalysts (159 gMeOHkgcat-1h-1). In situ XRD-PDF, XAFS and AP-XPS structural studies reveal that the inverse ZrO2/Cu catalysts are composed of islands of partially reduced 1-2 nm amorphous ZrO2 supported over metallic Cu particles. The ZrO2 islands are highly active for the CO2 activation. Meanwhile, an intermediate of formate adsorbed on the Cu at 1350 cm-1 is discovered by the in situ DRIFTS. This formate intermediate exhibits fast hydrogenation conversion to methoxy. The activation of CO2 and hydrogenation of all the surface oxygenate intermediates are significantly accelerated over the inverse ZrO2/Cu configuration, accounting for the excellent methanol formation activity observed.

A new approach for an ultrasensitive tactile sensor covering an ultrawide pressure range based on the hierarchical pressure-peak effect.

Flexible tactile sensors that imitate the skin tactile system have attracted extensive research interest due to their potential applications in medical diagnosis, intelligent robots and so on. However, it is still a great challenge to date to fabricate tactile sensors with both high sensitivity and wide detection range due to the difficulties in modulating the resistance variation in the sensing materials in a wide pressure range. Here, a tactile sensor with a novel design based on the hierarchical pressure-peak effect (HPPE) consisting of PVP nanowires and electroless deposition (ELD) silver PDMS micro-pyramids is reported. The HPPE can effectively modulate the resistance change rate by adjusting the change of contact area during compression deformation, and the HPPE tactile sensor was demonstrated to have both ultrahigh sensitivity (11.60-1108.75 kPa-1) and ultrawide pressure range (0.04-600 kPa). The designed HPPE tactile sensor is successfully utilized in detecting multi-level pressures including respiration, finger heart rate, pulse and foot pressures. Moreover, it is used to sense a subtle clamping force in the Leonardo Da Vinci surgical robot demonstrating the potential of the sensor in surgical robot applications. In all these cases, the sensor exhibits enough capability to respond quickly to ultrawide-range pressures with high accuracy and stability.

Novel Elastically Stretchable Metal-Organic Framework Laden Hydrogel with Pearl-Net Microstructure and Freezing Resistance through Post-Synthetic Polymerization.

Nanocomposite hydrogels (NCs) with mechanical properties suitable for a diverse range of applications can be made by combining polymer hydrogel networks with various inorganic nanoparticles. However, the mechanical properties and functions of conventional NCs are seriously limited by the poor structural or functional tunability of common nanofillers and by the low amounts of such fillers that can be added. Here, the fabrication of novel elastically stretchable and compressible nanocomposite hydrogels (MIL-101-MAAm/PAAm) with a distinctive pearl-net microstructure and a metal-organic framework (MOF) content in the range of 20-60 wt% through post-synthetic polymerization (PSP) is reported. The MOFs, which are compatible with polymers and have a high degree of modifiability in structure and functions, are used as nanofillers. Such MOF-laden hydrogels can withstand 500% tensile strain or 90% compressive strain without fracture and recover quickly upon unloading. They are also resistant to freezing at -25 °C. In addition, the problems associated with poor flexibility and processability of MOFs are overcome by the hybridization of hydrogel polymer matrices with MOFs. The results of this work not only provide a new perspective on preparing NCs but also indicate a promising path for applying MOFs in flexible devices.

Effect of Heterointerface on NO2 Sensing Properties of In-Situ Formed TiO2 QDs-Decorated NiO Nanosheets.

In this work, TiO2 QDs-modified NiO nanosheets were employed to improve the room temperature NO2 sensing properties of NiO. The gas sensing studies showed that the response of nanocomposites with the optimal ratio to 60 ppm NO2 was nearly 10 times larger than that of bare NiO, exhibiting a potential application in gas sensing. Considering the commonly reported immature mechanism that the effective charge transfer between two phases contributes to an enhanced sensitivity, the QDs sensitization mechanism was further detailed by designing a series of contrast experiments. First, the important role of the QDs size effect was revealed by comparing the little enhanced sensitivity of TiO2 particle-modified NiO with the largely enhanced sensitivity of TiO2 QDs-NiO. Second, and more importantly, direct evidence of the heterointerface charge transfer efficiency was detailed by the extracted interface bond (Ti-O-Ni) using XPS peak fitting. This work can thus provide guidelines to design more QDs-modified nanocomposites with higher sensitivity for practical applications.

Molecular sieving property adjusted by the encapsulation of Ag nanoparticles into ZnO@ZIF-71 nanorod arrays.

Ag NPs are encapsulated into ZIF-71 via a deposition-reduction method. The resulting products are tested as adjustable molecular sieves for hydrogen and acetone. The gas sensing performances show that the response to acetone is reduced and that to hydrogen increased, demonstrating an engineered selectivity. A novel design of molecular sieving MOF materials for gas separation in gas-sensing selectivity is thus provided.

High-Adhesion Stretchable Electrode via Cross-Linking Intensified Electroless Deposition on a Biomimetic Elastomeric Micropore Film.

For the stretchable electrode, strong interface adhesion is the primary guarantee for long service life, and the maximization of the tensile limit with remarkable electrical stability can expand the scope of its use. Here, a cost-effective strategy is proposed to fabricate a high-adhesion stretchable electrode. By modifying dopamine and functionalized silane on a polydimethylsiloxane (PDMS) substrate in sequence before the electroless deposition process, super-high adhesion up to 3.1 MPa is achieved between the PDMS substrate and silver layer, and the electrode exhibits extraordinary conductivity of 4.0 × 107 S/m. This process is also suitable for other common flexible substrates and metals. Moreover, inspired by the micro-/nanostructure on the surface of lotus leaf, a biomimetic elastomeric micropore film with a uniformly distributed micropore is fabricated by the one-step soft lithography replication process. The electrode exhibits a large tensile limit exceeding 70% uniaxial tensile and superior electrical stability from 6.3 to 11.5 Ω under 20% uniaxial tensile for more than 10 000 cycles. This study seeks a promising method to manufacture stretchable electrodes with high adhesion, large tensile limit, and excellent electrical stability, showing great potential to detect various biological signals including joint movement, surface electromyography, and so forth.

Multilevel Microstructured Flexible Pressure Sensors with Ultrahigh Sensitivity and Ultrawide Pressure Range for Versatile Electronic Skins.

Flexible pressure sensors as electronic skins have attracted wide attention to their potential applications for healthcare and intelligent robotics. However, the tradeoff between their sensitivity and pressure range restricts their practical applications in various healthcare fields. Herein, a cost-effective flexible pressure sensor with an ultrahigh sensitivity over an ultrawide pressure-range is developed by combining a sandpaper-molded multilevel microstructured polydimethylsiloxane and a reduced oxide graphene film. The unique multilevel microstructure via a two-step sandpaper-molding method leads to an ultrahigh sensitivity (2.5-1051 kPa-1 ) and can detect subtle and large pressure over an ultrawide range (0.01-400 kPa), which covers the overall pressure regime in daily life. Sharp increases in the contact area and additional contact sites caused by the multilevel microstructures jointly contribute to such unprecedented performance, which is confirmed by in situ observation of the gap variations and the contact states of the sensor under different pressures. Examples of the flexible pressure sensors are shown in potential applications involving the detection of various human physiological signals, such as breathing rate, vocal-cord vibration, heart rate, wrist pulse, and foot plantar pressure. Another object manipulation application is also demonstrated, where the material shows its great potential as electronic skin intelligent robotics and prosthetic limbs.