Moiré Enhanced Potentials in Twisted Transition Metal Dichalcogenide Trilayers Homostructures.

The exploration of moiré superlatticesholds promising potential to uncover novel quantum phenomena emerging from the interplay of atomic structure and electronic correlation . However, the impact of the moiré potential modulation on the number of twisted layers has yet to be experimentally explored. Here, this work synthesizes a twisted WSe2 homotrilayer using a dry-transfer method and investigates the enhancement of the moiré potential with increasing number of twisted layers. The results of the study reveal the presence of multiple exciton resonances with positive or negative circularly polarized emission in the WSe2 homostructure with small twist angles, which are attributed to the excitonic ground and excited states confined to the moiré potential. The distinct g-factor observed in the magneto-optical spectroscopy is also shown to be a result of the confinement of the exciton in the moiré potential. The moiré potential depths of the twisted bilayer and trilayer homostructures are found to be 111 and 212 meV, respectively, an increase of 91% from the bilayer structure. These findings demonstrate that the depth of the moiré potential can be manipulated by adjusting the number of stacked layers, providing a promising avenue for exploration into highly correlated quantum phenomena.

Strain-tunable valley polarization and localized excitons in monolayer WSe2.

Monolayer transition metal dichalcogenides (TMDs) have a crystalline structure with broken spatial inversion symmetry, making them promising candidates for valleytronic applications. However, the degree of valley polarization is usually not high due to the presence of intervalley scattering. Here, we use the nanoindentation technique to fabricate strained structures of WSe2 on Au arrays, thus demonstrating the generation and detection of strained localized excitons in monolayer WSe2. Enhanced emission of strain-localized excitons was observed as two sharp photoluminescence (PL) peaks measured using low-temperature PL spectroscopy. We attribute these emerging sharp peaks to excitons trapped in potential wells formed by local strains. Furthermore, the valley polarization of monolayer WSe2 is modulated by a magnetic field, and the valley polarization of strained localized excitons is increased, with a high value of up to approximately 79.6%. Our results show that tunable valley polarization and localized excitons can be realized in WSe2 monolayers, which may be useful for valleytronic applications.

Laser-Textured Hybrid Brass Pattern Array Surface for High-Efficiency Fog Collection.

Fog collection holds promise for addressing water shortage. However, the conventional fabrication of fog collection devices, normally chemical methods, suffers many challenges, such as complicated preparation and environmental issues. Herein, we proposed a green fabrication strategy to construct superhydrophobic/hydrophilic surfaces on the brass substrate via the combination of laser fabrication and heat treatment. The wettability of brass is directly dictated by the laser process parameters. The different superhydrophobic/hydrophilic hybrid pattern surface with a rectangular/triangular array was designed for an optimal fog collection performance. The maximum water collection efficiency of the prepared surface is measured up to 427.36 mg h-1 cm-2, which is 97% higher than that of the control sample. Furthermore, the surface can be folded into different forms to realize a flexible collector. We envision that our work provides a green fabrication strategy to construct a superwetting surface for highly efficient fog collection.

Optical power auto-alignment method with eugenics sorting for enhancing the alignment speed and robustness of fiber-grating couplers.

To auto-couple optical devices, a simple but effective method must have a high success rate, fast scanning speed, and high stability. For coupling accuracy, swarm intelligence algorithms set a large number of particles to find the optimal point, which can introduce accelerated geometric errors in practical engineering. In this study, we proposed a method for auto-alignment between single-mode fibers and grating couplers using the particle swarm optimization algorithm, which introduces a chaotic mapping and eugenics mechanism. With the help of chaotic mapping and eugenics mechanisms, the scanning speed and robustness increased remarkably. A series of simulations and experiments showed that this method could increase the efficiency and robustness by 90% and 50%, respectively, compared to the basic swarm intelligence algorithm.

Flexible and Precise Droplet Manipulation by a Laser-Induced Shape Temperature Field on a Lubricant-Infused Surface.

Light actuation on a lubricant-infused surface (LIS) has attracted great attention because of its flexibility and remote control of droplet motion. However, to actuate a droplet on a LIS flexibly and precisely by light, the key issue is to control two degrees of freedom of the droplet motion in real time. In this paper, we propose a C-shape temperature field (CSTF) induced by rapid and selective laser irradiation on a LIS. The CSTF could not only manipulate a single droplet precisely and flexibly but also process multiple droplets automatically and orderly in real time. The mechanism showed that the droplet was confined by the Marangoni force in two orthogonal directions. For single droplet manipulation, the CSTF had the capability of correcting the off-track droplet motion. Moreover, the droplet motion, including rectilinear motion and curvilinear motion, could be precisely and flexibly controlled by the motion of the CSTF. For manipulation of multiple droplets, coalescence of multiple droplets was successfully achieved by triple rotating CSTFs. Such a method was applied in the detection of 5 µL of bovine serum albumin (BSA) by triggering chromogenic reactions automatically and orderly, which improved the efficiency of the whole process. We believe that this method is a significant candidate for intelligent droplet manipulation.

Robust Hierarchical Porous PTFE Film Fabricated via Femtosecond Laser for Self-Cleaning Passive Cooling.

Passive cooling materials that spontaneously cool an object are promising choices for mitigating the global energy crisis. However, these cooling effects are usually weakened or lost when dust contaminates the surface structure, greatly restricting their applications. In this work, a robust hierarchical porous polytetrafluoroethylene (PTFE) film with coral-like micro/nanostructures is generated by a facile and efficient femtosecond laser ablation technique. Owing to its unique micro/nanostructures, the as-prepared surface exhibits an outstanding self-cleaning function for various liquids with ultralow adhesion. This self-cleaning characteristic enhances the durability of its passive cooling effect. It is demonstrated that the titanium (Ti) sheet covered with laser-ablated PTFE film can realize a maximum temperature decrease of 4 and 10 °C compared to the Ti sheet covered with pristine PTFE film and uncovered, respectively. This study reveals that femtosecond laser micromachining is a facile and feasible avenue to produce robust self-cleaning passive cooling devices.

Sevoflurane inhibits the migration, invasion and induces apoptosis by regulating the expression of WNT1 via miR-637 in colorectal cancer.

Colorectal cancer (CRC) is a common malignancy. Sevoflurane has been reported to involve in the progression in several cancers. However, the molecular mechanism of sevoflurane in CRC progression remains unclear. Quantitative real-time PCR and western blot was used to detect the expression of miR-637 and WNT1. Cell migration, invasion and apoptosis were detected by transwell assay, flow cytometry or western blot, respectively. The interaction between WNT1 and miR-637 was confirmed by luciferase reporter assay, RNA immunoprecipitation assay and pull-down assay. We found sevoflurane could inhibit cell migration and invasion but induced apoptosis in CRC. Besides, the miR-637 level was decreased in CRC tissues and cells but could be rescued by sevoflurane. MiR-637 overexpression enhanced the anticancer functions of sevoflurane in CRC cells, while miR-637 inhibition showed opposite effects. WNT1 was confirmed to be a target of miR-637 and was inhibited by sevoflurane or miR-637. Importantly, knockdown of WNT1 reversed the carcinogenic effects mediated by miR-637 inhibitor in CRC cells treated with sevoflurane. Collectively, sevoflurane inhibited cell migration, invasion and induced apoptosis by regulating the miR-637/WNT1 axis in colorectal cancer, indicating a novel insight into the effective clinical implication for the anesthetic in CRC treatment.

High-quality welding of glass by a femtosecond laser assisted with silver nanofilm.

Glass products with high joint strength are highly demanded in the field of microelectromechanical system (MEMS). While the quality requirement of MEMS is getting higher and higher, much attention has been paid to further improving the welding strength of the glass. Herein, a femtosecond laser welding method assisted by silver nanofilm for quartz glass is proposed. To optimize the welding results, the influence of the laser power on the location of the heat-affected zone is studied. The effect of coated silver nanofilm at the interface of two glass substrates on femtosecond laser absorptivity is conducted. Also, the welding spot size under different irradiation periods is investigated. In addition, the welding strength with and without the silver nanofilm is measured and compared. It is demonstrated that the welding strength was increased nearly 20% on average by our proposed method compared with direct femtosecond laser welding. In addition, even at the lower laser power than the welding threshold, the welding process could be realized by the proposed method.

Oxycodone stimulates normal and malignant hematopoietic progenitors via opioid-receptor-independent-ß-catenin activation.

Oxycodone is a common type of opioid used for the treatment of moderate to severe pain. Besides its analgesic effects on neuron cells, the effects of oxycodone on other cell types are yet to be elucidated. We previously demonstrated that oxycodone displayed both pro- and anti-cancer effects on bulk cancer cells. This work further investigated the effects of oxycodone on normal and malignant hematopoietic stem cells. Using hematopoietic CD34+ cells isolated from normal bone marrow (NBM) or patients with acute myeloid leukemia (AML), we showed that oxycodone activates hematopoietic cells regardless of cell development stage and malignant status. Oxycodone dose-dependently increases colony formation and self-renewal capacity of NBM and AML stem/progenitor cells, and promotes proliferation of AML bulk cells. NBM stem/progenitor cells are more sensitive to oxycodone than AML counterparts. In addition, oxycodone alleviates chemotherapy drug-induced toxicity in AML stem/progenitor cells. Mechanism studies demonstrate that oxycodone acts on hematopoietic cells in an opioid-receptor-independent manner. Oxycodone did not affect epithelial growth factor receptor (EGFR) signaling neither but stimulated Wnt/ß-catenin signaling. Rescue studies via depleting ß-catenin using genetic and pharmacological approaches confirmed that ß-catenin was required for the activation of hematopoietic cells induced by oxycodone. Our work demonstrates 1) the protective role of oxycodone in malignant hematopoietic cells from chemotherapy; 2) stimulatory effects of oxycodone in normal hematopoietic stem cells; and 3) ability of oxycodone in Wnt signaling activation.

Enhanced light extraction of light-emitting diodes with micro patterns by femtosecond laser micromachining for visible light communication.

A significant enhancement of light extraction of light-emitting diodes (LEDs) with micro patterns has been experimentally investigated. The micro patterns on the surface of a polymer layer are fabricated by a femtosecond laser Bessel beam for obtaining microhole arrays with large depth, resulting in the reduction of photon loss by total internal reflection (TIR) at the surface of the LED. The light output power of the LED is apparently increased by introducing the array patterns without influencing its current-voltage (I-V) characteristics. Moreover, the electroluminescence spectra of a multi-color LED and its angular radiation profiles with orthogonal and hexagonal patterns also have been explored. In addition, the optical field distributions of the micro patterns simulated by the finite difference time domain method have expressed the modulation effect of the array depth. Finally, the patterned LED as a transmitter is embedded in the visible light communication system for evaluating the transmission signal quality.

Sensitivity analysis and optimization of optical Y-branch structure parameters.

Aimed at the structural parameters in the new optical Y-branch, this paper uses the Morris screening method and Sobol method in global sensitivity analysis to analyze the sensitivity of each parameter when the input optical field introduces an offset. The sensitivity parameters of the optical Y-branch are selected, and global sensitivity analysis of the sensitivity parameters is performed. The results of sensitivity analysis improve the parameter optimization process of the optical Y-branch. Finally, the optical Y-branch is optimized to obtain a small insertion loss, good uniformity, low wavelength-dependent loss, and polarization-dependent loss.

Substrate-independent, switchable bubble wettability surfaces induced by ultrasonic treatment.

Surfaces with switchable bubble wettability have attracted increasing interest due to their wide applications in the field of underwater drag reduction, gas collection and site water treatment. In this paper, a fast, simple and substrate-independent method that achieved reversible switching between underwater superaerophilicity and superaerophobicity on femtosecond laser induced superhydrophobic surfaces by alternative ultrasonic treatment in water and drying in air was reported. After laser processing, the as-prepared superhydrophobic surface showed underwater superaerophilicity due to the trapped air layer. In contrast, after ultrasonic treatment, the trapped air layer was removed and after being dipped into water again, the surfaces showed underwater superaerophobicity. The underwater superaerophobic surface easily recovered its superaerophilicity by drying the sample in air. Therefore, the as-prepared superhydrophobic surfaces could capture or repel air bubbles in water by selectively switching between underwater superaerophilicity and superaerophobicity. Furthermore, by combining hole processing and double side treatment, the sample allowed bubbles to pass through when the surface had underwater superaerophilicity and the sample intercepted the bubbles when the surface had underwater superaerophobicity. This switchable bubble wettability may provide an efficient route for gas bubble and water separation.

Study on ablation threshold of fused silica by liquid-assisted femtosecond laser processing.

The femtosecond laser machining of fused silica in air and liquids is studied. The ablation threshold of fused silica is reduced from 2.22 to ${1.02}\;{{\rm J/cm}^2}$1.02J/cm2. In order to explore the ablation mechanism fabricated in a liquid medium, the absorption characteristics of water and alcohol are studied. It is found that alcohol could absorb more laser energy than water. By analyzing the variation trend of laser-induced electron density based on an ionization model, we find that alcohol requires lower laser energy to reach the electron density standard and form plasma than water and fused silica. Besides, we observe that a laser will induce bubbles in liquids after the formation of plasma, and the bubbles in alcohol will cause stronger impact pressure to the surface of fused silica than those in water. Therefore, the mechanism of threshold reduction should be owed to the assistance of liquids with different characteristics.

Broadband and wide-angle antireflective subwavelength microstructures on zinc sulfide fabricated by femtosecond laser parallel multi-beam.

The subwavelength microstructures (SWMS) on the surface of ZnS for antireflection in an infrared band have been theoretically designed and experimentally fabricated. The finite difference time domain (FDTD) simulation has been utilized to optimize geometry for obtaining high transmittance of SWMS. Then, during simulation for light field intensity distribution, the inner of SWMS emerges location and wavelength dependent light resonant region, which can be explained by Wood-Rayleigh (WR) law. Furthermore, according to refractive index gradient formation and light field coupling effect, the grating period and height are capable of regulating the band selection of antireflection and value of the transmittance, respectively. In addition, a rapid facile approach based on femtosecond laser parallel multi-beam has been proposed to experimentally realize the designed and optimal structures. The depth, period, and embedded nano-gratings of fabricated SWMS are tunable by controlling laser-processing parameters for antireflection in the wavelength of 8 µm-12 µm. Finally, the broadband and wide-angle antireflective SWMS on ZnS as well as robust mechanical strength and hydrophobicity have been achieved, expecting to be of great potential in an optoelectronic device application.

Laser Structuring of Underwater Bubble-Repellent Surface.

Bubbles in aqueous media are pervasive and unavoidable. However, underwater gas bubbles adhesion to the metal pipework can sometimes seriously damage the surface and reduce the useful life of devices. Herein, we report a simple way to fabricate underwater bubble-repellent surface by one-step femtosecond laser direct writing technology. The as-prepared surface exhibits superhydrophilicity in air and superaerophobicity in water, and the bubble contact angles reach 159±2.5° in water. The surface presents ultralow bubble adhesion, and the rolling angle of the bubble is small. The potential mechanism is also discussed. This method offers an easy route to prepare underwater superaerophobic surfaces with ultralow bubble adhesion, and it has potential applications in underwater bubble-repelling facilities.

Highly Sensitive Strain Sensor Based on a Novel Mach-Zehnder Interferometer with TCF-PCF Structure.

A highly sensitive strain sensor based on a novel fiber in line Mach-Zehnder interferometer (MZI) was demonstrated experimentally. The MZI was realized by splicing a section of photonic crystal fiber (PCF) with the same length of thin core fiber (TCF) between two single mode fibers (SMFs). The fringe visibility of MZI can reach as high as 20 dB in air. In particular, the strain sensitivity of -1.95 pm/µÎµ was achieved within a range from 0 to 4000 µÎµ. Furthermore, the strain properties of different length of MZI was investigated. It was found that the sensitivity was weekly dependent on the length of MZI. The strain sensitivities corresponding to the MZI with 35 mm PCF, 40 mm PCF and 45 mm PCF at 1550 nm band were -1.78 pm/µÎµ, -1.73 pm/µÎµ and -1.63 pm/µÎµ, respectively. Additionally, the sensor has advantages of simple fabrication, compact size and high sensitivity as well as good fringe visibility.

Flow Channel Influence of a Collision-Based Piezoelectric Jetting Dispenser on Jet Performance.

To improve the jet performance of a bi-piezoelectric jet dispenser, mathematical and simulation models were established according to the operating principle. In order to improve the accuracy and reliability of the simulation calculation, a viscosity model of the fluid was fitted to a fifth-order function with shear rate based on rheological test data, and the needle displacement model was fitted to a nine-order function with time based on real-time displacement test data. The results show that jet performance is related to the diameter of the nozzle outlet and the cone angle of the nozzle, and the impacts of the flow channel structure were confirmed. The approach of numerical simulation is confirmed by the testing results of droplet volume. It will provide a reliable simulation platform for mechanical collision-based jet dispensing and a theoretical basis for micro jet valve design and improvement.

A Novel Strain Sensor with Large Measurement Range Based on All Fiber Mach-Zehnder Interferometer.

We have proposed a high sensitive photonic crystal fiber (PCF) strain sensor based on the Mach-Zehnder interferometer (MZI). The sensing head is formed by all-fiber in-line single mode-multimode-photonic-crystal-single mode fiber (SMPS) structure, using only the splicing method. Such a strain sensor exhibited a high sensitivity of -2.21 pm/µÎµ within a large measurement range of up to 5000 µÎµ and a large fringe visibility of up to 24 dB. Moreover, it was found that the strain sensitivity was weekly dependent of the length of PCF or MMF. In addition, the sensor exhibited the advantages of simplicity of fabrication, high sensitivity and larger fringe visibility.

Femtosecond laser one-step direct-writing cylindrical microlens array on fused silica.

We demonstrate an efficient method for fabricating high-quality cylindrical microlens arrays (CMLAs) on the surface of fused silica, fully based on spatially shaping of a femtosecond laser beam from Gaussian to Bessel distribution. As the envelope of shaped spatial intensity distribution matches the profile of cylindrical microlens perfectly, a CMLA with more than 50 uniform microlenses is fabricated by simple line scanning. The radius and height of these microlens units can be finely controlled by adjusting the power of laser pulses. Excellent optical imaging and high-speed fabrication performances are also demonstrated by our fabricated CLMA.

Temperature sensitivity enhancement of platinum-nanoparticle-coated long period fiber gratings fabricated by femtosecond laser.

The temperature sensing performance of long period fiber gratings (LPFGs) written by femtosecond laser pulses coated with platinum nanoparticles (PtNPs) is proposed and demonstrated. It is found that the PtNPs increase the wavelength sensitivity of the LPFG significantly compared with the bare LPFG. The temperature sensitivities of the bare LPFG for three dips, corresponding to 1438, 1485, and 1585 nm, are 74.04, 77.23, and 86.26 pm/°C, respectively, when the temperature changes from 10°C to 500°C, whereas the corresponding sensitivities of PtNP coated LPFGs are up to 90.58, 93.51, and 103.43 pm/°C, respectively. Moreover, the PtNP coated LPFG has shown better wavelength repeatability. A small wavelength hysteresis of ∼0.5 nm is observed when the temperature is less than 300°C.