Wetting Behavior Research Articles

Surface Activity, Wettability, and Aggregation Behavior of Ecofriendly Fluorocarbon Surfactant Based on Double Perfluorinated Branched Short Chains.

This article reports the synthesis of a novel sulfonated fluorocarbon surfactant (SFDC) containing double C6 perfluorinated branched short chains and compares its surface properties with a similar structured compound (SFDC-L) in solutions. The critical micelle concentration (CMC) and the corresponding surface tension (γCMC) of SFDC aqueous solution are 9.77 × 10-3 mmol/L and 22.15 mN/m, respectively, indicating that SFDC has excellent surface properties. Besides, the addition of n-hexyltrimethylammonium bromide (HTAB) could further enhance the surface properties of SFDC. Meanwhile, the micellization, aggregation behavior, wettability, and adsorption at the air-water interface of SFDC and SFDC/HTAB mixture aqueous solutions are systematically investigated. Both SFDC and SFDC/HTAB show excellent wettability at low concentrations. The aggregation of SFDC and SFDC/HTAB mixtures in aqueous solution could be clearly seen as vesicles and rod-like micelles on TEM micrographs.

Excellent hydrophobicity and high mobility of condensate droplets on hierarchical nanostructured surfaces: Insights from MD simulations

Comprehending the fundamental physical mechanisms behind condensation and the formation of suspended droplets on hierarchical structured surfaces is of paramount importance in the design of anti-frosting surfaces. In this study, we characterize the nucleation, growth and dynamic wetting behaviors of condensate droplets on hierarchical nanostructured surfaces by molecular dynamics simulation, and reveal that hierarchical structures facilitate the rapid formation and high mobility of suspended droplet during condensation. The mechanism underlying the formation of suspended droplets on hierarchical surfaces is unveiled, which can be attributed to the spontaneous dewetting transition induced by confined growth of individual droplets. Additionally, the impact of solid fraction and secondary structure distribution on condensation and dynamic wetting is systematically discussed. The results indicate that an increase in solid fraction or the number of secondary structures enhances the stability of suspended droplets and improves the droplet mobility. In particular, the presence of bottom secondary structures on sidewalls plays a crucial role in the formation of suspended droplets on hierarchical surface. It is expected that the above findings could provide valuable guidance for optimizing the design of functionalized surfaces with anti-frosting and self-cleaning performance.

Effect of semi-permeable film stabilisation treatment on dry and wet cyclic corrosion behaviour of Q420qENH weathering steel plates and welded joints in deicing salt media

In this paper, the influence of semi-permeable film stabilisation on the corrosion trend, corrosion type and corrosion mechanism of bridge weathering steel in a deicing salt medium was investigated by dry and wet alternating accelerated corrosion test. The results indicate that the semi-permeable film stabilisation treatment reduces the inflection point of corrosion rate reduction of weathering steel plates and welded specimens in the deicing salt medium, reduces the value of n, which represents the trend of full-scale corrosion, and improves their resistance to full-scale corrosion. After 30 days of corrosion, the peak intensity ratios of Iβ-FeOOH+FeOCl /Iα-FeOOH for untreated plates and welded specimens were 1.092 and 1.132 times higher than that of the semi-permeable film stabilisation treatment specimens, respectively. With a reduction of defects and an increase in densification in the rust layer, and a significant reduction in the concentration of chloride ions at the interface between the rust layer and the substrate. During the whole corrosion process, the self-corrosion potential of the rust layer after the stabilisation treatment of the semi-permeable film was increased by 1.08–1.12 times, the impedance was increased by 1.13–1.32 times, and the electrochemical stability was significantly improved. The semi-permeable film in the pre-corrosion period effectively blocked the penetration of chloride ions, reducing the concentration of corrosion medium in the rust layer, reduced the generation of unstable phases of β-FeOOH and FeOCl. At the same time, the stabiliser treatment improves the Cu, Cr and Ni elements in the rust layer, promoted the formation of the stable phase α-FeOOH in the rust layer and the refinement of the rust grains, thus significantly improving the corrosion resistance of the weathering steel in the deicing salt medium.

Photochemical wet etching of (0 0 1) plane ß-phase Ga2O3, and its anisotropic etching behavior

The photochemical (PC) wet etching behavior of (001) plane β-phase Ga2O3(β-Ga2O3)single crystal was investigated using potassium hydroxide etchant solution under ultraviolet illumination in the temperature range of 80–95 °C. The etch rate was 1.65 nm/min at 80 °C, and increased up to 4.88 nm/min at 95 °C. The etch rate of the (001) plane β-Ga2O3shows strong temperature dependence with the activation energy of 0.798 eV. The PC wet etching characteristics of the (001) plane β-Ga2O3was compared with those of (2¯01) and (010) plane β-Ga2O3. The etch rates increased in order of the (010), (2¯01), and (001) plane, which is accordance with the increasing surface energy trend. The oval line-shaped grooves aligned along [010] direction were observed on the etched (001) plane β-Ga2O3 crystal surface after 30 min. PC wet etching at 80 °C.

Wetting permeability of surface active agent droplets impacting on a layer of coal dust

The wetting and penetration of the coal dust layer by liquid droplet is crucial for suppressing coal dust. A combination of experimental and simulation methods was employed to investigate the impact of surfactant concentration, droplet velocity, and particle size on the penetration properties and their underlying mechanisms. Droplet impact wetting experiments were employed to evaluate their dynamic wetting behavior on the coal dust layer. The experimental results show that increasing the impact velocity of droplets is advantageous for enhancing the maximum dimensionless wetting length. Increasing the surfactant concentration can expedite the droplet reaching maximum dimensionless wetting volume in the dust layer. The larger the particle size of coal dust, the shorter time required for droplet to reach maximum wetting volume. The research results provide a theoretical basis for selecting and efficiently applying surfactants in treating coal dust.

Polydimethylsiloxane Surface Modification of Microfluidic Devices for Blood Plasma Separation.

Over the last decade, researchers have developed a variety of new analytical and clinical diagnostic devices. These devices are predominantly based on microfluidic technologies, where biological samples can be processed and manipulated for the collection and detection of important biomolecules. Polydimethylsiloxane (PDMS) is the most commonly used material in the fabrication of these microfluidic devices. However, it has a hydrophobic nature (contact angle with water of 110°), leading to poor wetting behavior and issues related to the mixing of fluids, difficulties in obtaining uniform coatings, and reduced efficiency in processes such as plasma separation and molecule detection (protein adsorption). This work aimed to consider the fabrication aspects of PDMS microfluidic devices for biological applications, such as surface modification methods. Therefore, we studied and characterized two methods for obtaining hydrophilic PDMS surfaces: surface modification by bulk mixture and the surface immersion method. To modify the PDMS surface properties, three different surfactants were used in both methods (Pluronic® F127, polyethylene glycol (PEG), and polyethylene oxide (PEO)) at different percentages. Water contact angle (WCA) measurements were performed to evaluate the surface wettability. Additionally, capillary flow studies were performed with microchannel molds, which were produced using stereolithography combined with PDMS double casting and replica molding procedures. A PDMS microfluidic device for blood plasma separation was also fabricated by soft lithography with PDMS modified by PEO surfactant at 2.5% (v/v), which proved to be the best method for making the PDMS hydrophilic, as the WCA was lower than 50° for several days without compromising the PDMS's optical properties. Thus, this study indicates that PDMS surface modification shows great potential for enhancing blood plasma separation efficiency in microfluidic devices, as it facilitates fluid flow, reduces cell aggregations and the trapping of air bubbles, and achieves higher levels of sample purity.

Retinoic acid-releasing scaffold based on chitosan hydrogel and testis decellular plates

Introduction: The use of releasing scaffolds is promising for testes tissue engineering. Chitosan (CS) is a natural biopolymer extensively used as a delivery system. The decellularized testis provides a structure resembling natural extracellular matrix (ECM). All-trans retinoic acid (atRA) is an important factor for spermatogonia differentiation, meiosis completion, and mature sperm release. In this study, thermosensitive CS/βGP hydrogel was served as a novel atRA-releasing support for testis decellular plates (TDPs). Methods: The CS/βGP hydrogel was evaluated for gelation time, morphology, wettability, cytocompatibility, and atRA-releasing behavior. Mouse testes were treated with 1% SDS and evaluated for decellularization efficacy through morphological assessments, DNA content assays, and DAPI staining. TDPs were obtained from the decellularized testes and placed on an atRA-releasing CS/βGP hydrogel support. Results: The CS/βGP hydrogels were prepared with different formulations. It was found that increasing the βGP concentration significantly decreased the gelation time. The addition of atRA did not considerably affect the hydrophilicity of hydrogel. The in vitro release studies showed a sustained atRA release behavior, although an initial low burst release was recorded. Also, increasing the amount of atRA led to a decrease in the rate of drug release. The decellularization procedure successfully removed cells while preserving the ECM. The atRA-releasing CS-TDP scaffold was found to be non-toxic with good biocompatibility. Conclusion: Results showed that the novel atRA-releasing CS-TDP scaffold can sustainably deliver atRA to the culture system and create a cytocompatible environment for testicular cells. Therefore, this scaffold may be useful in developing new tissue engineering approaches for various types of male infertility diseases.

Study on the effects of inorganic salts and ionic surfactants on the wettability of coal based on the experimental and molecular dynamics investigations

Through the evaluation and preparation of a novel inorganic salt composite solution consisting of sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactants polyethylene glycol pisooctyl phenyl ether (Triton X-100), and inorganic salt Na2SO4, based on surface tension, contact angle, settling time, wetting rate, and changes in the surface microstructure and functional groups of coal, this study analyzed the wetting behavior of the solution on coal dust and its adsorption capacity on the surface of coal particles. The results demonstrate that the composite solution of inorganic salts can significantly enhance the wettability of coal samples, reducing the contact angle to 21.54° and lowering the surface tension to 26.10 mN/m. After treatment with the solution, the relative content of oxygen-containing functional groups in the microscopic structure of the coal sample increased to 59.6 % and pores more prominent than 25 nm increased to 34.63 %. Molecular dynamics (MD) simulations of the water-inorganic salt composite solution-coal system are conducted using Materials Studio software, revealing that after the addition of the composite solution, the self-diffusion coefficient (D) of water molecules is 6.3 × 10-9 m2/s, the starting point of the composite solution is 15 Å, and the system's interaction energy increase to 14000 kcal/mol. It further elucidated the modification of the surface molecular structure of coal dust by the inorganic salt composite solution, increasing hydrogen bonds, enhancing wetting, and demonstrating a solid adsorption capability of the inorganic salt composite solution on the surface of coal dust.

Thermogravimetric Analysis of Moisture in Natural and Thermally Treated Clay Materials.

Clays are a class of porous materials; their surfaces are naturally covered by moisture. Weak thermal treatment may be considered practical to remove the water molecules, changing the surface properties and making the micro- and/or mesoporosities accessible to interact with other molecules. Herein, a modulated thermogravimetric analysis (MTGA) study of the moisture behavior on the structures of five, both fibrous and laminar, clay minerals is reported. The effect of the thermal treatment at 150 °C, which provokes the release of weakly adsorbed water molecules, was also investigated. The activation energies for the removal of the adsorbed water (Ea) were calculated, and they were found to be higher, namely, from 160 to 190 kJ mol-1, for fibrous clay minerals compared to lamellar structures, ranging in this latter case from 80 to 100 kJ mol-1. The thermal treatment enhances the rehydration in Na-montmorillonite, stevensite, and sepiolite structures with a decrease in the energy required to remove it, while Ea increases significantly in palygorskite (from 164 to 273 kJ mol-1). As a proof of concept, the MTGA results are statistically correlated, together with a full characterization of the physico-chemical properties of the five clay minerals, with the adsorption of two molecules, i.e., aflatoxin B1 (AFB1) and β-carotene. Herein, the amount of adsorbed molecules ranges from 12 to 97% for the former and from 22 to 35% for the latter, depending on the particular clay. The Ea was correlated with AFB1 adsorption with a Spearman score of -0.9. When the adsorbed water is forcibly removed, e.g., under vacuum conditions and high temperatures, the structure becomes the most important, decreasing the Spearman score between β-carotene and Ea to -0.6.

A coupled approach of spatial dielectric mapping and unsupervised machine learning for damage detection and severity segmentation in polymer matrix composites

The inevitable presence of moisture within a polymer composite has allowed for the development of a novel dielectric nondestructive evaluation (NDE) technique which capitalizes on the behavior of moisture under an applied electromagnetic field. Relative permittivity of water which is bound to the polymer network differ significantly from that of water which is not bound to the network, and the preferential diffusion of this “free” water to damage sites permits the creation of spatial permittivity maps. Presently, this technique has shown capability for damage detection but has not achieved quantification, which is crucial for industry use. The introduction of machine learning algorithms to existing techniques in this field has proven valuable, thus, a machine learning approach for data processing and damage quantification to the existing dielectric technique was developed and applied in this work. BMI/Quartz samples and S2-Glass/Epoxy samples were fabricated and subjected to impact damage via drop tower. The BMI samples were impacted centrally at 9 J and the S2-Glass samples were subjected to two impact events of differing energies, 5 and 3 J. An unsupervised K-means clustering algorithm was applied to the acquired dielectric scans at different gravimetric moisture contents which has provided promising results for all samples. Specifically, within the two impact samples, the algorithm assigned a higher cluster center to the site with more damage, indicating the technique has the capability to both detect and quantify impact damage at all moisture levels examined.

A facile DNA coacervate platform for engineering wetting, engulfment, fusion and transient behavior.

Biomolecular coacervates are emerging models to understand biological systems and important building blocks for designer applications. DNA can be used to build up programmable coacervates, but often the processes and building blocks to make those are only available to specialists. Here, we report a simple approach for the formation of dynamic, multivalency-driven coacervates using long single-stranded DNA homopolymer in combination with a series of palindromic binders to serve as a synthetic coacervate droplet. We reveal details on how the length and sequence of the multivalent binders influence coacervate formation, how to introduce switching and autonomous behavior in reaction circuits, as well as how to engineer wetting, engulfment and fusion in multi-coacervate system. Our simple-to-use model DNA coacervates enhance the understanding of coacervate dynamics, fusion, phase transition mechanisms, and wetting behavior between coacervates, forming a solid foundation for the development of innovative synthetic and programmable coacervates for fundamental studies and applications.

A new approach to contact angle measurement and effects of evaporation on the contact angle

The solid material's wettability behavior is determined by the contact angle value. The wettability of materials is critical in the coating, lubricating, and insulating industries. In high-tech industries including corrosion resistance, water-oil separation, medical material production, implant technology, and friction reduction, the contact angle is very important. A new method called the full angle method was used to measure the contact angle and compared with current methods. The wettability behavior of plexiglass, which is employed in a variety of applications ranging from lighting to decorating, and industrial designs to accessory production, was explored in this study. The measurement of the contact angle was done by dropping 1.8 M (molar) of saltwater over the plexiglass materials. In order to examine the effect of evaporation on the contact angle, changes in contact angle, height and baseline were investigated depending on the waiting time.

Condensation of water on PDMS-coated copper surfaces for fresh water harvesting

With an increased need to solve fresh water scarcity for humanity in many places around the world, dew water harvesting is one promising approach to improve the situation. While condensation from humid air has been a research topic for many years, it is still unclear how surface wettability influences the condensation efficiency and the fresh water harvest. In this work, we contribute to bridging this knowledge gap by comparing the condensation efficiency of PDMS-coated hydrophobic and uncoated hydrophilic surfaces. We characterize the humid air velocity field to enable comparability of the present results on condensation efficiency with the results gained at other conditions. In addition, the surface wetting behavior prior to and after the condensation experiment is investigated to analyze the PDMS-coating longevity and allow to draw conclusions on their suitability for long term use in condensation applications.

Enhancing carbon capture: Exploring droplet wetting and gas condensation of carbon dioxide on nanostructured surfaces

The investigation of carbon dioxide (CO2) condensation on heat exchange surfaces is essential to the advancement of carbon capture, utilization, and storage (CCUS) technology. Molecular dynamics simulations are employed to explore the wetting and condensation behavior of CO2 on nanostructured surfaces. The results indicate that the contact angle of CO2 droplets on nanostructured surfaces is greater than that on smooth surfaces. Increasing the pillar height (h) or solid fraction (f) induces the transition of CO2 droplets from the Wenzel to Cassie state, resulting in an increased contact angle. Nanostructured surfaces significantly enhance the nucleation rate, with molecules initially nucleating at the bottom of the pillars. A higher h or f accelerates the nucleation rate during the condensation. Droplets in the Wenzel state exhibit higher heat transfer efficiency than those in the Cassie state. Additionally, the formation of Cassie-state CO2 droplets undergoes a dewetting transition, altering the heat conduction mode. The dewetting behavior of CO2 droplets favors their detachment from the surface, potentially reducing the initial heat resistance. Therefore, appropriately increasing h and f can promote nucleation and droplet growth, enhancing dewetting transition and mass transfer performance. These simulation results hold great importance for inspiring the design of future CO2-phobic surfaces and guiding CO2 condensation production.

Robust and stable organic sulfonate sodium salt-coated superhydrophilic mesh for ultra-fast gravity-drive oil-water separation

Due to its special wetting behavior and high selectivity, super-wetting mesh is considered as an ideal candidate material for efficient separation of water/oil mixture. However, the oil-water separation mesh suffers from the problems of poor stability and durability, leading to the failure of the separation. In this paper, a robust and stable superhydrophobic/superhydrophilic copper mesh had been successfully prepared by decorating the copper mesh via the chemical grafting of the 3-thiol-propyl trimethoxysilane (KH590) and the subsequent reaction with 2-acrylamide-2-methylpropane-1-sulfonate sodium (AMPS). It showed that the KH590 condensation compound was tightly coated on the surface and the superhydrophobic copper mesh (SUCM) possessed excellent superhydrophobicity towards various liquid droplets with a WCA of higher 150° and a sliding angle lower 5°, while the superhydrophilic copper mesh (SICM) had promising anti-oil pollution property with WCA near 0°. The SUCM and SICM also had excellent acid and alkali resistance. The obtained SICM had preeminent separation efficiency higher 99% and extremely high permeability flux of 33,441 L·m−²·h−¹ for gravity-driven toluene-water separation, and possessed excellent recyclability even after 20 cycles. Moreover, the SICM could be used to separate the oil-water mixture of aqueous solution with different pH (pH=5/7/8) and aqueous sodium chloride solution with different concentrations (5%/25%/50%/saturated aqueous sodium chloride solution). In addition, the SICM had outstanding anti-abrasion mechanical stability. This work provided a simple and effective method for the preparation of special wettability materials with excellent acid/alkali resistance and mechanical stability, and promoted the practical application of oil/water separation mesh.

Effects of moisture absorption analysis of kevlar/carbon/glass/polyurethane epoxy hybrid sandwich composites with nano silicon particles

ABSTRACT Hybrid sandwich polymer composites are widely used in aviation applications due to their attractive properties, such as their excellent strength capability, high modulus values, excellent stiffness properties, and greater wear resistance. This study aims to analyse the mechanical properties of degraded hybrid sandwich specimens exposed to moisture and investigate the moisture behaviour of the degraded sandwich panels. These panels are reinforced with woven fabrics made of kevlar, carbon, and glass fibres. The hand layup technique was employed to create the structures. The hybrid sandwich composite samples are submerged in normal seawater at ambient temperature for varied duration’s to measure the fibres’ water absorption characteristics. The study investigated the mechanical characteristics of an ageing moisture hybrid sample during tensile, flexural, and compressive tests. Novel stacking sequence arrangements (01 K/01 C/01 G/PUR/01 G/01 C/01 K) were used to enhance the stiffness, load-carrying capacity, yield strength, and other mechanical characteristics of the sandwich structures. The degraded sandwich panels demonstrated that water absorption significantly influences the tensile, flexural, and compressive properties of degraded sandwich structures compared with the results of regular sandwich panels. The tensile (31.67%, 40.40%, and 47.089%), flexural (63.13%, 66.05%, and 70.14%), compressive (33.14%, 39.37%, and 38.40%), and water absorption (3.75%, 3.97%, and 4.71%) test results were analysed.

Wet oxidation of TiZrHfNbTaV high-entropy alloys: Role of grain-boundary and interdendritic diffusion

Refractory high-entropy alloys (RHEAs) are sensitive to thermal oxidation, significantly restricting their service performance and potential applications. However, the wet oxidation behavior of RHEAs has remained poorly understood despite the potential risk of catastrophic oxidation caused by water vapor. In this study, the oxidation mechanism of an equiatomic TiZrHfNbTaV high-entropy alloy (HEA) has been investigated in a wet atmosphere at elevated temperatures. Synchronous oxidation of all elements occurs at temperatures below 800 °C. At temperatures above 800 °C, preferential oxidation of Nb, Ti, and Zr, and internal oxidation of V occur on HEAs, which are thermodynamically less preferred as compared with oxidations of more reactive Hf and Ta. Experimental and theoretical analyses show that the oxide grain boundaries and substrate interdendritic regions of HEAs act as diffusion pathways for V and oxidizing species during preferential and internal oxidation processes. This work provides a fundamental understanding of the oxidation of multicomponent alloys in wet environments, which is helpful in the development of effective oxidation resistance strategies and innovative surface engineering techniques.

Experimental study on dynamic wetting behavior of liquid droplets on the aluminum surfaces excited by ultrasonic waves

In this paper, an anti-frosting strategy utilizing ultrasonic excitation to drive droplets away from cold surfaces was proposed. Based on this strategy, experimental studies were conducted to investigate the dynamic wetting behavior of droplets on aluminum surfaces under ultrasonic excitation. Specifically, the vibration characteristics of the plate and the properties of the droplets were revealed under the influence of ultrasonic waves. The results indicate that the droplet will undergo three stages of spreading-movement-contraction under ultrasonic excitation and the maximum contact angle hysteresis and maximum diameter spreading rate exhibit a positive correlation with droplet volume and ultrasonic power. It is also found that ultrasonic excitation can significantly reduce the droplet contact angle, which can be reduced by up to 70°. The contact angle hysteresis, diameter spreading rate and movement velocity show almost the same trend with time under ultrasonic action, that is, increasing first and then decreasing. Notably, the contact angle hysteresis and the diameter spreading rate reached a peak later than the movement velocity, which is attributed to the droplet's deformation relies on the full propagation of the ultrasonic vibration inside the droplet, resulting in hysteresis. Finally, it is found that the droplet-wetting state is permanently changed under ultrasonic action and the final contact angle is greatly reduced compared to the initial value even after stopping ultrasonic excitation.

Robust and stable superhydrophilic MIL-101 (Cr)-coated copper mesh for highly efficient oil/water emulsion separation.

In this study, dip coating method was investigated to prepare superhydrophilic MIL-101 (Cr)-coated copper mesh for highly efficient oil/water emulsion separation. To increase the surface area of synthesized MIL-101 (Cr), a purification procedure was developed to remove unreacted H2BDC crystals present in the channel of the initial MIL-101 (Cr) sample synthesized. After that, a dispersing solution of MIL-101 (Cr) was needed to coat on the copper mesh. Thermoplastic polyurethane (TPU) was used as a binder in this procedure. The prepared membranes of M1 (once coated mesh) to M6 (six times coated mesh) were performed to separate oil/water emulsion effectively. Contact angle tests showed the superhydrophilic/underwater superoleophobic wettability behavior of MIL-101 (Cr)-coated copper meshes. The wetting mechanism of the prepared membranes is mostly relevant to the surface functional groups of purified MIL-101 (Cr). Also, the roughness of the nanostructured coated membranes was improved because of the uniform coating of MIL-101 (Cr) which is integrated into hydrophilic TPU. Oil/water separation results showed that M2 (twice coated mesh) showed the maximum amount of water flux (83076 L m-2h-1) in oil/water separation and M3 (three times coated mesh) had the best performance of oil/water emulsion with 99.99% separation efficiency.

Investigation of Microstructure, Oxides, Cracks, and Mechanical Properties of Ti-4Al-2V Joints Prepared Using Underwater Wet Laser Welding.

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.