Confined Liquid Research Articles

Ferroelectric benzimidazole additive-induced interfacial water confinement for stable 2.2 V supercapacitor electrolytes exposed to air.

Deep eutectic solvents (DESs) are known as low-cost and environmentally friendly electrolytes for supercapacitors. However, because DESs are particularly vulnerable to moisture adsorption in the air, the voltage window (<1.2 V) is significantly lower than expected. Herein, we report a new ferroelectric benzimidazole (BI) additive that, by restricting water electrochemical activity at the DES/carbon electrode interface, allows air-exposed DESs to reach a high voltage of 2.2 V. The optimized DES with 0.5 wt% BI addition not only increases the voltage but also the capacitance and energy density while maintaining excellent cycling stability. This study addresses the voltage drop of DESs in air, providing insights into the design of additives that inhibit interfacial water splitting.

Ionic guest in ionic host: ionosilica ionogel composites via ionic liquid confinement in ionosilica supports

Non-hydrolytic sol–gel strategies allow accessing all-ionic ionosilica ionogels containing up to 80 wt% of supported IL. These phases display modulable electrochemical properties.

Dynamics of Water and Other Molecular Liquids Confined Within Voids and on Surface of Lignin Aggregates in Aging Bio Crude Oils.

Neutron scattering methods were employed to study the microscopic structure and dynamics of Bio Crude Oils (BCOs) and their lignin fractions. The structure of the carbonaceous aggregates was investigated using Small Angle Neutron Scattering to reveal a fractal hierarchy as well as a growth of the aggregates as the aging of the BCO proceeds. Elastic Neutron Scattering measurements indicate that BCO liquid phase, comprised of water and other hydrogenated molecular liquids, is in a state of extreme confinement. Quasi-Elastic Neutron Scattering yields information on the molecular motions, indicating that long range translational diffusion is suppressed and only localized dynamics take place on the tens of picosecond time range. The obtained results provide quantitative information on the molecular activity, as aging proceed, in these reactive materials of relevance as potential renewable energy sources.

Water cluster in hydrophobic crystalline porous covalent organic frameworks

Progress over the past decades in water confinement has generated a variety of polymers and porous materials. However, most studies are based on a preconception that small hydrophobic pores eventually repulse water molecules, which precludes the exploration of hydrophobic microporous materials for water confinement. Here, we demonstrate water confinement across hydrophobic microporous channels in crystalline covalent organic frameworks. The frameworks are designed to constitute dense, aligned and one-dimensional polygonal channels that are open and accessible to water molecules. The hydrophobic microporous frameworks achieve full occupation of pores by water via synergistic nucleation and capillary condensation and deliver quick water exchange at low pressures. Water confinement experiments with large-pore frameworks pinpoint thresholds of pore size where confinement becomes dominated by high uptake pressure and large exchange hysteresis. Our results reveal a platform based on microporous hydrophobic covalent organic frameworks for water confinement.

Shell-thickness control of hollow SiO2 nanoparticles through post-treatment using sol–gel technique toward efficient water confinement

Hollow structures possess a confinement function, which enables the handling and use of functional liquids. In this study, we focus on the confinement of water in the inner spaces of hollow SiO 2 nanoparticles (HSNPs). Water is introduced into the hollow spaces passing through the mesopores of the shells. The introduced water is then confined by thickening the shell through a post-treatment using silicon alkoxides. HSNPs with a variety of shell thicknesses are prepared by tuning the synthetic conditions of the reaction media and the alkoxides. It is found that the amount of water retained in a hollow space is increased with shell thickness. The resultant water–HSNP nanocomposites exhibit effective far-infrared absorption. The facile confinement approach reported in this study will lead to highly functional complex nanocomposites, such as isolated metal nanoparticles–water–silica.

Intercalated water mediated electromechanical response of graphene oxide films on flexible substrates

The confinement of water between sub-nanometer bounding walls of layered two-dimensional materials has generated tremendous interest. Here, we examined the influence of confined water on the mechanical and electromechanical response of graphene oxide films, prepared with variable oxidative states, casted on polydimethylsiloxane substrates. These films were subjected to uniaxial strain under controlled humid environments (5 to 90% RH), while dc transport studies were performed in tandem. Straining resulted in the formation of quasi-periodic linear crack arrays. The extent of water intercalation determined the density of cracks formed in the system thereby, governing the electrical conductance of the films under strain. The crack density at 5% strain, varied from 0 to 3.5 cracks mm−1 for hydrated films and 8 to 22 cracks mm−1 for dry films, across films with different high oxidative states. Correspondingly, the overall change in the electrical conductance at 5% strain was observed to be ∼5 to 20 folds for hydrated films and ∼20 to 35 folds for the dry films. The results were modeled with a decrease in the in-plane elastic modulus of the film upon water intercalation, which was attributed to the variation in the nature of hydrogen bonding network in graphene oxide lamellae.

Structural Developments of the Reversible Confinement of Ionic Liquids in Nylon 6 Fibres: Solid State 13C Nuclear Magnetic Resonance

Reversible confinement of ionic liquids (ILs) among the polyamide molecules is used for suppressing or weakening the hydrogen bonds during the low-speed melt spinning process for the structural improvements of the nylon 6 fibres. The melt spinning process is followed by a hot drawing process and a subsequent extraction of the ILs. Afterwards, the resulting fibres are thermally stabilized so as to produce high performance nylon 6 fibres. Interestingly, the molecular structural developments of the IL-confined nylon 6 fibres took place during the stress-induced phase transformation (i.e. during the hot-drawing stage) – these developments lead to an ultimate molecular orientation which in turn caused improvements of the overall fibres’ properties. The solid state 13C nuclear magnetic resonance (NMR) tests revealed that non-aliphatic carbonyl chemical shifts at 172.6 ×10-6 and 172.9 ×10-6 took place and they are believed to be due to the γ crystal phases of the neat and of the 2% IL-confined nylon 6 fibres, respectively. Moreover, during the γ to α crystal phase transitions, the NMR peaks’ shift for the IL-confined fibres are either remained unchanged or are slightly increased. The Structural developments of the IL-confined and the reverted nylon 6 fibres have, also, been discussed.

High-Accuracy Pick-and-Place of Multiple Dies in Parallel Assisted by Capillary Self-Alignment

Abstract Self-assembly of components driven by liquid surface tension is an attractive complement and even alternative to traditional high-accuracy pick-and-place as it offers high accuracy despite inaccurate robotic part placement. While capillary self-alignment through liquid solder is the standard technology for flip-chip processes, this work presents self-alignment of dies on wetted receptors on a temporary carrier: Low-viscosity liquid is jetted on each receptor where the liquid is contained through generation of hydrophilic and hydrophobic sections on the temporary carrier by plasma treatment. Deterministic die feeding by low-accuracy pick-and-place is conducted for single dies, as well as for batches of three dies and nine dies optimizing the equipment for best throughput to achieve both high accuracy and high productivity. The industry-ready and fully automated chip-to-wafer pick-and-place process is implemented into a fan-out wafer-level packaging production flow proving that self-alignment is capable of easing the stringent requirement for robotic alignment capability for pick-and-place systems in fan-out packaging for the single die-level step in this production chain. The self-alignment process is optimized, and failure modes such as poor liquid confinement, surface contamination, or excess force are identified and eliminated. Post-bond accuracy of &amp;lt;3 μm @ 3 σ at each point of the die is reached for dies of 3.1 mm x 3.1 mm in size. Using parallel die handling, high speeds of around 10 000 units per hour are made possible.

Novel Confinement Possibility for Laser Shock: Use of Flexible Polymer Confinement at 1064 nm Wavelength

Through the years, laser shock peening became a treatment of choice in the aerospace industry to prolong the life of certain critical pieces. Water flow is commonly used as a confinement to improve the process capability but some applications cannot allow for water presence in the area of interest. In a previous article, an alternative to the water confinement was presented, a flexible polymer confinement was used and demonstrated the production of pressures equivalent to the water configuration treatment. However, laser parameters have been restricted to a wavelength in the visible range at 532 nm. In this paper, the study is extended to 1064 nm which is commonly used in LSP applications and with two different pulse durations. A 1064 nm near infra-red laser is used to do pressure characterization of shots with polymer confinement through Velocity Interferometer System for Any Reflector (VISAR) measurements coupled with Finite Element Modelling on Abaqus software. The results show that the pressures produced by the confinement is slightly lower with the 1064 nm wavelength, similar to what is observed with the classic water confined regime when switching from 532 nm to a near infra-red wavelength. Nevertheless, the high level of pressure produced by laser shock under the polymer confinement configuration allows for the treatment of common types of metal alloys used in the aerospace industry. Although the use of such a confinement has yet to be applicable to peening setups, it has already uses in some single shot configurations such as LasAT where it allows the avoidance of the water flow optimization.

Subwavelength LIPSS formation on SS304 by picosecond laser irradiation under water confinement

Laser induced periodic surface structures were generated in a single step by applying picosecond laser irradiation at different repetition rates on a surface area of 15 × 15 mm2 of a stainless steel-304 probe immersed in a confinement liquid medium and on ambient air. Periodicity modification from high to low spatial surface frequency LIPSS was observed by modifying the pulse repetition rate from 1.3 to 402 kHz at a constant fluence (7 J/cm2) under water confinement. Additional experiments at lower fluences (1.78 and 5.33 J/cm2) were performed to evaluate the periodicity under water confinement. Wettability analysis of the processed area yielded significative changes on the drop contact angle showing a wetting transition from hydrophilicity to hydrophobicity of the samples surface treated by multiple impact pulses under water confinement.

Enabling Superhydrophobicity-Guided Superwicking in Metal Alloys via a Nanosecond Laser-Based Surface Treatment Method.

Enabling capillary wicking on bulk metal alloys is challenging due to processing complexity at different size scales. This work presents a laser-chemical surface treatment to fabricate superwicking patterns guided by a superhydrophobic region over a large-area metal alloy surface. The laser-chemical surface treatment generates surface micro/nanostructures and desirable surface chemistry simultaneously. The superhydrophobic surface was first fabricated over the whole surface by laser treatment under water confinement and fluorosilane treatment; subsequently, superwicking stripes were processed by a second laser treatment in air and cyanosilane treatment. The resultant surface shows superwicking regions surrounded by superhydrophobic regions. During the process, superwicking regions possess dual-scale structures and polar nitrile surface chemistry. In contrast, random nanoscale structures and fluorocarbon chemistry are generated on the superhydrophobic region of the aluminum alloy 6061 substrates. The resultant superwicking region demonstrates self-propelling anti-gravity liquid transport for methanol and water. The combination of the capillary effect of the dual-scale surface microgrooves and the water affinitive nitrile group contributes toward the self-propelling movement of water and methanol at the superwicking region. The initial phase of wicking followed Washburn dynamics, whereas it entered a non-linear regime in the later phase. The wicking height and rate are regulated by microgroove geometry and spacing.

Exchange Counterion in Polycationic Hydrogels: Tunability of Hydrophobicity, Water State, and Floating Capability for a Floating pH Device.

Smart gel materials are capable of controlling and switching swelling, water state, and wettability properties triggered by external stimuli. In this study, we fabricated a series of polyelectrolyte hydrogels bearing a 3-trimethylammoniumpropyl pendant to a methacrylamide-based backbone and examined the switchability with hydrophobic-like counteranions. The exchange between the initial chloride and camphor sulfate (CaS), dodecyl sulfate (DS), and perfluorooctanoate (PFO) counterions was investigated. The kinetics of the exchange showed that the fast exchange (within 4 h) of PFO allowed for a favorable coordination for ion pairing, resulting in a decrease in hydration. The reversibility of the exchange to the Cl− ion was only enabled for the CaS ion due to its bulkiness, while the PFO and DS hydrogels were unable to exchange, even by using tetrabutylammonium chloride, which is a structurally similar reagent, due to aggregation or the coagulates in the collapsed state of the linear tails of the counterions. The hydrogels exhibited a modulable water state and water swelling. Moreover, the hydrogels containing DS and PFO, as counterions, showed surface hydrophobic (contact angle 90°) and high hydrophobic (110°) behavior, respectively. The Raman spectrometry fluorescence with a pyrene probe indicated an increase in strong hydrogen-bonded water molecules, water confinement, and hydrophobic domains in the PFO hydrogel. Moreover, the PFO-modified hydrogel demonstrated a free-floating ability on the water surface, with a strong water repellency, showing that it has the potential to be applied in a floating pH detection device to distinguish between volatile and nonvolatile bases in a controlled manner.

Lifetime-Associated Two-Dimensional Infrared Spectroscopy Reveals the Hydrogen-Bond Structure of Supercooled Water in Soft Confinement.

We demonstrate a method to address the problem of spectral overlap in multidimensional vibrational spectroscopy and use it to investigate supercooled aqueous sorbitol solutions. The absence of crystallization in these solutions has been attributed to “soft” confinement of water in subnanometer voids in the sorbitol matrix, but the details of the hydrogen-bond structure are still largely unknown. 2D-IR spectroscopy of the OH-stretch mode is an excellent tool to investigate hydrogen bonding, but in this case it seems difficult because of the overlapping water and sorbitol contributions to the 2D-IR spectrum. Using the difference in OH-stretch lifetimes of water and sorbitol we can cleanly separate these contributions. Surprisingly, the separated 2D-IR spectra show that the hydrogen-bond disorder of soft-confined water is independent of temperature and decoupled from its orientational order. We believe the approach we use to separate overlapping 2D-IR spectra will enhance the applicability of 2D-IR spectroscopy to study multicomponent systems.

Microstructure and performance evolution of Ti-6Al-4 V alloy coating by laser cladding and laser shocking composite remanufacture

Regarding occurrences of excessive tensile stress, low basket organization refinement and unoptimized mechanical properties of Ti-6Al-4 V layer during laser remanufacture, a new composite remanufacture process of laser cladding and laser shocking was proposed. Optimized pulse laser remanufacture process of low laser power and high duty cycle was adopted to prepare a homogeneous alloy layer on the Ti-6Al-4 V matrix. Water confinement and strong pulse laser was used to shock the cladding surface, as a strategy to tailor metallographic structure, mechanical properties and residual stress of the cladding layer. The experiment results showed that, the originally cladding layer was mainly composed α + β two-phase structure with some acicular martensite transformation, along with metallographic structure interlaced in basket organization. Microhardness of the layer was distributed between 345 ~ 445HV0.1, and residual stress distribution was −190 ~ 180 MPa.In addition, friction and wear coefficient was found in a range of 0.19 ~ 0.58.After shocking optimization, the α phase redissolution of the layer was aggravated, the α and β phase grains were refined. It was also noted some α phase particles were dispersed among the grains. The microhardness of the layer was increased to 365 ~ 478HV0.1, the residual stress is mainly distributed in −70 ~ -652Mpa.The tensile stress was all transformed into compressive stress, along with the friction and wear coefficient ranged in 0.04 ~ 0.15.These results confirmed the possibility of the laser remanufacture outcome improvement via adoption of the composite process of laser cladding and laser shocking.

Molecular dynamics study on water confinement in deep eutectic solvents

The nanoscopic properties of highly diluted water solutions in choline chloride + lactic acid deep eutectic solvent was studied using molecular dynamics simulations as a function of concentration and temperature with the objective of characterize the confinement of water in deep eutectic solvents as a non-regular confinement mechanism. The simulations allowed the analysis of changes in the properties of the deep eutectic solvent in response to the water presence as well as the behaviour of confined water in solvent cavities. The analysis of structural, energetic and dynamic factors provides for the first time the characterization of water confined in these environmentally friendly solvents. The results showed how water can be confined in deep eutectic solvents liquid cages maintaining water individuality with minor changes in the solvent properties, which can be used for tuning water properties for the development of technological applications.

Measurement and characterization of nanosecond laser driven shockwaves utilizing photon Doppler velocimetry

Laser driven shockwaves from nanosecond pulsed lasers were evaluated for pressure magnitude and duration using photon Doppler velocimetry (PDV). Specific investigations were performed on Ti-6Al-4V alloys and 7085-T7651 aluminum alloys with laser full-width half-max pulse lengths ranging from 6 to 20 ns and laser intensities of 2–10 GW/cm2. The rear surface velocity data obtained using a heterodyne PDV system and an automated signal processing algorithm are demonstrated and utilized to capture rear surface velocity profiles. Peak shockwave pressures measured under bare surface water confinement reached approximately 6 GPa. Shockwave loading durations were observed to correspond with laser pulse durations with impulse loading times on the order of 2×–4× the laser pulse duration.

Encapsulation and Release of Doxorubicin from TiO2 Nanotubes: Experiment, Density Functional Theory Calculations, and Molecular Dynamics Simulation.

Titanium dioxide (TiO2) nanotubes are attractive materials for drug-delivery systems because of their biocompatibility, chemical stability, and simple preparation. In this study, we loaded TiO2 nanotubes with anticancer drug doxorubicin (DOX) experimentally and in all-atom molecular dynamics (MD) simulations. The release of doxorubicin from the nanotubes was studied by high-performance liquid chromatography (HPLC) and confocal Raman spectroscopy, and drug-release profiles were evaluated under various conditions. The polyethylene glycol (PEG) coating and capping of the nanotubes led to a marked increase in the water contact angles from about 16 to 33° in keeping with reduced wettability. The capping retarded the release rate without decreasing the overall release amount. The MD simulations further show that the DOX molecule diffusion coefficients (Di) are in the order of 10-10 m2/s. The DOX molecules show a plethora of short- and long-range H-bonding interactions with TiO2 nanotube walls and water. Calculated radial distribution functions (RDFs) and combined radial/angular distribution functions (CDFs) allowed gauging the strength of these hydrogen bonds. The strength does not fully correlate with the pKa values of DOX atoms which we assign to the confinement of DOX and water in the tubes. The lifetimes of hydrogen bonds between the DOX atoms and water molecules are shorter than that of the DOX...TiO2 interactions, and DOX...DOX aggregation does not play an important role. These results suggest TiO2 nanotubes as promising candidates for controllable drug-delivery systems for DOX or similar antiproliferative molecules.

Thermo-poro-mechanics under adsorption applied to the anomalous thermal pressurization of water in undrained clays

Pore fluid pressurization, one of the main causes of soil instability, is known to be anomalously high for interstitial water in clay submitted to undrained heating. This anomaly is attributed to the confinement of water in nanometric micropores. In this work, we use molecular simulation to investigate how confinement affects the thermo-mechanical properties of water and we use a new poromechanical formulation (Laurent and Tulio in Int J Eng Sci 152:103296, 2020) to relate these confined properties to the macroscopic pressurization of water during undrained heating. This new formulation considers the effects of confinement on the thermo-mechanical moduli of water in micropores, and, in particular, it accounts for the break of extensivity with respect to the volume (Gibbs–Duhem equation not valid). The predictions regarding water thermal pressurization are consistent with the available experimental data when considering a double porosity medium (micro- and macro-pores) with osmotic equilibrium between the porosities. It suggests that the excess fluid pressurization arises from the drainage of water from the micro-porosity to the macro-porosity. The proposed poromechanics offers the first quantitative thermo-hydro-mechanical description of clay based on the physics of adsorption with wide perspectives for applications and transposition to other adsorption-sensitive materials (cement-based materials, wood, bones, microporous carbons etc.).

Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

In order to realize the utilization of cement-based materials in the special extreme environment, the deep sea, the authors have launched a project targeted at creating a technology platform with in-situ methods and systems for monitoring and evaluating cement-based materials located at deep ocean bottom sites. The first in-situ test in the world with a view to investigating the time-dependence of the volumetric stability and microstructure of Portland cement mortar following its long-term exposure to deep-sea conditions is currently underway at a 3515-m depth in the Nankai Trough. This paper reviews previous studies about the influences of deep-sea hydraulic pressure on cement-based materials, verifies the action of short-term hydraulic pressure using Portland cement mortars on a laboratory scale, and introduces the ongoing progress of in-situ deep-sea tests. Results from laboratory tests indicate that dimensional changes were provoked by liquid water infiltration and confinement while under short-term hydraulic pressure, however, time-dependent behavior under stresses such as creep has not appeared. Weight gain, changes in pore-size distribution, compressive strength and bending strength of the cement mortar were monitored after pressurization and depressurization processes.

Tentative Confinement of Ionic Liquids in Nylon 6 Fibers: A Bridge between Structural Developments and High-Performance Properties

A reversible confinement of ionic liquid (IL) among the amide segments has been carried out for the preparation of high-modulus and high-strength aliphatic semicrystalline nylon 6 fibers. In this research work, the suppression or the weakening of the hydrogen bonds during the conventional low-speed melt spinning process is followed by a hot-drawing stage and a subsequent IL extraction of the IL out of the 2% wt IL-confined fibers and an immediate thermal stabilization process for the improvement of the properties of the pristine nylon 6 fibers. The resulted crystal structural developments of the IL-confined fibers are attributed to ultimate molecular orientations, which have contributed to the developments of the overall fiber properties. Here, the influences of the IL on the γ and the α crystal phases, the γ-α transition, the morphological properties, and the tensile properties are investigated. The FTIR reported, experimentally, additional peaks at 1237 cm–1 for the γ crystal phase and at 1417 and 1476 cm–1 for the α crystal phase, in conformity with the theoretical computations. The XRD demonstrated that the conventional low-speed melt spinning can successfully be used to prepare as-spun IL-confined fibers having highly improved properties. The so prepared as-spun IL-confined fibers are found to have a γ phase structure that has a small crystal size and high crystal perfections. Fortunately, the γ-to-α crystal phase transition for the IL-confined nylon 6 fibers can be acquired during the hot-drawing stage (stress-induced phase transformation). Furthermore, the IL extraction process followed by a thermal stabilization process, interestingly, has led to significant increases in both of the tensile strengths and the tensile moduli of the reverted nylon 6 fibers. The values that are found are 8.46 cN/dtex for the tensile strength and 39.09 cN/dtex for the tensile modulus. The structure–property relationships between the IL-confined and the reverted nylon 6 fibers have also been discussed.