Evaporation Solution Research Articles

Molecular Dynamics Simulation of the Enhanced Evaporation Characteristics of Pure Water and Ion Solutions by the Electric Field

ABSTRACT In this study, the evaporation of pure water and NaCl solution films under different electric fields was investigated using molecular dynamics, and the intrinsic mechanism of enhanced evaporation by electric fields was analyzed from the perspectives of forces and thermodynamics. The simulations showed that, apart from a slight inhibitory effect of a direct current electric field on the evaporation efficiency of pure water, square wave electric fields promoted the evaporation of both pure water and NaCl solution, as well as direct current electric fields on NaCl solution, with the effect increasing with the strength and frequency of the field. For example, under a 200 GHz square wave electric field, the evaporation rates of the pure water and NaCl solution films were 8.33 and 2.65 times higher than under the direct current electric field, respectively; under horizontal electric fields of 0.1 V/nm and 0.3 V/nm, the evaporation rates of the NaCl solution film were 1.13 and 1.66 times higher than natural evaporation, respectively. The rate of evaporation efficiency is reflected in the change of molecular kinetic energy. The reasons for these phenomena are closely related to microscopic parameters and properties such as intermolecular forces, the number of hydrogen bonds, and the coordination number.The application of different electric fields affects the microscopic properties between molecules, leading to changes in the evaporation rate.

Innovative ammonia harvesting from wastewater: A controlled closed-loop process at high pH for enhanced nutrient recovery

This study presents a new, sustainable, high-pH recirculating batch process for the regeneration of NH4+-laden cation exchange resins, while recovering the ammonia as a pure, reusable, solid salt (NH4Cl). The process efficiently recycles a minimal volume of regeneration solution while reducing NaCl consumption between cycles. The regeneration solution, containing a high concentration of NaCl maintained at high pH (pH > 11) allows Na+ to replace the desorbed NH4+, which, due to the high pH, completely transforms into NH3. Real time pH monitoring of the regeneration solution and the column effluent provided accurate tracking of the regeneration rate and allowed concise endpoint determination. Ammonia was recovered by evaporation of the exhausted regeneration solution followed by sublimation (and thereafter deposition) of NH3 and HCl, which produced pure NH4Cl salt.The optimal working conditions for the cation exchange regeneration were identified as 1 M NaCl, pH 12.0, and regeneration solution volume of 1 bed volume. Single-column application of six adsorption-regeneration cycles (no zeolite replacement) showed that the process conditions do not degrade the resin’s adsorption performance. Cost assessment of two possible ammonia recovery options indicated that while stripping NH3 from the regeneration solution and reabsorbing it in an acidic solution is operationally easier, the sublimation-based approach yields a more valuable product. For an optimized sublimation approach, a low regeneration solution volume, combined with a high resin capacity for NH4+, are essential.This process demonstrates a sustainable solution for ammonia salt recovery from wastewater, offering a circular approach that does not only add an important control to the regeneration step, but also harvests ammonia as a reusable product.

Highly efficient purification of the process solution when producing lithium hydroxide by caustification

Relevance. The need to develop highly effective methods for purifying the process solution from impurity calcium and aluminum ions for the industrial production of lithium hydroxide at the Chemical Metallurgical Plant JSC in Krasnoyarsk. Aim. Development of methods for reducing the content of impurity calcium and aluminum ions in the process solution of lithium hydroxide after caustification to a concentration of 5–10 mg/l. Methods. Evaporation and crystallization, precipitation of colloidal sediments of aluminum and calcium with an ammonia buffer solution, chemical precipitation with 8-hydroxyquinoline. Results and conclusions. The effectiveness of the applied methods for purifying a process solution of lithium hydroxide from calcium and aluminum ions was shown: evaporation followed by crystallization, precipitation with an ammonia buffer solution, precipitation in the form of hydroxyquinolates. It was experimentally established that when using the evaporation method followed by crystallization, the degree of extraction of impurity aluminum ions Al3+ is achieved 29%; and calcium ions Ca2+ – 56%. When cleaning the process solution by precipitation of aluminum hydroxide colloid with an ammonia buffer solution, the degree of extraction for aluminum ions Al3+ was 96%; for calcium ions Ca2+ – 67%. The use of the chemical precipitation method with 8-hydroxyquinoline in an alkaline solution showed the degree of extraction of aluminum ions Al3+ 20%; and calcium ions Ca2+ – 76%. It was established that the method of evaporation and crystallization of the process solution does not require the use of special reagents. A method using an ammonia buffer solution to remove impurity calcium and aluminum ions shown to be simple and effective. For the first time, a method was proposed for cleaning the process solution after caustification using an aqueous-alkaline solution of 8-hydroxyquinoline, excluding the use of organic, flammable and toxic solvents.

Ammonium Oxathioamidate

Ammonium oxathioamidate (1) was synthesised by the reaction between O-ethyl-thioxamate (oxalic acid-1-amide-2-O-ethyl ester) and ammonium hydrogen carbonate in water solution. Compound 1 was fully characterised by both microanalytical (elemental analysis, melting point determination) and spectroscopic means (FT-IR and NMR spectroscopy). Crystals suitable for single-crystal X-ray diffraction were isolated by slow evaporation of an ethanol solution of the compound. The analysis of the crystal packing reveals the prominent role exerted by intermolecular hydrogen bonding (HB) and chalcogen bonding (ChB) interactions.

Control Patterning of Cyanobiphenyl Liquid Crystals for Electricity Applications.

Controlling molecular self-assembly from organic solution evaporation is an important strategy for developing many functional materials and systems. In this work, it is demonstrated that 4-octyloxy-4'-cyanobiphenyl (8OCB) liquid crystals can be patterned into well-oriented stripes with very high micrometer-scale precision using a sandwich system through a dewetting method. The preparation temperature, concentration, and surface energy are combined to control the morphology and orientation of 8OCB microstripe arrays assisted by silicon micropillars. Microstripes prepared below the isotropic temperature were uniform, well-ordered, and showed high electricity. In addition, 8OCB molecules have a strong tendency toward antiparallel alignment, nearly standing up on the substrate with long axes parallel to the microstripe. Also, we point out the mechanism for the self-assembly process of 8OCB on the air-liquid and liquid-solid surface.

Porous polyimide composite films containing mesoporous hollow silica nanospheres with ultralow dielectric constant and dissipation loss

Porous polyimide hybrid films with ultralow dielectric constant and dissipation loss were synthesized during chemical imidization and rapid evaporation of polymer solutions. Polyimide (PI) of bis(4-aminophenyl)-1,4-diisopropylbenzene (BISP) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) were synthesized in N-methylpyrrolidinone (NMP) to yield the corresponding poly(amic acid)s (PAA)s, which were then chemically imidized. To reduce the dielectric properties of the porous PI films, amine-functionalized, surface-modified hollow silica nanoparticles (AHNS) with various sizes from 100 nm to 1 μm, prepared via sol-gel process, were added with PAA at 3, 5, or 10 % weight content, followed by chemical imidization to produce the porous PI/AHNS films. To avoid the high-volume shrinkage of wet gels and maintain the high porosity of the PI with low polarizability, AHNS nanoparticles were added to the porous structure of the PI xerogels as a physical crosslinker. The polyimide hybrid film with 10 nm AHNS nanoparticles at 10 % weight content showed a dielectric constant of 1.151 and a dissipation rate of 0.001 at a frequency of 10 GHz.

Structural design and characterization of a new type of organic nonlinear optical flavanone crystal

Two new crystals were designed and obtained: the chalcone derivative HMMP (1-(2‑hydroxy-4-methoxyphenyl)-3-(4-(methylthio)phenyl)prop‑2-en-1-one) and the flavanone derivative 7M4MC (7‑methoxy-2-(4-(methylthio)phenyl)chroman-4-one). Yellow bulk 7M4MC single crystal with dimensions of 3 × 2 × 1 mm3 and orange-yellow needle-like HMMP single crystal were grown by solution evaporation. 7M4MC crystal belongs to the P21 space group of the monoclinic structure, which has a non-centrosymmetric structure. HMMP crystal monoclinic, belongs to the P21/m space group with a centrosymmetric structure. In the 7M4MC molecule, the methoxy and methylthio groups act as electron donors (D) and the carbonyl group acts as an electron acceptor (A), forming a d-π-A-π-D structure with an electron gradient. 7M4MC exhibits a high degree of second-harmonic generation intensity (11 × KDP), a broad transmission range (600–1600 nm, >88 %), an elevated optical energy bandgap (Eg = 2.57 eV), high thermal stability (Tm = 105 °C) and excellent dielectric properties (εr ≈ 2.1). This work not only provides two new crystals but also offers a viable molecular design option by changing the degree of intramolecular distortion by altering the backbone structure.

The process of evaporation of a colloidal solution of stabilized Boron nitride nanoparticles

Purpose. Characterization of the chemical structure of boron nitride nanoparticles by IR spectroscopy during the evaporation of their colloidal system and their sizes by small-angle X-ray scattering.Methods. The solvent evaporation process from the colloidal system was studied using a Nicolet iS 50 FT-IR spectrometer in the mid-IR range (400 – 4000 cm-1), with an attenuated total reflectance accessory with a diamond crystal (incident angle of 45°) and a liquid cell (200 μL). The sizes of the colloidal particles were determined using an smallangle X-ray scattering diffractometer in linear collimation mode (resolution 0.03 nm-1, copper anode X-ray tube 2.2 kW, λ = 0.154 nm, exposure time 30 s).Results. The IR spectrum of boron nitride nanoparticles powder was measured, containing lines characteristic of cubic (952 cm-1) ) – c-BN and hexagonal crystalline phases (758, 1301, and 1372 cm-1) – h-BN. The average size of boron nitride nanoparticles in the colloidal system, according to small-angle X-ray scattering data, was 46 and 84 nm. The size of stearic acid, which acts as a stabilizing shell, was 0.8, 1.3, and 2.5 nm. Analysis of the IR spectra showed complete evaporation of the solvents (hexane and chloroform) from a drop of colloidal solution 1.2 mm thick within 30 minutes.Conclusion. In this work, the average sizes of boron nitride nanoparticles stabilized with stearic acid in a colloidal system were determined and the process of its evaporation was studied.

1-Nitronaphthalene, a non-OD, non-MDO polytype

Abstract Crystals of 1-nitronaphthalene were grown by evaporation of a methanol solution. The structure [P21/c, a = 13.2780(13) Å, b = 3.8131(3)° Å, c = 31.851(3) Å, β = 91.173(8), V = 1,612.3 Å3] was solved from a crystal twinned by twofold rotation about [100]. Twinning is explained by the polytype character: layers with (idealized) p2111 symmetry can connect via either 1‾ or 21 operations, leading to geometrically distinct pairs of layers. In the twin individuals, the two kinds of contacts alternate, at the composition plane two subsequent contacts of the same type are realized.

Boosting corrosion resistance of Mg-Li alloy: Implanting bioinspired superhydrophobic surfaces into MAO matrix for enhanced protection

The corrosion problem has significantly impeded the practical application of Mg-Li alloys. In this report, a method that combines micro-arc oxidation (MAO) with electrochemical deposition is developed to create a superhydrophobic matrix on Mg-Li substrate. The combination approach harnesses the superiority of both coverages, including MAO as the dense, firmly bonded ceramic oxide layer on the metal substrate and the superhydrophobic surface (SHS) implanted into MAO matrix. The MAO-SHS coating exhibits high mechanical stability, maintaining the superhydrophobicity due to the “implanting effect” even after a long distance of friction effect. For corrosion inhibition, compared to the bare Mg-Li with icorr of 9.26 × 10−5 A/cm2, the icorr for MAO and MAO-SHS is 7.83 × 10−6 A/cm2 and 7.50 × 10−9 A/cm2, respectively, representing the reduction of approximately one and four orders of magnitude. Focusing the atmospheric corrosion inhibition, MAO-SHS proves to manipulate the dynamic evolution of saline solution evaporation and salt particle deliquation. The salt particle crystalized from saline solution on MAO-SHS is found to have significantly smaller contact area than that of the bare Mg-Li and MAO. By employing atomic force microscopy, the adhesion force of salt particle is revealed as ca. 45 nN, 13 nN, and 2 nN for salt particle on Mg-Li, MAO, and MAO-SHS, respectively. This suggests that the salt can be more easily removed from the MAO-SHS surface, thereby reducing the susceptibility to corrosion. The in situ deliquation is conducted to understand the formation of the droplet on different surfaces. The air in the SHS layer hinders chloride ingress and the SHS layer seals the pores in MAO layer, proving the synergistic effect afforded by MAO-SHS to achieve superior corrosion resistance.

A Surface-Enhanced Raman Scattering Substrate with Tunable Localized Surface Plasmon Resonance Absorption Based on AgNPs.

In this paper, a three-layer structure of silver particle (AgNP)-dielectric-metal is proposed and constructed based on the characteristics of AgNPs that can excite LSPR (Localized Surface Plasmon Resonance) in free space. In order to overcome the problem of AgNPs easily oxidizing in the air, this paper synthesizes AgNPs using the improved Tollens method and effectively suppresses the coffee-ring effect by changing the solution evaporation conditions, so that the distribution of AgNPs in the deposition area is relatively uniform. The structure proposed in this paper takes advantage of the flexibility of nanoparticle application. The AgNPs deposited on the dielectric layer can effectively localize energy and regulate the LSPR of the device well. The structure can not only achieve precise regulation of the LSPR resonance peak of AgNPs but also can be used as a SERS substrate.

Investigations of structure, thermal stability and optical properties of a new NLO crystal (C3H5N2)+(CF3COO)-

New NLO imidazolium trifluoro acetate (C3H5N2)+(CF3COO)- single crystals were synthesized by solution evaporation method, with its structure, thermal stability, absorption spectrum, photoluminescence and second order nonlinear optical (NLO) properties were systematically investigated. This crystal features 0-dimensional noncentrosymmetric structure with orthorhombic space group I212121 which consist of isolated organic imidazolium cation (C3H5N2)+ and trifluoro acetate anion (CF3CO2)-. A high thermal stability up to 125 °C, and the absorption edge at 260 nm with a wide band gap of 4.55 eV were respectively determined. In addition, the photoluminescence performance with an emission peak at 363 nm can be ascribed to the π-π* transition absorption of imidazole ring. Notably, moderate phase-matching SHG response of 0.64 times KH2PO4 was evaluated for (C3H5N2)+(CF3COO)-. All the results indicate the potential applications of (C3H5N2)+(CF3COO)- in optical field.

Design and characterization of novel broadband chalcone-based THz optical crystals

By combining extended π-conjugated structures and halogen substituents, two novel chalcone-based optical THz crystals were designed: CBC (C22H17ClO2, Pc) and TFBC (C23H17F3O2, P21). These crystals were synthesized and successfully grown using the solution evaporation method. The effects of different types and quantities of halogen substituents on hydrogen bonding interactions, molecular alignment, and nonlinear strength were analyzed. The second harmonic generation (SHG) efficiency, thermal stability, transmission spectra, dielectric constant, and THz generation of the crystals were characterized. Theoretical calculations were conducted to determine the hyperpolarizability, band gap, density of states, and nonlinear optical coefficients of the crystals. The results showed that the synthesized crystals exhibited higher transparency (≥85%) and SHG efficiencies of 9.5 times and 6.2 times that of standard potassium dihydrogen phosphate (KDP), respectively, compared to previously reported chalcone NLO crystals. For the first time, the THz generation efficiency of the two crystals was confirmed through the optical rectification method, with TFBC demonstrating a wider THz spectrum range compared to CBC.

Four-wave mixing temperature sensor based on graphene oxide-coated microfiber hybrid waveguide

Utilizing a hybrid waveguide comprising microfiber and graphene oxide (GO), this study introduced an innovative temperature sensor based on four-wave mixing (FWM) effect. The methodology involved a tunable continuous wave (TCW) laser and a self-engineered all-fiber mode-locked laser operating at 1560 nm. The microfiber, featuring a minimum diameter of 10 μm, was fabricated through the flame fusion tapering technique, and the microfiber surface was coated with a GO film through the spontaneous evaporation of a GO solution. To improve the stability and robustness of the sensor, a layer of polydimethylsiloxane (PDMS) was applied to the surface as a protective coating. The GO film compensated for dispersion in conjunction with microfiber, enhanced nonlinearity and facilitated low-power FWM phenomena. Furthermore, it increased temperature sensing sensitivity. By measuring the center wavelength shift of the idler and signal light, we achieved a temperature sensing sensitivity of −2.08 nm/℃ from −15 ℃ to 20 ℃ using the CW laser at 1540 nm. This sensor also had a resolution of 0.024 ℃, a response time of 0.12 s and a maximum temporal resolution of 0.08 s. Our study marks the initial investigation of a temperature sensing mechanism employing the FWM phenomenon within this unique hybrid waveguide. It serves as a proof of concept for using a microfiber combined with the two-dimensional material GO film to generate nonlinear FWM for temperature sensing. Continuous optimization of experimental conditions and waveguide dimensions is expected to enhance sensing performance. This opens up new avenues for future research in novel optical sensing technology, particularly in the exploration of high-performance sensors through the integration of nonlinear phenomena with different two-dimensional materials, showcasing substantial research potential.

A Series of Cyclopentadienyl Lanthanum Complexes with Metalloid Germanium Clusters.

A series of cyclopentadienyllanthanum complexes with the disilylated metalloid germanium cluster [Ge9(Hyp)2]2- [Hyp = Si(SiMe3)3] has been prepared and fully characterized. The synthetic procedure is based on the salt metathesis reaction of two different cyclopentadienyllanthanum diiodides CpLaI2 (Cp: Cp*, pentamethylcyclopentadienyl; Cpttt, 1,2,4-tri-tert-butylcyclopentadienyl) with K2[Ge9(Hyp)2] in tetrahydrofuran (THF) with a subsequent extraction with n-hexane. The composition of the obtained compounds and the mode of coordination of the germanium cluster to the rare-earth metal are strongly influenced by the steric demand of the cyclopentadienyl ligands and the crystallization conditions. The centrosymmetric dimeric compounds with the common formula [CpLa(solv)(η2,3-Ge9(Hyp)2)]2 [1, Cp = Cp*, solv-THF; 2, Cp = Cpttt, solv-NCCH2C(Me)NSiMe3] have been isolated by the slow evaporation of a n-hexane solution, while a mononuclear complex [CptttLa(THF)2(η3-Ge9(Hyp)2)] (4) was found by crystallization from THF. The repeated recrystallization of 1 from n-hexane afforded the asymmetric dimer [Cp*La(THF)(η2,3-Ge9(Hyp)2)][Cp*La(η2,3-Ge9(Hyp)2)] (3) with only one coordinated THF molecule.

Highly Luminescent TCNQ in Melamine.

Optical properties of molecules change drastically as a result of interactions with surrounding environments as observed in solutions, clusters, and aggregates. Here, we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Colored single crystals are synthesized by slow evaporation of aqueous tetrahydrofuran solutions of melamine and TCNQ. Single-crystal X-ray diffraction reveals the lattice structure of pure melamine, meaning that the color is of impurities. Both mass spectrometry and UV-vis spectroscopy combined with density-functional theory calculations elucidate that the impurity species are neutral TCNQ and its oxidation product, dicyano-p-toluoyl cyanide anion (DCTC-), whose concentrations in a melamine crystal can be controlled by adjusting the molar ratio between melamine and TCNQ in the precursor solution. Fluorescence excitation-emission wavelength mappings on the precursor solutions illustrate dominant emissions from DCTC- while the emission from TCNQ is quenched by the resonance energy transfer to DCTC-. On the contrary, TCNQ in crystalline melamine is a bright fluorophore whose emission wavelength centered at 450 nm with internal quantum yields as high as 19% and slow fluorescence lifetimes of about 2 ns. The method of encapsulating molecules into transparent melamine would make many other molecules fluorescent in solids.

Controlling Spatial Morphology of Microparticle Deposits via Thermocapillary Flows: Effect of Boundary Geometry.

The production of particle deposits with a desired distribution geometry has significant potential for materials science, printing, and coating technologies. Most methods for achieving well-defined assemblies rely on the spontaneous evaporation of colloidal solutions on substrates with predetermined properties, or on precise control of particle arrangement by external stimuli. Here, we present a combined method that enables the production of centimeter-scale microparticle deposits with a desired geometric shape. The method is based on controlling the massive transport of microparticles by thermocapillary flow in a layer of volatile liquid in a cell with borders of the desired geometry. Capillary forces cause the liquid to be distributed in the cell, forming corner wetting menisci and the flat layer in the central area. The formation of particle deposits occurs in two stages, determined by the flow regime. At the initial stage, the axisymmetric thermocapillary flow occurs in the flat part of the layer, resulting in the circular shape of the particle deposit. During the transition to the second stage of assembling thermocapillary flow is localized in the corner wetting menisci that results in reshaping the current particle deposit to match the geometry of the cell borders. Here, we demonstrated the creation of circular, square, and triangular shapes of the patterns of polystyrene microparticles using a point heater located at the geometric center of the cell. The proposed method is reliable, easy to implement, and potentially capable of producing a wide variety of deposit geometries, making it an attractive technique for patterning and modifying surface properties with particles of any type.

Probing the limits of tetraalkylthiuram disulfide synthesis by direct reaction of secondary amines with CS2: The structures of Cy2NC(S)SSC(S)NCy2 and Cy2NC(S)SSSSC(S)NCy2

Reaction of Cy2NH with CS2 in NaOH/H2O, followed by oxidation with I2, yields a complex mixture that includes the tetracyclohexylthiuram disulfide, Cy2NC(S)SSC(S)NCy2, in mixture with S8 and the tetrasulfide Cy2NC(S)SSSSC(S)NCy2. Direct reaction of 2 eq of Cy2NH with CS2 in EtOH, followed by I2 oxidation, does not yield isolable Cy2NC(S)SSC(S)NCy2, even though other tetraalkylthiuram disulfides are effectively produced by this protocol. Deprotonation of Cy2NH with t BuLi, followed by treatment with CS2 and then oxidative coupling with I2 yields Cy2NC(S)SSC(S)NCy2 in ∼74% yield, suggesting secondary amines that are branched at the α carbon may generally require this lattermost approach to the corresponding tetraalkylthiuram disulfide. Evaporation of an Et2O solution of the crude product mixture obtained from the CS2/NaOH/H2O reaction yielded a triclinic form of Cy2NC(S)SSC(S)NCy2, which contained two independent molecules in its asymmetric unit with opposite C 2 handedness. This same product mixture contained Cy2NC(S)SSSSC(S)NCy2, which was identified crystallographically in monoclinic C2/c and is the first such tetrasulfide to be characterized by X-ray diffraction. A second polymorph of Cy2NC(S)SSC(S)NCy2, obtained by evaporation of an acetone solution, is disordered across a mirror plane in monoclinic P21/m. This monoclinic polymorph of Cy2NC(S)SSC(S)NCy2 is the only tetraalkylthiuram disulfide found to crystallize on a mirror plane.

Comments on “Investigations on growth, XRD, strain, FTIR, UV–Vis NIR, photoluminescence, SHG, and z-scan analyses of l-cysteine picrate single crystal for NLO and optical limiting applications”

Alexandar et al. (Inorg. Chem. Commun. 159 (2024) 111751) report to have grown “l-cysteine picrate” crystal (LCP) by evaporation of an aqueous solution containing equimolar ratios of l-cysteine and picric acid at 40 °C in a constant temperature bath. A critical analysis of the reported infrared spectral and X-ray powder data, reveals that the LCP crystal is, in fact, picric acid. Previously, Alexandar et al. has claimed to have grown a so-called “l-methioninium picrate” crystal (LMP) (J. Nonlinear Opt. Phys. Mater. 25 (2016) 1650052) which is also improperly characterized as it is devoid of any picrate and LMP is indeed l-methionine. Taking as examples LCP, LMP and the supposedly new crystals “l-methionine succinic acid” (Chem. Phys. Impact 6 (2023) 100203) and “(4-nitrophenyl) methionine” (Indian J. Phys. 97 (2023) 3835) which are, in fact, succinic acid and l-methionine, respectively, we highlight a combined use of infrared spectra and X-ray diffraction data for accurate characterization of known crystals.

Reconstruction of Chitosan Network Orders Using the Meniscus Splitting Method for Designing pH-Responsive Materials.

Chitosan is a product of deacetylated chitin and a natural polymer that is attractive as a functional and biocompatible material in the pursuit of alternative materials to synthetic plastics for a sustainable society. Although hierarchical architectures, from precise molecular structures to nanofibers and twisted structures, have been clarified, the expansion of the anisotropic microstructures of chitosan into millimeter-scale materials is in the process of development. In this study, a chitosan network was reconstructed from an aqueous solution by using the meniscus splitting method to form a three-dimensionally ordered microstructure. A chitosan membrane deposited on the millimeter scale formed a useful anisotropically pH-responsive hydrogel. During the evaporation of the aqueous solution from a finite space, chitosan underwent ordered deposition by capillary force to form a membrane with oriented microstructures and microlayers. Unlike the cast films formed between solid-liquid and air-liquid interfaces, this membrane formed between two air-liquid interfaces. As a result, the membranes with ordered microstructures were capable of signifying directional swelling in aqueous environments and reversible/irreversible swelling-deswelling changes by controlling the pH range. We envision that the anisotropic pH response of the chitosan network can be utilized under physiological conditions as a next-generation material.