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The size distribution and elastic modulus of micron-sized particles dispersed in liquid can be quantitatively evaluated by ultrasonic spectroscopy at a megahertz frequency range combined with a scattering theory. Conventional theories dealing with the wavelength comparable with the micron-sized particles consider viscosity for liquid droplets in emulsions and elasticity for solid particles in suspension, but very few studies have simultaneously considered viscosity and elasticity for the dispersed phase. In this study, a toluene (Tol) solution of polystyrene (PS) was dispersed in a continuous phase (water), and the ultrasonic properties of the PS-Tol/water emulsion were investigated. Furthermore, when Tol is dried from the PS-Tol droplet, spherical solid PS particles are obtained in water. Using such a drying-in-liquid method, the processes of solid PS particle formation from PS-Tol liquid droplets were analyzed ultrasonically. Since these solid PS particles are in a glassy state at room temperature, the process from emulsion to solid polymer must go through a rubbery state or transition region, where viscosity becomes important in addition to elasticity for solid particles. The objective of this study is to demonstrate a methodology to quantitatively reproduce the ultrasonic spectra of microparticles associated with the drying of organic solvents using a model that takes account of both elasticity and viscous loss., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

When nanoparticles in Brownian motion in liquid are irradiated with ultrasonic waves in the megahertz frequency range, scattering from the particles occurs, albeit at a very low intensity. The diffusion coefficient and the corresponding particle size can be calculated by analyzing the time correlation function of the ultrasound pulses. Since ultrasonic waves with long wavelengths in comparison with the particle size are unfavorable for detecting such small particles, increasing the energy of the ultrasonic waves is a primary solution. Increasing the energy, conversely, causes an unexpected acoustic flow. Consequently, a method using a strong ultrasound pulse while suppressing this acoustic flow field is required. In this study, we apply (1) a focused transducer with high ultrasonic energy, (2) a high-frequency sensor enhancing scattering performance, and (3) a short pulse repetition time to achieve high-speed and high-precision nanoparticle measurement while confining the sample in a narrow space to eliminate the acoustic flow. This enables direct tracking of nanoparticle motion by observing diffusive motion without perturbation particle dynamics. We specifically investigated a suspension of silica particles with a hydrodynamic radius of 15 nm and also achieved particle size discrimination in mixtures. The time correlation analysis using megahertz ultrasound pulses also takes advantage of ultrasonic waves' inherent advantages, such as high-speed, high-precision particle size analysis in the submicron range beyond the wavelength of visible light., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The latex agglutination test is employed to visualize antigen-antibody reactions through the aggregation of antibody-coated particles in the presence of an antigen. In the present study, we developed an ultrasound scattering technique to detect latex agglutination in an optically turbid media. However, the ultrasonic technique had less sensitivity to the dilute particle suspension than the optical techniques because of its wavelength. Therefore, we applied a time-correlation approach to detect small amounts of these aggregates using a sophisticated noise correction algorithm in the frequency domain. The lowest concentration of avidin used to detect aggregations of the biotin-coated particle using the ultrasound scattering technique was found to be 0.625 μg/ml. Furthermore, since the density differences between the particle and liquid were larger for silica suspensions than for polystyrene (PS) suspensions, a larger signal was proposed to be expected from silica suspensions. Nevertheless, it was found that latex agglutinations with the PS particle were more sensitive than those with the silica particles. The dynamic ultrasound scattering analysis along the sedimentation direction also supported the presence of strongly scattered intensity components of the PS aggregates, which is proposed to be due to the resonance scattering from PS spherical particles. Therefore, this technique can be employed to enhance scattering signals from particles for application in the agglutination test using ultrasound., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Patterning nanocrystals in polymer films is essential for the widespread use of nanocrystals in various fields from optics to electronics; therefore, the development of patterning methods for nanocrystals is an important task. Here, we report a unique approach for patterning silver nanowires (AgNWs) using a thermodynamic driving force induced by transient concentration gradients in reaction mixtures. The procedure starts with the preparation of a photocurable monomer solution containing homogeneously dispersed AgNWs. Ultraviolet illumination through a straight-line mask reduces the polymerization rate of monomers in the masked area, decreasing the polymer concentration in comparison with that in the unmasked area. Such transient polymer concentration gradients yield imbalances in the chemical potentials of AgNWs, inducing the migration of AgNWs to form a straight-line pattern of AgNWs. The pattern of AgNWs was visualized via photoluminescence imaging under a laser scanning confocal microscope and compared with the light patterns applied to the mixture. These observations revealed that the magnitude of the AgNW migration is enhanced as the transient concentration gradient increases by thickening the mask to decrease the intensity of light passing through the mask. The structural features of the AgNW pattern were reproduced using numerical simulations based on a set of reaction-diffusion equations, which suggested the key role of the polymerization kinetics characterized by the Trommsdorff-Norrish effect. Moreover, as the AgNW pattern becomes clearer, the electrical resistance along the patterns decreases and more complex patterns can be produced, indicating the potential of the method. Overall, the present patterning method constitutes a simple approach that only requires illumination through a mask to generate the AgNW pattern, which renders it a promising alternative for patterning nanocrystals in polymer films.

Pickering emulsions comprising liquid droplets stabilized by solid microparticles have gained much attention in the field of cosmetics, inks, and drug delivery systems. To ensure that microparticles in Pickering emulsions are localized at the surface of liquid droplets, ultrasonic spectroscopy analysis combined with scattering function theory was conducted in this study. Two specific cases were investigated: (1) silica particles and liquid droplets independently dispersed in liquid and (2) silica particles effectively localized at the surface of the droplets. It was found that the core-shell model was effective for analyzing nanoparticles anchored at the surface of oil droplets. Conversely, it was found that an effective shell comprised of solid particles was no longer observed as the particle size or the distance between solid particles increased. When a large solid particle was applied, the ultrasonic spectra resembled those of conventional surfactant-stabilized emulsions without solid stabilizers., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Ultrasonic scattering method is a promising technique to evaluate the particle size distribution and/or the elastic properties of particle suspended in liquid. Among the wide variety of scattering theories, the ECAH theory proposed by Epstein-Carhart-Allegra-Hawley is one of the most relevant acoustic scattering theories to reproduce the ultrasonic spectroscopy data for the particle suspensions. However, the original theory assumes that the shear contribution is provided for either elastic solid or viscous liquid. Thus, the viscoelastic effect of particle to the frequency spectra of the attenuation coefficient and the phase velocity has gained less attention and is not fully understood yet. In order to minimize the number of unknown parameters for the analysis of viscoelastic suspensions, we employed the multiple echo-reflection ultrasonic spectroscopy (MERUS) technique, which allowed us to determine the material properties, prior to the complicated scattering analysis. In this study, we prepared the particle suspensions of poly(methyl methacrylate) (PMMA), bisphenol-A polycarbonate (PC) and cross-linked poly(dimethyl siloxane) (PDMS) and the acoustic spectra were measured by the ultrasonic spectroscopy. Then, we demonstrated the effect of the particle viscosity on the spectra by using the viscoelastic ECAH model at the wavelength comparable with the particle size., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Dynamic ultrasound scattering allows us to investigate the particle motion and its average size via the time-evolution analysis of the scattering amplitude in optically turbid media. Recently, we proposed a novel particle sizing method that simultaneously analyzes the depth dependences on the sedimentation velocity and the scattered intensity without prior knowledge about the shape of the size distribution (Ultrasonics, 65 (2016) 59-68). In this study, the applicability of the technique to Fluorinert/water dilute and concentrated emulsions (up to 40 vol%) was examined. For the bimodal distribution of the emulsion, the size distribution of the particles was successfully obtained by directly probing the particle motion with different sizes as a function of the sample depth. The validity of the analysis was also investigated by comparing with conventional ultrasonic spectroscopy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The development of methods to pattern nanocrystals with different sizes and shapes remains a challenge. In this study, we demonstrate a unique class of bottom-up approaches to assemble nanocrystals into patterns. Our approach for patterning nanocrystals focuses on the utilization and control of the chemical reaction of solvents surrounding nanocrystals. The photopolymerization of solvent molecules through a photomask creates time-dependent concentration gradients of the solvents. Dispersed nanocrystals such as silver nanowires (AgNWs) migrate and are gradually organized and integrated into the polymerizing films based on the concentration gradients. The AgNW-embedded film properties are determined by the organized AgNW structures and include light transmission and electrical conductivity. Overall, the demonstrated method is very simple, widely applicable to various nanocrystals and solvents, and can thus contribute to the development of a new class of nanocrystal patterning methods., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The size distribution and mechanical properties of microparticle dispersed in liquid can be characterized by ultrasonic spectroscopy with the aid of acoustic scattering theories. In order to carry out the accurate analysis of the particles, the basic properties, such as the density, viscosity, longitudinal and shear velocities and intrinsic attenuation coefficient of the particle must be known prior to the analysis. Particularly, for soft elastomers or rubbers which exhibit complex mechanical properties with comparable real and imaginary parts, such fundamental information should be provided prior to the particle analysis to minimize the uncertainty of estimation associated with the number of adjustable parameters. In this study, we examined the acoustical properties of poly(methyl methacrylate)(PMMA) and cross-linked poly(dimethyl siloxane) sheets having different cross-linker concentrations by Multiple-Echo Reflection Ultrasonic Spectroscopy which simultaneously enabled us to acquire 4 fundamental properties, the ultrasound attenuation coefficient, phase velocity, density, and thickness (MERUS4 for solid plate). In addition, it was confirmed that the acoustic spectra of PMMA particles dispersed in water were reproduced well with the physical properties determined by MERUS4 using the PMMA plates., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Carbon black (CB) suspension exhibits various structures depending on the properties of solvent and dispersant as well as the preparation process of suspension. In most cases, CB particles do not exist as independent nanoparticles but as aggregates or agglomerates. In order to evaluate the size distribution at different level of hierarchal structure, we carried out static/dynamic ultrasound scattering analysis for the CB suspensions in alcohol and/or water with or without Nafion, a perfluorinated polymer. The potential of the dynamic ultrasound scattering technique was demonstrated by discriminating diffusing nanoparticles and micron-sized aggregates/agglomerates without dilution of the sample. Particularly, suppression of large agglomerates by addition of Nafion was clearly observed. Phosphotungstic acid (PWA), a family of polyoxometalate, was also employed to obtain smaller unit structures of the CB particles without formation of aggregation after decomposition of CB. The possible structures of the CB/PWA suspensions with and without Nafion were also discussed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ultrasound attenuation coefficient and phase velocity of moderately concentrated suspensions of charged silica particles were measured as a function of frequency. The attenuation coefficients were found to be significantly smaller than the theoretical prediction, and such a difference did not appear in the neutral particle suspensions under the corresponding concentrations. In this study, we have investigated the acoustic spectra of silica particles with different particle sizes, concentrations as well as salt concentrations. It was revealed that the noticeable deviation from the theoretical estimation only appeared in the case of large particle sizes close to the wavelength of ultrasound, and could be circumvented by addition of small amount of salt to suppress the electrostatic interactions of the charged silica particles., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, we demonstrate that vertically aligned gold nanowire array electrodes provide rapid ion and electron transport to the electrode-electrolyte interface. The charge-transport properties of the nanowire electrodes were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy under a constant-volume device configuration. The total charge stored in the corresponding devices increases monotonically with the length of the nanowires owing to the concomitant increase in the electroactive real surface area of the electrode. A remarkable feature of the electrodes is that the internal resistance associated with charge transport decreases with increasing nanowire length. The electric double-layer capacitance per unit electroactive surface area remains constant up to high charge/discharge rates. Our results demonstrate that charge migration occurs rapidly on the surfaces of the nanowires regardless of their length and the charge/discharge rate used. Thus, vertically aligned nanowire array electrodes show promise as current collectors for next-generation electrochemical energy-storage devices.

The attenuation coefficient and the phase velocity of micrometer-sized polydivinylbenzene particles in water were investigated by ultrasound spectroscopy equipped with 10-30MHz longitudinal wave transducers. While the surrounding liquid could be assumed to be inviscid for large particles with the size comparable to the wavelength of longitudinal ultrasound, the viscous and thermal waves were considered to have important roles with decreasing the particle size because the particle size becomes comparable with those wavelengths. In this study, these contributions were systematically investigated by changing the particle-size., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The size distribution and the elasticity of thermo-responsive gel particles dispersed in water were examined in-situ by ultrasonic spectroscopy (US). Poly(N-isopropylacrylamide) (PNIPAM) gel particles, undergoing volume phase transition at 34°C were synthesized by redox polymerization in emulsion, and the temperature dependence of the acoustic properties was examined. The longitudinal velocity and the attenuation coefficient of particle exhibited a drastic change at the transition temperature, indicating the increase in the mechanical properties, such the longitudinal, bulk and shear moduli, due to the shrinkage of particles upon temperature stimulation. The shear modulus of monodisperse particles, and also the stiffness of the gel particles were evaluated., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Nanostructured electrodes are at the forefront of advanced materials research, and have been studied extensively in the context of their potential applications in energy storage and conversion. Here, we report on the properties of core-shell (gold-polypyrrole) hybrid nanowires and their suitability as electrodes in electrochemical capacitors and as electrocatalysts. In general, the specific capacitance of electrochemical capacitors can be increased by faradaic reactions, but their charge transfer resistance impedes charge transport, decreasing the capacitance with increasing charge/discharge rate. The specific capacitance of the hybrid electrodes is enhanced due to the pseudocapacitance of the polypyrrole shells; moreover, the electrodes operate as an ideal capacitive element and maintain their specific capacitance even at fast charge/discharge rates of 4690 mA/cm 3 and 10 V/s. These rates far exceed those of other types of pseudocapacitors, and are even superior to electric double layer-based supercapacitors. The mechanisms behind these fast charge/discharge rates are elucidated by electrochemical impedance spectroscopy, and are ascribed to the reduced internal resistance associated with the fast charge transport ability of the gold nanowire cores, low ionic resistance of the polypyrrole shells, and enhanced electron transport across the nanowire's junctions. Furthermore, the hybrid electrodes show great catalytic activity for ethanol electro-oxidation, comparable to bare gold nanowires, and the surface activity of gold cores is not affected by the polypyrrole coating. The electrodes exhibit improved stability for electrocatalysis during potential cycling. This study demonstrates that the gold-polypyrrole hybrid electrodes can store and deliver charge at fast rates, and that the polypyrrole shells of the nanowires extend the catalytic lifetime of the gold cores.

Pseudocapacitors have been widely studied in the context of their potential applications in portable electronics and energy regeneration. However, the internal resistance within these devices hampers charge transport and limits their performance. As a result, maximum charge/discharge rates are typically limited to a few hundred mV s -1 for pseudocapacitors. Beyond this limit, capacitance rapidly decreases and devices become incapable of storing energy. Here, we design electrodes in which coaxial nanowires made of highly conductive metal cores and pseudocapacitive organic shells are fabricated into a seamless, monolithic, and vertically aligned structure. The design of this structure reduces its internal resistance, and devices fabricated using these electrodes exhibit excellent energy capacity even when charged/discharged at high rates of more than a few hundred mV s -1 . The energy density obtained in these devices corresponds to the maximum energy density predicted by the Trasatti method, and the coaxial-nanowire structure of the electrodes enhances the charge storage capacity and rate capability simultaneously., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanobubbles are expected to dissolve in milliseconds. Experimental evidence of nanobubbles that were stable for days had thus been first received with circumspection. If the large number of experimental confirmations has now made clear that surface nanobubbles could exist, bulk nanobubbles are still subject to debate. When observations are reported, the main problem is to make sure the observed particles are really made of gas. We show that ultrasound is an ideal tool for investigating the existence of bulk nanobubbles: 1) it is sensitive to minute quantities of gas, 2) it allows one to determine the bubble size distribution, 3) it discriminates unambiguously between gaseous and solid/liquid inclusions. To illustrate the efficiency of ultrasonic detection, we performed size measurements of bubbles produced by a commercial nano-/microbubble generator. No nanobubble was detected with this device. It would be insightful to use ultrasonic detection in experimental situations for which stable nanobubbles were reported., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Poly(ethyl acrylate)/poly(methyl methacrylate) (PEA/PMMA) polymer networks (IPNs) with spatially graded bicontinuous morphology were designed and controlled by taking advantage of the spinodal decomposition process induced by photopolymerization of the MMA monomer. Spatial gradients of the quench depth, induced by the gradients of light intensity, were generated along the path of the excitation light travelling through the mixture. Bicontinuous structures with uniaxial gradient of characteristic length scales were obtained by two different methods: simply irradiating the mixture with strong light intensity along the Z-direction and using the so-called computer-assisted irradiation (CAI) method with moderate intensity to generate the light intensity gradient exclusively in the XY plane. These experimental results suggest that the combination of these two irradiation methods could provide polymer materials with biaxially co-continuous gradient morphology. An analysis method using the concept of spatial correlation function was developed to analyze the time-evolution of these graded structures. The experimental results obtained in this study suggest a promising method to design gradient polymers in the bulk state (3D) as well as on the surface (2D) by taking advantage of photopolymerization.

A novel ultrasound technique called Frequency-Domain Dynamic ultraSound Scattering (FD-DSS) was employed to determine sedimentation velocities and the diameters of microparticles in a highly turbid suspension. The paper describes the importance of the scattering vector q for dynamic scattering experiments using broadband ultrasound pulses because q (or frequency) corresponds to the spatial length scale whereas the pulses involve inevitable uncertainty in the time domain due to the frequency distribution of broadband pulse. The results obtained from Stokes velocity of monodispersed silica and polydivinylbenzene (PDVB) particles were compared to those obtained by a Field Emission Scanning Electron Microscope (FE-SEM). A novel method to extract the particle size distribution is also demonstrated based on an ultrasound scattering theory., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Size and elastic properties of micro-particles suspended in liquid can be acoustically determined by ultrasound attenuation and velocity measurements with the aid of elastic scattering theories and a dispersion relation. While quantitative evaluation for hard micron-sized spheres using the theories is available in literature, that for hollow particles is not yet achieved. In this study, we show that the shell thickness and the elastic modulus of hollow particles can be quantitatively evaluated by ultrasound spectroscopy. Several kinds of microparticles including polystyrene rigid particles, polydivinylbenzene rigid particles, borosilicate hollow particles, and phenolic-resin hollow particles were examined as a function of the particle concentration., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Multi-echo reflection ultrasound spectroscopy (MERUS), which enables one to simultaneously evaluate the attenuation coefficient α, the sound velocity v and the density ρ, has been developed for measurements of elastic moduli. In the present study, the technique was further developed to analyze systems undergoing gelation where an unphysical decrease in the apparent density was previously observed after polymerization. The main reason for this problem was that the shrinkage accompanying the gelation led to a small gap between the cell wall and the sample, resulting in the superposition of the reflected signals which were not separable into individual components. By taking into account the multiply reflecting echoes at the interface of the gap, the corrected densities were systematically obtained and compared with the results for the floating test. The present technique opens a new route to simultaneously evaluate the three parameters α, v and ρ and also the sample thickness for solid thin films., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Compared with a nano-sized particle, dynamics of a micron-sized particle in a liquid is often associated with sedimentation (or floating) due to its relatively large mass. The motion of more than two particles is dominated by the hydrodynamic interactions, which are known to persist over a fairly long range, e.g., several millimeters, in suspensions. The particle size may be obtained from the dynamic ultrasound scattering (DSS) technique by the analysis of velocity fluctuations, whose origin is believed to take root in the particle-number fluctuations among temporally formed domains involving collective motion of particles with a certain cut-off length. In this study, such collective particle motion in highly turbid solutions was visualized by means of the phase-mode DSS technique with a single element transducer. Quantitative agreement between the velocity fluctuations obtained by the phase- and conventional amplitude-mode analyses was confirmed, followed by examination of the concentration and the particle size dependences on the dynamic structures induced by the long-ranged interactions. It was found that the phase mode-DSS was a promising method to evaluate the time-dependent structures of the micro-particles in highly turbid suspensions., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Ultrasound spectroscopy is a powerful tool to investigate the viscoelastic properties of materials. The longitudinal elastic moduli M' and M(″), or the adiabatic compressibility κ(S) can be evaluated from ultrasound velocity v and attenuation coefficient α via the relation M'=ρv(2) and M(″)=2ραv(3)/ω, where ρ is the density and ω is the angular frequency. So far, the density was independently measured by other equipments or its variation during the chemical reaction has been ignored in the previous literatures. Here we propose a multiple echo method to simultaneously evaluate α, v, ρ, from a single acquisition, enabling us to monitor the polymerization process of acrylamide, where the three parameters vary independently during the reaction. This allows us to analyze the time evolution of the acoustic parameters for polymeric or gelling systems with the better understanding., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Trans-cis photoisomerization of an azobenzene derivative chemically labeled on polystyrene (PSAzo) was utilized as a tool to reversibly drive the phase separation of a PSAzo/poly(vinyl methyl ether) (PSAzo/PVME) blend under various experimental conditions. By using light scattering and UV-vis spectrophotometry, it was found that trans --> cis photoisomerization of azobenzene took place upon irradiation with 365 nm UV light, leading to an increase in solubility of the mixture. The enhancement in the affinity between the two polymers arises from an increase in the hydrophilicity of azobenzene chemically labeled on the PSAzo chains upon trans --> cis isomerization. Effects of the affinity between the cis-PSAzo and PVME on the phase separation kinetics of the PSAzo/PVME blends were also revealed by combining experiments on thermally induced phase separation and light-induced dissolution. In contrast to the phase separation induced by a temperature drop where the dissolution of the periodic structures with shorter wavelengths is dominating, it was found that structures with longer wavelengths are predominantly dissolved during the reverse quench induced by irradiation with 365 nm UV light. These experimental results not only reveal a unique mode-selection process driven by UV light but also suggest a tool to control morphology of photoreactive polymer mixtures.

Interpenetrating polymer networks (IPNs) with spatially graded co-continuous structures were constructed by photo-cross-linking a homogeneous mixture of photo-reactive polystyrene and methyl methacrylate monomer. For a given thickness, irradiation with weak ultraviolet (UV) light results in a co-continuous morphology uniform throughout the sample. However, as the irradiation intensity increases to some certain extent, spatially graded co-continuous morphology in the micrometre scales emerges due to the significant effect of the gradient of the light intensity along the irradiation direction. These 3-dimensional graded structures were observed by using laser scanning confocal microscopy (LSCM) and were analyzed by digital image analysis. The depth dependence of these graded structures can be well expressed by a power law with an exponent depending strongly on the irradiation intensity. The time-evolution of the graded morphology was monitored at different depths of the same irradiated sample. It was found that the phase separation does not follow conventional laws of kinetics, but instead exhibits the autocatalytic behavior, reflecting the effects of the heat produced by the photopolymerization of MMA monomer on the phase separation process. The experimental data obtained in this study suggest a method of producing polymeric materials with spatially graded structures in the micrometer scales by solely changing the irradiation intensity.

Morphology is the decisive factor controlling practical properties such as impact strength or transparency in multiphase polymeric materials. The co-continuous structure formed by polymers has been of great interest to material scientists because of their superiority over those with random morphology. Although a number of efforts--including forcibly freezing the spinodal structure of polymer blends--have been made to produce materials with co-continuous structures, an efficient method for controlling their regularity is still lacking. Here, we demonstrate a novel method using periodic photo-crosslinking to control the length-scale distribution of the spinodal structure in binary polymer blends. It was found that the period distribution of the resulting co-continuous structure became significantly narrow under this periodic forcing. Also, there exists a particular irradiation frequency at which the periodic structure exhibits a minimum, indicating the existence of an ordering process driven by the external modulation frequency. Our findings reveal an easy way to produce polymer materials that is not only useful for optical applications, but also promising for biological separation, such as hemodialysis.