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PurposeIn the context of influencer marketing, this study examines the effects of explicit advertising disclosure on consumers' inference regarding influencers' sincere recommendation intent, and its consequences for consumers' purchase intentions.Design/methodology/approachIn Study 1, participants were randomly assigned to the conditions of explicit advertising disclosure (e.g. #AD, #Sponsored) and subtle advertising disclosure (e.g. #ThankYou), and indicated their inference regarding influencers' recommendation motives and their own purchase intentions. One-way ANOVA analysis reveals the effect of advertising disclosure on consumers' purchase intentions and the PROCESS model indicates the mediating role of consumers' inferences regarding influencers' sincere recommendation intent. In Study 2, we implemented a 2 (explicit vs. subtle advertising disclosure) × 2 (moderate vs. large size of followers) between-subjects design, using a two-way ANOVA analysis. We analyzed the moderated mediation effect via the PROCESS model.FindingsConsumers are less inclined to purchase products when influencers express explicit advertising disclosures, compared to when the advertising disclosures are subtle (Study 1). These negative effects of advertising disclosure can be caused by consumers' inferences regarding influencers' sincere recommendation intent in terms of posting content (Studies 1 and 2). Additionally, the negative effect is particularly prominent when an influencer has a large (vs. moderate) number of followers (Study 2).Originality/valueBy examining (1) the effects of explicit advertising disclosure on consumers' inference regarding influencers' persuasion motives and (2) the role of the influencer's number of followers, this research provides both theoretical and practical insights for understanding how best to implement influencer marketing.

Water loss can be delayed by trapping it within a polymeric network, i.e. hydrogel. However, the dynamic response of natural materials has not been explained to maintain water levels relatively constant against varying environmental conditions. In this study, patterned polymeric materials formed on plant seeds are observed to provide effective water retention ability against repeated dehydration-rehydration procedures. The perpendicular line pattern (layer-by-layer stack) of the polymer films induces lateral line patterns (surface lines) by a typical wrinkling mechanism, which contributes to the characteristic water interaction. The anisotropic line patterns on the seed surface generate more hydrophilic properties over the isotropic patterns against drying-out. The matric potential (Ψ

Patterns in materials are not just decoration but also important for function. In view of this, the dynamics of patterning procedures in materials has been investigated as an important developmental procedure. In this study, nanoscale components in a continuum are traced in terms of natural patterning procedures. Externally applied compressive or extensive forces to an elastic thin sheet commonly induce an orientated lateral line pattern. From a nanoscale element point of view, the dynamics of natural arrangements, forming anisotropic patterns in preference to isotropy, still remains unclear. In this study, new developmental procedures for line patterns are suggested by stimuli-responsive viscoelastic nanocomposite network model systems. Forces originating from an internal source without directional orientation generate lines in preference to isotropic patterns. With repeated, non-oriented (or isotropic) and self-modulated strain variations, stress is accumulated to drive anisotropic orientations and further lines. The anisotropic elemental arrangement is justified by the equilibrium between the short-range attraction and long-range repulsion from a bottom-up viewpoint. This study suggests a new material design methodology that is useful for electrical devices, biomedical devices and other patterned soft condensed matter in conjunction with line patterns typically generated in a broad range of viscoelastic materials.

Considering the safety issues of Li ion batteries, an all-solid-state polymer electrolyte has been one of the promising solutions. Achieving a Li ion conductivity of a solid-state electrolyte comparable to that of a liquid electrolyte (&gt, 1 mS/cm) is particularly challenging. Even with characteristic ion conductivity, employment of a polyethylene oxide (PEO) solid electrolyte has not been sufficient due to high crystallinity. In this study, hybrid solid electrolyte (HSE) systems have been designed with Li1.3Al0.3Ti0.7(PO4)3 (LATP), PEO and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). A hybrid solid cathode (HSC) is also designed using LATP, PEO and lithium cobalt oxide (LiCoO2, LCO)&mdash, lithium manganese oxide (LiMn2O4, LMO). The designed HSE system has 2.0 &times, 10&minus, 4 S/cm (23 &deg, C) and 1.6 &times, 3 S/cm (55 &deg, C) with a 6.0 V electrochemical stability without an additional separator membrane introduction. In these systems, succinonitrile (SN) has been incorporated as a plasticizer to reduce crystallinity of PEO for practical all-solid Li battery system development. The designed HSC/HSE/Li metal cell in this study operates without any leakage and short-circuits even under the broken cell condition. The designed HSC/HSE/Li metal cell in this study displays an initial charge capacity of 82/62 mAh/g (23 &deg, C) and 123.4/102.7 mAh/g (55 &deg, C). The developed system overcomes typical disadvantages of internal resistance induced by Ti ion reduction. This study contributes to a new technology development of all-solid-state Li battery for commercial product design.

Considering the safety issues of Li ion batteries, all-solid-state polymer electrolyte has been one of the promising solutions. In this point, achieving a Li ion conductivity in the solid state electrolytes comparable to liquid electrolytes (>1 mS/cm) is particularly challenging. Employment of polyethylene oxide (PEO) solid electrolyte has not been not enough in this point due to high crystallinity. In this study, hybrid solid electrolyte (HSE) systems are designed with Li1.3Al0.3Ti0.7(PO4)3(LATP), PEO and Lithium hexafluorophosphate (LiPF6) or Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Hybrid solid cathode (HSC) is also designed using LATP, PEO and lithium cobalt oxide (LiCoO2, LCO)—lithium manganese oxide (LiMn2O4, LMO). The designed HSE system displays 3.0 × 10−4 S/cm (55 ℃) and 1.8 × 10−3 S/cm (23 ℃) with an electrochemical stability as of 6.0 V without any separation layer introduction. Li metal (anode)/HSE/HSC cell in this study displays initial charge capacity as of 123.4/102.7 mAh/g (55 ℃) and 73/57 mAh/g (25 °C). To these systems, Succinonitrile (SN) has been incorporated as a plasticizer for practical secondary Li ion battery system development to enhance ionic conductivity. The incorporated SN effectively increases the ionic conductivity without any leakage and short-circuits even under broken cell condition. The developed system also overcomes the typical disadvantages of internal resistance induced by Ti ion reduction. In this study, optimized ionic conductivity and low internal resistance inside the Li ion battery cell have been obtained, which suggests a new possibility in the secondary Li ion battery development.

In vascular plants, the xylem network constitutes a complexmicrofluidic system. The relationship between vascularnetwork architecture and functional hydraulic regulationduring actual water flow remains unexplored. Here, wedeveloped a method to visualize individual xylem vesselsof the 3D xylem network of Arabidopsis thaliana, and toanalyze the functional activities of these vessels using syn-chrotronX-raycomputedtomographywithhydrophilicgoldnanoparticles as flowtracers. We showhow the organizationof the xylem network changes dynamically throughout theplant, and reveal how the elementary units of this transportsystem are organized to ensure both long-distance axialwater transport and local lateral water transport. Xylemvessels form distinct clusters that operate as functionalunits, and the activity of these units, which determineswater flow pathways, is modulated not only by varying thenumber and size of xylem vessels, but also by altering theirinterconnectivity and spatial arrangement. Based on thesefindings, we propose a regulatory model of water transportthat ensures hydraulic efficiency and safety.Keywords: Arabidopsis thaliana Gold nanoparticle Hydraulic regulation Synchrotron X-ray CT Water trans-port Xylem network.Abbreviations: AuNP, gold nanoparticle; DAB, days afterbolting; SEM, scanning electron microscopy; SXRCT, synchro-tron X-ray computed tomography; VB, vascular bundle.

Mass transport in porous materials is widespread in nature, and its usefulness attracts large attention for engineering applications. Plant leaves have nano-/microporous structures to pull water from root to the tip of leaves, and they finally release water to the air. In this hydraulic phenomenon called transpiration, plant leaves provide the main driving force for water transport in plants without any mechanical pump system. The morphological structure of plant leaves has been optimized through a long history of evolution to adapt to the environmental changes. In this aspect, we focus on the morphological features of plant leaves, which probably enhance leaf transpiration. The tissue organization in the hydraulic pathways inside the leaves for transpiration was investigated in this study. Inspired by the morphological structure of mesophyll cells in a plant, two analogous models were fabricated using hydrogel to study the effect of pore size on water transport. One model had nanoporous unitary structure, and the other had nano-/microporous hierarchical structure. As a result, the hydrogel model with nano-/microporous hierarchical structure induced higher evaporation and greater swelling ratio, compared with the model with nanoporous unitary structure. X-ray images of the water transport in the hydrogel models show that the porous structures of mesophyll cells can generate the Laplace pressure at the water–air interface in the air spaces.

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies.

The morphology of polymeric self-assembled structures can be changed by environmental conditions, including pH, temperature, and various additives such as ions, cosolvents, nanoparticles (NPs), and so on. Studies have focused on the size and shape of NPs to investigate the effect of NP incorporation into polymeric structures. In this study, qualitative NP effect is experimentally investigated in terms of the compatibility of NPs with the self-assembled templates. Hydrophobically/hydrophilically surface-modified gold nanoparticles (AuNP) of 20 nm diameter systematically modify the surfactant number (Ns) of the self-assembled organic templates accordingly, where the driving force is determined by the hydrophilic–lipophilic force balance. AuNPs grown in situ at equlibrium in the template, decrease the Ns, reflecting selective growth of NPs in one of the self-assembly domains. Fractal density (α) and correlation length (ζ) of the self-assembled structures are prominently increased by any type of AuNP incorporation.

Self-assembled colloidal nanoparticle (NP) clusters are one of the bottom-up processing products to construct complex two- and three-dimensional optical materials. We show metal NP clusters chemically linked by a light-sensitive organic ligand to build up nanophotonic hybrid structures. NPs are spheres identical in size with narrow polydispersity, enabling systematic structural modifications. Before randomly aggregating and settling down, the chemical interlinking of NPs behaves like a polymerization procedure, generating characteristic cluster structures with a specific fractal dimension (D). The absorbance in the UV-vis and THz regions is significantly modified depending on the cluster structures. In contrast with physical aggregation, the absorbance of chemically linked NPs can be blue-shifted in the UV-vis region, which is prominently beneficial for solar energy utilization. Applied electron beams modify the cluster structures and induce blue-shifts in UV-vis light absorbance. These types of chemically constructed NP clusters can be a general method for new metamaterial design useful for effective light energy use.

The current study regarding the rapidly developing sharing economy businesses based on ICT explored how motivation for the sharing economy and perceived security affect both attitude and loyalty toward one of the sharing economy businesses, Airbnb. The results from the structural equation modeling analysis showed that enjoyment and reputation had a positive effect on attitude toward Airbnb, whereas other motivation aspects such as sustainability and economic benefits seemed not to have any significant effect. In addition, mobile users’ security perceptions of Airbnb, which were found to be significantly influenced by governmental regulations and Airbnb’s security policy, were likely to positively contribute to the attitudes toward Airbnb. Finally, the paper stressed the growing importance of consumers’ security perceptions for building a successful business based on the sharing economy while at the same time articulating the drivers that motivate enjoyment and reputation.

Biocompatible polymeric encapsulants have been widely used as a delivery vehicle for a variety of drugs and imaging agents. In this study, X-ray contrast agent (iopamidol) is encapsulated into a polymeric microparticle (polyvinyl alcohol) as a particulate flow tracer in synchrotron X-ray imaging system. The physical properties of the designed microparticles are investigated and correlated with enhancement in the imaging efficiency by experimental observation and theoretical interpretation. The X-ray absorption ability of the designed microparticle is assessed by Beer-Lambert-Bouguer law. Particle size, either in dried state or in solvent, primarily dominates the X-ray absorption ability under the given condition, thus affecting imaging efficiency of the designed X-ray contrast flow tracers.

Inorganic nanoparticles in the self-assembled organic/biological templates are of great interest in nanoparticle-mediated therapy, biosafety, and hybrid functional material design for photonic devi...

Time-resolved dynamic imaging of bio-fluids can provide valuable information for clinical diagnosis and treatment of circulatory disorders. Quantitative information on non-transparent blood flows can be directly obtained by particle-tracing dynamic X-ray imaging, which needs better spatial resolution and enhanced image contrast compared to static imaging. For that use, tracer particles tagging along the flow streams are critically required. In this study, taking the advantage of high X-ray absorption, gold nanoparticles (AuNPs) are incorporated into human red blood cells (RBC) to produce contrast-enhanced tracers designed for dynamic X-ray imaging of blood flows. RBCs are advantageous tracers for blood flow measurements since they are natural and primary components of blood. The loading efficiency of AuNPs into RBCs is investigated in terms of the surface properties of the AuNPs. The AuNP-incorporated RBC provides a potential in the dynamic X-ray imaging of blood flows which can be used for clinical applications.

In situ monitoring of a biofluid can provide important information on circulatory disorders and a basic understanding on the metabolic mechanisms of living organisms. X-ray imaging has significant advantages as one of the most popular diagnostic tools to seethrough various biological systems. Particle traced velocity field measurement is one of the most popular methods for quantitative analysis of dynamic flow motion. In this study we have developed chitosan microparticles incorporating gold nanoparticles (AuNP) as a new enhanced contrast flow tracer for dynamic X-ray imaging. Gold is a useful material possessing high X-ray absorption ability and also biocompatibility. We chose chitosan as an AuNP delivery system because it can effectively trap AuNPs at high yield. In particular, the unique gold ion reduction ability of and compatibility with surface-modified chitosans are effectively utilized. The physical properties of the Au-chitosan microparticles can be controlled by varying the molecular weight of the chitosan employed and the AuNP incorporation methodology. The environment of the particles and the type of applied X-ray essentially determine the imaging efficiency. The designed chitosan microparticles incorporating Au have been successfully applied to track the digestive mechanisms occurring in delicate insects such as live mosquitoes.

X-ray-based imaging is one of the most powerful and convenient methods in terms of versatility in applicable energy and high performance in use. Different from conventional nuclear medicine imaging, contrast agents are required in X-ray imaging especially for effectively targeted and molecularly specific functions. Here, in contrast to much reported static accumulation of the contrast agents in targeted organs, dynamic visualization in a living organism is successfully accomplished by the particle-traced X-ray imaging for the first time. Flow phenomena across perforated end walls of xylem vessels in rice are monitored by a gold nanoparticle (AuNP) (approximately 20 nm in diameter) as a flow tracing sensor working in nontransparent biofluids. AuNPs are surface-modified to control the hydrodynamic properties such as hydrodynamic size (DH), zeta-potential, and surface plasmonic properties in aqueous conditions. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray nanoscopy (XN), and X-ray microscopy (XM) are used to correlate the interparticle interactions with X-ray absorption ability. Cluster formation and X-ray contrast ability of the AuNPs are successfully modulated by controlling the interparticle interactions evaluated as flow-tracing sensors.

To control physical properties of the temperature-responsive biomedical materials for targeted applications in easy and safe way biocompatible additives are tried. Systematic controls are studied to obtain effectively controlled results in molecular interaction viewpoint. Thermothickening behaviors of the polyphosphazenes grafted with poly(ethylene glycol) (PEG) and amino acid ester are uniquely modified by physical mixing with another PEG molecules. Depending on the length of the added PEGs and the type of the subtituents of the polyphosphazenes, there are characteristic changes in the maximum viscosity (ηmax) and the phase transition temperature (Tmax) reflecting peculiar molecular interactions. For the short chain PEG addition, hydrophobic co-association of the end-capped methyl group of the added PEGs seems to play an important role while for the longer chain PEG additions the interaction between the added and the substituted PEGs seems to be dominating, which changes the ηmax and Tmax in a unique way. Longer PEG substituted polyphosphazene is not much affected by the type of the PEGs added probably because of more effective intra-molecular self-interaction than interaction with added ones. For the less hydrophobic amino acid ester substituted polyphosphazene the interaction between the substituted and the added PEGs dominates the de-hydration, which leads to the changes in the phase transition temperature sensitive to the length of the added PEGs. This unique thermothickening modification of the thermosenstitive and biocompatible polyphosphazenes is proposed to be contributed to the special and competitive hydrogen bonding between PEG–water and PEG–PEG molecules, which changes under different conditions like concentration, molecular weight and temperature.

Ion and pH effects on the phase transition behaviors are studied with a series of thermosensitive neutral and acidic poly(organophosphazene) counterparts. Poly(organophosphazenes) are substituted by hydrophobic L-isoleucine ethyl ester (IleOEt) and hydrophilic alpha-amino-omega-methoxy-poly(ethylene glycol) 550 Da (PEG550) together with a relatively small amount of glycylglycine ally ester (GlyGlyOALL). After deprotection, GlyGlyOALL changes into glycylglycine (GlyGlyOH), and neutral GlyGlyOALL and acidic GlyGlyOH polymers with same substituent ratios are compared as counterparts. All the synthesized poly(organophosphazenes) in this work exhibit lower critical solution temperature (LCST) for which sequential phase transitions are suggested: (i) homogeneous solution, (ii) homogeneous gel, (iii) heterogeneous gel, to (iv) heterogeneous solution as hydrophobicity increases either driven by temperature or substituent composition. Ions act on the hydrophobicity modification of the polymers where the polymers with lower hydrophobic/hydrophilic ratios are more sensitively salted-out by NaCl, while those with higher ratios are more effectively salted-in by NaI. At higher concentration of the added ions, the acid group effect on the cloud point becomes deactivated. Meanwhile, because of the conflicting role of amine and carboxylic acid in pH-responsiveness, neutral and acidic polymer counterparts exhibit opposite tendencies in the cloud points. Systematically controlled responsiveness to temperature, ion, and pH changes are created in random amphiphilic graft copolymers, poly(organophosphazenes). The results highlight the importance of the cooperative function of the dominant components in the poly(organophosphazenes) and also expand the general understanding in designing stimuli-responsive smart materials especially useful for various biomedical applications.

Temperature-responding physical hydrogels are promising materials as injectable drug delivery carriers which could hold useful bioactive materials inside the polymer networks for further controlled releases. Aimed at desired qualities at body temperature, those gel characteristics need to be adjusted carefully. In this point of view, surfactant is one of the useful molecules to be used by simple formulations without harmful chemical reactions. In this study, thermothickening of amphiphilic nonionic polyphosphazene solution is modified by anionic and cationic surfactants with different alkyl chains and counter-ions. Specified in the thermothickening system, a maximum viscosity (ηmax) and a temperature at that point (Tmax) are changed independently reflecting unique intermolecular interactions. At low concentration (1–9 mM) of the added surfactant, the ηmax is maximized at 3 mM surfactant regardless of the surfactant type while the Tmax is increased continuously along with the surfactant concentration. From a kinetic point of view, this 3 mM surfactant at the maximized ηmax reflects a polymer-dominating interaction and highly favorable polymer–surfactant interaction with a low selectivity in the surfactant type. However, the magnitude of the maximum viscosity (ηmax) is dependent on the surfactant tail, which reflects the lifetime and the strength of the hydrophobic domains of the polymer network affected by the surfactants. Meanwhile, the magnitude of the Tmax depended on the surfactant head group, which means the interfacial tension of the polymer solutions changed by the surfactants. At high concentration (10 and 30 mM) of the cationic surfactants added to the polymer solutions with two different viscosities, the cationic surfactants are supposed to interact either with the hydrophobic parts of the aggregated polymer with high viscosity or on the backbone of the less- or non-aggregated polymer with low viscosity. Ionic surfactants change the thermothickening of the amphiphilic nonionic polyphosphazene solution in a unique tail- or head-dependent way. Moreover, the concentration of the added surfactants and the association pattern of the pure polymer solutions are also crucial for the thermothickening phase behaviors. Temperature-responsive polyphosphazenes in this work exhibit unique and controllable interactions with ionic surfactants.

The relative effectiveness of anions and cations in altering macromolecular conformation was reported to be independent of the nature of the macromolecule. However, in terms of the degree of changes, macromolecule-dependent ion action cannot be underestimated. The designed poly(organophosphazenes) have been selected for this study due to its versatility of the substitution with a fixed backbone. To set up the systematic explanation on the ion action related with molecular interactions, ions and polymers are arranged based on the water binding ability. As a characteristic factor specific in the thermothickening system, the temperature at which the viscosity of the polymer solution reaches the maximum (Tmax) has been compared. Anions with strong water binding ability more effectively lower the Tmax of the hydrophobic poly(organophosphazenes). Meanwhile, the Tmax of the cation-complexed poly(organophosphazenes) are lowered by the sequence of water binding ability of the complexed cations. In both the anion and cation interactions, poly(organophosphazenes) substituted by longer PEG and more hydrophilic amino acid ester, show differentiated result due to different interaction with water when compared with other polymer systems in this study. Ion interaction with poly(organophosphazenes) mediated by water supports interfacial interactions expressed by interaction parameters, which strongly depends on the polymer structure and ion type. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2022–2034, 2008

Nanoparticles have been developed in broad biomedical research in terms of effective cellular interactions to treat and visualize diseased cells. Considering the charge and polar functional groups of proteins that are embedded in cellular membranes, charged nanoparticles have been strategically developed to enhance electrostatic cellular interactions. In this study, we show that cellular uptake efficiency, pathway, and spatial distribution of gold nanoparticles in a cell are significantly modulated based on the surface condition of gold nanoparticles and human cancer cells that were tuned by controlling the pH of the medium and by introducing an electron beam. Cellular uptake efficiency is increased when electrostatic attraction is induced between the cells and the gold nanoparticles. Cell surface modification changes the cellular uptake pathways of the gold nanoparticles and concentrates the gold nanoparticles at the membrane region. Surface modification of the gold nanoparticles also contributes to deep penetration and homogeneous spatial distributions in a cell.

Understanding the morphological structure of membranes is essential to improve performance of membrane-based applications. In this paper, macroporous membranes were investigated and two methods introduced as an alternative for characterization of stereo-structure of the membranes. We combined the use of synchrotron X-ray nanotomography and small-angle X-ray scattering to examine the internal structure of cellulose acetate membranes with studies of the capture of surface-modified gold nanoparticles within these membranes. Finally, the morphological structures of macroporous membranes were visualized and their relationships with penetration tendency of surface-modified gold nanoparticles were explained.

Drying procedure is a powerful method to modulate the bottom-up assembly of basic building component. The initially weak attraction between the components screened in a solution strengthens as the solvent evaporates, organizing the components into structures. Drying is process-dependent, irreversible and nonequilibrated, thus the mechanism and the dynamics are influenced by many factors. Therefore, the interaction of the solvent and the elements during the drying procedure as well as the resulting pattern formations are strongly related. Nonetheless still many things are open in questions in terms of their dynamics. In this study, nanoscale dehydration procedure is experimentally investigated using a nanoparticle (NP) model system. The role of water is verified in a single NP scale and the patterns of collective NP clusters are determined. Stepwise drying procedures are proposed based on the location from which water is removed. Effective water exodus from a unit NP surface enhances the attractive interaction in nanoscale and induces heterogeneous distribution in microscale. This study provides fundamental proof of systematic relation between the dehydration process and the resultant cluster patterns in hierarchical multiscales.

Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications.

Collective interaction occurs in many natural and artificial matters in broad scales. In a biological system, collective spatial organization of live individuals in a colony is important for their viability determination. Interactive motions between a single individual and an agglomerate are critical for whole procedure of the collective behaviors, but few has been clarified for these intermediate range behaviors. Here, collective interactions of microscale matters are investigated with human cells, plant seeds and artificial microspheres in terms of commonly occurring spatial arrangements. Human cancer cells are inherently attractive to form an agglomerate by cohesive motion, while plant chia seeds are repulsive by excreting mucilage. Microsphere model is employed to investigate the dynamic assembly equilibrated by an attraction and repulsion. There is a fundamental analogy in terms of an onset of regular pattern formation even without physical contact of individuals. The collective interactions are suggested to start before the individual components become physically agglomerated. This study contributes to fundamental understanding on the microscale particulate matters and natural pattern formation which are further useful for various applications both in academic and industrial areas.

Repeatability of the responsiveness with time is one important concern for effective durable functions of stimuli-responsive materials. Although the increase in the yield and tensile strength of the hybrid composite materials by nanoparticle (NP) incorporation has been reported, exact NP effect on stimuli-responsiveness is rarely reported. In this study, a set of nanoscale actuating system is demonstrated by a thermo-sensitive process operated by polyethylene glycol (PEG) linked by gold nanoparticle (AuNP). This designed nanocomposite exclusively provides an artificial on/off gate function for selective passages of permeate molecules. The results demonstrate high repetition efficiency with sharp responding in a timely manner. In terms of the morphology changes induced by repeated swelling-deswelling mechanics, the nanocomposite exhibits phase separation between AuNP clusters and PEG domains. This leads to a delay in responsiveness in a cumulative way with time. Acting as stable junction points in the nanocomposite network structures, the incorporated AuNPs contribute to maintain repeatability in responsiveness. This study contributes to new-concept smart material design and fundamental understanding on the hybrid nanomaterials for various applications in terms of a dynamic mechanical behavior.

Direct visualization of water-conducting pathways and sap flows in xylem vessels is important for understanding the physiology of vascular plants and their sap ascent. Gold nanoparticles (AuNPs) combined with synchrotron X-ray imaging technique is a new promising tool for investigating plant hydraulics in opaque xylem vessels of vascular plants. However, in practical applications of AuNPs for real-time quantitative visualization of sap flows, their interaction with a vascular network needs to be verified in advance. In this study, the effect of AuNPs on the water-refilling function of xylem vessels is experimentally investigated with three monocot species. Discrepancy in the water uptakes starts to appear at about 20 min to 40 min after the supply of AuNP solution to the test plant by the possible gradual accumulation of AuNPs on the internal structures of vasculature. However conclusively, it is observed that the water-refilling speeds in individual xylem vessels are virtually unaffected by hydrophilically surface-modified AuNPs (diameter similar to 20 nm). Therefore, the AuNPs can be effectively used as flow tracers in the xylem vessels in the first 20 similar to 30 min without any physiological barrier. As a result, AuNPs are found to be useful for visualizing various fluid dynamic phenomena occurring in vascular plants.

Cellular uptake pathway of nanoparticle (NP) is different from that of free drugs. Therefore, NP-mediated nanotherapeutics can be designed to overcome the adverse effects of free drugs. However, synthetic NPs are typically trapped in the endosome and have difficulty to reach the cytosol because of the characteristic endocytosis, where the endosomal membranes wrap-up the introduced NPs. In this study, the Spacer molecules linking the apoptotic anticancer drug and the gold NP (AuNP) are designed and cellular uptake procedure and drug deployment in the cancer cells are controlled. X-ray nanoscopy and two-photon microscopy are employed to observe the AuNPs in a cell in-situ without additional dye molecule or imaging agent introduction on an AuNP. We confirm that the effective design of the Spacer molecules importantly control the cellular interaction of the AuNPs. This technology can be generalized to broad biomedical applications utilizing nanotherapeutics-mediated diagnosis and new-concepted disease treatment technologies.

Detailed information on the location and the size of tumor cells circulating through lymphatic and blood vessels is useful to cancer diagnosis. Metastasis of cancers to other non-adjacent organs is reported to cause 90% of deaths not from the primary tumors. Therefore, effective detection of circulating tumors cells (CTCs) related to metastasis is emphasized in cancer treatments. With the use of synchrotron X-ray micro-imaging techniques, high-resolution images of individual flowing tumor cells were obtained. Positively charged gold nanoparticles (AuNPs) which were inappropriate for incorporation into human red blood cells were selectively incorporated into tumor cells to enhance the image contrast. This approach enables images of individual cancer cells and temporal movements of CTCs to be captured by the high X-ray absorption efficiency of selectively incorporated AuNPs. This new technology for in vivo imaging of CTCs would contribute to improve cancer diagnosis and cancer therapy prognosis.

Biocompatible polymeric encapsulants have been widely used as a delivery vehicle for a variety of drugs and imaging agents. In this study, X-ray contrast agent (iopamidol) is encapsulated into a polymeric microparticle (polyvinyl alcohol) as a particulate flow tracer in synchrotron X-ray imaging system. The physical properties of the designed microparticles are investigated and correlated with enhancement in the imaging efficiency by experimental observation and theoretical interpretation. The X-ray absorption ability of the designed microparticle is assessed by Beer-Lambert-Bouguer law. Particle size, either in dried state or in solvent, primarily dominates the X-ray absorption ability under the given condition, thus affecting imaging efficiency of the designed X-ray contrast flow tracers.

To measure instantaneous velocity fields of venous blood flow in a rat using X-ray particle tracking method. Gold nanoparticles (AuNPs) incorporated chitosan microparticles were applied as biocompatible flow tracers. After intravenous injection of the AuNP-chitosan particles into 7- to 9-week-old male rat vein, X-ray images of particle movement inside the cranial vena cava were consecutively captured. Individual AuNP-chitosan particles in the venous blood flow were clearly observed, and the corresponding velocity vectors were successfully extracted. The measured velocity vectors are in good agreement with the theoretical velocity profile suggested by Casson. This is the first trial to measure blood flow in animals under in vivo conditions with X-ray imaging technique. The results show that X-ray particle tracking technique has a great potential for in vivo measurements of blood flow, which can extend to various biomedical applications related with the diagnosis of circulatory vascular diseases.

We have recently reported on poly(vinyl alcohol) microparticles containing X-ray contrast agent, iopamidol, designed as a flow tracer working in synchrotron X-ray imaging ( Biosens. Bioelectron. 2010 , 25 , 1571 ). Although iopamidol is physically encapsulated in the microparticles, it displays a great contrast enhancement and stable feasibility in in vitro human blood pool. Nonetheless, a direct relation between the absolute amount of incorporated iopamidol and the enhancement in imaging efficiency was not observed. In this study, physical properties of the designed microparticle are systematically investigated experimentally with theoretical interpretation to correlate an enhancement in X-ray imaging efficiency. The compositional ratio of X-ray contrast agent in polymeric microparticle is controlled as 1/1 and 10/1 [contrast agent/polymer microparticle (w/w)] with changed degree of cross-linkings. Flory-Huggins interaction parameter (χ), retractive force (τ) and degree of swelling of the designed polymeric microparticles are investigated. In addition, the hydrodynamic size (D(H)) and ζ-potential are evaluated in terms of environment responsiveness. The physical properties of the designed flow tracer microparticles under a given condition are observed to be strongly related with the X-ray absorption efficiency, which are also supported by the Beer-Lambert-Bouguer law. The designed microparticles are almost nontoxic with a reasonable concentration and time period, enough to be utilized as a flow tracer in various biomedical applications. This study would contribute to the basic understanding on the physical property connected with the imaging efficiency of contrast agents.

In applying the X-ray particle image velocimetry (PIV) technique to biofluid flows, the most pivotal prerequisite is suitable flow tracing sensors which should be detected effectively by the X-ray imaging system. In this study, to design those flow tracing sensors, X-ray contrast agent Iopamidol was encapsulated into the poly(vinyl alcohol) (PVA) microparticles crosslinked by glutaraldehyde (GA). The characteristics of the fabricated particle sensors were determined by optical microscopy, scanning electron microscopy, dynamic light scattering, laser Doppler electrophoresis and nuclear magnetic resonance spectroscopy ( 1 H NMR). The amount of Iopamidol in the microparticles was measured using the energy dispersive X-ray spectroscopy (EDS) and 1 H NMR. The physical properties of the PVA microparticles are effectively controlled in terms of the average particle size, degree of crosslinking, degree of swelling and encapsulation efficiency of Iopamidol. By changing the amount of crosslinker, the degree of crosslinking and the efficiency of the Iopamidol encapsulation reached to the optimal. To some extent, the zeta-potential of the PVA microparticles is increased in less ionic media where the particles can effectively repel each other prohibiting aggregation. The X-ray absorption ability of the designed tracing sensors was examined by a synchrotron X-ray imaging technique. The X-ray absorption coefficients of the particle sensors were expressed by an exponential law assuming the spherical shape of the microparticles. The X-ray contrast agent, Iopamidol, was successfully encapsulated into the bio-compatible and bio-degradable PVA. With the controlled physical properties of the flow tracing sensors designed in this study, the particle sensors exhibit excellent X-ray absorption contrast fairly applicable in biological systems.

This paper describes the synthesis and characterization of poly(butadiene)m-poly(L-lysine)n (m-n = 107-200, 107-100, and 60-50) block copolymers. The polymers are prepared in a two-step process whereby amine-terminated polybutadiene is used to initiate the ring-opening polymerization of the epsilon-benzyloxycarbonyl L-lysine N-carboxyanhydride. After deprotection, the self-assembly of the block copolymers in aqueous media were studied using dynamic light scattering, transmission electron microscopy, and circular dichroism spectroscopy. These block copolymers were found to form either spherical micelles or rod-like micelles at high pH depending on the composition of the block copolymer. As the pH is decreased, the micelles swell due to charge-charge repulsions between corona chains and from the helix-coil transition of the polypeptide block. The two systems that form rod-like micelles at high pH also exhibit a pH-induced rod-sphere transition at low pH. This transition was verified from Kratky analysis of the static light scattering data and via CONTIN analysis of the dynamic light scattering data, which shows a bimodal distribution in particle sizes.

This laboratory investigation considers the effects of emulsions (via adding surfactants) and the formation and deposition of paraffin wax. This study relates the properties of added surfactant and emulsion characteristics with their wax deposition tendency. Parameters considered include the surfactant HLB (Hydrophilic Lipophilic Balance), molecular weight, and surfactant concentration. Two different series of commercial nonionic surfactants are included in this study; Triton-X (ethoxylated phenols) and Tween (sorbitan) products. The hydrocarbon phase is a model oil; a mixture of paraffin's with carbon numbers from C21 to C48 dissolved in n-decane (C10). Emulsion characterization was done by IFT (interfacial tension), viscosity measurement, and optical microscopy. The wax deposition measurements were performed in a novel cell apparatus where stirring controls the hydrodynamics and mixing energy. The study results indicate adding surfactants to promote emulsification can reduce the tendency for wax deposition. Properties that induce tighter emulsions such as lower interfacial tension and greater shear rate lead to reduced paraffin deposition. Furthermore, the wax that does deposit from an emulsion is softer (lower average molecular weight) versus wax that deposits in the absence of any chemical. In contrast, the wax that deposits in the presence of some commercial polymer-based wax inhibitors can be even harder (higher average molecular weight) than the deposit formed in the absence of any chemical additive.

The hierarchical relation of microscale structures with those of zoomed-in nanoscale in a composite material is one of the challenging issues. In terms of multiscale regional analogy of fractal, identical motifs are repeated on different size scales. However, idealized packing schemes are typically known to break down beyond a length scale of a few clusters. Here, we propose a new packing scheme - the structural analogy investigated by gold nanoparticle (AuNP) clusters describes a deformed self-similarity in multiscales. The clusters are directly imaged in microscale and in submicroscale using X-ray microscopy (XM) and X-ray nanoscopy (XN) without sample distortion in the hierarchical field-of-view up to 600 μm. We show that the broad-range ordering has the characteristics of a fractal with a dimension (D) between 1 and 2. This D value is smaller in XN scale than in XM scale, indicating dense cluster formation in large scale. The D values are independent from the pathways of cluster growth and compatibility of AuNPs with the polymer template. The nanoparticle cluster growth induced by block copolymer self-assembly is characteristically different from those occurring in free-space where the conventional diffusion- or reaction-limited aggregations are dominant. Our findings provide a new perspective in organic-inorganic hybrid nanomaterials and has broad implications in understanding their structure-property relationship for various applications.