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BACKGROUND The associations between diffusion kurtosis imaging (DKI)-derived parameters and clinical prognostic factors of breast cancer have not been fully evaluated; this knowledge may have implications for outcome prediction and treatment strategies. PURPOSE To determine associations between quantitative diffusion parameters derived from DKI and diffusion-weighted imaging (DWI) and the prognostic factors and molecular subtypes of breast cancer. STUDY TYPE Retrospective. POPULATION A total of 383 women (mean age, 53.8 years; range, 31-82 years) with breast cancer who underwent preoperative breast MRI including DKI and DWI. FIELD STRENGTH/SEQUENCE A 3.0 T; DKI using a spin-echo echo-planar imaging (EPI) sequence (b values: 200, 500, 1000, 1500, and 2000 sec/mm2 ), DWI using a readout-segmented EPI sequence (b values: 0 and 1000 sec/mm2 ) and dynamic contrast-enhanced breast MRI. ASSESSMENT Two radiologists (J.Y.K. and H.S.K. with 9 years and 1 year of experience in MRI, respectively) independently measured kurtosis, diffusivity, and apparent diffusion coefficient (ADC) values of breast cancer by manually placing a regions of interest within the lesion. Diffusion measures were compared according to nodal status, grade, and molecular subtypes. STATISTICAL TESTS Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction, receiver operating characteristic (ROC) analysis, and multivariate logistic regression analysis. (Statistical significance level of P

It becomes important to manage adequately spent nuclear fuels (SNFs) for storage away from reactor and/or final disposal as the plant onsite capacity nearly reaches to saturation state. Although the Korean government has enacted relevant regulations and safety measures including several kinds of test for transport cask, a matter of interest should be extended to protect radioactive contents against accidents in conjunction with their future retrievability as well as transportability if necessary. The objective of this study is to demonstrate integrity of typical SNF rods in a developing dual purpose cask under six postulated 9 m free drop scenarios. At first, a series of finite element (FE) analyses of simplified spent fuel assembly (SFA) with external volume and equivalent mass were performed to find out the most severely damaged ones taking into account heavy computational cost. Subsequently, paired FE analyses were also carried out after detailed modeling of the selected SFA with fuel rods arrangement and practical material properties. Finally, structural integrity of the critical SNF rods was evaluated according to the vertical or oblique drop scenarios. The calculated maximum plastic strains at Zircaloy cladding were compared with specific failure criteria dependent on burn-up levels, of which engineering meaning and incorporated conservatism were discussed.

The authors report a successful thrombectomy using the AngioJet Rheolytic Thrombectomy System (AngioJet) and an embolic protection device in a patient with femorofemoral bypass graft occlusion. Lower extremity CT angiograms showed occlusion in the left-to-right femorofemoral bypass graft. A rheolytic thrombectomy using the AngioJet and balloon angioplasty restored blood flow to the right lower extremity, and distal embolization may be effectively prevented by placing an embolic protection device within the right superficial femoral artery during the procedure.

Stimuli-interactive structural color (SC) of a block copolymer (BCP) photonic crystal (PC) uses reversible alteration of the PC using external fluids and applied forces. The origin of the diffusional pathways of a stimulating fluid into a BCP PC has not been examined. Here, we directly visualize the vertically oriented screw dislocations in a one-dimensional lamellar BCP PC that facilitate the rapid response of visible SC. To reveal the diffusional pathway of the solvent via the dislocations, BCP lamellae are swollen with an interpenetrated hydrogel network, allowing fixation of the swollen state and subsequent microscopic examination. The visualized defects are low-energy helicoidal screw dislocations having unique, nonsingular cores. Location and areal density of these dislocations are determined by periodic concentric topographic nanopatterns of the upper surface-reconstructed layer. The nonsingular nature of the interlayer connectivity in the core region demonstrates the beneficial nature of these defects on sensing dynamics.

A triboelectric nanogenerator (TENG) is of tremendous interest owing to its high energy efficiency with a simple device architecture and applicability to various materials. Most previous topological surface modifications introduced for further improving the performance of a TENG are detrimental because they require expensive and/or harsh (e.g., high temperature and acidity) postetching processes, which limit the material choice and design of its components. Herein, we demonstrate an one-step route for developing rapid wet-processable surface-conformal triboelectric nanoporous films (STENFs). Our method is based on a simple supramolecular assembly of a ternary polymer blend suitable for various conventional solution processes such as spin-, bar-, spray-, and dip-coating. The one-step wet process of a ternary solution produces thin large-area films in which self-assembled, ordered nanopores of approximately 33 nm in diameter are developed even without an additional etching process. The study reveals that the small amount of amine-terminated poly(ethylene oxide) added to the binary blend of sulfonic-acid-terminated poly(styrene) and poly(2-vinylpyridine) efficiently activates the formation of spontaneous nanopores as a pore-generating agent. Our STENF significantly enhances the open-circuit voltage up to 1.5 times higher than that of a planar one, leading to an improved power density of approximately 77 μW/cm

The encapsulation of lead halide perovskite nanocrystals (PNCs) with an inert protective layer against moisture and the environment is a promising approach to overcome hinderances for their practical use in optoelectronic and biomedical applications. Herein, a facile method for synthesizing highly luminescent and biocompatible CsPbBr3@SiO2 core–shell PNCs with a controlled SiO2 thickness, which are suitable for both cell imaging and drug delivery, is reported. The synthesized CsPbBr3@SiO2 core–shell PNCs exhibit bright green emission at 518 nm upon excitation of 374 nm. Interestingly, a significant increase in the photoluminescence intensity is observed with an increase in the SiO2 shell thickness, which varies with the increasing reaction time. Cytotoxicity results indicate that the CsPbBr3@SiO2 core–shell PNCs are nontoxic, making them suitable for in vitro cell imaging using HeLa cells. Furthermore, doxorubicin physically adsorbed on the surface of CsPbBr3@SiO2 core–shell PNCs is efficiently released in cells when the drug-loaded perovskite nanoprobes are injected in the cells, indicating that these core–shell nanoparticles can be used for drug loading and delivery. The results of this study suggest that the CsPbBr3@SiO2 core–shell PNCs can pave the way for new biomedical applications and processes.

The development of high-performance printable electrical circuits, particularly based on liquid metals, is fundamental for device interconnection in flexible electronics, motivating numerous attempts to develop a variety of alloys and their composites. Despite their great potential, rewritable and printable electronic circuits based on liquid metals are still manufactured on demand. In this study, we demonstrate liquid metal-based hydrogels suitable for rewritable, printable electrical circuits. Our liquid metal hydrogels are based on sedimentation-induced composites of eutectic gallium-indium (EGaIn) particles in poly(ethylene glycol) diacrylate (PEGDA). The EGaIn particles are vertically phase-segregated in the PEGDA. When a composite surface with high EGaIn content is gently scratched, the surface covering PEGDA is removed, followed by the rupture of the native oxide layers of the particles, and the exposed EGaIn becomes conductive. The subsequent water-driven swelling of PEGDA on the scratched surface completely erases the conductive circuit, causing the system to reset. Our friction-responsive liquid metal hydrogel exhibits writing-erasing endurance for 20 cycles, with a dramatic change in the electrical resistance from metal (∼1 Ω) to insulator (∼107 Ω). By employing surface friction pen printing, we demonstrate mechanically flexible, rewritable, printable electrical conductors suitable for displays.

The irradiation of dry seeds is the most widely-used irradiation method for improving seed-propagated crops, however, the irradiation of other tissues also has useful effects. The irradiation of plant reproductive organs, rather than seeds, for mutation breeding has advantages, such as producing non-chimeric progeny. However, the mutation frequency and spectrum produced using this method have not been analyzed on a genome-wide level. We performed a genotype-by-sequencing analysis to determine the frequencies of single-base substitutions and small (1&ndash, 2 bp) insertions and deletions in hot pepper (Capsicum annuum L.) plants derived from crosses using gamma-irradiated female or male gametophytes. The progeny of irradiated gametophytes showed similar or higher DNA mutation frequencies, which were dependent on the irradiation dose and irradiated tissue, and less biased single base substitutions than progeny of irradiated seeds. These characteristics were expected to be beneficial for development of mutation population with a high frequency of small DNA mutations and performing reverse-genetics-based mutation screening. We also examined the possible use of this irradiation method in manipulating the meiotic recombination frequency, however, no statistically significant increase was detected. Our results provide useful information for further research and breeding using irradiated gametophytes.

While establishment of appropriate policies and securing key technologies on spent nuclear fuels are state-of-the-arts in the world due to saturation of fuel pools and/or temporary facilities, the details of transportation, storage and repository are different depending on the situation in each country. Thereby, accurate integrity assessment of specific transportation casks and contained fuel assemblies as well as their breakdown effects on the public and environment are becoming more important. The purpose of this study is to carry out parametric stress analyses of spent nuclear fuel assembly in a prototypal dual purpose cask under development. As the representative postulated accident conditions, four scenarios were selected such as vertical, horizontal, corner and oblique drop from 9 m height on the ground. Then, taking into account computational cost, a simple model that considers only the equivalent mass of the fuel assembly was made for preliminary finite element analyses to determine the most dangerous drop condition and critical location. Subsequently, a detailed model that considers the acceleration of fuel assembly was made based on the preliminary analysis results and finite element analyses were carried out to calculate engineering parameters. Resulting membrane and bending stress intensities were compared with allowable design limits, of which findings will be used as technical background for development of transportation cask and management of the spent nuclear fuel integrity.

A 3D touchless display is created where a human finger position is visualized in structural colors of a soft photonic crystal., The development of a lightweight, low-power, user-interactive three-dimensional (3D) touchless display in which a human stimulus can be detected and simultaneously visualized in noncontact mode is of great interest. Here, we present a user-interactive 3D touchless sensing display based on multiorder reflection structural colors (SCs) of a thin, solid-state block copolymer (BCP) photonic crystal (PC). Full-visible-range SCs are developed in a BCP PC consisting of alternating lamellae, one of which contains a chemically cross-linked, interpenetrated hydrogel network. The absorption of a nonvolatile ionic liquid into the domains of the interpenetrated network allows for further manipulation of SC by using multiple-order photonic reflections, giving rise to unprecedented visible SCs arising from reflective color mixing. Furthermore, by using a hygroscopic ionic liquid ink, a printable 3D touchless interactive display is created where 3D position of a human finger is efficiently visualized in different SCs as a function of finger-to-display distance.

Development of a human-interactive display enabling the simultaneous sensing, visualisation, and memorisation of a magnetic field remains a challenge. Here we report a skin-patchable magneto-interactive electroluminescent display, which is capable of sensing, visualising, and storing magnetic field information, thereby enabling 3D motion tracking. A magnetic field-dependent conductive gate is employed in an alternating current electroluminescent display, which is used to produce non-volatile and rewritable magnetic field-dependent display. By constructing mechanically flexible arrays of magneto-interactive displays, a spin-patchable and pixelated platform is realised. The magnetic field varying along the z-axis enables the 3D motion tracking (monitoring and memorisation) on 2D pixelated display. This 3D motion tracking display is successfully used as a non-destructive surgery-path guiding, wherein a pathway for a surgical robotic arm with a magnetic probe is visualised and recorded on a display patched on the abdominal skin of a rat, thereby helping the robotic arm to find an optimal pathway., Designing human-interactive displays enabling the simultaneous sensing, visualization, and memorization of a magnetic field remains a challenge. Here, the authors present a skin-patchable magneto-interactive electroluminescent display by employing a magnetic field-dependent conductive gate, thereby enabling 3D motion tracking.

Triboelectric nanogenerators (TENG) is of great interest as an emerging power harvester due to its simple device architecture and high efficiency. Despite development of various surface modification techniques for enhancing the performance of a TENG with a given triboelectric pair of materials, a method capable of being used universally on a variety of surfaces and improving the performance of TENGs with diverse surfaces remains a challenge. Here, we demonstrate a novel transfer-printing technique of hierarchically dewetted polymer droplets on various TENG surfaces for performance enhancement of the TENGs. Our method is based on controlled dewetting of a thin supramolecular assembled film of two end-functionalized polymer blends on a prepatterned poly(dimethyl siloxane) mold, followed by the physical pattern-transfer of arrays of the dewetted droplets consisting of supramolecular assembled nanostructures on a TENG contact surface. The hierarchically dewetted microdroplets comprising soft-etched nanopores efficiently improve the performance of a TENG by more than three times compared to one without the transferred pattern. The pattern-transfer is successfully achieved on various surfaces including not only oxides, plastics, rubbers, and metals, but also fabrics, coins, vegetables, and shells, making our approach a convenient way for enhancing the triboelectric performance of a given TENG.

Since the conventional fluorine-based electro-active polymers release toxic residues into the environment during their syntheses and decomposition processes, eco-friendly piezoelectric polymers are urgently demanded in the field of energy-related soft materials. Here, we derive a high-performance biodegradable chitin polymer from squid pen material and demonstrate its utility as a flexible piezoelectric material. The readily controlled ferroelectric chitin film confers excellent piezoelectricity under external mechanical pressure, resulting in comparable performance with that of conventional fluorine-based piezoelectric polymers. In particular, the sufficient piezoelectric behavior in chitin film allows us to not only realize a high-fidelity paper-type speaker and microphone that operates over a wide frequency range without significantly deteriorating the input and output sounds but also demonstrate transparent speaker consisting of AgNWs electrodes onto freestanding chitin film which also enables to resemble the original sound. Finally, the biodegradable chitin polymer can be successfully dissolved by chitinase enzyme within eight days without any toxic residues remained.

Mutation breeding is largely performed by forward and reverse genetics-based approaches. In the latter, Target Induced Local Lesions IN Genomes (TILLING) can be used to screen mutants harboring mutations in a target gene whose function can be predicted with available functional genomic information. In TILLING, it is necessary to use an analytical system for accurate and efficient screening of target gene mutants among several randomly mutagenized lines. Therefore, we optimized a capillary electrophoresis-based TILLING system that can quickly and easily analyze many samples and confirmed its performance by applying it to pepper mutation populations. First, optimal conditions concerning heteroduplex DNA formation, type and concentration of endonucleases, and concentration, pooling depth, and size of PCR amplicons were determined in an analytical system using a capillary electrophoresis apparatus without labeled primers. The results showed that CelII endonuclease (Surveyor™) had higher sensitivity than CelI. While the recommended concentration in the manufacturer’s manual was 1×, we obtained higher sensitivity when the amount of PCR product and concentration of the endonucleases were at 180 ng and 0.5× for CelII and 120 ng and 2× for CelI. Meanwhile, the maximum pooling depth for DNA from individuals in mutant populations inversely correlated to PCR amplicon size. The limitation of DNA pooling was 4× for a 1872-bp amplicon, while at least 16× pooling was possible for a 672-bp amplicon. Using this optimized system, TILLING was performed on 2615 individuals from the mutant populations developed in a Korean pepper landrace, “Yuwolcho,” to screen lines bearing a mutation in CCS (capsanthin/capsorbin synthase). We were able to select a mutant line with a substituted base pair in the translational start codon of CCS. The capillary electrophoresis-based TILLING system optimized in this study is expected to be useful in practical applications for reverse genetics-based breeding and functional genomics studies.

The development of electrically responsive sensors based on the capacitance, voltage, and resistance that can detect and simultaneou sly visualize the large strain involved with human motion is in great demand. Here, we demonstrate a highly stretchable, large strain capacitive sensor that can visualize strain based on the strain-responsive structural color (SC). Our device contains an elastomeric sensing film that produces a capacitance change under strain, in which a self-assembled block copolymer (BCP) photonic crystal (PC) film with 1D periodic in-plane lamellae aligned parallel to the film surface is embedded for the efficient visualization of strain. The capacitance change arises from changes in the dimensions of the elastomer film under strain. The mechanochromic BCP PC film responds to strain, giving rise to an SC change with strain. The initial red SC of the sensor blueshifts and turns blue when the sensor is stretched to 100%, resulting in a full-color SC alteration as a function of the strain. Our BCP SC strain sensor exhibits a fast strain response with multi-cycle reliability of both the capacitance and SC changes over 1000 cycles. This property allows for efficient visible recognition not only of the strained positions during finger bending and poking with a sharp object but also of the shapes of the strained objects. A strain sensor that changes color when stretched has been developed by a team in Korea. Flexible sensors that measure pressure or strain could find application as wearable health monitors. One route to achieve such sensors is to use dielectric films whose capacitance changes in response to mechanical stimulus. However, an easy way is needed for wearers to read the output. Cheolmin Park from Yonsei University and colleagues constructed a polymer-based material with a periodic structure that reflects light of different colors depending on the degree to which it is extended. Specifically, they created a block copolymer soft-solid film with one-dimensional periodic layers. The capacitance changes under strain as a result of the dimensional change of the elastomer film, causing the initially red sensor to turn blue when fully stretched. A novel block copolymer structural color strain sensor was developed, capable of electrically sensing a strain in capacitance change with simultaneous visualization of the strain. A thin mechanochromic bilayer of a block copolymer structural film with 1-D periodic lamellae placed on an ionic gel layer allowed for direct visualization of strain while sensing in capacitance when embedded in an elastomeric dielectric medium. Our block copolymer structural strain sensor was suitable for a reflective mode electronic skin which readily recognized human motion of the finger, elbow, and knee.

Versatile control of cylindrical nanostructures formed by supramolecular assembly of end-functionalized polymer blends is demonstrated not only in their orientation over large areas but also in their surface chemical functionalities. Two binary blends consisting of supramolecular analogues of diblock copolymers with complementary end-sulfonated and aminated groups are investigated, viz., mono-end-functionalized polymers of (i) one-end-sulfonated polystyrene (SPS) and one-end-aminated poly(butadiene) (APBD) and (ii) one end-aminated polystyrene (APS) and one end-sulfonated poly(butadiene) (SPBD). The orientation of the cylinders with respect to the substrate surface depends on the solvent annealing time; either hexagonally ordered vertical cylinders or in-plane ones are readily obtained by controlling the solvent annealing time. Selective chemical etching of one of the polymers provides four different chemically modified nanostructures, viz., hexagonally ordered cylindrical holes and cylindrical posts with either sulfonate or amine surface functional groups. Additional supramolecular assembly is successfully achieved by solution coating either polymers or organic dyes that complementarily interact with the functional groups on the nanostructures. Furthermore, the supramolecularly assembled nanostructures are controlled by confining them to topographically pre-patterned Si substrates with pattern geometries of various shapes and sizes to produce globally ordered vertical or in-plane cylinders with chemical functionalities on their surfaces.

The development of pressure sensors that are effective over a broad range of pressures is crucial for the future development of electronic skin applicable to the detection of a wide pressure range from acoustic wave to dynamic human motion. Here, we present flexible capacitive pressure sensors that incorporate micropatterned pyramidal ionic gels to enable ultrasensitive pressure detection. Our devices show superior pressure-sensing performance, with a broad sensing range from a few pascals up to 50 kPa, with fast response times of

Mutagenesis using ionizing radiation has been widely used for the development of genetic and breeding resources with novel characteristics. Although mutation breeding using X- and gamma-rays has been attempted in peppers, information on the effectiveness of other ionizing radiation and a comparative analysis of mutagenic effects of different forms of radiation is limited. Therefore, we investigated and compared the biological effectiveness and mutagenesis efficiency of gamma-rays and a carbon beam (a heavy ion beam) in a chili pepper landrace of Korea, ‘Yuwol-cho’. The survival and shoot growth rate obtained by irradiation at serial doses showed that the LD50 was about 140 and 35 Gy, and the RD50 was about 80 and 32 Gy for gamma rays and carbon beams, respectively. The optimal doses for mutation breeding for these forms of radiation were estimated to be 80-100 and 15-20 Gy for gamma rays and carbon beams, respectively. We also developed M2 populations consisting of 1,836 lines by gamma-ray irradiation (100 Gy) and 154 lines by carbon beam irradiation (20 Gy). The frequency of dwarf or male sterile individuals showed that the mutagenic effect of the carbon beam was higher than that of gamma-rays. We identified individuals in each population with various developmental mutations through phenotypic analysis and categorized the mutations into four groups (mutations in plant architecture and development, leaf, flower, or fruits). This study provides basic information for mutation breeding using ionizing radiation and useful materials for the identification of genes related to the diverse characteristics in chili pepper.

In addition to attracting pollinators and protecting plants from photooxidative damages, carotenoids play important roles in signaling related to plant development and physiological changes through their cleaved derivatives, apocarotenoids. Yellow chrysanthemum flower petals [ Chrysanthemum morifolium (Ramat.)] are the result of a deleted or suppressed carotenoid cleavage dioxygenase gene ( CmCCD4a ). Therefore, investigating the global gene expression patterns in chrysanthemum mutants producing yellow petals represents an appropriate strategy to analyze the effects of signaling mediated by carotenoid derivatives. We compared the transcriptomes of chrysanthemum cultivars producing white petals with purple stripes (‘Noble Wine’) and its mutant producing yellow petals with purple stripes (‘ARTI-Yellow Star’). Read mapping and polymerase chain reaction analysis revealed that CmCCD4a is absent in the ARTI-Yellow Star genome, while at least three CmCCD4a gene family members are actively transcribed in ‘Noble Wine’ plants. These results indicate that the deletion of CmCCD4a may be responsible for the development of yellow petals in ARTI-Yellow Star flowers. During comparisons of gene expression patterns between Noble Wine and ARTI-Yellow Star, we detected numerous significantly up-regulated plastid protein-coding genes as well as significantly or mildly up-regulated carotenoid biosynthesis genes in ARTI-Yellow Star plants. The up-regulated plastid protein-coding genes belong to a broad range of functional categories related to translation, photosynthesis, reactive oxygen species scavenging, oxidative phosphorylation, transcription, processing, terpenoid metabolism, and chlorophyll metabolism. Our results present a possible relationship between CmCCD4a and regulation of plastid protein-coding genes.

While tremendous efforts have been made for developing thin perovskite films suitable for a variety of potential photoelectric applications such as solar cells, field-effect transistors, and photodetectors, only a few works focus on the micropatterning of a perovskite film which is one of the most critical issues for large area and uniform microarrays of perovskite-based devices. Here we demonstrate a simple but robust method of micropatterning a thin perovskite film with controlled crystalline structure which guarantees to preserve its intrinsic photoelectric properties. A variety of micropatterns of a perovskite film are fabricated by either microimprinting or transfer-printing a thin spin-coated precursor film in soft-gel state with a topographically prepatterned elastomeric poly(dimethylsiloxane) (PDMS) mold, followed by thermal treatment for complete conversion of the precursor film to a perovskite one. The key materials development of our solvent-assisted gel printing is to prepare a thin precursor film with a high-boiling temperature solvent, dimethyl sulfoxide. The residual solvent in the precursor gel film makes the film moldable upon microprinting with a patterned PDMS mold, leading to various perovskite micropatterns in resolution of a few micrometers over a large area. Our nondestructive micropatterning process does not harm the intrinsic photoelectric properties of a perovskite film, which allows for realizing arrays of parallel-type photodetectors containing micropatterns of a perovskite film with reliable photoconduction performance. The facile transfer of a micropatterned soft-gel precursor film on other substrates including mechanically flexible plastics can further broaden its applications to flexible photoelectric systems.

Fine nano-sized magnetite particles were synthesized and then used to treat backside grinding (BG) wastewater for the removal of silica nanoparticles (SiO 2 ). Batch experiments were conducted to examine the effects of the magnetite dosage, pH, stirring intensity (G) and duration (t d ), magnetic field strength and sedimentation time on the removal of SiO 2 . The optimum dosage of magnetite was determined as 16 mg/L, which had the best SiO 2 removal of about 97%, under the conditions of initial pH 5.9, stirring intensity 900 S −1 , stirring duration 30 min, sedimentation time 30 min and magnetic field strength 317 mT. The synthesis of nano-sized magnetite particles 10 nm in diameter led to a reduction in the magnetite dosage needed for the removal of SiO 2 . The pH was maintained at less than 10 to obtain the high SiO 2 removal mentioned above. When the pH was over 10, the Fe detached from magnetite particles which subsequently led to a decrease in SiO 2 removal. Magnetite aggregation was affected by both G and t d . Increasing the values of G and t d enhanced the removal of SiO 2 . When the multiple values of G and t d , i.e., Gt d reached 12,000, a SiO 2 removal of 95% was achieved. The relationship between the magnetic field strength and sedimentation time was also evaluated. An increase in the magnetic field strength improved the removal of SiO 2 . Specifically, the SiO 2 removal was greatly dependent on the sedimentation time when the magnetic field strength was weak. The results of this study can be used in the design and operation of a magnetite aggregation process to treat BG wastewater for the removal of SiO 2 .

Spreading liquid droplets on solid surfaces is a core topic in physical chemistry with significant technological implications. Liquid metals, which are eutectic alloys of constituent metal atoms with low melting temperatures, are practically useful, but difficult to spread on solid surfaces because of their high surface tension. This makes it difficult to use liquid metals as deformable on-board microcircuitry electrodes, despite their intrinsic deformability. In this study, it is discovered that eutectic gallium-indium (EGaIn) can be spread onto the surface of chemically cross-linked hydrogels consisting of aliphatic alkyl chains with numerous hydroxyl groups (OH), thus facilitating the development of directly micropatterned EGaIn electrodes. More importantly, EGaIn patterned on a hydrogel autonomously reconciliates its surface to form a firm hydrogel interface upon mechanical deformation of the hydrogel. This autonomous surface reconciliation of EGaIn on hydrogels allows researchers to reap the benefits of chemically modified hydrogels, such as reversible stretching, self-healing, and water-swelling capability, thereby facilitating the fabrication of superstretchable, self-healable, and water-swellable liquid-metal electrodes with very high conductance tolerance upon deformation. Such electrodes are suitable for a variety of deformable microelectronic applications.

Epitaxial crystallization of thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films is important for the full utilization of their ferroelectric properties. Epitaxy can offer a route for maximizing the degree of crystallinity with the effective orientation of the crystals with respect to the electric field. Despite various approaches for the epitaxial control of the crystalline structure of PVDF-TrFE, its epitaxy on a semiconductor is yet to be accomplished. Herein, the epitaxial growth of PVDF-TrFE crystals on a single-crystalline organic semiconductor rubrene grown via physical vapor deposition is presented. The epitaxy results in polymer crystals globally ordered with specific crystal orientations dictated by the epitaxial relation between the polymer and rubrene crystal. The lattice matching between the c-axis of PVDF-TrFE crystals and the (210) plane of orthorhombic rubrene crystals develops two degenerate crystal orientations of the PVDF-TrFE crystalline lamellae aligned nearly perpendicular to each other. Thin PVDF-TrFE films with epitaxially grown crystals are incorporated into metal/ferroelectric polymer/metal and metal/ferroelectric polymer/semiconductor/metal capacitors, which exhibit excellent nonvolatile polarization and capacitance behavior, respectively. Furthermore, combined with a printing technique for micropatterning rubrene single crystals, the epitaxy of a PVDF-TrFE film is formed selectively on the patterned rubrene with characteristic epitaxial crystal orientation over a large area.

H.E. and H.S.K. contributed equally to this work. This research was supported by the Samsung Research Funding Center of Samsung Electronics under Project No. SRFC-MA1301-03. This research was also supported by a grant from the National Research Foundation of Korea (NRF) funded by the Korean government (MEST) (No. 2017R1A2A1A05001160). H.E. and H.S.K. conducted most of the experiments, including the fabrication of devices and analysis of data, and prepared the manuscript. M.K., M.J.K., T.H.P., and J.H. contributed to the measurement and analysis of the optical properties of the BCP SC film. Y.K. and D.Y.R. synthesized the BCPs, and H.L. and E.K. fabricated the photothermal-conversion layer. C.P. and Y.K. supervised the project, analyzed the data. All authors discussed the results and contributed to the paper.

Structural colors (SCs) of photonic crystals (PCs) have attracted much attention due to their broad applications in the field of displays, sensors, and media boards. Compared with different PCs, the block copolymer (BCP) based PCs has an easy processing route due to the self-assembled microstructure of BCP. Here, we demonstrate a non-volatile, multi-level optical information storage of BCP SC. Our method is based on the controlled cross-linking of the BCP PC's microdomains resulting from the photo-thermal conversion. The process of photo-thermal writing is accomplished by time, power, and position controlled near infrared (NIR) laser exposure on a poly (styrene-block-quaternized 2-vinyl pyridine) (PS-b-QP2VP) PC on a photo-thermal conversion layer consists of poly (3,4-ethylenedioxythiophene) doped with tosylate. The localized heat arising from the NIR-to-thermal conversion of the photo-thermal conversion layer is exerted on the BCP PC with alternating in-plane PS and QP2VP lamellae stacks. Thermal cross-linking consequentially occurs between quaternized pyridines due to heat transfer, which results in a programmed SC upon reading process with a swelling agent, ethanol. The degree of cross-linking of QP2VP domains is dependent upon laser-power and exposure time, allowing for multi-colored recording of SC per single spot, giving rise to a novel multi-level optical recording media based on BCP SC.

Structural colors (SCs) of photonic crystals (PCs) arise from selective constructive interference of incident light. Here, an ink-jet printable and rewritable block copolymer (BCP) SC display is demonstrated, which can be quickly written and erased over 50 times with resolution nearly equivalent to that obtained with a commercial office ink-jet printer. Moreover, the writing process employs an easily modified printer for position- and concentration-controlled deposition of a single, colorless, water-based ink containing a reversible crosslinking agent, ammonium persulfate. Deposition of the ink onto a self-assembled BCP PC film comprising a 1D stack of alternating layers enables differential swelling of the written BCP film and produces a full-colored SC display of characters and images. Furthermore, the information can be readily erased and the system can be reset by application of hydrogen bromide. Subsequently, new information can be rewritten, resulting in a chemically rewritable BCP SC display.

The residual vibration when a robot manipulator is operated at high speed needs to be suppressed. These vibrations are generated by the resonance of a flexible object being moved by the robot, and research on control algorithms and motion profiles is ongoing to reduce them. In this paper, we propose a method to reduce the residual vibration of an object moved by a robot manipulator by optimizing the acceleration/deceleration time calculated using the object&rsquo, s natural frequency. The relationship between acceleration/deceleration time and the residual vibration in a trapezoidal velocity profile is considered by analyzing the scenario when the jerking motion characteristic of such vibrations occurs. The results of experiments using a commercial robot show that residual vibrations can be reduced by the proposed method without the need for an additional feedback control algorithm while transferring a flexible object over small and large distances.

One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2-vinylpyridine) (PS-b-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

Liquid-phase exfoliation (LPE) of transition metal dichalcogenide (TMD) nanosheets is a facile, cost-effective approach to large-area photoelectric devices including photodetectors and non-volatile memories. Non-destructive exfoliation of nanosheets using macromolecular dispersing agents is beneficial in rendering the TMD nanocomposite films suitable for mechanically flexible devices. Here, an efficient LPE of molybdenum disulfide (MoS2) with an amine modified poly(styrene-co-maleic anhydride) co-polymer (AM-PSMA) is demonstrated, wherein the maleic anhydrides were converted into maleic imides with primary amines using N-Boc-(CH2) n -NH2. The exfoliation of nanosheets was facilitated through Lewis acid-base interaction between the primary amine and transition metal. The results demonstrate that the exfoliation depends upon both the fraction of primary amines in the polymer chain and their distance from the polymer backbone. Under optimized conditions of primary amine content and its distance from the backbone, AM-PSMA gave rise to a highly concentrated MoS2 nanosheet suspension that was stable for over 10 d. Exfoliation of several other TMDs was also achieved using the optimized AM-PSMA, indicating the scope of AM-PSMA applications. Furthermore, a flexible composite film of AM-PSMA and MoS2 nanosheets fabricated by vacuum-assisted filtration showed excellent photoconductive performances including a high I on/I off ratio of 102 and a fast photocurrent switching of 300 ms.