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Small-angle X-ray scattering is used to probe the solution behavior of two similar electron donor polymers. Differences in aggregate crystallinity are observed upon cooling for the two polymers which is then correlated with the film morphology.

We report a novel elastomer possessing high stretchability, elasticity and self-healing ability, achieved by thio-β-diketone-Cu(ii) coordination and H-bonding dual crosslinking. Flexible sensors are fabricated based on the elastomer.

We report an asymmetric metal–ligand coordination strategy for reconfigurable elastomers. EXAFS is first introduced to monitor the structure change in M–L crosslinked polymers during stretching at the molecular level.

The report of the 19th National Congress of the Communist Party of China first proposed the strategy of rural revitalization. This proposal constitutes a major strategic deployment for work related to “agriculture, the countryside and farmers” based on China’s national and agricultural conditions and scientific analysis of the new problems faced by agricultural and rural reform in the new era. China’s agricultural development is facing multiple challenges, such as market competition, resource scarcity, environmental constraints, labor exodus, and technological innovation. Additionally, China’s agricultural production is inefficient, farmers’ income is low, and the hollowing out of the countryside has further intensified. To address these challenges, the Party Central Committee made the major decision to implement the rural revitalization strategy, and governments at all levels have introduced a series of policies to support agriculture. However, with the rapid advancement of industrialization and urbanization, the proportion of agricultural output to the total output of the national economy and the proportion of the agricultural labor force to the social labor force are not decreasing, and the idea of seizing the opportunities offered by agriculture is no longer able to solve the current dilemma faced by agricultural and rural development. Expanding the function of agriculture and actively docking with the industry and the service industry are a major strategic initiative for actively adapting to the new normal of economic development. They also represent major innovative thinking to accelerate the transformation of the agricultural development mode. Only when industries are prosperous can rural revitalization have a strong material foundation. To achieve industrial prosperity, industrial integration is the key. Therefore, the realization of rural industrial revitalization must take the path of industrial integration and development. At present, research on rural industrial integration is limited to the local regions, such as provinces and cities, and analysis at the level of national rural industrial integration is lacking. Accelerating the integrated development of rural industries is key to promoting rural revitalization. This paper scientifically establishes an evaluation index system for the level of rural industrial integration development based on five related aspects: society, the economy, resources, facilities, and the environment. Factor analysis is used to reduce the dimensionality of the evaluation index system, and cluster analysis is used to classify the rural industrial integration development level of each province in China into different tiers. The results show that there are obvious regional differences in the levels of rural industrial integration development in China. The provinces and cities with development levels that are higher than average (i.e., scores ranging from 0.291 to 0.915) are concentrated in the eastern coastal areas and inland riverine areas. In contrast, those with development levels that are lower than average (i.e., scores ranging from −0.504 to −0.750) are concentrated in Northern China, the northeastern noncoastal areas and northwestern areas. In addition, provinces can be divided into five development tiers of rural industrial integration. Based on this information, national, provincial, and municipal improvement strategies are proposed to address the differences in development among and the prospects for each province, and to effectively promote the integration of rural industries in China.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version Y.L., Z.L., M.Z., and X.C. acknowledge the National Research Foundation, Singapore (NRF) under NRF’s Medium Sized Centre: Singapore Hybrid-Integrated Next-Generation μElectronics (SHINE) Centre funding programme, and AME programming funding scheme of Cyber Physiochemical Interface (CPI) project (no. A18A1b0045). Y.L. acknowledges National Natural Science Foundation of China (62201243). C.J. acknowledges funding support from the National Key R&D Program of China (no. 2019YFA0706100), the National Natural Science Foundation of China (82151305), Lingang Laboratory (LG-QS-202202-09). T.Q.T. and N.E.L. acknowledge support by the Basic Science Research Program (no. 2020R1A2C3013480) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT. A.F. acknowledges the AFOSR (grant FA9550-22-1-0423). Y.L. and Y.Z. would like to acknowledge the NSF (award no. 2134664) and NIH (award no. R01HD108473) for financial support. X.F. acknowledges the support from the National Natural Science Foundation of China (grant no. U20A6001). L.Y. would like to thank the A*STAR Central Research Fund (CRF) and the AME Programmatic A18A1b0045 (Cyber Physiochemical Interfaces) for funding support. C.F.G. acknowledges the National Natural Science Foundation of China (no. T2225017). T.Q.T. acknowledges the Brain Pool Program (No. 2020H1D3A2A02111068) through the National Research Foundation (NRF) funded by the Ministry of Science. Z.L. acknowledges the support from RIE2020 AME Programmatic Grant funded by A*STAR-SERC, Singapore (Grant No. A18A1b0045). X.G. acknowledges funding support through the Shanghai Science and Technology Commission (grant no. 19JC1412400), the National Science Fund for Excellent Young Scholars (grant no. 61922057). C.D. acknowledges National Science Foundation CAREER: Conformable Piezoelectrics for Soft Tissue Imaging (grant no. 2044688) and MIT Media Lab Consortium funding. D.K. and O.G.S. acknowledge Leibniz Association and the German Research Foundation DFG (Gottfried Wilhelm Leibniz Program SCHM 1298/22-1, KA5051/1-1 and KA 5051/3-1), as well as the Leibniz association (Leibniz Transfer Program T62/2019). C.W. acknowledges the National Key Research and Development Program of China (grant no. 2021YFA1202600), National Natural Science Foundation of China (grant no. 62174082). A.V.-Y.T., E.Z., Y.Z., X.Z., and J.P. acknowledge the National Research Foundation, Singapore (NRF) under NRF’s Medium Sized Centre: Singapore Hybrid-Integrated Next-Generation μElectronics (SHINE) Centre funding programme, and AME programming funding scheme of Cyber Physiochemical Interface (CPI) project (no. A18A1b0045). R.Z. acknowledges National Natural Science Foundation of China (grant no. 51735007) and Beijing Natural Science Foundation (grant no. 3191001). N.M. acknowledges the support by JST PRESTO Grant Number JPMJPR20B7 and JST Adaptable and Seamless Technology transfer Program through Target-driven R&D (ASTEP) grant number JPMJTM22BK. C.P. acknowledges the Korean government (Ministry of Science and ICT, MSIT) (2022R1A4A3032923). M.W. acknowledges the National Key R&D Program of China under Grant (2021YFB3601200). X.Z. acknowledges National Natural Science Foundation of China (no. 62074029). S.X. acknowledges the 3M nontenured faculty award. T.-W.L. and D.-G.S. acknowledge the Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (grant no. NRF-2022M3C1A3081211). C.T.L. would like to acknowledge support from the Institute for Health Innovation and Technology (iHealthtech), the MechanoBioEngineering Laboratory at the Department of Biomedical Engineering and the Institute for Functional Intelligent Materials (I-FIM) at the National University of Singapore (NUS). C.T.L. also acknowledges support from the National Research Foundation and A*STAR, under its RIE2020 Industry Alignment Fund − Industry Collaboration Projects (IAF-ICP) (grant no. I2001E0059) − SIA-NUS Digital Aviation Corp Lab and the NUS ARTIC Research (grant no. HFM-RP1). X.Y. acknowledges funding support by City University of Hong Kong (grant no. 9667221). T.X. and X.Z. acknowledge National Natural Science Foundation of China (22234006). B.C.K.T. acknowledges Cyber-Physiochemical Interfaces CPI, A*STAR A18A1b0045. H.G. acknowledges a research start-up grant (002479-00001) from Nanyang Technological University and the Agency for Science, Technology and Research (A*STAR) in Singapore. W.G. acknowledges National Science Foundation grant 2145802. D.J.L. acknowledges support from the US National Science Foundation grant number CBET-2223566. G.Y. acknowledges support from The Welch Foundation award F-1861, and Camille Dreyfus Teacher-Scholar Award. M.D.D. acknowledges funding support from NSF (grant no. EEC1160483). J.-H.A acknowledges the National Research Foundation of Korea (NRF-2015R1A3A2066337). J.C. acknowledges the Henry Samueli School of Engineering & Applied Science and the Department of Bioengineering at the University of California, Los Angeles for startup support and a Brain & Behavior Research Foundation Young Investigator Grant. K.T. acknowledges JST AIP Accelerated Program (no. JPMJCR21U1) and JSPS KAKENHI (grant no. JP22H00594). P.S.W. acknowledges the National Science Foundation (CMMI1636136) for support. A.M.A., M.C.H., and P.S.W. thank the National Institute on Drug Abuse (DA045550) for support. S.M. and X.C. appreciated the support from the Smart Grippers for Soft Robotics (SGSR) Programme under the National Research Foundation, Prime Minister’s Office, Singapore under its Campus of Research Excellence and Technological Enterprise (CREATE) programme.

All-polymer solar cells (all-PSCs) based on polymerized small molecular acceptors (PSMAs) have made significant progress recently. Here, we synthesize two A-DA’D-A small molecule acceptor based PSMAs of PS-Se with benzo[c][1,2,5]thiadiazole A’-core and PN-Se with benzotriazole A’-core, for the studies of the effect of molecular structure on the photovoltaic performance of the PSMAs. The two PSMAs possess broad absorption with PN-Se showing more red-shifted absorption than PS-Se and suitable electronic energy levels for the application as polymer acceptors in the all-PSCs with PBDB-T as polymer donor. Cryogenic transmission electron microscopy visualizes the aggregation behavior of the PBDB-T donor and the PSMA in their solutions. In addition, a bicontinuous-interpenetrating network in the PBDB-T:PN-Se blend film with aggregation size of 10~20 nm is clearly observed by the photoinduced force microscopy. The desirable morphology of the PBDB-T:PN-Se active layer leads its all-PSC showing higher power conversion efficiency of 16.16%., Through development of non-fullerene acceptors, OPVs have reached efficiencies of 18%, yet the inadequate operational lifetime still poses a challenge for the commercialisation. Here, the authors investigate the origin of instability of NFA solar cells, and propose some strategies to mitigate this issue.

Flower-like polyacrylonitrile (PAN) particles have shown promising performance for numerous applications, including sensors, catalysis, and energy storage. However, the detailed formation process of these unique structures during polymerization has not been investigated. Here, we elucidate the formation process of flower-like PAN particles through a series of in situ and ex situ experiments. We have the following key findings. First, lamellar petals within the flower-like particles were predominantly orthorhombic PAN crystals. Second, branching of the lamellae during the particle formation arose from PAN's fast nucleation and growth on pre-existing PAN crystals, which was driven by the poor solubility of PAN in the reaction solvent. Third, the particles were formed to maintain a constant center-to-center distance during the reaction. The separation distance was attributed to strong electrostatic repulsion, which resulted in the final particles' spherical shape and uniform size. Lastly, we employed the understanding of the formation mechanism to tune the PAN particles' morphology using several experimental parameters including incorporating comonomers, changing temperature, adding nucleation seeds, and adjusting the monomer concentration. These findings provide important insights into the bottom-up design of advanced nanostructured PAN-based materials and controlled polymer nanostructure self-assemblies.

Recent work in structure–processing relationships of polymer semiconductors have demonstrated the versatility and control of thin-film microstructure offered by meniscusguided coating (MGC) techniques. Here, we analyze the qualitative and quantitative aspects of solution shearing, a model MGC method, using coating blades augmented with arrays of pillars. The pillars induce local regions of high strain rates—both shear and extensional—not otherwise possible with unmodified blades, and we use fluid mechanical simulations to model and study a variety of pillar spacings and densities. We then perform a statistical analysis of 130 simulation variables to find correlations with three dependent variables of interest: thin-film degree of crystallinity and transistor field-effect mobilities for charge-transport parallel (Μpara) and perpendicular (Μperp) to the coating direction. Our study suggests that simple fluid mechanical models can reproduce substantive correlations between the induced fluid flow and important performance metrics, providing a methodology for optimizing blade design. Polymer semiconductors have opened up a new frontier of electronics that can be flexible, stretchable, implantable, or biodegradable. While the chemical and electronic properties of these materials are important for their function as the active material in organic electronic devices, the manner by which these organic semiconductors are deposited onto a substrate can significantly influence its charge-transport properties. While a variety of techniques have been investigated to enhance charge-transport behavior, there are few reports approaching the issue in terms of the fluid dynamical considerations relevant during deposition from the solution phase. In this article, we analyze the fluid flow that occurs during thin-film deposition by solution shearing, a representative meniscusguided coating method amenable to high-throughput processing. We investigate a variety of variables related to fluid flow that can be estimated from fluid mechanical simulations of solution shearing with a coating blade patterned with a regular array of pillars used to induce higher fluid strain rates. We find correlations suggestive of underlying relationships between strain rates associated with certain directions and polymer charge-transport properties in the final deposited film. This article establishes a statistical approach using simulation data that can guide patterned blade design to enhance polymer deposition and realize high-performance devices.

Land circulation can promote large-scale operations, improve land-use efficiency, and increase farmers’ income. Taking 186 rural households in Ledong County in Hainan Province, the study uses binary logistic regression to analyze the factors affecting farmers’ willingness to transfer land. The results show that age, education level, and family labor force were negatively correlated with farmers’ willingness to accept land circulation. Meanwhile, gender, nonagricultural population, source of family income, annual family income, infrastructure, and understanding of policy were positively correlated with willingness to transfer. Recommendations regarding strengthening the training and education of farmers, increasing publicity, improving farmers’ awareness of land circulation, promoting market supervision, enhancing the land circulation market mechanism, and improving the rural security system are proposed. Ledong should also strengthen policy support regarding the cultivation of new agricultural business entities, and establish an intermediary service platform for land circulation. This study, therefore, aims to provide a theoretical and practical basis for a farmland circulation mechanism and the large-scale operation of agricultural land in Ledong County.

Combining the acceptor–donor–acceptor-type fused ring-based molecular architecture into a polymeric backbone is a promising strategy to design polymer acceptors for high-performance all-polymer sol...

Polymeric materials in nature regularly employ ordered, hierarchical structures in order to perform unique and precise functions. Importantly, these structures are often formed and stabilized by the cooperative summation of many weak interactions as opposed to the independent association of a few strong bonds. Here, we show that synthetic, flexible polymer chains with periodically placed and directional dynamic bonds collectively assemble into supramolecular nanofibers when the overall molecular weight is below the polymer's critical entanglement molecular weight. This causes bulk films of long polymer chains to have faster dynamics than films of shorter polymer chains of identical chemical composition. The formation of nanofibers increases the bulk film modulus by over an order of magnitude and delays the onset of terminal flow by more than 100 °C, while still remaining solution processable. Systematic investigation of different polymer chain architectures and dynamic bonding moieties along with coarse-grained molecular dynamics simulations illuminate governing structure-function relationships that determine a polymer's capacity to form supramolecular nanofibers. This report of the cooperative assembly of multivalent polymer chains into hierarchical, supramolecular structures contributes to our fundamental understanding of designing biomimetic functional materials.

Semitransparent organic photovoltaic cells (ST-OPVs) are emerging as a solution for solar energy harvesting on building facades, rooftops, and windows. However, the trade-off between power-conversion efficiency (PCE) and the average photopic transmission (APT) in color-neutral devices limits their utility as attractive, power-generating windows. A color-neutral ST-OPV is demonstrated by using a transparent indium tin oxide (ITO) anode along with a narrow energy gap nonfullerene acceptor near-infrared (NIR) absorbing cell and outcoupling (OC) coatings on the exit surface. The device exhibits PCE = 8.1 ± 0.3% and APT = 43.3 ± 1.2% that combine to achieve a light-utilization efficiency of LUE = 3.5 ± 0.1%. Commission Internationale d’eclairage chromaticity coordinates of (0.38, 0.39), a color-rendering index of 86, and a correlated color temperature of 4,143 K are obtained for simulated AM1.5 illumination transmitted through the cell. Using an ultrathin metal anode in place of ITO, we demonstrate a slightly green-tinted ST-OPV with PCE = 10.8 ± 0.5% and APT = 45.7 ± 2.1% yielding LUE = 5.0 ± 0.3% These results indicate that ST-OPVs can combine both efficiency and color neutrality in a single device.

Next-generation light-emitting displays on skin should be soft, stretchable and bright

In order to apply polymer semiconductors to stretchable electronics, they need to be easily deformed under strain without being damaged. A small number of conjugated polymers, typically with semicrystalline packing structures, have been reported to exhibit mechanical stretchability. Herein, a method is reported to modify polymer semiconductor packing-structure using a molecular additive, dioctyl phthalate (DOP), which is found to act as a molecular spacer, to be inserted between the amorphous chain networks and disrupt the crystalline packing. As a result, large-crystal growth is suppressed while short-range aggregations of conjugated polymers are promoted, which leads to an improved mechanical stretchability without affecting charge-carrier transport. Due to the reduced conjugated polymer intermolecular interactions, strain-induced chain alignment and crystallization are observed. By adding DOP to a well-known conjugated polymer, poly[2,5-bis(4-decyltetradecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione-(E)-1,2-di(2,2'-bithiophen-5-yl)ethene] (DPPTVT), stretchable transistors are obtained with anisotropic charge-carrier mobilities under strain, and stable current output under strain up to 100%.

The anonymous system Tor uses an asymmetric algorithm to protect the content of communications, allowing criminals to conceal their identities and hide their tracks. This malicious usage brings serious security threats to public security and social stability. Statistical analysis of traffic flows can effectively identify and classify Tor flow. However, few features can be extracted from Tor traffic, which have a weak representational ability, making it challenging to combat cybercrime in real-time effectively. Extracting and utilizing more accurate features is the key point to improving the real-time detection performance of Tor traffic. In this paper, we design an efficient and real-time identification scheme for Tor traffic based on the time window method and bidirectional statistical characteristics. In this paper, we divide the network traffic by sliding the time window and then calculate the relative entropy of the flows in the time window to identify Tor traffic. We adopt a sequential pattern mining method to extract bidirectional statistical features and classify the application types in the Tor traffic. Finally, extensive experiments are carried out on the UNB public dataset (ISCXTor2016) to validate our proposal’s effectiveness and real-time property. The experiment results show that the proposed method can detect Tor flow and classify Tor flow types with an accuracy of 93.5% and 91%, respectively, and the speed of processing and classifying a single flow is 0.05 s, which is superior to the state-of-the-art methods.

Shape memory polymers are promising materials in many emerging applications due to their large extensibility and excellent shape recovery. However, practical application of these polymers is limited by their poor energy densities (up to ∼1 MJ/m3). Here, we report an approach to achieve a high energy density, one-way shape memory polymer based on the formation of strain-induced supramolecular nanostructures. As polymer chains align during strain, strong directional dynamic bonds form, creating stable supramolecular nanostructures and trapping stretched chains in a highly elongated state. Upon heating, the dynamic bonds break, and stretched chains contract to their initial disordered state. This mechanism stores large amounts of entropic energy (as high as 19.6 MJ/m3 or 17.9 J/g), almost six times higher than the best previously reported shape memory polymers while maintaining near 100% shape recovery and fixity. The reported phenomenon of strain-induced supramolecular structures offers a new approach toward achieving high energy density shape memory polymers., We report an approach to achieve a high energy density shape memory polymer based on the formation of strain-induced supramolecular nanostructures, which immobilize stretched chains to store entropic energy.

The ability to deposit polymer semiconductors (PSCs) over a large area at near-ambient conditions makes them exciting candidates for low-cost, large-area electronic applications. Given the sensitiv...

Summary Advances in stretchable conductors have been one of the main driving forces behind the realization of wearable and epidermal electronics. However, retaining constant strain-property relationships under varying strain and strain rate remains a challenge. Here, we demonstrate a 3D structuring approach toward strain-accommodating, biocompliant conductors. In contrast to previous stretchable conductors, this method leads to polymeric materials with conductance that has zero dependence on (1) both tensile and compressive strain over an 80% strain range, and (2) strain rate from 2.5%/min to 2,560%/min. Their Young's moduli can be controllably tuned between 10 and 300 kPa. In addition, these conductors are ultra-lightweight and can be molded into virtually any shape and size. Their properties mimic the dynamic and softness of biological systems, rendering this a versatile platform for designing electronic materials that can potentially form intimate interfaces with humans.

The field of organic electronics aspires to enable the fabrication of low-cost, solution-processed optoelectronic devices with unique mechanical, electrical, optical, and chemical properties. Criti...

All-polymer solar cells (all-PSCs) are the most promising power generators for flexible and portable devices due to excellent morphology stability and outstanding mechanical property. Previous work indicates high crystallinity is beneficial to device performance but detrimental to mechanical property, therefore identifying the optimized ratio between crystalline and amorphous domains becomes important. In this work, we demonstrated highly efficient and mechanically robust all-PSCs by blade-coating technology in ambient environment based on PTzBI:N2200 system. By controlling the aggregation in solution state and ultrafast film formation process, a weakly ordered molecular packing morphology as well as small phase separation is obtained, which leads to not only the good photovoltaic performance (8.36%-one of the best blade-cast device in air) but also prominent mechanical characteristic. The controlled film shows a remarkable elongation with the crack onset strain of 15.6%, which is the highest result in organic solar cells without adding elastomers. These observations indicate the great promise of the developed all-PSCs for practical applications toward large-area processing technology.

Supramolecular polymer sorting is a promising approach to separating single-walled carbon nanotubes (CNTs) by electronic type. Unlike conjugated polymers, they can be easily removed from the CNTs after sorting by breaking the supramolecular bonds, allowing for isolation of electronically pristine CNTs as well as facile recycling of the sorting polymer. However, little is understood about how supramolecular polymer properties affect CNT sorting. Herein, chain stoppers are used to engineer the conformation of a supramolecular sorting polymer, thereby elucidating the relationship between sorting efficacy and polymer conformation. Through NMR and UV-vis spectroscopy, small-angle X-ray scattering (SAXS), and thermodynamic modeling, it is shown that this supramolecular polymer exhibits ring-chain equilibrium, and that this equilibrium can be skewed toward chains by the addition of chain stoppers. Furthermore, by controlling the stopper-monomer ratio, the sorting yield can be doubled from 7% to 14% without compromising the semiconducting purity (>99%) or properties of sorted CNTs.

Doping of organic semiconductors is a powerful tool to optimize the performance of various organic (opto)electronic and bioelectronic devices. Despite recent advances, the low thermal stability of the electronic properties of doped polymers still represents a significant obstacle to implementing these materials into practical applications. Hence, the development of conducting doped polymers with excellent long-term stability at elevated temperatures is highly desirable. Here, we report on the sequential doping of the ladder-type polymer poly-(benzimidazobenzophenanthroline) (BBL) with a benzimidazole-based dopant (i.e., N-DMBI). By combining electrical, UV-vis/infrared, X-ray diffraction, and electron paramagnetic resonance measurements, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, and microstructure of the sequentially doped polymer films as a function of the thermal annealing temperature. Importantly, we observed that the electrical conductivity of N-DMBI-doped BBL remains unchanged even after 20 h of heating at 190 degrees C. This finding is remarkable and of particular interest for organic thermoelectrics. Funding Agencies|Swedish Research CouncilSwedish Research Council [2016-03979]; AForsk [18-313, 19310]; Olle Engkvists Stiftelse [204-0256]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Finnish Cultural FoundationFinnish Cultural Foundation; Finnish Foundation for Technology Promotion; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [Dnr KAW 2014.0041]

Different temperatures, solvents, and additives are used as influencing parameters to drive molecular packing and phase separation for the development of the controlled evolution of nanostructures for organic solar cells (OSCs). The temperature-dependent aggregation (TDA) features of polymers are explored by investigating aggregation in solution and solid thin-film states using solution small-angle neutron scattering (SANS), soft/hard X-ray scattering, and transmission electron microscopy (TEM) characterizations. In situ grazing incidence wide angle X-ray scattering (GIWAXS) reveals that the nucleation process is highly significant and responsible for the ultimate film morphology. Processing conditions such as temperatures, solvents, and additives were used to influence the nucleation and evolution of film morphology. The nucleation process may improve the polymer packing and phase separation. It may translate into optimized multilength scale domains and efficient charge percolation pathways, a strong imp...

The emergence of wearable electronics puts batteries closer to the human skin, exacerbating the need for battery materials that are robust, highly ionically conductive, and stretchable. Herein, we introduce a supramolecular design as an effective strategy to overcome the canonical tradeoff between mechanical robustness and ionic conductivity in polymer electrolytes. The supramolecular lithium ion conductor utilizes orthogonally functional H-bonding domains and ion-conducting domains to create a polymer electrolyte with unprecedented toughness (29.3 MJ m−3) and high ionic conductivity (1.2 × 10−4 S cm−1 at 25 °C). Implementation of the supramolecular ion conductor as a binder material allows for the creation of stretchable lithium-ion battery electrodes with strain capability of over 900% via a conventional slurry process. The supramolecular nature of these battery components enables intimate bonding at the electrode-electrolyte interface. Combination of these stretchable components leads to a stretchable battery with a capacity of 1.1 mAh cm−2 that functions even when stretched to 70% strain. The method reported here of decoupling ionic conductivity from mechanical properties opens a promising route to create high-toughness ion transport materials for energy storage applications., Typically, ion conducting polymers exhibit a trade-off between mechanical robustness and ionic conducting performance. Here, the authors utilize supramolecular chemistry obtaining extremely tough electrolytes with high ionic conductivity and enabling stretchable lithium-ion batteries.

Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material’s resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. In this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole–terthiophene donor–acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of...

Herein, we report a de novo chemical design of supramolecular polymer materials (SPMs-1–3) by condensation polymerization, consisting of (i) soft polymeric chains (polytetramethylene glycol and tetraethylene glycol) and (ii) strong and reversible quadruple H-bonding cross-linkers (from 0 to 30 mol %). The former contributes to the formation of the soft domain of the SPMs, and the latter furnishes the SPMs with desirable mechanical properties, thereby producing soft, stretchable, yet tough elastomers. The resulting SPM-2 was observed to be highly stretchable (up to 17 000% strain), tough (fracture energy ∼30 000 J/m2), and self-healing, which are highly desirable properties and are superior to previously reported elastomers and tough hydrogels. Furthermore, a gold, thin film electrode deposited on this SPM substrate retains its conductivity and combines high stretchability (∼400%), fracture/notch insensitivity, self-healing, and good interfacial adhesion with the gold film. Again, these properties are all highly complementary to commonly used polydimethylsiloxane-based thin film metal electrodes. Last, we proceed to demonstrate the practical utility of our fabricated electrode via both in vivo and in vitro measurements of electromyography signals. This fundamental understanding obtained from the investigation of these SPMs will facilitate the progress of intelligent soft materials and flexible electronics. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Transition metal sulfides have been widely studied as electrocatalysts for the hydrogen evolution reaction (HER). Though elemental doping is an effective way to enhance sulfide activity for the HER, most studies have only focused on the effect of doping sulfide edge sites. Few studies have investigated the effect of doping the basal plane or the effect of doping concentration on basal plane activity. Probing the dopant concentration dependence of HER activity is challenging due to experimental difficulties in controlling dopant incorporation. Here, we overcome this challenge by first synthesizing doped transition metal oxides and then sulfurizing the oxides to sulfides, yielding core/shell Co-doped WS2/W18O49 nanotubes with a tunable amount of Co. Our combined density functional theory (DFT) calculations and experiments demonstrate that the HER activity of basal plane WS2 changes non-monotonically with the concentration of Co due to local changes in the binding energy of H and the formation energy of S-vacancies. At an optimal Co doping concentration, the overpotential to reach −10 mA cm−2 is reduced by 210 mV, and the Tafel slope is reduced from 122 to 49 mV per decade (mV dec−1) compared to undoped WS2 nanotubes.

Conjugated polymers are the key material in thin-film organic optoelectronic devices due to the versatility of these molecules combined with their semiconducting properties. A molecular-scale understanding of conjugated polymers is important to the optimization of the thin-film morphology. We examine the solution-phase behavior of conjugated isoindigo-based donor-acceptor polymer single chains of various chain lengths using atomistic molecular dynamics simulations. Our simulations elucidate the transition from a rod-like to a coil-like conformation from an analysis of normal modes and persistence length. In addition, we find another transition based on the solvent environment, contrasting the coil-like conformation in a good solvent with a globule-like conformation in a poor solvent. Overall, our results provide valuable insights into the transition between conformational regimes for conjugated polymers as a function of both the chain length and the solvent environment, which will help to accurately parametrize higher level models.

Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. We report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Furthermore we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.

Skeleton-based action recognition plays an important role in the field of human action recognition. Recently, with the introduction of Graph Convolution Network (GCN), GCN has achieved superior performance in the field of skeleton-based human action recognition. In this work, we propose a high-order GCN model. In this model, we introduce the expression of high-order skeletons and establish a new high-order adjacency matrix. Through this matrix, the relationship between skeleton nodes and non-neighbor nodes has being established. In addition, based on the degree of node association of different hierarchical neighborhoods, the value of the matrix expresses the importance of different hierarchies. As a result, the proposed model extracts the co-occurrence feature of the skeleton which is superior to the local features and improves the recognition rate. We evaluate our model on two human skeleton action datasets, Kinetics-skeleton and NTU RGB+D, and then further explore the influence of skeleton nodes based on different hierarchies on the recognition results.

In this paper, we propose a new attention model by integrating multi-scale features to recognize human action. We introduce multi-scale features through different sizes of convolution kernel on both spatial and temporal fields. The spatial attention model considers the relationship between detail and integral of the human action, therefore our model can focus on the significant part of the action on the spatial field. The temporal attention model considers the speed of action, in order that our model can concentrate on the pivotal clips of the action on the temporal field. We verify the validity of multi-scale features in the benchmark action recognition datasets, including UCF-101 (\(88.8\%\)), HMDB-51 (\(60.0\%\)) and Penn (\(96.3\%\)). As a result that the accuracy of our model outperforms the previous methods.

The power conversion efficiency of polymer solar cells (PSCs) is strongly affected by active layer morphology. Here, two solvent additives (ODT: octance‐1,8‐dithiol; DIO: 1,8‐diiodooctane) are used to optimize the bulk heterojunction morphology of FTAZ:ITIC‐Th based PSCs and ≈11% efficiency is obtained, which is 10% higher than the untreated device. Based on the morphological characterizations, the influence of binary solvent additives on manipulating molecular packing and phase separation of blend films is successfully revealed. More importantly, in situ grazing incidence wide‐angle X‐ray scattering characterization is adopted to explore the crucial role played by these two solvent additives at different stages of the film‐forming process, that is, ODT influences the initial stage of the film‐forming process, while DIO later establishes the ultimate photoactive film formation. Due to the impacts of two additives at different film processing stages, an optimal ratio of ODT:DIO (0.375%:0.125%) is obtained, which helps in realizing the optimized morphology.

The performance of organic solar cells (OSCs) depends crucially on the morphology in bulk heterojunctions (BHJs), including the degree of crystallinity of the polymer and the amount of each material phase: aggregated donor, aggregated acceptor, and molecular mixed donor : acceptor phase. In this paper, we report the BHJ morphology of as-cast blend films incorporating the polymer PIPCP as the donor and [6,6]-phenyl-C

It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm2 V−1 s−1. The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics., Polymer monolayer field-effect transistors hold promise for faster circuits, but their performance is currently limited by the polymer packing disorder. Li et al. pre-aggregate polymers in a solution to achieve high carrier mobility of 3 cm2 V−1s−1 in monolayers and utilize them in integrated circuits.

Efficiencies of organic photovoltaic (OPV) devices have been steadily climbing, but there is still a prominent gap in understanding the relationship between fabrication and performance. Side chain substitution is one processing parameter that can change OPV device efficiency considerably, primarily because of variations in morphology. In this work, we explain the morphological link between side chain selection and device performance in one polymer to aid in the development of design rules more broadly. We study the morphology of an OPV active layer using a PBDTTPD-backbone polymer with four different side chain configurations, which are shown to change device efficiency by up to 4 times. The optimal device has the smallest domain sizes, the highest degree of crystallinity, and the most face-on character. This is achieved with two branched 2-ethylhexyl (2EH) side chains placed symmetrically on the BDT unit and a linear octyl (C8) side chain on the TPD unit. Substituting either side chain (C14 on BDT and/or 2EH on TPD) makes the orientation less face-on, while the TPD side chain primarily affects domain size. For all side chains, the addition of fullerene increases polymer crystallization compared to the neat film, but the degree of mixing between polymer and fullerene varies with side chain. Interestingly, the optimal device has a negligible amount of mixed phase. The domain sizes present in the optimal system are remarkably unchanged with a changing fullerene ratio between 10 and 90%, hinting that the polymer preferentially self-assembles into 10-20 nm crystallites regardless of concentration. The formation of this crystallite may be the key factor inhibiting mixed phase.

Materials with synchronous capabilities of color change and actuation have prospects for application in biomimetic dual-stealth camouflage and artificial intelligence. However, color/shape dual-responsive devices involve stimuli that are difficult to control such as gas, light or magnetism, and the devices show poor coordination. Here, a flexible composite film with electrochromic/actuating (238° bending angle) dual-responsive phenomena, excellent reversibility, high synchronization, and fast response speed (< 5 s) utilizes a single active component, W18O49 nanowires. From in situ synchrotron X-ray diffraction, first principles calculations/numerical simulations, and a series of control experiments, the actuating mechanism for macroscopic deformation is elucidated as pseudocapacitance-based reversible lattice contraction/recovery of W18O49 nanowires (i.e. nanostructure change at the atomic level) during lithium ion intercalation/de-intercalation. In addition, we demonstrate the W18O49 nanowires in a solid-state ionic polymer-metal composite actuator that operates stably in air with a significant pseudocapacitive actuation., Materials that exhibit synchronous color change and actuation may benefit biomimetic camouflage, but stimuli can be difficult to control. Here the authors report a composite with electricity-driven electrochromic and actuating capabilities for use in a solid-state ionic polymer-metal composite actuator.

Regulating the crystallization of donor and acceptor to maintain balanced carrier mobility is of great importance to fabricate efficient organic solar cells (OSCs). Herein, the balanced crystallinity between donor and acceptor was finely controlled in blade-coated OSCs. By adding high crystalline FOIC into PBDB-T:ITIC system, a balanced carrier mobility was achieved, resulting in the much improved fill factor. The optimized ternary device exhibits an increased current density, due to the enhanced light-harvesting efficiency with complementary absorption and the morphology change. Morphology characterization demonstrated that the ternary film exhibits a highly balanced crystallinity between the donor and acceptor on account of the formation of acceptor alloy. Moreover, the ternary film not only possesses a small domain size, but also exhibits a high domain purity as compared to both binary films. Encouragingly, a highest power conversion efficiency (PCE) of 10.68% was obtained for the blade-coated ternary OSCs. In addition, the blade-coated flexible large-area (105 mm2) OSC based on PBDB-T:ITIC:FOIC ternary system also exhibits a high PCE of 9.81%, showing great potential in the high-throughput fabrication of OSCs.

Herein, we report an all-polymer solar cell with a PCE of over 5% fabricated with non-halogenated solvent. Our method of polymer side-chain engineering using polystyrene enhanced the solubility of polymers in toluene. The phase separation size of the polymer–polymer blend was controlled by tuning the additive concentration. Three different additives were employed and studied. To the best of our knowledge, this is the highest performing all-polymer solar cell fabricated with both non-halogenated solvent and non-halogenated additive, which highlights its potential toward environmentally friendly manufacturing of all-polymer organic solar cells.

Remote sensing image classification is challenging due to low separation between different classes and difficulty in learning discriminative features. GAN (Generative Adversarial Model) is promising for this task due to the generator in reproducing samples and the discriminator for improving the generator. Among GANs variants for image translation and image classification tasks, Pix2Pix performs best. However, Pix2Pix is limited in explicitly capturing the relationship between the source domain and the reconstructed ones from the target domain. To address the above problem, an improved Pix2Pix is proposed in this paper, where a controller is added to Pix2Pix whose role is to improve classification performance and enhance training stability. Experiments demonstrate the effectiveness and advantages of the proposed approach.

The collaboration of multiple agents is required in many real world applications, and yet it is a challenging task due to partial observability. Communication is a common scheme to resolve this problem. However, most of the communication protocols are manually specified and can not capture the dynamic interactions among agents. To address this problem, this paper presents a novel Attentional Communication Model (ACM) to achieve dynamic multi-agent cooperation. Firstly, we propose a new Cooperation-aware Network (CAN) to capture the dynamic interactions including both the dynamic routing and messaging among agents. Secondly, the CAN is integrated into Reinforcement Learning (RL) framework to learn the policy of multi-agent cooperation. The approach is evaluated in both discrete and continuous environments, and outperforms competing methods promisingly.

Termination and hydration of the forsteritic (Fo90Fa10) olivine (0 1 0) surface have been investigated with high-resolution specular X-ray reflectivity and Atomic Force Microscopy. The surface was prepared by polishing a naturally grown {0 1 0} face, from which we found the polished surface in acidic (pH 3.5) alumina suspension exhibits regular steps while the basic (pH 9.5) silica polished surface is irregularly roughened, indicating there are two distinguishable mechanochemical processes for the surface dissolution. The quantitative interpretation of the regular steps from the alumina-polished surface suggests that the observed step heights correspond to multiples of crystallographic unit cell. Only this atomically terraced surface is investigated with the high-resolution X-ray reflectivity (HRXR) to determine the surface termination and hydration. The basic silica paste polished surface turned out too rough to measure with X-ray reflectivity. HRXR reveals that the alumina polished olivine (0 1 0) surface in pure water is terminated at a plane including half-occupied metal ion sites (M1), an oxygen vacancy site, and a silicate tetrahedral unit with one of its apices pointing outward with respect to the surface. An ideal termination with the oxygen vacancy would fulfill the stoichiometry of the formula unit; however, in the observation, the vacancy site is filled by an adsorbed water species and about a quarter of the remaining metal ions are further depleted. The terminating plane generates two distinct atomic layers in the laterally averaged electron density profile, on which two highly ordered adsorbed water layers are formed. The first layer formation is likely through the direct interaction with the M1 plane and the second layer is likely through the hydrogen bonding interaction with the first water layer. With this multilayered adsorbed water structure, the surface metal ion is partially hydrated by the vacancy-filling water species and adsorbed water molecules. The bulk water links to these distinct adsorbed water layers, with weak density oscillations that almost completely damp out after the first bulk water layer. The total thickness of the layered water structure including the two distinct adsorbed layers and the first layer of bulk water is slightly less than 1 nm, which corresponds to roughly three molecular layers of water. These results describe the steric constraints of the surface metal ion hydration and the iron redox environment during water–olivine interactions in this particular crystallographic orientation.

The phase separation between donor and acceptor molecules within the active layer of an organic solar cells dictates the morphology and hence is key to the recombination rate and ultimately the performance of the organic solar cell. Molecular dynamics (MD) simulation is a suitable technique to understand this phenomenon; however, conventional all-atom MD simulations cannot reach the appropriate length and time scales to compare with macroscopic observation. Even with the many available coarse-grained MD models, it is difficult to reach these scales. Therefore, we introduce here a 2D compact model to overcome this challenge, built by multiscale coarse-graining. First, we simulate systems including conjugated polymers, fullerenes, and organic solvents using all-atom MD to extract information about molecular conformation and packing. This includes an analysis of polymer solution behavior, fullerene clustering, and binary and tertiary mixing properties. These results are then used to systematically parameterize the molecules used in 2D coarse-grained MD simulations. The 2D simulations probe experimentally relevant length scales that were previously intractable to sample by other MD simulation methods. Using this model, we explore ternary systems including polymer, fullerene, and solvent molecules to investigate the phase separation process between polymer donors and fullerene acceptors. In this scheme, we additionally introduce explicit solvent evaporation to emulate realistic processing conditions. We quantify phase separation domain sizes that are comparable to experimentally observed values from resonant soft x-ray scattering. In addition, we extend this framework to other chemical species to demonstrate the flexibility of the approach.

Despite having surpassed 10% power conversion efficiency (PCE), widely held as the threshold for commercial viability, high performance organic photovoltaics (OPVs) are still mostly constrained to lab-scale devices fabricated by spin coating. Efforts to produce scalable printed OPVs trail significantly in efficiency, highlighting the need to better understand the processing-morphology-performance relationship in the context of linear printing processes. Here we investigate the OPV system PTB7-Th/PC71BM, which has demonstrated >10% PCE via spincoating but only exhibits ~1% PCE when roll-to-roll printed. Of particular interest is the ubiquitous alcohol wash post-treatment applied to the dried active layer, which induces a significant improvement in device performance, and its crucial role for printed films. While it has been speculated that the primary utility of the alcohol post-treatment is to remove the additive 1,8-diiodooctane (DIO) residue in the dried film, we find here that the wash process itself dramatically impacts morphology in printed films regardless of the presence of DIO. Here we employ various x-ray characterization techniques to probe phase separation, crystallinity, and molecular orientation, as well as in-situ grazing-incidence x-ray diffraction (in-situ GIXD) to monitor morphological evolution during the isopropanol post-treatment process. It is discovered that isopropanol induces significant donor polymer alignment and enhanced π-π degree of crystallinity. Through the understanding gained in this study, we are able to achieve a roll-to-roll printed OPV with 5% PCE, which is to our knowledge the highest reported performance for a roll-to-roll printed single junction photoactive layer on a flexible substrate.

A polymer is described that is conductive and stretchable, which can lead to electronics that can conform to the human body., Previous breakthroughs in stretchable electronics stem from strain engineering and nanocomposite approaches. Routes toward intrinsically stretchable molecular materials remain scarce but, if successful, will enable simpler fabrication processes, such as direct printing and coating, mechanically robust devices, and more intimate contact with objects. We report a highly stretchable conducting polymer, realized with a range of enhancers that serve a dual function: (i) they change morphology and (ii) they act as conductivity-enhancing dopants in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The polymer films exhibit conductivities comparable to the best reported values for PEDOT:PSS, with over 3100 S/cm under 0% strain and over 4100 S/cm under 100% strain—among the highest for reported stretchable conductors. It is highly durable under cyclic loading, with the conductivity maintained at 3600 S/cm even after 1000 cycles to 100% strain. The conductivity remained above 100 S/cm under 600% strain, with a fracture strain of 800%, which is superior to even the best silver nanowire– or carbon nanotube–based stretchable conductor films. The combination of excellent electrical and mechanical properties allowed it to serve as interconnects for field-effect transistor arrays with a device density that is five times higher than typical lithographically patterned wavy interconnects.

It remains a challenging task to track an object robustly due to factors such as pose variation, illumination change, occlusion, and background clutter. In the past decades, a number of researchers have been attracted to tackling these difficulties, and they proposed many effective methods. Among them, sparse representation-based tracking method is a promising. While much success has been demonstrated, there are several issues that still need to be addressed. First, the introduction to trivial occlusion templates brings a high computational cost of this method. Second, the utilization of raw template object representation makes this method difficult to adopt sophisticated object features. To solve these problems, we consider the sparse representation problem in a kernel space and propose a kernel sparse representation (KSR)-based tracking algorithm. Under the kernel representation, it is not necessary to introduce trivial occlusion templates in order to reduce the computational cost. Furthermore, multikernel fusion allows our method to use multiple sophisticated object features, such as spatial color histogram and spatial gradient-orientation histogram, and let these features complement each other during the tracking process. Comparative experiments on challenging scenes demonstrate that our KSR-based tracking algorithm outperforms the state-of-the-art approaches in tracking accuracy.

This work was supported by Air Force Office of Scientific Research (Grant No. FA9550-18-1-0143) for financial support. M.N. acknowledges financial support from the European Commission through a Marie-Curie Individual Fellowship (EC Grant Agreement Number: 747461). H.T. was supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program at Stanford University, administered by Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the Office of the Director of National Intelligence. S.Z. and X.G. thank the financial support from U.S. Department of Energy, Office of Science, Office of Basic Energy Science under award number DE-SC0019361 and National Science Foundation Office of Integrative Activities #1757220. J.M. acknowledges Samsung Scholarship for financial support. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-1542152. GIXD measurement was carried out at the Stanford Synchrotron Radiation Laboratory (SSRL), a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.