This article presents a facile approach to centimeter-scale colloidal photonic crystals (PCs) with narrow stopbands assembled on low-adhesive superhydrophobic substrates. The full-width-at-half-maxima of the stopbands are just 12 nm. The narrow stopbands of colloidal PCs are ascribed to the combined effects of perfectly ordered assembly structure, large-scale crack elimination, decreased void fraction, and sufficient thickness of the colloidal PCs. These properties result from a self-assembly process on a low-adhesive superhydrophobic substrate. Latex suspension on this substrate displays a receding three-phase contact line during evaporation, which releases tensile stress induced by latex shrinkage and results in complete elimination of cracks in the colloidal PCs. Furthermore, the simultaneous assembly of latex particles on the outermost layer of a spread liquid film contributes to the perfectly ordered assembly structure. This facile fabrication of centimeter-scale colloidal PCs with narrow stopbands will offer significant insights into the design and creation of novel optical devices.

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Hydrogels that are mechanically tough and capable of strong underwater adhesion can lead to a paradigm shift in the design of adhesives for a variety of biomedical applications. We hereby innovatively develop a facile but efficient strategy to prepare hydrogel adhesives with strong and instant underwater adhesion, on-demand detachment, high toughness, notch-insensitivity, selfhealability, low swelling index, and tailorable surface topography. Specifically, a polymerization lyophilization conjugation fabrication method was proposed to introduce tannic acid (TA) into the covalent network consisting of polyethylene glycol diacrylate (PEGDA) of substantially high molecular weight. The presence of TA facilitated wet adhesion to various substrates by forming collectively strong noncovalent bonds and offering hydrophobicity to allow water repellence and also provided a reversible cross-link within the binary network to improve the mechanical performance of the gels. The long-chain PEGDA enhanced the efficacy and stability of TA conjugation and contributed to gel mechanics and adhesion by allowing chain diffusion and entanglement formation. Moreover, PEGDA/TA hydrogels were demonstrated to be biocompatible and capable of accelerating wound healing in a skin wound animal model as compared to commercial tissue adhesives and can be applied for the treatment of both epidermal and intracorporeal wounds. Our study provides new, critical insight into the design principle of all-in-one hydrogels with outstanding mechanical and adhesive properties and can potentially enhance the efficacy of hydrogel adhesives for wound healing.

Cracking of photonic crystals (PCs) has received considerable attention because of its severe limitation to PC's applications in high-performance optics devices. Although enormous efforts have been focused on the understanding and elimination of the uncontrolled cracks in the self-assembly process, no reliable, low cost and scalable methods have been demonstrated for the fabrication of large (cm or more) crack-free single-crystalline PCs. Herein, we present a facile, reliable approach for the assembly of crack-free single-crystalline PCs on the centimeter scale by the synergistic effects of substrate deformation and monomer infiltration/polymerization. The co-assembling monomer infiltrates and polymerizes in the interstices of the colloidal spheres to form an elastic polymer network, which could lower the tensile stress generated from colloid shrinkage and strengthen the long-range interactions of the colloidal spheres. Otherwise, the timely transformation of the flexible substrate releases the residual stress. This facile, scalable and environment-friendly approach to centimeter-scale crack-free singlecrystalline PCs will not only prompt the practical applications of PCs in high-performance optics devices, but also have great implications for the fabrication of crack-free thin films in other fields, such as wet clays, coating and the ceramic industry.Scheme 1 Fabrication process for crack-free photonic crystals (PCs) by polymerization-assisted assembly on aluminium foil. In the assembly process, the monomer polymerizes and forms an elastic polymer in the interstices of the colloidal spheres. The elastic deformation of the as-formed polymer counteracts the volume change resulted from latex shrinkage and decreases the tensile stress generated. Meanwhile, the substrate deformation releases the residual stress. Both contribute to the achievement of crack-free single-crystalline PCs. Polymerization-assisted assembly and flexible substrate J Zhou et al Figure 1 Scanning electronic microscopy images, ultraviolet-vis spectra of the crack-free PNIPAm/colloid composite opal (a-c) and poly N-isopropyl acrylamide inverse opal (d-f) photonic crystals (PCs) assembled on Al foils. The inset in (a) is a digital photograph of crack-free PC taken at an angle of ca 451 from the sample surface, and the scale bar is 1 cm. The inset in (b) is the magnified SEM image. These SEM images indicate that cracks have been completely eliminated from the PCs. Narrower full-width-at-half-maximum is observed for the crack-free colloidal PCs compared with that of cracked PCs. Polymerization-assisted assembly and flexible substrate J Zhou et al This work is licensed under the Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 Unported License. To view a copy of this license, visit http:// creativecommons.org/licenses/by-nc-nd/3.0/ Supplementary Information accompanies the paper on the NPG Asia Materials website (http://www.nature.com/am) Polymerization-assisted assembly and flexible substrate J Zhou et al

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Inkjet printing lines with controllable footprints is the prerequisite of fabricating high-quality patterns. However, achieving precise footprints of lines by inkjet printing is still a challenge because of the difficulty in controlling coalescences of ink droplets. Here, controllable footprint lines were fabricated by adjusting the ink droplets' dynamic wettability which is depended on the ink droplets' surface tension difference. The experimental surface tension difference of 0.77-1.50 mN/m leads to appropriate surface dynamic wettability to ink droplets and the formation of straight lines, which agrees well with the theoretical results. These results will pave the way for printing electronics and patterns.

The popularity of Online To Offline (O2O) service platforms has spurred the need for online task assignment in real-time spatial data, where streams of spatially distributed tasks and workers are matched in real time such that the total number of assigned pairs is maximized. Existing online task assignment models assume that each worker is either assigned a task immediately or waits for a subsequent task at a fixed location once she/he appears on the platform. Yet in practice a worker may actively move around rather than passively wait in place if no task is assigned. In this paper, we define a new problem <u>F</u>lexible <u>T</u>wo-sided <u>O</u>nline task <u>A</u>ssignment (FTOA). FTOA aims to guide idle workers based on the prediction of tasks and workers so as to increase the total number of assigned worker-task pairs. To address the FTOA problem, we face two challenges: (i) How to generate guidance for idle workers based on the prediction of the spatiotemporal distribution of tasks and workers? (ii) How to leverage the guidance of workers' movements to optimize the online task assignment? To this end, we propose a novel two-step framework, which integrates offline prediction and online task assignment. Specifically, we estimate the distributions of tasks and workers per time slot and per unit area, and design an online task assignment algorithm, <u>P</u>rediction-oriented <u>O</u>nline task <u>A</u>ssignment in <u>R</u>eal-time spatial data (POLAR-OP). It yields a 0.47-competitive ratio, which is nearly twice better than that of the state-of-the-art. POLAR-OP also reduces the time complexity to process each newly-arrived task/worker to O(1). We validate the effectiveness and efficiency of our methods via extensive experiments on both synthetic datasets and real-world datasets from a large-scale taxi-calling platform.

Graphical Abstract Highlights d Haploid ESCs display PGC-like methylation profiles following in vitro cultivation d Parthenogenetic and androgenetic haploid ESCs show different demethylation dynamics d phESCs carrying 3 deleted imprinted regions support normal growth of bimaternal mice d ahESCs carrying 7 deleted imprinted regions produce live full-term bipaternal mice SUMMARYUnisexual reproduction is widespread among lower vertebrates, but not in mammals. Deletion of the H19 imprinted region in immature oocytes produced bimaternal mice with defective growth; however, bipaternal reproduction has not been previously achieved in mammals. We found that cultured parthenogenetic and androgenetic haploid embryonic stem cells (haESCs) display DNA hypomethylation resembling that of primordial germ cells. Through MII oocyte injection or sperm coinjection with hypomethylated haploid ESCs carrying specific imprinted region deletions, we obtained live bimaternal and bipaternal mice. Deletion of 3 imprinted regions in parthenogenetic haploid ESCs restored normal growth of fertile bimaternal mice, whereas deletion of 7 imprinted regions in androgenetic haploid ESCs enabled production of live bipaternal mice that died shortly after birth. Phenotypic analyses of organ and body size of these mice support the genetic conflict theory of genomic imprinting. Taken together, our results highlight the factors necessary for crossing same-sex reproduction barriers in mammals.