Covalently introducing sulfur in a thiol-rich metal-organic framework toward advanced lithium-sulfur batteries

The severe shuttle effect and sluggish reaction kinetics have hindered the commercial application of high-energy lithium-sulfur (Li-S) batteries. In this work, a dual-thiol metal-organic framework (MOF) was in situ synthesized on carbon nanotubes, and sulfur was covalently connected to this composite (UiO-66(SH)2@CNT) to form a MOF-sulfur copolymer (S-UiO-66(SH)2@CNT). Benefiting from the strong covalent interaction between thiol groups and sulfur species, the S-UiO-66(SH)2@CNT cathode can retard the shuttle effect and simultaneously strengthen the redox kinetics of polysulfides. As a result, a discharge capacity of 791 mAh g-1 is achieved at a current density of 0.2 C, whereas the S/UiO-66@CNT cathode using the blend of UiO-66@CNT and sulfur as active materials only shows a specific capacity of 670 mAh g-1. Moreover, the S-UiO-66(SH)2@CNT cathode exhibits a higher capacity retention of 93.27 % at 0.5 C during 200 cycles compared with that of the S/UiO-66@CNT cathode (64.94 %). This work will provide significant inspiration for the design of advanced MOFs and cathodes for excellent Li-S batteries

Folding artificial mucosa with cell-laden hydrogels guided by mechanics models

The surfaces of many hollow or tubular tissues/organs in our respiratory, gastrointestinal, and urogenital tracts are covered by mucosa with folded patterns. The patterns are induced by mechanical instability of the mucosa under compression due to constrained growth. Recapitulating this folding process in vitro will facilitate the understanding and engineering of mucosa in various tissues/organs. However, scant attention has been paid to address the challenge of reproducing mucosal folding. Here we mimic the mucosal folding process using a cell-laden hydrogel film attached to a prestretched tough-hydrogel substrate. The cell-laden hydrogel constitutes a human epithelial cell lining on stromal component to recapitulate the physiological feature of a mucosa. Relaxation of the prestretched tough-hydrogel substrate applies compressive strains on the cell-laden hydrogel film, which undergoes mechanical instability and evolves into morphological patterns. We predict the conditions for mucosal folding as well as the morphology of and strain in the folded artificial mucosa using a combination of theory and simulation. The work not only provides a simple method to fold artificial mucosa but also demonstrates a paradigm in tissue engineering via harnessing mechanical instabilities guided by quantitative mechanics models. Keywords: mucosa; hydrogel; mechanical instabiity; tissue engineering; biomechanicsNational Science Foundation (U.S.) (Award CMMI-1661627)United States. Office of Naval Research (Award N00014-17-1-2920

Effective Dual Polysulfide Rejection by a Tannic Acid/Fe^III Complex-Coated Separator in Lithium–Sulfur Batteries

The solubility behaviour of polysulfides in electrolyte solutions is a major bottleneck prior to the practical application of the lithium–sulfur battery. To address this issue, we fabricate a tannic acid/Fe^III complex-coated polypropylene (PP) separator (TA/Fe^III-PP separator) via a simple, fast, and green method. Benefiting from dual-confinement effects based on Lewis acid–base interactions between Fe^III and polysulfides as well as the dipole–dipole interactions between rich phenol groups and polysulfides, the migration of polysulfides is effectively suppressed. Meanwhile, the porous structure of the PP separator is not destroyed by an additional coating layer. Thus, the TA/Fe^III-PP separator can retain rapid lithium ion transport, eventually leading to a significant improvement in both the discharge capacity and rate performance of the corresponding lithium–sulfur cells. The cell with the TA/Fe^III-PP separator presents a low capacity fade of 0.06% per cycle over 1000 cycles at 2.0 C, along with a high Coulombic efficiency of >97% over 300 cycles at 0.5 C. With respect to the one with the bare PP separator, the cell with the TA/Fe^III-PP separator exhibits a 1.7-fold increase in the discharge capacity at 3.0 C. The proposed simple and economical approach shows great potential in constructing advanced separators to retard the shuttle effect of polysulfides for lithium–sulfur batteries

Superprotonic conduction of intrinsically zwitterionic microporous polymers based on easy-to-make squaraine, croconaine and rhodizaine dyes

Porous organic polymers (POPs) have been prepared via a novel metal free polycondensation between a tritopic indole-based monomer and squaric, croconic and rhodizonic acids. Each of the three POPs exhibited high BET surface areas (331–667 m(2) g(−1)) and zwitterionic structures. Impedance measurements revealed that the intrinsic POPs were relatively weak proton conductors, with a positive correlation between the density of oxo-groups and the proton conduction. Doping the materials with LiCl vastly improved the proton conductivity up to a value of 0.54 S cm(−1) at 90 °C and 90% relative humidity

High stretchability, strength, and toughness of living cells enabled by hyperelastic vimentin intermediate filaments

In many developmental and pathological processes, including cellular migration during normal development and invasion in cancer metastasis, cells are required to withstand severe deformations. The structural integrity of eukaryotic cells under small deformations has been known to depend on the cytoskeleton including actin filaments (F-actin), microtubules (MT), and intermediate filaments (IFs). However, it remains unclear how cells resist severe deformations since both F-actin and microtubules yield or disassemble under moderate strains. Using vimentin containing IFs (VIFs) as a model for studying the large family of IF proteins, we demonstrate that they dominate cytoplasmic mechanics and maintain cell viability at large deformations. Our results show that cytoskeletal VIFs form a stretchable, hyperelastic network in living cells. This network works synergistically with other cytoplasmic components, substantially enhancing the strength, stretchability, resilience, and toughness of cells. Moreover, we find the hyperelastic VIF network, together with other quickly recoverable cytoskeletal components, forms a mechanically robust structure which can mechanically recover after damage.National Cancer Institute (U.S.) (Grant 1U01CA202123

Sphingosine-1-Phosphate Alleviates Irradiation Induced Salivary Gland Hypofunction through Preserving Endothelial Cells and Resident Macrophages

Radiotherapy for head-and-neck cancers frequently causes long-term hypofunction of salivary glands that severely compromises quality of life and is difficult to treat. Here, we studied effects and mechanisms of Sphingosine-1-phosphate (S1P), a versatile signaling sphingolipid, in preventing irreversible dry mouth caused by radiotherapy. Mouse submandibular glands (SMGs) were irradiated with or without intra-SMG S1P pretreatment. The saliva flow rate was measured following pilocarpine stimulation. The expression of genes related to S1P signaling and radiation damage was examined by flow cytometry, immunohistochemistry, quantitative RT-PCR, Western blotting, and/or single-cell RNA-sequencing. S1P pretreatment ameliorated irradiation-induced salivary dysfunction in mice through a decrease in irradiation-induced oxidative stress and consequent apoptosis and cellular senescence, which is related to the enhancement of Nrf2-regulated anti-oxidative response. In mouse SMGs, endothelial cells and resident macrophages are the major cells capable of producing S1P and expressing the pro-regenerative S1P receptor S1pr1. Both mouse SMGs and human endothelial cells are protected from irradiation damage by S1P pretreatment, likely through the S1pr1/Akt/eNOS axis. Moreover, intra-SMG-injected S1P did not affect the growth and radiosensitivity of head-and-neck cancer in a mouse model. These data indicate that S1P signaling pathway is a promising target for alleviating irradiation-induced salivary gland hypofunction

Spin‐coating fabrication of high‐yield and uniform organic thin‐film transistors via a primer template growth

Publication status: PublishedAbstractSolution coating of organic semiconductors offers great potential for achieving low‐cost and high‐throughput manufacturing of large‐area and flexible electronics. However, the solution processability of semiconducting small molecules for fabricating uniform and reliable thin‐film devices poses challenges due to the low viscosities of small‐molecule solutions. Here, we report a universal approach employing a primer template (PT) to enhance the spreadability of small‐molecule solutions on silicon wafers, enabling the spin‐coating fabrication of uniform thin films composed of millimeter‐scale grains with complete large‐area coverage and well‐ordered molecular packing. Using PT, we fabricated organic thin‐film transistors (OTFTs) using solutions containing various small molecules such as rubrene and 2‐decyl‐7‐phenyl‐[1]benzothieno[3,2‐b][1]benzothiophene. The device yield of all fabricated OTFTs is consistently 100% while achieving a high average mobility of 1.62 cm2 V−1 s−1 with a device‐to‐device variation of 7.7% measured in ambient air condition. In addition, the utilization of PT resulted in a batch‐to‐batch variation of 12.5% in device performance over dozens of OTFT devices. The key industrial manufacturing metrics, such as device yield, reproducibility, and performance uniformity of the PT OTFTs, are among the best for devices fabricated using solution spin‐coating techniques.</jats:p