This work reports a new class of liquid crystal elastomers (LCEs) cross‐linked with poly(ether‐thiourea) comprising a triethylene glycol spacer (LCE‐TUEG) wherein thiourea bonds impart a hydrogen ...bonding capability as well as permit dynamic covalent bond (DCB) exchange at elevated temperatures. While hydrogen bonding enhances the mechanical properties of LCE‐TUEG, the DCB allows the macromolecular network rearrangement of the LCEs, resulting in various useful properties that are not present in conventional LCEs, including the ability to undergo welding, melt and solution reprocessing, reprogrammable actuation, and self‐healing. By exploiting these dynamic features, electrically powered artificial muscles are fabricated that can be actuated by Joule heating using a resistive wire. In particular, an excellent specific work is demonstrated (≈65 J kg−1) for the artificial muscle, and full recyclability of both the LCE matrix and the metallic heating wire is achieved. Furthermore, a biomimetic artificial hand is created by welding and assembling multiple LCE‐TUEG films embedded with heating wires, followed by mechanical alignment. The integration of a microcontroller to the artificial hand enables the selective actuation of each finger, and various hand gestures are successfully demonstrated.
A new class of exchangeable liquid crystal elastomers (LCEs) incorporating thiourea bonds is developed, which offers various useful properties such as welding, melt‐ and solution reprocessing, reprogrammable actuation, and self‐healing. Based on the dynamic features of LCEs, an electrically powered artificial muscle and an artificial hand are fabricated, which can undergo selective actuation by integrating a microcontroller through Joule heating.
Here, we report that CRISPR guide RNAs (gRNAs) with a 5'-triphosphate group (5'-ppp gRNAs) produced via in vitro transcription trigger RNA-sensing innate immune responses in human and murine cells, ...leading to cytotoxicity. 5'-ppp gRNAs in the cytosol are recognized by DDX58, which in turn activates type I interferon responses, causing up to ∼80% cell death. We show that the triphosphate group can be removed by a phosphatase in vitro and that the resulting 5'-hydroxyl gRNAs in complex with Cas9 or Cpf1 avoid innate immune responses and can achieve targeted mutagenesis at a frequency of 95% in primary human CD4
T cells. These results are in line with previous findings that chemically synthesized sgRNAs with a 5'-hydroxyl group are much more efficient than in vitro-transcribed (IVT) sgRNAs in human and other mammalian cells. The phosphatase treatment of IVT sgRNAs is a cost-effective method for making highly active sgRNAs, avoiding innate immune responses in human cells.
In recent years, the “Kirigami” have been exploited to engineer stretchable electronics that exhibit enhanced deformability without sacrificing their mechanical and electrical properties. However, ...kirigami‐inspired engineering is often limited to passive mechanical stretching for 3D shape morphing. To counter this problem, in this study, azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are monolithically integrated with patterned reduced graphene oxide (rGO), called azo‐LCN/rGO, to achieve on‐demand shape reconfiguration in response to external stimuli (UV, NIR, solar rays, and portable light); in addition, the azo‐LCN/rGO exhibit highly enhanced mechanical and electrical properties. The cross‐sectional area and thickness of rGO patterns are controlled using a masking technique and evaporative self‐assembly. By the spatial patterning of rGO, insulating azo‐LCNs are converted into electrically conducting structures (381.9 S cm−1). The elastic modulus of <2 µm thick azo‐LCN can be tailored in the range of 1.3–6.4 GPa by integration with rGO layers of thickness less than 2 µm. Upon UV irradiation, azo‐LCN/rGO exhibit both for/backward in‐plane bending as well as out‐of‐plane chiral twisting, thus overcoming the typical trade‐off relationship between elastic modulus and deformability. Finally, an on‐demand contactless shape reconfiguration in azo‐LCN/rGO by UV irradiation in conjunction with passive mechanical strain is demonstrated.
Mechanically robust and shape‐reconfigurable kirigami‐patterned reduced graphene oxide‐azobenzene‐functionalized liquid crystalline polymer networks (kirigami‐engineered azo‐LCN/rGO) are developed for application in stretchable electronics. Kirigami principles are employed to overcome the limitations of material strain capacity. The fabricated kirigami‐engineered azo‐LCN/rGO exhibit shape tunability by passive/active shape transitions under normal stress, light, and thermal stimuli, respectively, without any deterioration in electrical conductivity.
Polyamide reverse osmosis (RO) membranes with carbon nanotubes (CNTs) are prepared by interfacial polymerization using trimesoyl chloride (TMC) solutions in n-hexane and aqueous solutions of ...m-phenylenediamine (MPD) containing functionalized CNTs. The functionalized CNTs are prepared by the reactions of pristine CNTs with acid mixture (sulfuric acid and nitric acid of 3:1 volume ratio) by varying amounts of acid, reaction temperature, and reaction time. CNTs prepared by an optimized reaction condition are found to be well-dispersed in the polyamide layer, which is confirmed from atomic force microscopy, scanning electron microscopy, and Raman spectroscopy studies. The polyamide RO membranes containing well-dispersed CNTs exhibit larger water flux values than polyamide membrane prepared without any CNTs, although the salt rejection values of these membranes are close. Furthermore, the durability and chemical resistance against NaCl solutions of the membranes containing CNTs are found to be improved compared with those of the membrane without CNTs. The high membrane performance (high water flux and salt rejection) and the improved stability of the polyamide membranes containing CNTs are ascribed to the hydrophobic nanochannels of CNTs and well-dispersed states in the polyamide layers formed through the interactions between CNTs and polyamide in the active layers.
Graphene oxides coated by tannic acid (GOT) can be obtained easily by the self-polymerization of tannic acid in basic buffer solution on a graphene oxide surface. Polyamide reverse osmosis ...nanocomposite membranes containing GOT in the active layer were prepared by the interfacial polymerization using an organic solution containing trimesoyl chloride and an aqueous solution containing m-phenylene diamine and GOT. The polyamide membrane containing GOT (PA-GOT) showed significantly improved performances such as water flux, chlorine resistance, and antimicrobial properties, compared to the polyamide membrane without any additives and the polyamide membranes containing only tannic acid and/or graphene oxide. These high performances of PA-GOT membrane could be ascribed to a various of advantageous properties of GOT such as improved hydrophilicity, oxidative stress capability, barrier property, and compatibility with the polymer matrix.
Polyamide nanocomposite membrane containing graphene oxide coated by natural polyphenol, tannic acid exhibits much improved chlorine-resistant and antimicrobial properties. These improvements originate from the synergistic combinations of tannic acid and graphene oxide, which can increase the oxidative stress capacity, barrier properties, and radical scavenging ability.
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•The surface of graphene oxide (GO) was modified by natural polyphenol, tannic acid (TA).•The modification of GO was simple and eco-friendly.•The GO coated by TA (GOT) was incorporated in polyamide reverse osmosis membrane via interfacial polymerization.•The polyamide membrane containing GOT (PA-GOT membrane) exhibited improved membrane performance such as water flux, chlorine-resistant properties, and antimicrobial properties.•The high performance of PA-GOT membrane was ascribed to the synergistic combination of TA and GO in GOT.
The design and implementation of a high-efficiency nonisolated single-stage on-board battery charger (OBC) for electric vehicles are presented. Reviewing the conventional topologies, a suitable ...circuit structure is determined to charge a battery in a wide spectrum of input and output conditions. Additionally, a suitable strategy for a highly efficient OBC is presented through the analysis of selected topology. A detailed theoretical analysis, operating strategy, and experimental results on a 3.7-kW prototype are presented in order to evaluate the performance of the proposed system.
Thermadapt shape memory polymers (SMPs), utilizing a variety of dynamic covalent bond exchange mechanisms, have been extensively studied in recent years but it is still challenging to address several ...constraints in terms of limited accuracy and complexity for constructing 3D shape memory structures. Here, an effective and facile preparation of thermadapt SMPs based on elemental sulfur‐derived poly(phenylene polysulfide) networks (PSNs) is presented. These SMPs possess intrinsic near‐infrared (NIR)‐induced photothermal conversion properties for spatiotemporal control of their plasticity and elasticity. The NIR‐controllable plasticity and elasticity of the PSNs enable versatile shape manipulation of 3D multi‐shape memory structures, including building block assembly, reconfiguration, shape fixing/recovery, and repair.
Photo‐controllable plasticity and elasticity of elemental sulfur‐derived poly(phenylene polysulfide) networks (PSNs) with intrinsic near‐infrared (NIR) responsiveness are presented. The NIR‐induced spatiotemporal control of plasticity and elasticity in the PSNs enables versatile shape manipulation of 3D multi‐shape memory structures, including building block assembly, reconfiguration, shape fixing/recovery, and repair.
Silicon has garnered significant attention as a promising anode material for high-energy density Li-ion batteries. However, Si can be easily pulverized during cycling, which results in the loss of ...electrical contact and ultimately shortens battery lifetime. Therefore, the Si anode binder is developed to dissipate the enormous mechanical stress of the Si anode with enhanced mechanical properties. However, the interfacial stability between the Si anode binder and Cu current collector should also be improved. Here, a multifunctional thiourea polymer network (TUPN) is proposed as the Si anode binder. The TUPN binder provides the structural integrity of the Si anode with excellent tensile strength and resilience due to the epoxy-amine and silanol-epoxy covalent cross-linking, while exhibiting high extensibility from the random coil chains with the hydrogen bonds of thiourea, oligoether, and isocyanurate moieties. Furthermore, the robust TUPN binder enhances the interfacial stability between the Si anode and current collector by forming a physical interaction. Finally, the facilitated Li-ion transport and improved electrolyte wettability are realized due to the polar oligoether, thiourea, and isocyanurate moieties, respectively. The concept of this work is to highlight providing directions for the design of polymer binders for next-generation batteries.
Nutrient dynamics function globally, flowing from rivers to the ocean (estuarine-coastal zone), and are vulnerable to climate change. Microbial habitats can be affected by marine nutrient dynamics ...and may provide a clue to predict microbial responses to environmental heterogeneity in estuarine-coastal zones. We surveyed surface seawater in Gwangyang Bay, a semi-enclosed estuary in Korea, from 2016 to 2018 using a metabarcoding approach with prokaryotic 16S and eukaryotic 18S rRNA genes. Bacterial and microeukaryotic communities in these waters showed distinct local communities in response to environmental heterogeneity and community transition at spatiotemporal scales in the estuarine-coastal zone. The relative abundance of prokaryotic and eukaryotic operational taxonomic units suggested a microbial trophic interaction in the Gwangyang Bay waters. We found that the community assembly process in prokaryotic communities was primarily influenced by biological interaction (immigration-emigration), whereas that in eukaryotic communities was more affected by environmental stress (habitat specificity) rather than by biotic factors. Our findings in the Gwangyang Bay waters may provide information on underlying (biotic or abiotic) factors of the assembly process in microbial communities in the estuarine-coastal zone.
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