Ionic fuel-powered hydrogel actuators for soft robotics.

HYPOTHESIS: Hydrogel actuators powered by chemical fuels are pivotal in autonomous soft robotics. Nevertheless, chemical waste accumulation caused by chemical fuels hampers the development of programmable and reusable hydrogel actuating systems. We propose the concept of ionic fuel-powered soft robotics which are constructed by programmable salt-responsive actuators and use waste-free ionic fuels. EXPERIMENTS: Herein, soft hydrogel actuators were developed by orchestrating the Janus bilayer hydrogels' capacity for swelling and shrinking. Decomposable and easily removable ionic fuels were applied to power the actuators. Swelling tests were used to evaluate the deformability of the hydrogels. Tensile tests were performed to investigate the modulus of the hydrogels. The bonded interface composed of the interpenetrating polymer chains from both hydrogel layers bilayer was evidenced by the optical microscopy and scanning electron microscopy. The ionic conductivities of solutions were determined by a conductivity meter. Furthermore, a range of biomimetic soft robots with various shapes and asymmetrical structures have been designed and fabricated to execute complex functions. FINDINGS: The programmable actuators powered by ionic fuel exhibit adjustable bending orientations, amplitudes, and durations, along with consistent cyclic actuations enabled by replenishment of the fuel without noticeable loss in performance. Many life-like programmable soft robotic systems were designed, indicating spatiotemporally controllable functions.

Hierarchically Structured Cellulose Acetate@Silk Protein Membrane with Enhanced Mechanical and Electromagnetic Interference Shielding Performances.

Compared to conventional fibers, electrospun porous nanofibers with hierarchical structures often involve additional active sites, interfaces, and internal spaces which boost the performances of functional materials. Here in this study, coaxial composite cellulose acetate@silk fibroin (CA@SF) fibrous membranes are constructed through an electrostatic spinning technique combining solvent-induced phase separation. Hierarchical core-shell structures on the fibers are achieved, which significantly increases the surface area and benefits the mechanical property, flux, as well as the electroless deposition of Ag nanoparticles. The total electromagnetic shielding efficiency of the sandwiched hierarchical CA@SF@Ag composite membrane with a thickness of only 100 µm reaches up to 100 dB, surpassing around 82% beyond nonhierarchical ones. To be noticed, when post-treated by ethanol, the membrane enables an enhanced tensile strength of up to 10 MPa with a thickness of only 50 µm. Our findings pave the way to the application of electrospun fiber membranes in the field of ultrathin electromagnetic shielding films.

Comparison of antimicrobial activities and resistance mechanisms of eravacycline and tigecycline against clinical Acinetobacter baumannii isolates in China.

Tigecycline (TGC) is currently used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections, while eravacycline (ERV), a new-generation tetracycline, holds promise as a novel therapeutic option for these infections. However, differences in resistance mechanism between ERV and TGC against A. baumannii remain unclear. This study sought to compare the characteristics and mechanisms of ERV and TGC resistance among clinical A. baumannii isolates. A total of 492 isolates, including 253 CRAB and 239 carbapenem-sensitive A. baumannii (CSAB) isolates, were collected from hospitalized patients in China. The MICs of ERV and TGC against A. baumannii were determined by broth microdilution. Genetic mutations and expressions of adeB, adeG, adeJ, adeS, adeL, and adeN in resistant strains were examined by PCR and qPCR, respectively. The in vitro recombination experiments were used to verify the resistance mechanism of ERV and TGC in A. baumannii. The MIC90 of ERV in CRAB and CSAB isolates were lower than those of TGC. A total of 24 strains resistant to ERV and/or TGC were categorized into three groups: only ERV-resistant (n = 2), both ERV- and TGC-resistant (n = 7), and only TGC-resistant (n = 15). ST208 (75%, n = 18) was a major clone that has disseminated in all three groups. The ISAba1 insertion in adeS was identified in 66.7% (6/9) of strains in the only ERV-resistant and both ERV- and TGC-resistant groups, while the ISAba1 insertion in adeN was found in 53.3% (8/15) of strains in the only TGC-resistant group. The adeABC and adeRS expressions were significantly increased in the only ERV-resistant and both ERV- and TGC-resistant groups, while the adeABC and adeIJK expressions were significantly increased and adeN was significantly decreased in the only TGC-resistant group. Expression of adeS with the ISAba1 insertion in ERV- and TGC-sensitive strains significantly increased the ERV and TGC MICs and upregulated adeABC and adeRS expressions. Complementation of the wildtype adeN in TGC-resistant strains with the ISAba1 insertion in adeN restored TGC sensitivity and significantly downregulated adeIJK expression. In conclusion, our data illustrates that ERV is more effective against A. baumannii clinical isolates than TGC. ERV resistance is correlated with the ISAba1 insertion in adeS, while TGC resistance is associated with the ISAba1 insertion in adeN or adeS in A. baumannii.

Ultrastrong, flexible thermogalvanic armor with a Carnot-relative efficiency over 8.

Body heat, a clean and ubiquitous energy source, is promising as a renewable resource to supply wearable electronics. Emerging tough thermogalvanic device could be a sustainable platform to convert body heat energy into electricity for powering wearable electronics if its Carnot-relative efficiency (ηr) reaches ~5%. However, maximizing both the ηr and mechanical strength of the device are mutually exclusive. Here, we develop a rational strategy to construct a flexible thermogalvanic armor (FTGA) with a ηr over 8% near room temperature, yet preserving mechanical robustness. The key to our design lies in simultaneously realizing the thermosensitive-crystallization and salting-out effect in the elaborately designed ion-transport highway to boost ηr and improve mechanical strength. The FTGA achieves an ultrahigh ηr of 8.53%, coupling with impressive mechanical toughness of 70.65 MJ m-3 and substantial elongation (~900%) together. Our strategy holds sustainable potential for harvesting body heat and powering wearable electronics without recharging.

Mimosa-Inspired Body Temperature-Responsive Shape Memory Polymer Networks: High Energy Densities and Multi-Recyclability.

Inspired by the Mimosa plant, this study herein develops a unique dynamic shape memory polymer (SMP) network capable of transitioning from hard to pliable with heat, featuring reversible actuation, self-healing, recyclability, and degradability. This material is adept at simulating the functionalities of artificial muscles for a variety of tasks, with a remarkable specific energy density of 1.8 J g-1-≈46 times higher than that of human skeletal muscle. As an intelligent manipulator, it demonstrates remarkable proficiency in identifying and handling items at high temperatures. Its suitable rate of shape recovery around human body temperature indicates its promising utility as an implant material for addressing acute obstructions. The dynamic covalent bonding within the network structure not only provides excellent resistance to solvents but also bestows remarkable abilities for self-healing, reprocessing, and degradation. These attributes significantly boost its practicality and environmental sustainability. Anticipated to promote advancements in the sectors of biomedical devices, soft robotics, and smart actuators, this SMP network represents a forward leap in simulating artificial muscles, marking a stride toward the future of adaptive and sustainable technology.

Healable, Recyclable, and Upcyclable Gel Membranes for Efficient Carbon Dioxide Separation.

Ionic liquids (ILs) are prized for their selective dissolution of carbon dioxide (CO2), leading to their widespread use in ionogel membranes for gas separation. Despite their advantages, creating sustainable ionogel membranes with high IL contents poses challenges due to limited mechanical strength, leakage risks, and poor recyclability. Herein, we leverage copolymerized and supramolecularly bound ILs to develop ionogel membranes with high mechanical strength, zero leakage, and excellent self-healing and recycling capabilities. These membranes exhibit superior ideal selectivity for gas separation compared to other reported ionogel membranes, achieving a CO2/nitrogen selectivity of 61.7 and a CO2/methane selectivity of 24.6, coupled with an acceptable CO2 permeability of 186.4 Barrer. Additionally, these gas separation ionogel membranes can be upcycled into ionic skins for sensing applications, further enhancing their utility. This research outlines a strategic approach to molecularly engineer ionogel membranes, offering a promising pathway for developing sustainable, high-performance materials for advanced gas separation technologies.

Regulating Bacterial Culture through Tailored Silk Inverse Opal Scaffolds.

Controlling the growth of microbial consortia is of great significance in the biomedical field. Selective bacterial growth is achieved by fabricating silk inverse opal (SIO) scaffolds with varying pore sizes ranging from 0.3 to 4.5 µm. Pore size significantly influences the growth dynamics of bacteria in both single and mixed-strain cultures. Specially, the SIO-4.5 µm scaffold is observed to be more favorable for cultivating S. aureus, whereas the SIO-0.3 µm scaffold is more suitable for cultivating E. coli and P. aeruginosa. By adjusting the secondary conformation of silk fibroin, the stiffness of the SIO substrate will be altered, which results in the increase of bacteria on the SIO by 16 times compared with that on the silk fibroin film. Manipulating the pore size allows for the adjustment of the S. aureus to P. aeruginosa ratio from 0.8 to 9.3, highlighting the potential of this approach in regulating bacterial culture.

Marangoni-flow-assisted assembly of single-walled carbon nanotube films for human motion sensing.

Single-walled carbon nanotubes (SWCNTs) present excellent electronic and mechanical properties desired in wearable and flexible devices. The preparation of SWCNT films is the first step for fabricating various devices. This work developed a scalable and feasible method to assemble SWCNT thin films on water surfaces based on Marangoni flow induced by surface tension gradient. The films possess a large area of 40 cm × 30 cm (extensible), a tunable thickness of 15∼150 nm, a high transparency of up to 96%, and a decent conductivity. They are ready to be directly transferred to various substrates, including flexible ones. Flexible strain sensors were fabricated with the films on flexible substrates. These sensors worked with high sensitivity and repeatability. By realizing multi-functional human motion sensing, including responding to voices, monitoring artery pulses, and detecting knuckle and muscle actions, the assembled SWCNT films demonstrated the potential for application in smart devices.

Emergence of eravacycline heteroresistance in carbapenem-resistant Acinetobacter baumannii isolates in China.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is resistant to almost all antibiotics. Eravacycline, a newer treatment option, has the potential to treat CRAB infections, however, the mechanism by which CRAB isolates develop resistance to eravacycline has yet to be clarified. This study sought to investigate the features and mechanisms of eravacycline heteroresistance among CRAB clinical isolates. A total of 287 isolates were collected in China from 2020 to 2022. The minimum inhibitory concentration (MIC) of eravacycline and other clinically available agents against A. baumannii were determined using broth microdilution. The frequency of eravacycline heteroresistance was determined by population analysis profiling (PAP). Mutations and expression levels of resistance genes in heteroresistant isolates were determined by polymerase chain reaction (PCR) and quantitative real-time PCR (qRT-PCR), respectively. Antisense RNA silencing was used to validate the function of eravacycline heteroresistant candidate genes. Twenty-five eravacycline heteroresistant isolates (17.36%) were detected among 144 CRAB isolates with eravacycline MIC values ≤4 mg/L while no eravacycline heteroresistant strains were detected in carbapenem-susceptible A. baumannii (CSAB) isolates. All eravacycline heteroresistant strains contained OXA-23 carbapenemase and the predominant multilocus sequence typing (MLST) was ST208 (72%). Cross-resistance was observed between eravacycline, tigecycline, and levofloxacin in the resistant subpopulations. The addition of efflux pump inhibitors significantly reduced the eravacycline MIC in resistant subpopulations and weakened the formation of eravacycline heteroresistance in CRAB isolates. The expression levels of adeABC and adeRS were significantly higher in resistant subpopulations than in eravacycline heteroresistant parental strains (P < 0.05). An ISAba1 insertion in the adeS gene was identified in 40% (10/25) of the resistant subpopulations. Decreasing the expression of adeABC or adeRS by antisense RNA silencing significantly inhibited eravacycline heteroresistance. In conclusion, this study identified the emergence of eravacycline heteroresistance in CRAB isolates in China, which is associated with high expression of AdeABC and AdeRS.

Exceptional Lithography Sensitivity Boosted by Hexafluoroisopropanols in Photoresists.

Advanced lithography requires highly sensitive photoresists to improve the lithographic efficiency, and it is critical, yet challenging, to develop high-sensitivity photoresists and imaging strategies. Here, we report a novel strategy for ultra-high sensitivity using hexafluoroisopropanol (HFIP)-containing fluoropolymer photoresists. The incorporation of HFIP, with its strong electrophilic property and the electron-withdrawing effect of the fluorine atoms, significantly increases the acidity of the photoresist after exposure, enabling imaging without conventional photoacid generators (PAGs). The HFIP-containing photoresist has been evaluated by electron beam lithography to achieve a trench of ~40 nm at an extremely low dose of 3 µC/cm2, which shows a sensitivity enhancement of ~10 times compared to the commercial system involving PAGs, revealing its high sensitivity and high-resolution features. Our results demonstrate a new type of PAGs and a novel approach to higher-performance imaging beyond conventional photoresist performance tuning.

Tailoring Interfaces of All-Carbon Electromagnetic Interference Shielding Materials for Boosting Comprehensive Performance.

Electromagnetic interference (EMI) shielding materials with lightweight, high shielding effectiveness, excellent chemical stability, especially minimized secondary electromagnetic pollution, are urgently desired for integrated electronic systems operating in harsh working environments. Here in this study, by systematically engineering and matching the interfacial properties of carbon-based membrane materials, i.e., graphite paper, whisker carbon nanotube paper (WCNT paper), carbon nanotube film (CNT film), bucky paper (BP), and carbon cloth (CC) with three-dimensional (3D) porous carbon nanotube sponge (CNTS), we successfully constructed a series of multifunctional all-carbon EMI shielding materials, which exhibit excellent average shielding effectiveness of over 90 dB with a thickness of about 1 mm and dramatically minimized secondary electromagnetic reflection. Moreover, benefiting from the all-carbon nature and engineered interfaces, our CMC materials also exhibit excellent photothermal and Joule heating performances. These results not only provide guidance for designing advanced multifunctional all-carbon EMI shielding materials but also shed light on the hidden mechanism between interfaces and performances of composite materials.

Effect of outer spherical shell opening structure on the sensitivity of double spherical shell electric field sensor.

A double spherical shell (DSS) electric field sensor based on charge sensing has characteristics of small size and simple fabrication, which are appropriate for measuring complex electric field environments, but the sensitivity is low. To improve the sensitivity of the DSS electric field sensor, we theoretically analyze the effect of the diameter of the outer spherical shell opening on the sensitivity of the sensor. The sensors with outer spherical shell apertures of 2, 4, and 6 mm are designed and manufactured, and the sensor's sensitivity, linearity, hysteresis, and repeatability are tested. The relative error of the sensor is evaluated by measuring the rotational characteristics of the sensor. The experimental results show that the sensor sensitivity increases with the increase in hole diameter, while the sensor has good linearity, hysteresis, and repeatability after opening the hole. The rotational characteristics experiments' results show that the sensors' relative errors with different apertures are 18, 23, and 31%, respectively. The DSS open-hole structure is more suitable for electric field measurements than the conventional flat plate structure.

Volatile Droplets on Water are Sculpted by Vigorous Marangoni-Driven Subphase Flow.

The shapes of highly volatile oil-on-water droplets become strongly asymmetric when they are out of equilibrium. The unsaturated organic vapor atmosphere causes evaporation and leads to a strong Marangoni flow in the bath, unlike that previously seen in the literature. Inspecting these shapes experimentally on millisecond and submillimeter time and length scales and theoretically by scaling arguments, we confirm that Marangoni-driven convection in the subphase mechanically stresses the droplet edges to an extent that increases for organic droplets of smaller contact angle and accordingly smaller thickness. The viscous stress generated by the subphase overcomes the thermodynamic Laplace pressure. The oil droplets develop copious regularly spaced fingers, and these fingers develop spike-shaped and branched treelike structures. Unlike this behavior for single-component (surfactant-free) oil droplets, droplets composed of two miscible (surfactant-free) organic liquids develop a rim of the less volatile component along the droplet perimeter, from which jets of monodisperse smaller droplets eject periodically due to the Rayleigh-Plateau instability. When evaporation shrinks droplets to µm size, their shapes fluctuate chaotically, and ellipsoidal shapes rupture into smaller daughter droplets when subphase convection flow pulls them in opposite directions. The shape of the evaporating oil droplets is kneaded and sculpted by vigorous flow in the water subphase.

Dry-Spinning of Artificial Spider Silk Ribbons From Regenerated Natural Spidroin in an Organic Medium.

Natural spider silks with striking performances achieve extensive investigations. Nonetheless, a lack of consensus over the mechanism of the natural spinning hinders the development of artificial spinning methods where the regenerated spider silks generally show poor performances compared with the natural fibers. As is known, the Plateau-Rayleigh instability tends to break solution column into droplets and is considered a main challenge during fiber-spinning. Here in this study, by harnessing the viscoelastic properties of the regenerated spidroin dope solution via organic salt-zinc acetate (ZA), this outcome can be avoided, and dry-spinning of long and mechanically robust regenerated spider silk ribbons can be successfully realized. The as-obtained dry-spun spider silk ribbons show an enhanced modulus up to 14 ± 4 GPa and a toughness of ≈51 ± 9 MJ m-3 after the post-stretching treatment, which is even better than that of the pristine spider silk fibers. This facile and flexible strategy enriches the spinning methodologies which bypass the bottleneck of precisely mimicking the complex natural environment of the glands in spiders, shining a light to the spider-silk-based textile industrial applications.

Oil-on-water droplets faceted and stabilized by vortex halos in the subphase.

For almost 200 y, the dominant approach to understand oil-on-water droplet shape and stability has been the thermodynamic expectation of minimized energy, yet parallel literature shows the prominence of Marangoni flow, an adaptive gradient of interfacial tension that produces convection rolls in the water. Our experiments, scaling arguments, and linear stability analysis show that the resulting Marangoni-driven high-Reynolds-number flow in shallow water overcomes radial symmetry of droplet shape otherwise enforced by the Laplace pressure. As a consequence, oil-on-water droplets are sheared to become polygons with distinct edges and corners. Moreover, subphase flows beneath individual droplets can inhibit the coalescence of adjacent droplets, leading to rich many-body dynamics that makes them look alive. The phenomenon of a "vortex halo" in the liquid subphase emerges as a hidden variable.

Mutations in porin LamB contribute to ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae.

Ceftazidime-avibactam (CAZ-AVI) shows promising activity against carbapenem-resistant Klebsiella pneumoniae (CRKP), however, CAZ-AVI resistance have emerged recently. Mutations in KPCs, porins OmpK35 and/or OmpK36, and PBPs are known to contribute to the resistance to CAZ-AVI in CRKP. To identify novel CAZ-AVI resistance mechanism, we generated 10 CAZ-AVI-resistant strains from 14 CAZ-AVI susceptible KPC-producing K. pneumoniae (KPC-Kp) strains through in vitro multipassage resistance selection using low concentrations of CAZ-AVI. Comparative genomic analysis for the original and derived mutants identified CAZ-AVI resistance-associated mutations in KPCs, PBP3 (encoded by ftsI), and LamB, an outer membrane maltoporin. CAZ-AVI susceptible KPC-Kp strains became resistant when complemented with mutated blaKPC genes. Complementation experiments also showed that a plasmid borne copy of wild-type lamB or ftsI gene reduced the MIC value of CAZ-AVI in the induced resistant strains. In addition, blaKPC expression level increased in four of the six CAZ-AVI-resistant strains without KPC mutations, indicating a probable association between increased blaKPC expression and increased resistance in these strains. In conclusion, we here identified a novel mechanism of CAZ-AVI resistance associated with mutations in porin LamB in KPC-Kp.

Material patterning on substrates by manipulation of fluidic behavior.

Patterned materials on substrates are of great importance for a wide variety of applications. In solution-based approaches to material patterning, fluidic flow is inevitable. Here we demonstrate not only the importance of fluidic behavior but also the methodology of engineering the flow pattern to guide the material crystallization and assembly. We show by both experiment and simulation that substrate heating, which is generally used to accelerate evaporation, produces irregular complex vortexes. Instead, a top-heating-bottom-cooling (THBC) set-up offers an inverse temperature gradient and results in a single Marangoni vortex, which is desired for ordered nanomaterial patterning near the contact line. We then realize the fabrication of large-scale patterns of iodide perovskite crystals on different substrates under THBC conditions. We further demonstrate that harnessing the flow behavior is a general strategy with great feasibility to pattern various functional materials ranging from inorganic, organic, hybrid to biological categories on different substrates, presenting great potential for practical applications.

Pencil-Drawing Skin-Mountable Micro-Supercapacitors.

In this study, integrated plaster-like micro-supercapacitors based on medical adhesive tapes are fabricated by a simple pencil drawing process combined with a mild solution deposition of MnO2 . These solid micro-supercapacitors not only exhibit excellent stretchability, flexibility, and biocompatibility, but also possess outstanding electrochemical performances, such as exceptional rate capability and cycling stability. Hence they may act as skin-mountable and thin-film energy storage devices of high efficiency to power miniaturized and wearable electronic devices.

Blown Bubble Assembly of Graphene Oxide Patches for Transparent Electrodes in Carbon-Silicon Solar Cells.

Graphene oxide (GO) sheets have a strong tendency to aggregate, and their interfaces can impose limitations on the electrical conductivity, which would hinder practical applications. Here, we present a blown bubble film method to assemble GO sheets with a uniform distribution over a large area and further interconnect individual GO sheets by transforming the bubble film into graphitized carbon. A conventional polymer was used to facilitate the bubble blowing process and disperse GO sheets in the bubble. Then, the bubble film was annealed on a Cu substrate, resulting in a highly transparent reduced GO (RGO)-carbon hybrid structure consisting of RGO patches well adhered to the carbon film. We fabricated RGO-carbon/Si solar cells with power conversion efficiencies up to 6.42%, and the assembled RGO patches hybridized with carbon film can form an effective junction with Si, indicating potential applications in thin film electronic devices and photovoltaics.

ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells.

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells.