Biological Tissue-Inspired Ultrasoft,Ultrathin,and Mechanically Enhanced Microfiber Composite Hydrogel for Flexible Bioelectronics

Hydrogels offer tissue-like softness,stretchability,fracture toughness,ionic conductivity,and compatibility with biological tissues,which make them promising candidates for fabricating flexible bioelectronics.A soft hydrogel film offers an ideal interface to directly bridge thin-film electronics with the soft tissues.However,it remains difficult to fabricate a soft hydrogel film with an ultrathin configuration and excellent mechanical strength.Here we report a biological tissue-inspired ultrasoft microfiber composite ultrathin(<5μm)hydrogel film,which is currently the thinnest hydrogel film as far as we know.The embedded microfibers endow the composite hydrogel with prominent mechanical strength(tensile stress~6 MPa)and anti-tearing property.Moreover,our microfiber composite hydrogel offers the capability of tunable mechanical properties in a broad range,allowing for matching the modulus of most biological tissues and organs.The incorporation of glycerol and salt ions imparts the microfiber composite hydrogel with high ionic conductivity and prominent anti-dehydration behavior.Such microfiber composite hydrogels are promising for constructing attaching-type flexible bioelectronics to monitor biosignals.

Correction:Monodomain Liquid Crystals of Two‑Dimensional Sheets by Boundary‑Free Sheargraphy

In this article Florian Puchtler at affiliation‘University of Bayreuth’,Josef Breu at affiliation‘University of Bayreuth’,and Ziliang Wu at affiliation‘Zhejiang University’was missing from the author Min Cao,Senping Liu,Qingli Zhu,Ya Wang,Jingyu Ma,Zeshen Li,Dan Chang,Enhui Zhu,Xin Ming,Florian Puchtler,Josef Breu,Ziliang Wu,Yingjun Liu,Yanqiu Jiang,Zhen Xu,Chao Gao list.

Highly Sensitive Ultrathin Flexible Thermoplastic Polyurethane/Carbon Black Fibrous Film Strain Sensor with Adjustable Scaffold Networks

In recently years,high-performance wearable strain sensors have attracted great attention in academic and industrial.Herein,a conductive polymer composite of electrospun thermoplastic polyurethane(TPU)fibrous film matrix-embedded carbon black(CB)particles with adjustable scaffold network was fabricated for high-sensitive strain sensor.This work indicated the influence of stereoscopic scaffold network structure built under various rotating speeds of collection device in electrospinning process on the electrical response of TPU/CB strain sensor.This structure makes the sensor exhibit combined characters of high sensitivity under stretching strain(gauge factor of 8962.7 at 155%strain),fast response time(60 ms),outstanding stability and durability(>10,000 cycles)and a widely workable stretching range(0–160%).This high-performance,wearable,flexible strain sensor has a broad vision of application such as intelligent terminals,electrical skins,voice measurement and human motion monitoring.Moreover,a theoretical approach was used to analyze mechanical property and a model based on tunneling theory was modified to describe the relative change of resistance upon the applied strain.Meanwhile,two equations based from this model were first proposed and offered an effective but simple approach to analyze the change of number of conductive paths and distance of adjacent conductive particles.

Cellulose-MXene composites: New platforms with outstanding multifunctional characteristics

The progress of society has caused a quick rise in the requirement for materials with superior functionalities.Hybrid composite materials demonstrate exceptional performance due to the synergistic effects resulting from the combination of unique properties exhibited by their constituent components.This advantageous characteristic enables these materials to leverage the collective strengths of each component,leading to their outstanding performance.By leveraging the strengths of each individual component,the shortcomings can be overcome and the strong points can be shared effectively.

Polymer nanofibre composite nonwovens with metal-like electrical conductivity

Bendable and breathable polymer nanofibre nonwovens with metal-like electrical conductivity are required for lightweight electrodes and electric shielding design with applications in batteries,functional textiles,sensors,cars,aerospace,constructions,mobile phones,and medical devices.Metal-like conductivity in polymer nonwovens has not been achieved till now due to the limitation of the existing processing techniques.We show here,the metal-like electrical conductivity of 750,000 S/m in polyacrylonitrile(PAN),poly(ε-caprolactone)(PCL)nonwoven using very low content of silver nanowires(AgNW;3.35 vol%).The key to the high conductivity was the homogenous distribution of AgNW in nonwoven made by wet-laid process using short electrospun fibre and AgNW dispersion.Above a threshold of 0.36 vol%AgNW,the conductivity of the nonwoven increased by seven orders of magnitude,which we attribute to the onset of percolation of the AgNW.Our nonwoven-AgNW composites show fast heating and cooling within a few seconds at a voltage of 1.1 V,which is in the range of portable devices.These composites are also breathable and bendable.The electrical conductivity was independent of the bending angle of the composite,which is important for applications mentioned above and would help other scientists to design new conductive materials in the future.

Impact of Molecular Shape on Supramolecular Copolymer Synthesis in Seeded Living Polymerization of Perylene Bisimides

Supramolecular polymerization properties have been studied for a series of perylene bisimide(PBI)dyes containing identical hydrogen-bonding amide groups in imide positions but variable number or size of alkoxy substituents in bay-positions.

Electrospinning of ABS nanofibers and their high filtration performance

Acrylonitrile-butadiene-styrene(ABS)is a commercial polymer for widely industrial applications due to its good mechanical and physical properties.However,there are only countable reports regarding its fibers from electrospinning.Comprehensive investigation on its optimized electrospinning parameters is missing.Herein,ABS fibers with different fiber diameters were produced by electrospinning.The electrospinning conditions,including the solvents,solution concentrations and amounts of different salt additives,have been comprehensively investigated.The morphologies of electrospun ABS fibers are studied by scanning electron microscopy and Raman spectroscopy.Different fiber diameters and coating densities are applied for filtration applications,which showed excellent filtration performance.The filtration efficiency of up to 99%,low pressure drop of<30 Pa,and high filtration quality factor of up to 0.477 are achieved from the electrospun ABS fibers coated on microfibrous polypropylene substrates.In addition,the electrospun ABS fibers also shows good thermal stability and other applications such as oil/water separation.

Conductivity of Poly(methyl methacrylate)/Polystyrene/Carbon Black and Poly(ethyl methacrylate)/Polystyrene/Carbon Black Ternary Composite Films

Poly(methyl methacrylate)(PMMA)/polystyrene(PS)/carbon black(CB)and poly(ethyl methacrylate)(PEMA)/PS/CB ternary composite films were obtained using solution casting technique to investigate double percolation effect.In both PMMA/PS/CB and PEMA/PS/CB ternary composite films,the CB particles prefer to locate into PS phase based on the results of calculating wetting coefficient,which is also confirmed by SEM images.The conductivity of the films was investigated,and the percolation threshold(￠c)of both ternary composite films with different polymer blend ratios was determined by fitting the McLachlan GEM equation.Conductivity of PMMA/PS/CB ternary composite films showed a typical double percolation effect.However,due to the double emulsion structure of PEMA/PS polymer blends,the PEMA/PS/CB ternary composite films(PEMA/PS=50/50)showed a higher￠c,even CB only located in PS phase,which conflicts with the double percolation effect.A schematic diagram combined with SEM images was proposed to explain this phenomenon.

Virtually Wall-Less Tubular Sponges as Compartmentalized Reaction Containers

Sponges are open cellular materials with numerous interesting features.However,the potential of compartmentalized sponges has not been explored although many new properties and applications could be envisioned.We found that compartmentalized fbrous ultraporous polymer sponges with superhydrophobic surfaces could be designed as virtually wall-less reaction containers.With this,for example,the efcient removal of CO_(2) from water and the controlled mineralization of calcium carbonate are possible.Te high porosity(>99%)and superhydrophobicity make these sponges ideal candidates to hold alkanolamine solution for absorbing CO_(2) and exchange gas through the walls of the sponges.Te tubular sponge exhibits a much higher evaporation rate than a glass tube with the same diameter due to the much larger contact area between water and air.Terefore,the spongy reaction container also possesses a much faster adsorption rate,smaller equilibration time and higher efciency for CO_(2) adsorption than the glass tube container.In addition,these tubular sponges are also utilized to precipitate calcium carbonate by ammonium carbonate decomposition,which can control the deposition rates and products by tailoring the porosity and surface chemistry in the future.Tese new sponges provide an ideal basis for numerous new applications,for example,as breathable pipe lines for gas-liquid exchange,slag slurry carbonization,humidifer,and blood enricher.

Pt/TiO_(2–x) nanofibrous aerogel for effective nitrogen reduction: A simple strategy for simultaneous Pt formation and TiO_(2–x) vacancy engineering

Electrocatalysis plays an increasingly important role in converting atmospheric molecules(e.g.,N_(2),CO_(2) and H_(2)O)to value-added products(e.g.,NH_(3),C_(2)H_(4)and H_(2)).However,developing a simple strategy for preparing catalysts with high performance for the effective conversion of clean energy is still full of chal-lenges.Herein,we describe a straightforward,one-step reduction method to achieve the formation of Pt nanoparticles(NPs)and the vacancy engineering of TiO_(2-x)nanofibers(NFs)simultaneously,which can be accomplished in 5 min.Furthermore,a Pt/TiO_(2-x)nanofibrous aerogel(NA)with an ordered cellular archi-tecture is prepared through a directional freezing technology.The Pt/TiO_(2-x)NA with excellent mechanical properties can be made into a self-supporting electrode for electrocatalytic N_(2)reduction reaction(NRR),showing high NH_(3) yield rate(4.81×10^(-10)mol/s cm^(-2))and Faraday efficiency(14.9%)at-0.35 V vs.RHE.

Effects of solvents and temperature on spherulites of self-assembled phloroglucinol tristearate

Herein,phloroglucinol tristearate(PhgTS)was used to study the crystallization process due to its unique symmetric structure containing a benzene ring and three aliphatic chains.Spherulites of crystallized PhgTS from four solvents under diverse conditions were analyzed in detail and their formation process was studied.Maltese cross is shown by PhgTS spherulites obtained from aprotic solvents via polarized optical microscopy.In comparison,no Maltese cross can be observed from branch-like crystals formed from protic solvents.Independent on the micro-scaled morphology,lamellae were found to be the basic blocks constructing both PhgTS spherulites and branch-like crystals,which were formed predominantly by stacked PhgTS molecules.Although differential characters of the solvents did not affect the formation of lamellas,the solvents played a crucial role in the formation of self-assembled microscaled morphologies.In particular,the morphologies of spherulites were strongly affected by the concentration of PhgTS solutions,surrounding tempera-ture and evaporation rate of solvents.Generally,a higher concentration of PhgTS led to more homogeneous spherulites,a lower evaporation rate resulted in more compact spherulites,and a higher surounding temperature generated preferentially more ring-banded spherulites of PhgTS.

Experimental and Theoretical Study on Piezoresistive Behavior of Compressible Melamine Sponge Modified by Carbon-based Fillers

High-performance compression sensors have been playing an increasingly important role in human motion detection,health monitoring and human-machine interfaces over recent years.However,it remains a great challenge to develop theoretical models providing practical guidance to the sensor design.Herein,carbon black(CB),carbon nanotubes(CNTs)and graphene nanoplatelets(GNPs)were respectively incorporated into porous melamine sponges by a facile approach of dip-coating to fabricate compression sensors.Uniaxial compression-resistance tests show that the compressibility,stability and piezoresistive sensitivity of sensors could be tailored by the filler type and concentration.A model considering the number of conductive pathways(NCP)is given to describe the relationship between the resistance change and applied compression,showing extremely good agreement with the experimental data.Also,the correlation between the equivalent filler volume fraction and conductivity is described by the other two models proposed by McLachlan and Kirkpatrick,revealing the electrical percolation thresholds(Φc)for the conductive systems under compression.Among the three fillers,CB particles endowed the composite with the best piezoresistive sensitivity but the largestΦc due to its small size and aspect ratio.A combination of experimental study and theoretical model opens up a way of further understanding the piezoresistive sensing behavior as well as optimizing the electrical property and piezoresistivity of compressive conductive polymer composite.