A Multifunctional Airfow Sensor Enabled by Optical Micro/nanofber

Fiber-optic anemometers have attracted an increasing attention over the past decade owing to their high sensitivity,wide dynamic range,low power consumption,and immunity to electromagnetic interference.However,expensive instruments may limit their practical applications.Herein,a new type of airfow sensor based on optical micro/nanofber(MNF)is proposed and realized.The sensing element is a fexible polydimethylsiloxane(PDMS)cantilever embedded with a U-shaped MNF.Upon exposure to airfow,the induced defection of the cantilever results in a bending-dependent transmittance variation of the embedded MNF.The performance of the sensor can be engineered by tuning the cantilever thickness and/or the MNF diameter.When four cantilevers are arranged in two orthogonal directions,the transmittance of each cantilever will be dependent on both fow speed and direction.By analysing the output signals of the four cantilevers,omnidirectional airfow with fow speed within 15 m/s were experimentally measured.In addition,a variety of voice and respiratory signals can be monitored and distinguished in real-time using an optimized cantilever with a resolution of 0.012 m/s,presenting great potential for health monitoring applications.

Electrospinning of Neat Graphene Nanofbers

Macroscopic assembly of graphene sheets has renovated the preparation of neat carbonaceous fbers with integrating high performance and superior functionalities,beyond the pyrolysis of conventional polymeric precursors.To date,graphene microfbers by the liquid crystalline wet-spinning method have been established.However,how to reliably prepare continuous neat graphene nanofbers remains unknown.Here,we present the electrospinning of neat graphene nanofbers enabled by modulating colossally extensional fow state of graphene oxide liquid crystals.We use polymer with mega molecular weight as transient additives to realize the colossal extensional fow and electrospinning.The neat graphene nanofbers feature high electronic quality and crystallinity and exhibit high electrical conductivity of 2.02×10^(6) S/m that is to be comparable with single crystal graphite whisker.The electrospinning of graphene nanofbers was extended to prepare large-area fabric with high fexibility and superior specifc electrical/thermal conductivities.The electrospinning of graphene nanofbers opens the door to nanofbers of rich two-dimensional sheets and the neat graphene nanofbers may grow to be a new species after conventional carbonaceous nanofbers and whiskers in broad functional applications.

Advances in Biosensing and Environmental Monitoring Based on Electrospun Nanofbers

Electrospun nanofbers(NFs)are directly produced by electrospinning technology.They are useful in a series of applications such as excellent performance in biosensing and environmental monitoring,due to their large specifc surface area and high porosity.The wide range of materials used provide a solid foundation and core guarantee for electrospun NFs to sense,which are used in a variety of polymers,small molecules,colloidal particles,and composites.Biosensing primarily aims at small biomolecules,biomacromolecules,wearable human motion monitoring,and food safety testing.Environmental monitoring encompasses the detection of gases,humidity,volatile organic compounds,and monitoring the degradation of heavy metal ions.We aim to sort out some recent research for electrospun NFs in the sensing area,which may inspire emerging smart sensing devices and bring a novel approach for biomedical development and environmental remediation.We highlight the powerful applications of electrospun NFs in the rapidly growing feld of wearable electronic devices,which may spur the industry’s novel perspectives on the development of wearables.Finally,we point out some unresolved difculties in the sensing feld for electrospun NFs and propose possible and novel ideas for this development.

Diameter Refnement of Electrospun Nanofbers:From Mechanism,Strategies to Applications

Electrospinning has drawn wide attention for its powerful capacity to produce ultrafne nanofbers(UNFs)from various materials.These UNFs demonstrated signifcantly enhanced performance,such as ultra-high surface area,more porosity and stronger mechanical properties.Here,we comprehensively review their basic principles,state-of-the-art methods and preponderant applications.We begin with a brief introduction to the refnement theory of polymer jets,followed by discussion of factors afecting fber refnement.We then discuss the refning strategies from the aspects of solution properties,spinning parameters,auxiliary force and post-treatment.Afterward,we highlight the most relevant and recent applications associated with the remarkable features of UNFs,including fltration materials,supercapacitors,biomedical materials and other applications.At the end,we ofer perspectives on the challenges,opportunities,and new directions for future development of electrospun UNFs.

Polyacrylonitrile Nanofber‑Reinforced Flexible Single‑Ion Conducting Polymer Electrolyte for High‑Performance,Room‑Temperature All‑Solid‑State Li‑Metal Batteries

Single-ion conducting polymer electrolytes(SIPEs)can be formed by anchoring charge delocalized anions on the side chains of a crosslinked polymer matrix,thereby eliminating the severe concentration polarization efect in conventional dual-ion polymer electrolytes.Addition of a plasticizer into the polymer matrix confers advantages of both liquid and solid electrolytes.However,plasticized SIPEs usually face a trade-of between conductivity and mechanical strength.With insufcient strength,potentially there is short-circuiting failure during cycling.To address this challenge,a simple and mechanicallyrobust SIPE was developed by crosslinking monomer lithium(4-styrenesulfonyl)(trifuoromethylsulfonyl)imide(LiSTFSI)and crosslinker poly(ethylene glycol)diacrylate(PEGDA),with plasticizer propylene carbonate(PC),on electrospun polyacrylonitrile nanofbers(PAN-NFs).The well-fabricated polymer matrix provided fast and efective Li^(+) conductive pathways with a remarkable ionic conductivity of 8.09×10^(-4) S cm^(−1) and a superior lithium-ion transference number close to unity(t_(Li+)=0.92).The introduction of PAN-NFs not only improved the mechanical strength and fexibility but also endowed the plasticized SIPE with a wide electrochemical stability window(4.9 V vs.Li^(+)/Li)and better cycling stability.Superior longterm lithium cycling stability and dynamic interfacial compatibility were demonstrated by lithium symmetric cell testing.Most importantly,the assembled all-solid-state Li metal batteries showed stable cycling performance and remarkable rate capability both in low and high current densities.Therefore,this straightforward and mechanically reinforced SIPE exhibits great potential in the development of advanced all-solid-state Li-metal batteries.

Multi‑compartment Organ‑on‑a‑Chip Based on Electrospun Nanofber Membrane as In Vitro Jaundice Disease Model

Organ-on-a-chip(OOC)is now becoming a potential alternative to the classical preclinical animal models,which reconstitutes in vitro the basic function of specifc human tissues/organs and dynamically simulates physiological or pathological activities in tissue and organ level.Despite of the much progress achieved so far,there is still an urgent need to explore new biomaterials to construct a reliable and efcient tissue-tissue interface and a general fabrication strategy to expand from single-organ OOC to multi-organ OOC in an easy manner.In this paper,we propose a novel strategy to prepare doublecompartment organ-on-a-chip(DC-OOC)using electrospun poly(l-lactic acid)/collagen I(PLLA/Col I)nanofber membrane as tissue-tissue interface.The unique features of PLLA/Col I nanofber membrane like excellent biocompatibility,strong afnity to multiple cells,adjustable orientation,controllable thickness and porosity endow the tissue-tissue interface with excellent semi-permeability,appropriate mechanical support,inducible cell orientation,good cell adhesion and proliferation.The integration of 3D printing technology during the fabrication process enables precise size control of the tissue-tissue interface and stable bonding with microfuidic channels.More importantly,our fabrication strategy and OOC confguration makes it easy to extend from DC-OOC to multi-compartment organ-on-a-chip(MC-OOC).To show its possible application,in vitro jaundice disease model is established by constructing blood vessel/skin/liver/lung organ-on-a-chip via MC-OOC.The downward trends of the cell viability after perfusion of bilirubin,the variation in cell sensitivity to bilirubin for diferent type of cells and recovery of cell viability after blue light therapy prove the feasibility of this jaundice disease model.We believe this general strategy of constructing tissue-tissue interface and multi-organ OOC can be used for many other in vitro physiological and pathological models.

Engineered Spindles of Little Molecules Around Electrospun Nanofbers for Biphasic Drug Release

Biphasic drug release is a popular advanced drug controlled release profle that has been drawing increasing attention from many felds.Electrospun nanofbers and their derivatives can be act as a strong platform for developing biphasic release dosage forms.In this study,a modifed coaxial electrospinning was implemented,in which little molecule solutions that contain a drug ibuprofen(IBU)and polyethylene glycol(PEG)were exploited as a sheath fuid to surround the core solutions composed of polymer ethyl cellulose(EC)and IBU.The prepared nanofber-based structural hybrids,i.e.,engineered spindles-on-astring(SOS)products,were successfully created and subjected to a series of characterizations.Scanning electron microscopy and transmission electron microscopy results showed the engineered SOS structures.IBU and the carriers EC and PEG had good compatibility,as suggested by X-ray difraction and Fourier transform infrared spectroscopy assessments.In vitro dissolution tests verifed that the SOS products were able to provide a typical biphasic release profle,releasing 40%of the loaded IBU within 1 h in an immediate manner in the frst phase,and the rest of the IBU in a sustained manner in the second phase.A combined mechanism of erosion and difusion is proposed for manipulating the IBU molecule release behaviors.

The Critical Roles of the Gas Flow in Fabricating Polymer Nanofbers:A Mini‑review

Polymer nanofbers attract more and more attention from academia and industry continuously due to their desirable properties,including high specifc surface area,high porosity,and numerous chemically-active surface groups on the fber surface.Gas fow was widely adopted to fabricate nanofbers such as solution blown,melt blown,gas fow-assisted melt electrospinning,and bubble electrospinning.However,a comprehensive review covered the roles that gas fow played in fabricating nanofbers,and their mechanism has not been analysed yet.This review classifes the roles of gas fow into jet initialization,jet stretching,increasing production,surface modifcation,and inhibition of thermal degradation,to deepen the understanding of gas fow during nanofber preparation.The mechanism of gas fows in the above felds is reviewed in detail.

Characterization of TEMPO-oxidized chitin nanofbers with various oxidation times and its application as an enzyme immobilization support

Chitin nanofbers have recently received increased attention and are considered to be a promising material for a wide range of applications because of their excellent characteristics.In this study,2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)-oxidized chitin nanofbers(CNFs)with various oxidation times were prepared and characterized.CNFs with diferent oxidation times were then utilized for enzyme immobilization,using chymotrypsin as a model enzyme.The efects of oxidation time on enzyme immobilization were explored.Results showed characteristics of chitin nanofbers can be controlled by adjusting oxidation time.CNFs treated with TEMPO for 360 min showed the lowest crystallinity(79.13±1.43%),the shortest length(241.70±74.61 nm),the largest width(12.67±3.43 nm),and the highest transmittance(73.01%at 800 nm).The activity of immobilized enzymes and enzyme loading showed good correlation to the carboxylate content of CNFs.The enzyme efciency based on CNFs and the content of carboxylate groups peaked at the oxidization time of 60 min.When the additional amount of chymotrypsins(CTs)was 500 or 2000 mg/g carrier,the highest loading amount of CTs was 307.17±4.08 or 726.82±12.05 mg/g carrier,respectively.

Preparation and Mechanical Properties of PAN/HNTs Composite Nanofibers

The enhanced composite nanofibers have attracted great attention for application in recent years. The electrospinning technique was considered to be a prospective production pattern for them. This paper provided a promising technique to prepare the polyacrylonitrile （PAN）/halloysite nanotube （HNT） composite nanofbers by using the electrospinning method. The PAN/HNTs composite nanofbers with well enhanced performance were successfully fabricated from a mixture of PAN/DMF/HNTs dispersion solution processed by the electrospinning technique. For achieving good dispersion in PAN polymer, the highly dispersed HNTs were obtained by using polycarboxylate modifcation employing the in-situ spray-drying method. The structure and properties of the composite nanofbers were characterized by TEM, XRD, EDX, IR, and DSC techniques. The obtained PAN/HNTs composite nanofbers with different HNTs contents were about 300-500 nm in diameter. In addition, the mechanical properties of PAN/HNTs composite nanofbers were tested, which exhibited an excellently enhanced performance.

Advanced functional nanofibers:strategies to improve performance and expand functions

Nanofbers have a wide range of applications in many felds such as energy generation and storage,environmental sensing and treatment,biomedical and health,thanks to their large specifc surface area,excellent fexibility,and superior mechanical properties.With the expansion of application felds and the upgrade of application requirements,there is an inevitable trend of improving the performance and functions of nanofbers.Over the past few decades,numerous studies have demonstrated how nanofbers can be adapted to more complex needs through modifcations of their structures,materials,and assembly.Thus,it is necessary to systematically review the feld of nanofbers in which new ideas and technologies are emerging.Here we summarize the recent advanced strategies to improve the performances and expand the functions of nanofbers.We frst introduce the common methods of preparing nanofbers,then summarize the advances in the feld of nanofbers,especially up-to-date strategies for further enhancing their functionalities.We classify these strategies into three categories:design of nanofber structures,tuning of nanofber materials,and improvement of nanofbers assemblies.Finally,the optimization methods,materials,application areas,and fabrication methods are summarized,and existing challenges and future research directions are discussed.We hope this review can provide useful guidance for subsequent related work.

Physicochemical and in Vitro Antibacterial Evaluation of Metronidazole Loaded Eudragit S‑100 Nanofbrous Mats for the Intestinal Drug Delivery

Metronidazole(MTZ)loaded Eudragit S-100(ES-100)nonwoven nanofbrous mats were successfully electrospun and evaluated for intestinal drug delivery.MTZ was varied in the range of 1–15%(w/w)in ES-100 nanofbrous mats,the morphological characterization of nanofbrous mats was carried out using FE-SEM and the average diameter of nanofber was found in the range 150–600 nm.WAXD and DSC demonstrated the amorphous nature of MTZ in ES-100 nanofbrous mats.Their contact angle analysis confrmed the hydrophobic nature.The mechanical strength of ES-100 nanofbrous mats decreased with increasing MTZ concentration.The drug release profles showed 74%MTZ release from ES-100d within 2 h at pH 6.8 which is the colonic environment.Antibacterial activities against gram-positive bacteria(Staphylococcus aureus)and gramnegative bacteria(Escherichia coli)showed that the ES-100 nanofbrous mats loaded with MTZ exhibited good activity.