Preparation and Characterization of Chitosan Nanofibers Containing Silver Nanoparticles

Chitosan(CS)nanofibers containing silver nanoparticles(AgNPs)were prepared by in-situ reducing method.A water soluble carboxymethyl chitosan(CMCT)was applied for the preparation of AgNPs.The impact factor such as the concentration of CMCT,silver nitrate(AgNO_3)content,temperature and the heating time during the preparation of AgNPs were studied.The result showed that the proper value of the concentration of CMCT,AgNO_3content,temperature and the heating time were set as0.1%,20μL AgNO_3(1.7 mol/L),90°and 3 h,separately and the maximum concentration of AgNPs could be acquired.To solve the spinnability of chitosan nanofiber,a super high molecular weight polyethylene oxide(PEO)was introduced to the system,and a new mixed solvent system was prepared by adding acetic acid,dimethyl sulfoxide(DMSO)and several drops of Triton X-100TMto distilled water.CS/PEO(80/20)with the concentration of 3%was dissolved in the mixed solvent to prepare electrospinning solution for CS/PEO(80/20)nanofiber fabrication.The CS containing AgNPs electrospun solution could be prepared by replacing the distilled water to silver nanoparticle solution during the preparation of mixed solvent.Ultraviolet visible(UV-Vis)spectra and transmission electron microscope(TEM)results showed that silver nanoparticles were prepared successfully.CS membranes with and without AgNPs were acquired via a traditional electrospinning equipment.These two nanofiber membranes were characterized by scanning electron microscope(SEM)images and mechanical testing.It could be noticed from the SEM images that there was a good morphology and random distribution for the nanofibers with an average fiber diameter of 180 nm.The mechanical property results showed that the addition of AgNPs decreased the mechanical strength significantly but the mechanical strength could still support wound dressing application.

Enzymatic Activity of Escherichia Coil Lactate Dehydrogenase and Cytochrome c Oxidase

The catalytic activity of two common bacterial enzymes, lactate dehydrogenase （LDH） and cytochrome c oxidase （COX） from Escherichia coli was examined following bacterial exposure to microwave （MW） radiation under well-defined experimental conditions. The experiments were conducted in a specialized microwave processing apparatus, with an exposure frequency of 18 GHz, and a temperature profile that was restricted to below 40℃ to avoid thermal degradation of the bacteria. The absorbed power was calculated to be 1,500 kW/m3 and the electric field was determined to be 300 Wm. Both values were theoretically confirmed using Computer Simulation Technology （CST） Microwave Studio 3D Electromagnetic Stimulation Software. Results showed that the activity of both enzymes was increased following MW radiation compared to negative controls and thermally treated samples subjected to similar temperature profiles. It is suggested that the increase in COX and LDH enzyme activity could not be explained by conventional heating alone, but was rather a result of micro-thermal effects that incorporated ＇undetectable＇ thermal mechanisms.

Dynamic torsional buckling of multi-walled carbon nanotubes embedded in an elastic medium

In this paper the dynamic torsional buckling of multi-walled carbon nanotubes （MWNTs） embedded in an elastic medium is studied by using a continuum mechanics model. By introducing initial imperfections for MWNTs and applying the preferred mode analytical method, a buckling condition is derived for the buckling load and associated buckling mode. In particular, explicit expressions are obtained for embedded double-walled carbon nanotubes （DWNTs）. Numerical results show that, for both the DWNTs and embedded DWNTs, the buckling form shifts from the lower buckling mode to the higher buckling mode with increasing the buckling load, but the buckling mode is invari- able for a certain domain of the buckling load. It is also indicated that, the surrounding elastic medium generally has effect on the lower buckling mode of DWNTs only when compared with the corresponding one for individual DWNTs.

Finite Element Analysis for In-Plane Crushing Behaviour of Aluminium Honeycombs

A number of finite element simulations were performed to analyze the in-plane crushing behaviour of aluminium honeycombs and the results are presented and discussed. The simulations include both X1 and X2 cases. All the analyses are quasi-static, and can be divided into three groups, which are designed to investigate the effects of cell size, foil thickness and yield stress of the foil material, respectively, on the structural response of honeycombs. The result indicates that these factors can significantly affect the plateau stresses of honeycomb cellular structures in both directions, and the plateau stresses in X2 direction are slightly smaller than those in X1 direction. The simulation results were further compared with published theoretical predictions and show higher values. The difference was then analyzed and a new expression for the plateau stress of honeycombs was suggested.

A Theoretical Processing Map for Laser Cladding： Experimental Validation with Laser Cladding of Ti-6AI-4V Powder on a Ti-6AI-4V Substrate

A theoretical processing map for the laser cladding of Ti-6AI-4V powder on a Ti-6AI-4V substrate was developed. The map was constructed with the aid of a new analytical model for laser cladding, which is detailed in this paper. The map is a series of loci that relate laser traversing speed with laser power for a given melt pool depth and clad height. Several of the developed parameters were experimentally trialled on Ti-6Al-4V clad on Ti-6Al-4V and produced clads of sound metallurgical quality. These maps would be useful for industrial engineers developing new cladding procedures or the research engineer developing understanding of the fundamental aspects of laser cladding. Additive manufacturing or laser engineered net shaping （LENS） could also use this type of map for the development of process parameters.

On the development of modular polyurethane-based bioelastomers for rapid hemostasis and wound healing

Massive hemorrhage may be detrimental to the patients,which necessitates the advent of new materials with high hemostatic efficiency and good biocompatibility.The objective of this research was to screen for the effect of the different types of bio-elastomers as hemostatic dressings.3D loose nanofiber sponges were prepared;PU-TA/Gel showed promising potential.Polyurethane(PU)was synthesized and electrospun to afford porous sponges,which were crosslinked with glutaraldehyde(GA).FTIR and 1H-NMR evidenced the successful synthesis of PU.The prepared PU-TA/Gel sponge had the highest porosity and water absorption ratio.Besides,PU-TA/Gel sponges exhibited cytocompatibility,negligible hemolysis and the shortest clotting time.PU-TA/Gel sponge rapidly induced stable blood clots with shorter hemostasis time and less bleeding volume in a liver injury model in rats.Intriguingly,PU-TA/Gel sponges also induced good skin regeneration in a full-thickness excisional defect model as revealed by the histological analysis.These results showed that the PU-TA/Gel-based sponges may offer an alternative platform for hemostasis and wound healing.

Regulation of nerve cells using conductive nanofibrous scaffolds for controlled release of Lycium barbarum polysaccharides and nerve growth factor

Currently,more and more patients suffer from peripheral nerve injury due to trauma,tumor and other causes worldwide.Biomaterial-based nerve conduits are increasingly recognized as a potential alternative to nerve autografts for the treatment of peripheral nerve injury.However,an ideal nerve conduit must offer topological guidance and biochemical and electrical signal transduction mechanisms.In this work,aligned conductive nanofibrous scaffolds comprising polylactic-co-glycolic acid and multiwalled carbon nanotubes(MWCNTs)were fabricated via coaxial electrospinning,and nerve growth factor(NGF)and Lycium barbarum polysaccharides(LBP)purified from the wolfberry were loaded on the core and shell layers of the nanofibers,respectively.LBP were confirmed to accelerate long-distance axon regeneration after severe peripheral nerve injury.In addition,the synergistic promotion of LBP and NGF on nerve cell proliferation and neurite outgrowth was demonstrated.MWCNTs were introduced into the aligned fibers to further increase the electrical conductivity,which promoted the directional growth and neurite extension of neurons in vitro.Further,the combination of conductive fibrous scaffolds with electrical stimulation that mimics endogenous electric fields significantly promoted the differentiation of PC12 cells and the axon outgrowth of neurons.Based on robust cell-induced behaviors,conductive composite fibers with optimized fiber alignment may be used for the promotion of nerve recovery.

Fabrication and characterization of Antheraea pernyi silk fibroin-blended P（LLA-CL） nanofibrous scaffolds for peripheral nerve tissue engineering

Electrospun nanofibers have gained widespreading interest for tissue engineering application. In the present study, ApF/P（LLA-CL） nanofibrous scaffolds were fabricated via electrospinning. The feasibility of the material as tissue engineering nerve scaffold was investigated in vitro. The average diameter increased with decreasing the blend ratio of ApF to P（LLA-CL）. Characterization of 13C NMR and FTIR clarified that there is no obvious chemical bond reaction between ApF and P（LLA-CL）. The tensile strength and elongation at break increased with the content increase of P（LLA-CL）. The surface hydrophilic property of nanofibrous scaffolds enhanced with the increased content of ApF. Cell viability studies with Schwann cells demonstrated that ApFIP（LLA-CL） blended nanofibrous scaffolds significantly promoted cell growth as compare to P（LLA-CL）, especially when the weight ratio of ApF to P（LLA-CL） was 25：75. The present work provides a basis for further studies of this novel nanofibrous material （ApF/P（LLA-CL）） in peripheral nerve tissue repair or regeneration.

Exceeding the limit of plasmonic light trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets

The solar cell market is predominantly based on textured screen-printed solar cells.Due to parasitic absorption in nanostructures,using plasmonic processes to obtain an enhancement that exceeds 2.5%of the short-circuit photocurrent density is challenging.In this paper,a 7.2%enhancement in the photocurrent density can be achieved through the integration of plasmonic Al nanoparticles and wrinkle-like graphene sheets.For the first time,we experimentally achieve Al nanoparticle-enhanced solar cells.An innovative thermal evaporation method is proposed to fabricate low-coverage Al nanoparticle arrays on solar cells.Due to the ultraviolet(UV)plasmon resonance of Al nanoparticles,the performance enhancement of the solar cells is significantly greater than that from Ag nanoparticles.Subsequently,we deposit wrinkle-like graphene sheets over the Al nanoparticle-enhanced solar cells.Compared with planar graphene sheets,the bend carbon layer also exhibits a broadband light-trapping effect.Our results exceed the limit of plasmonic light trapping in textured screen-printed silicon solar cells.

Advanced fabrication for electrospun three-dimensional nanofiber aerogels and scaffolds

Electrospinning is a versatile strategy for creating nanofiber materials with various structures,which has broad application for a myriad of areas ranging from tissue engineering,energy harvesting,filtration and has become one of the most important academic and technical activities in the field of material science in recent years.In addition to playing a significant role in the construction of two-dimensional(2D)nanomaterials,electrospinning holds great promise as a robust method for producing three-dimensional(3D)aerogels and scaffolds.This article reviews and summarizes the recent advanced methods for fabricating electrospun three-dimensional nanofiber aerogels and scaffolds,including gas foaming,direct electrospinning of 3D nanofibrous scaffold,short nanofibers assembling into 3D aerogels/scaffolds,3D printing,electrospray,origami and cell sheet engineering,centrifugal electrospinning,and other methods.Besides,intriguing formation process,crosslinking pathway,properties,and applications of 3D aerogels and scaffolds are also introduced.Taken together,these aerogels and scaffolds with various excellent features present tremendous potential in various fields.

A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction

Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate （A- SA）. Carboxymethyl chitosan was modified with ethylenediamine （ED） in the presence of water-soluble N-（3-Dimethylaminopropyl）-N＇-ethylcarbodiimide hydrochloride （EDC） to introduce additional amino groups to get amino-carboxymethyl chitosan （A-CS）. Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff＇s base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff＇s base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.

Three-dimensional nanoconfinement of broadband optical energy in all-dielectric photonic nanostructure

We demonstrate the confinement of broadband optical energy in the visible to near-infrared regime in a threedimensional nanoscale volume with high energy efficiency in a nanostructure consisting of multiple nanoslits in dielectric chacolgenide material.We find that a broadband optical field can be confined down to the scale of 1 nm(λ∕650)with a confinement volume ofλ3∕3×10^(4).The figure of merit of the nanostructure can be up to 10 times that achieved by plasmonic lensing and nanofocusing.Our work opens a new way for truly nanoscaled photonics applicable to nanolithograpy,nanoimaging,lab-on-chip nanosensing,single-molecule detection,and nanospectroscopy.

GASTROINTESTINAL ABNORMALITIES IDENTIFIED BY FLUORESCENCE ENDOMICROSCOPY

Real-tine in vivo microscopic imaging has becomne a reality with the advent of confocal and nonlinear endomicroscopy.These devices are best utilized in conjunction with standard white light endoscopy.We evaluated the use of fuorescence endomicroscopy in detecting microscopic abnormalities in colonic tisues.Mice of C57bl/6 strain had intraperitoneal injection with azoxymethane once every week for five weeks and littermates,not exposed to azoxymethane served as controls.After 14 weeks,intestines were imaged by fuorescence endomicroscopy.The images show obvious cellular structural diferences between those two groups of mice.The difference in endomicroscopy imaging can be used for identifying tissues suspicious for neoplasia or other changes,leading to early diagnosis of gastrointestinal track of cancer.

Evaluation of a New Design to Improve the Flexibility of the Nucleus Standard Straight Array Cochlear Implant

Cochlear implants can successfully provide auditory information for bilaterally profoundly deaf patients by electrically stimulating auditory nerve fibres via an electrode array, which is surgically implanted into the scala tympani of the cochlea. It is therefore important that the electrode array does not cause damage to the fine intracochlear structures during the process of insertion, as this can result in the loss of spiral ganglion cells, which are necessary for the implant to evoke auditory percepts. There is strong evidence that trauma and damage during insertion of electrode arrays into the human cochlea are related to the stiffness of the electrode array. Previous studies were conducted to experimentally determine the stiffness properties of electrode arrays using three-point flexural bending and buckling tests.In this paper, the design of nucleus straight electrode array is modified to give a greater flexibility to further reduce the risk of trauma to delicate structures of the cochlea during surgical insertion of the electrode array. This is achieved by reducing the cross-sectional area of the electrode array at selected positions over its length. Improvements in the flexibility of the new straight electrode array and the bending behavior at its tip have been demonstrated using finite element analysis. Loads applied to the tip of the electrode array at different angles with respect to the longitudinal axis of the electrode array showed that the modified design caused the tip to be more flexible and therefore better able to curl around the inner spiral of the scala tympani and thus less likely to penetrate the basilar membrane during insertion. Loads applied at other positions along the electrode array showed that bending occurred more readily using the modified design thereby reducing the friction and shear stresses at the contact interface between the electrode array and the delicate cochlea structures.

Multi‑Functional Fibrous Dressings for Burn Injury Treatment with Pain and Swelling Relief and Scarless Wound Healing

As one of the most common forms of skin injuries,skin burns are often accompanied by edema pain,suppuration of infection,slow tissue regeneration,and severe scar formation,which significantly delay wound healing as well as affect the quality of life.We prepared multifunctional electrospun poly(L-lactide-co-glycolide)/gelatin(P/G)-based dressings to synergistically harness the therapeutic benefits of peppermint essential oil(T),burn ointment(B),and Oregano essential oil(O)(P/G@TBO)for skin regeneration in punch and burn injury models.The P/G@TBO can afford the sustained release of bioactive cues for up to 72 h as well as remarkably promote cell migration(ca.P/G@TBO,89%vs.control group,51%)at 24 h.The P/G@TBO membranes also showed significant angiogenic effect as well as antibacterial and anti-inflammatory properties than that of the control group in vitro.Moreover,P/G@TBO dressings enabled fast wound healing(ca.P/G@TBO,100%wound closure vs.control group,95%)in a full-thickness excisional defect model up to 14 days in rats.Further evaluation of membranes in different animal models,including tail wagging model,facial itch model,and hot burn injury model showed significant pain relieve effect as well as itching and swelling relief functions during earlier stages of wound healing.Membranes were next transplanted into a scalded wound model in rats and an ear punch wound model in rabbits,which manifested antibacterial and anti-inflammatory properties and promoted re-epithelialization to achieve scarless wound healing percentage wound closure at day 28:P/G@TBO,96%vs.control group 66%.Taken together our approach of simultaneously harnessing T,B,and O to enable multifunctionality to fibrous dressings may hold great promise for burn wound healing applications and other related disciplines.

A Study of Melt Flow Analysis of an ABS-Iron Composite in Fused Deposition Modelling Process

Fused deposition modelling (FDM) is a filament based rapid prototyping system which offers the possibility of introducing new composite material for the FDM process as long as the new material can be made in feedstock filament form. Swinburne has been undertaking extensive research in development of new composite materials involving acrylonitrile-butadiene-styrene (ABS) and other materials including metals. In order to predict the behaviour of new ABS based composite materials in the course of FDM process, it is necessary to investigate the flow of the composite material in liquefier head. No such study is available considering the geometry of the liquefier head. This paper presents 2-D and 3-D numerical analysis of melt flow behaviour of a representative ABS-iron composite through the 90-degree bent tube of the liquefier head of the fused deposition modelling process using ANSYS FLOTRAN and CFX finite element packages. Main flow parameters including temperature, velocity, and pressure drop have been investigated. Filaments of the filled ABS have been fabricated and characterized to verify the possibility of prototyping using the new material on the current FDM machine. Results provide promising information in developing the melt flow modelling of metal-plastic composites and in optimising the FDM parameters for better part quality with such composites.

In vitro evaluation of electrospun gelatin-glutaraldehyde nanofibers

The gelatin-glutaraldehyde （gelatin-GA） nanofibers were electrospun in order to overcome the defects of ex-situ crosslinking process such as complex process, destruction of fiber morphology and decrease of porosity. The morphological structure, porosity, thermal property, moisture absorption and moisture retention performance, hydrolytic resistance, mechanical property and biocompatibiUty of nanofiber scaffolds were tested and characterized. The gelatin-GA nanofiber has nice uniform diameter and more than 80% porosity. The hydrolytic resistance and mechanical property of the gelatin-GA nanofiber scaffolds are greatly improved compared with that of gelatin nanofibers. The contact angle, moisture absorption, hydrolysis resistance, thermal resistance and mechanical property of gelatin-GA nanofiber scaffolds could be adjustable by varying the gelatin solution concentration and GA content. The gelatin- GA nanofibers had excellent properties, which are expected to be an ideal scaffold for biomedical and tissue engineering applications.

Multifunctional bioactive core-shell electrospun membrane capable to terminate inflammatory cycle and promote angiogenesis in diabetic wound

Diabetic wound(DW)healing is a major clinical challenge due to multifactorial complications leading to prolonged inflammation.Electrospun nanofibrous(NF)membranes,due to special structural features,are promising biomaterials capable to promote DW healing through the delivery of active agents in a controlled manner.Herein,we report a multifunctional composite NF membrane loaded with ZnO nanoparticles(NP)and oregano essential oil(OEO),employing a new loading strategy,capable to sustainedly co-deliver bioactive agents.Physicochemical characterization revealed the successful fabrication of loaded nanofibers with strong in vitro anti-bacterial and anti-oxidant activities.Furthermore,in vivo wound healing confirmed the potential of bioactive NF membranes in epithelialization and granulation tissue formation.The angiogenesis was greatly prompted by the bioactive NF membranes through expression of vascular endothelial growth factor(VEGF).Moreover,the proposed NF membrane successfully terminated the inflammatory cycle by downregulating the pro-inflammatory cytokines interleukin6(IL-6)and matrix metalloproteinases-9(MMP-9).In vitro and in vivo studies revealed the proposed NF membrane is a promising dressing material for the healing of DW.

Review of Laser Assisted Machining of Ceramics (Invited Paper)

Laser assisted machining(LAM) takes the advantages of local heating and softening of workpiece by laser beam in front of the cutting tool.The local softening of workpiece at the shear zone enables much easier plastic deformation during machining.This paper reviews the up-to-date progress on LAM of ceramics.It covers the laser beam integration with cutting tools,analysis of temperature distribution around the cutting region,material removal mechanism,tool wear mechanism,and optimization of LAM.The benefit of LAM and its optimization are discussed in terms of material removal temperature.

Electrospinning:An emerging technology to construct polymer-based nanofibrous scaffolds for diabetic wound healing

A chronic wound in diabetic patients is a major public health concern withsocioeconomic and clinical manifestations.The underlying medical condition of diabeticpatients deteriorates the wound through physiological,metabolic,molecular,and cellularpathologies.Consequently,a wound enters a vicious pathological inflammatory cycle.Many therapeutic approaches are in practice to manage diabetic wounds hence ensuringthe regeneration process.Polymer-based biomaterials have come up with hightherapeutic promises.Many efforts have been devoted,over the years,to build aneffective wound healing material using polymers.The electrospinning technique,although not new,has turned out to be one of the most effective strategies in buildingwound healing biomaterials due to the special structural advantages of electrospunnanofibers over the other formulations.In this review,careful integration of allelectrospinning approaches has been presented which will not only give an insight intothe current updates but also be helpful in the development of new therapeutic materialconsidering pathophysiological conditions of a diabetic wound.