Liquid Metal-Based Self-Healable and Elastic Conductive Fiber in Complex Operating Conditions

Flexible conductive fibers are essential for wearable electronics and smart electronic textiles.However,in complex operating conditions,conductive fibers will inevitably fracture or damage.Herein,we have developed an elastic conductive self-healable fiber(C-SHF),of which the electrical and mechanical properties can efficiently heal in a wide operating range,including room temperature,underwater,and low temperature.This advantage can be owed to the combination of reversible covalent imine bond and disulfide bond,as well as the instantaneous self-healing ability of liquid metal.The C-SHF,with stretchability,conductivity stability,and universal self-healing properties,can be used as an electrical signal transmission line at high strain and under different operating conditions.Besides,C-SHF was assembled into a double-layer capacitor structure to construct a self-healable sensor,which can effectively respond to pressure as a wearable motion detector.

Stretchable and self-healing conductive fibers from hierarchical silver nanowires-assembled network

Conductive fibers(CFs)with features of high conductivity,stretchability,self-healability,and electromechanical stability are key components of the increasingly popular wearable electronics.However,since the lack of structural design of conductive network and interfacial interaction between soft polymer and conductive additives,it is still hard to enable CFs to meet above requirements.Here,we describe a facial drawing method from a hydrogel reservoir which is remolded into ultrathin and stretchable CFs with excellent multi-responsive self-healability.The hydrogel reservoir was fabricated in synergy of an ice-templating method and in situ polymerization using the assembled framework as a crosslinker.Relying on the effective fabrication mechanism,the diameter of CFs could be well-tuned from 90 to 400μm by adjusting the dipping depth of the glass rod,accompanied with conductivity increased from 0.75 to 2.5 S/m.Since the hierarchical network structure was well maintained in the CFs,professional performances have been proved on the stretchability and electromechanical stability.The presence of massive hydrogen bonding and Ag–S bond enabled the CFs with excellent self-healability under the conditions of contact,electric field,and near infrared light,respectively.Excitingly,the CFs with high sensing property could be integrated into an advanced textile sensor through an effective healing-induced integration strategy,demonstrating its great potentials as superior two-dimensional(2D)electronic skins.

Conductive fibers for biomedical applications

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues.Thus,various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration,or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals.Benefiting from the outstanding advantages of flexibility,structural diversity,customizable mechanical properties,and tunable distribution of conductive components,conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment,in return to ensure stable functioning of such constructs during physiological deformation.Herein,this review starts by presenting current fabrication technologies of conductive fibers including wet spinning,microfluidic spinning,electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies.To provide an update on the biomedical applications of conductive fibers and fiber assemblies,we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration,implantable healthcare bioelectronics,and wearable healthcare bioelectronics.To conclude,current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Highly conductive fiber with design of dual conductive Ag/CB layers for ultrasensitive and wide-range strain sensing

Recently the ever-increasing demand for wearable electronics has greatly triggered the development of flexible strain sensors.However,it is still challenging to simultaneously achieve high sensitivity,wide working range,and good wearability.Herein,we developed a highly stretchable fiber strain sensor based on wet-spun porous polyurethane(PU)fiber,and especially a unique conductive network of dual silver(Ag)/carbon black(CB)layers is constructed.Under strain,the rapid crack propagation on the brittle Ag layer brings a large resistance change and thus high sensitivity,while the tunneling-effect dominated CB layer bridges the separated Ag islands to maintain the integrity of conductive pathways under large strain.By means of the synergistic effect of Ag/CB layers,this composite fiber of Ag/CB@PU presents not only high conductivity of 5139.9 S/m,but also ultrahigh sensitivity with a gauge factor of 2.52×10^(6) and a wide working range of up to 200%.Besides that,it is also capable of detecting very tiny strain of 0.1%and working stably for over 8000 cycles.Using mature weaving technology,this fiber strain sensor can be seamlessly integrated into the textile to conformally track different movements of the human body.Together with the facile all-solution-based fabrication protocol,this work proposed a new strategy to prepare high-performance fiber strain sensor,promising the textile-based wearable applications.

Conductive Polyacrylonitrile Fiber Prepared by Copper Plating with L-Ascorbic Acid as Reducing Agent

Conductive polyacrylonitrile fibers were prepared by electroless copper plating under weak alkaline conditions,with L-ascorbic acid as reducing agent.The influences of CuSO_(4)·5H_(2)O,L-ascorbic acid,2,2′-bipyridine and K_(4)Fe(CN)_(6) concentration on the conductivity and mass gain percentage of the fibers were studied.The morphological structure of the fibers was characterized by scanning electron microscopy(SEM),and the mechanical properties of the fibers were analyzed through the mechanical property test.The results showed that the optimal reaction conditions were as follows:26 g/L CuSO_(4)·5H_(2)O,26 g/L L-ascorbic acid,12 mg/L 2,2′-bipyridine,7 mg/L K 4Fe(CN)6,and 38℃.The volume resistivity of the conductive PAN fibers prepared by the process was only 3.84×10^(-3)Ω·cm.

Preparation of Core/Shell Electrically Conductive Fibers by Efficient Coating Carbon Nanotubes on Polyester

Conducting fibers with improved properties and functionalities are needed for diverse applications.Here we report the fabrica-tion of core/shell conductive Dacron fibers by dip-coating method through originating from multi-walled carbon nanotubes(MWCNTs)coated on polyester fibers.The annealing process was conducted to enhance interaction between the conductive shell and polyester core as well as within the MWCNTs network.The properties of two kinds of MWCNTs dispersions and the electrical properties of conductive fibers were studied,respectively.The results show that both MWCNTs-polyurethane resin(MWCNTs-WPU)dispersion and MWCNTs-acrylic resin(MWCNTs-PAA)dispersion present a typical characteristic of pseudo-plastic fluid and an excellent wetting ability to polyester fibers.The ultimate tensile stress and elongation at break for the MWCNTs-PAA coated fiber are 261 MPa and 25.43%.The ultimate tensile stress and the elongation at break are both increasing with the increasing of MWCNTs contents,due to the strong interface bonding ability between the conduc-tive shell and polyester core and strengthen the MWCNTs network.The electrical resistance of the obtained fibers can be controlled in the range from 732 to 30Ω/cm by changing MWCNTs content,dipping times and annealing temperature.It was found that it is able to light a LED.All results suggest that the conductive fibers embody a good synergy effect of carbon nanotubes and polymers.Therefore,the fabricated conductive fibers have a widely prospect for being applied in the field of flexible electronics.

Water-Resistant and Stretchable Conductive Ionic Hydrogel Fibers Reinforced by Carboxymethyl Cellulose

Conductive ionic hydrogels(CIH)have been widely studied for the development of stretchable electronic devices,such as sensors,electrodes,and actuators.Most of these CIH are made into 3D or 2D shape,while 1D CIH(hydrogel fibers)is often difficult to make because of the low mechanical robustness of common CIH.Herein,we use gel spinning method to prepare a robust CIH fiber with high strength,large stretchability,and good conductivity.The robust CIH fiber is drawn from the composite gel of sodium polyacrylate(PAAS)and sodium carboxymethyl cellulose(CMC).In the composite CIH fiber,the soft PAAS presents good conductivity and stretchability,while the rigid CMC significantly enhances the strength and toughness of the PAAS/CMC fiber.To protect the conductive PAAS/CMC fiber from damage by water,a thin layer of hydrophobic polymethyl acrylate(PMA)or polybutyl acrylate(PBA)is coated on the PAAS/CMC fiber as a water-resistant and insulating cover.The obtained PAAS/CMC-PMA and PAAS/CMC-PBA CIH fibers present high tensile strength(up to 28 MPa),high tensile toughness(up to 43 MJ/m~3),and good electrical conductivity(up to 0.35 S/m),which are useful for textile-based stretchable electronic devices.

STUDY ON THE CONDUCTING FIBER REINFORCED PLASTIC

The conductive fiber reinforced plastic was prepared by dispersing electrical conducting filler particles such as aluminum powder, graphite and carbon black to glass fiber reinforced resin. The effects that each or double kinds of fillers, also the conductive fiber cloth had done on the electrical and mechanical properties of plastic composites were studied. This paper also provided discussion on the conductive mechanism of fiber reinforced plastic. (Author abstract) 8 Refs.

Performance improvement of continuous carbon nanotube fibers by acid treatment

Continuous CNT fibers have been directly fabricated in a speed of 50 m/h-400 m/h,based on an improved chemical vapor deposition method.As-prepared fibers are further post-treated by acid.According to the SEM images and Raman spectra,the acid treatment results in the compaction and surface modification of the CNTs in fibers,which are beneficial for the electron and load transfer.Compared to the HNO3 treatment,HClSO_3 or H_2SO_4 treatment is more effective for the improvement of the fibers＇ properties.After HCISO_3 treatment for 2 h,the fibers＇ strength and electrical conductivity reach up to-2 GPa and-4.3 MS/m,which are promoted by-200%and almost one order of magnitude than those without acid treatment,respectively.The load-bearing status of the CNT fibers are analyzed based on the downshifts of the G＇ band and the strain transfer factor of the fibers under tension.The results reveal that acid treatment could greatly enhance the load transfer and inter-bundle strength.With the HCISO3 treatment,the strain transfer factor is enhanced from-3.9%to-53.6%.

Stretchable electrothermochromic fibers based on hierarchical porous structures with electrically conductive dual-pathways

Stretchable color-changing fibers are urgently demanded for smart textiles/clothing due to their perfect implantability,permeability of vapor and heat,and flexibility/stretchability.Herein,stretchable electrothermochromic fibers were fabricated with unconventional stretchable conductive fibers as core layers and thermochromic coatings as shell layers.In the stretchable conductive fibers,hierarchical porous structures with percolative one-dimensional(1 D)conductive networks were constructed through phase inversion of carbon nanotube/polyurethane(CNT/PU)solutions.With the deposition of silver nanoparticles(AgN Ps)on the surface of micro-pores,electrically conductive dual-pathways consisting of0 D AgN Ps and 1 D CNTs were formed to significantly enhance the electric conductivity and thus improve the electrothermal performance of the fibers.More importantly,because of the connective CNTs and AgN Ps,such dual-pathways ensured the electron transport under the stretching state,preventing the sharp decay of conductivity and electrothermal performance.Through the continuous wet-spinning method,the stretchable conductive fibers can be easily obtained with the length up to several meters.At last,stretchable electrothermochromic fibers were prepared with two color-changing modes and implanted into textile perfectly,advancing their applications in wearable display and military adaptive camouflage of smart clothing.

Advanced Fiber Materials for Wearable Electronics

Fiber materials are highly desirable for wearable electronics that are expected to be flexible and stretchable.Compared with rigid and planar electronic devices,fiber-based wearable electronics provide significant advantages in terms of flexibility,stretchability and breathability,and they are considered as the pioneers in the new generation of soft wearables.The con-vergence of textile science,electronic engineering and nanotechnology has made it feasible to build electronic functions on fibers and maintain them during wear.Over the last few years,fiber-shaped wearable electronics with desired designability and integration features have been intensively explored and developed.As an indispensable part and cornerstone of flexible wearable devices,fibers are of great significance.Herein,the research progress of advanced fiber materials is reviewed,which mainly includes various material preparations,fabrication technologies and representative studies on different wearable applications.Finally,key challenges and future directions of fiber materials and wearable electronics are examined along with an analysis of possible solutions.

MXene fibers for electronic textiles:Progress and perspectives

The rapid evolution of portable and wearable electronic devices has fueled the development of smart functional textiles that are able to conduct electricity,sense body movements,or store energy.One main challenge inhibiting the further development of functional textile-based electronics is the lack of robust functional fibers with suitable electrical,electrochemical and sensing functionalities.MXenes,an emerging family of two-dimensional(2D)materials,have shown to be promising candidates for producing functional fibers due to their exceptional electrical and electrochemical properties combined with solution processability.The unique ability of MXenes to readily form liquid crystal phases in various solvents has allowed them to generate additive-free fibers using a wet spinning process.In this work,we review the recent exciting developments in the fabrication of neat MXenes fibers and present a critical evaluation of practical challenges in MXenes processing that influence the macroscale material properties and the performance of the subsequent devices.We also provide our assessment for the future opportunities and challenges in producing MXene fibers to help pave the way for their widespread use in advanced wearable applications.

Recent Progress for Gallium-Based Liquid Metal in Smart Wearable Textiles

The development of smart textiles has presentend new requirements for integrated devices that can be compatible with both conductivity and deformation.At room temperature,liquid metal presents both metallic properties and flexible properties,as well as low toxicity and biocompatible,which makes it more and more popular on the research of liquid metal based electronic devices.This review summarizes the basic physical properties,and the key points to be fabricated into fibers and fabrics including oxides and wettability.Meantime,the application in the field of textiles is presented.Liquid metal based electrical conductive fibers and flexible sensors can be fabricated mainly by injection and printing,as well as direct-writing for smart fabrics.Liquid metal can be integrated as functional components for smart wearable devices in the future by assembling the as-prepared fibers and fabrics with textile technology,such as twisting,sewing,knitting,and embroidering.

Liquid Metal Fibers

Liquid metal(LM)is a type of metal or alloy that has a low melting point near room temperature and exhibits the properties of both liquids and metals.Such unconventional materials have been gaining increasing attention within the scientific and industrial communities.Recently,fiber-shaped LM and its composites have especially attracted diverse interest owing to their unique merits,such as excellent conductivity,intrinsic stretchability,facile phase transition,and the ability to be woven or knitted into smart fabrics.This review is dedicated to summarizing different aspects of LM-based fibers,such as their material components,fabrication and design strategies,and remarkable applications by way of their representative properties.Typical fabrication approaches,such as 3D printing of pure LM wire,coating the LM shell on the surface of the fiber,injecting a LM core into hollow fibers,and spinning of LM and polymer hybrids have been comparatively illustrated.Moreover,emerging applications that primarily utilize LM fibers have been demonstrated.Finally,future directions and opportunities in the field are discussed.This categorization of LM fibers is expected to facilitate further investigation and practice in the coming society.

Clinical Characteristics, Electrophysiology, and Skin Biopsy of 38 Peripheral Neuropathy Cases with Small Fiber Involvement of Various Etiologies

Background：In small fiber neuropathy （SFN）,thinly myelinated Aδ and unmyelinated C fibers are primarily affected,resulting in sensory and/or autonomic symptoms.Various etiologies have been shown to be associated with SFN.This study was aimed to analyze a variety of features in peripheral neuropathy （PN） with small fiber involvement.and to compare disease severity among patients with idiopathic PN,PN associated with impaired glucose tolerance （IGT）,and metabolic syndrome （MS） PN.Methods：Thirty-eight PN patients with small fiber involvement were enrolled from December 20,2013 to May 31,2016.Patients were divided into idiopathic PN,IGT-related PN,and MS-related PN groups.Detailed medical history and small fiber neuropathy were investigated,and symptom inventory questionnaire was conducted,as well as the visual analog scale.Nerve conduction studies and skin biopsies were also performed.The differences among the groups were analyzed using analysis of variance and Kruskal-Wallis test.Results：Eight patients were diagnosed with pure SFN.lntraepidermal nerve fiber density （I ENFD） weakly correlated with motor conduction velocity （MCV） （r =0.372,P =0.025）,and proximal （r =0.383,P =0.021） and distal （r =0.358,P 0.032） compound muscle action potential （CMAP） of the tibial nerve.IENFD also weakly correlated with MCV of the peroneal nerve （r=0.399,P =0.016）.IENFD was shown to be significantly different among all groups （x2 =9.901,P-0.007）.IENFD was significantly decreased （x2 =23.000,P=0.003） in the MS-related PN group compared to the idiopathic PN group.The MCV of the tibial nerve was significantly different among all groups （x2 =8.172,P 〈 0.017）.The proximal （F =4.336,P =0.021） and distal （F =3.262,P =0.049） CMAP of the tibial nerve was also significantly different among all groups.Conclusions：IENFD of patients included in the present study weakly correlated with various electrophysiological parameters.Small and large fibers are more involved in patients with MS-related PN than in patients with idiopathic PN.

Facile and Large-scale Fabrication of Self-crimping Elastic Fibers for Large Strain Sensors

Stretchable conductive fibers offer unparalleled advantages in the development of wearable strain sensors for smart textiles due to their excellent flexibility and weaveability.However,the practical applications of these fibers in wearable devices are hindered by either contradictory properties of conductive fibers(high stretchability versus high sensing stability),or lack of manufacturing scalability.Herein,we present a facile approach for highly stretchable self-crimping fiber strain sensors based on a polyether-ester(TPEE)elastomer matrix using a side-by-side bicomponent melt-spinning process involving two parallel but attached components with different shrinkage properties.The TPEE component serves as a highly elastic mechanical support layer within the bicomponent fibers,while the conductive component(E-TPEE)of carbon black(CB),multiwalled carbon nanotubes(MWCNTs)and TPEE works as a strain-sensitive layer.In addition to the intrinsic elasticity of the matrix,theTPEE/E-TPEE bicomponent fibers present an excellent form of elasticity due to self-crimping.The self-crimping elongation of the fibers can provide a large deformation,and after the crimp disappears,the intrinsic elastic deformation is responsible for monitoring the strain sensing.The reliable strain sensing range of theTPEE/E-TPEE composite fibers was 160%-270%and could be regulated by adjusting the crimp structure.More importantly,the TPEE/E-TPEE fibers had a diameter of 30-40 pm and tenacity of 40-50 MPa,showing the necessary practicality.This work introduces new possibilities for fiber strain sensors produced in standard industrial spinning machines.

Seamlessly-integrated Textile Electric Circuit Enabled by Self-connecting Interwoven Points

Flexible,breathable and lightweight electronic textiles hold great promise to change the ways we intact with electronics.Electrical connections among functional components are indispensable for system integrations of electronic textiles.However,it remains challenging to achieve mechanically and electrically robust connections to fully integrate with interwoven architecture and weaving process of textiles.Here,we reported a seamlessly-integrated textile electric circuit by weaving conductive fibers with self-connecting capacity at the interwoven points.Selfconnecting conductive fibers(SCFs)were prepared by coating modified polyurethane conductive composites onto nylon fibers.Electrical connections were achieved at interwoven points in less than 5 s once the weft and warp SCFs were woven together,due to the designed dynamic bonds of aromatic disulfide metathesis and hydrogen bonds in the modified polyurethane(MPU).The self-connecting point was electrically stable(varied by less than 6.7%in electrical resistance)to withstand repeated deformations of bending,pressing and even folding.Such a selfconnecting strategy could be generalized to weave full-textile electronics capable of receiving signals and displaying with enhanced interfacial stability,offering a new way to unify fabrication of electronics and weaving of textiles.