Ignition processes and characteristics of charring conductive polymers with a cavity geometry in precombustion chamber for applications in micro/nano satellite hybrid rocket motors

The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.

PEDOT:PSS:From conductive polymers to sensors

PEDOT:PSS conductive polymers have received tremendous attention over the last two decades owing to their high conductivity,ease of processing,and biocompatibility.As a flexible versatile material,PEDOT:PSS can be developed into various forms and has had a significant impact on emerging sensing applications.This review covers the development of PEDOT:PSS from material to physical sensors.We focus on the morphology of PEDOT:PSS in the forms of aqueous dispersions,solid films,and hydrogels.Manufacturing processes are summarized,including coating,printing,and lithography,and there is particular emphasis on nanoimprinting lithography that enables the production of PEDOT:PSS nanowires with superior sensing performance.Applications to various physical sensors,for humidity,temperature,pressure,and strain,are demonstrated.Finally,we discuss the challenges and propose new directions for the development of PEDOT:PSS.

Recent progress in design of conductive polymers to improve the thermoelectric performance

Organic semiconductors,especially polymer semiconductors,have attracted extensive attention as organic thermoelectric materials due to their capabilities for flexibility,low-cost fabrication,solution processability and low thermal conductivity.However,it is challenging to obtain high-performance organic thermoelectric materials because of the low intrinsic carrier concentration of organic semiconductors.The main method to control the carrier concentration of polymers is the chemical doping process by charge transfer between polymer and dopant.Therefore,the deep understanding of doping mechanisms from the point view of chemical structure has been highly desired to overcome the bottlenecks in polymeric thermoelectrics.In this contribution,we will briefly review the recently emerging progress for discovering the structure–property relationship of organic thermoelectric materials with high performance.Highlights include some achievements about doping strategies to effectively modulate the carrier concentration,the design rules of building blocks and side chains to enhance charge transport and improve the doping efficiency.Finally,we will give our viewpoints on the challenges and opportunities in the field of polymer thermoelectric materials.

Additive manufacturing(3D printing)of electrically conductive polymers and polymer nanocomposites and their applications

Additive manufacturing,or three-dimensional(3D)printing,offers a unique solution for fabricating complex geometries with high tolerances.Currently,many commercial additive manufacturing machines focus on the printing of polymers with limited functionalities.However,conductive polymers(CPs)can be processed to enable the additive manufacturing of conductive,low-density,and low-cost parts for a myriad of applications.This review summarizes the relevant achievements in the additive manufacturing of conductive polymers(CPs)and conductive polymer nanocomposites,with a discussion of the advantages and limitations of processing and printing these materials compared with alternative traditional manufacturing methods and their properties.Finally,the prospective applications of these additive manufacturing printed conductive materials are explored.

Flexible Polydimethylsiloxane Composite with Multi-Scale Conductive Network for Ultra-Strong Electromagnetic Interference Protection

Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.

Wearable and stretchable conductive polymer composites for strain sensors:How to design a superior one?

Wearable and stretchable strain sensors have potential values in the fields of human motion and health monitoring,flexible electronics,and soft robotic skin.The wearable and stretchable strain sensors can be directly attached to human skin,providing visualized detection for human motions and personal healthcare.Conductive polymer composites(CPC)composed of conductive fillers and flexible polymers have the advantages of high stretchability,good flexibility,superior durability,which can be used to prepare flexible strain sensors with large working strain and outstanding sensitivity.This review has put forward a comprehensive summary on the fabrication methods,advanced mechanisms and strain sensing abilities of CPC strain sensors reported in recent years,especially the sensors with superior performance.Finally,the structural design,bionic function,integration technology and further application of CPC strain sensors are prospected.

Alcohol-dispersed polymer complex as an effective and durable interface modifier for n-i-p perovskite solar cells

Abundant interfacial defects remain a significant challenge that hampers both the efficiency and stability of perovskite solar cells(PSCs).Herein,an alcohol-dispersed conducting polymer complex,denoted as PEDOT:F(Poly(3,4-ethylene dioxythiophene):Perfluorinated sulfonic acid ionomers),is introduced into the interface between perovskite and hole transporting layer in regular-structured PSCs.PEDOT:F serves as a multi-functional interface layer(filling grain boundaries and covering perovskite's grain-surface)to achieve a robust interaction with organic groups within perovskites,which could induce a structural transformation of PEDOT to increase its conductivity for the efficient hole-transport.Furthermore,the strong interaction between PEDOT and perovskites could promote an effective coupling of undercoordinated Pb~(2+)ions with the lone electron pairs near O&S atoms in PEDOT molecules,thereby enhancing defect passivation.Additionally,PEDOT:F with inherent hydrophobic properties prevents effectively moisture invasion into perovskites for the improved long-term stability of the PSCs.Consequently,the PEDOT:F-based PSCs achieved a champion efficiency of 24.81%,and maintained ca.92%of their initial efficiency after 7680 h of storage in a dry air environment,accompanied by the enhanced photothermal stability.

Highly Elastic,Bioresorbable Polymeric Materials for Stretchable,Transient Electronic Systems

Substrates or encapsulants in soft and stretchable formats are key components for transient,bioresorbable electronic systems;however,elastomeric polymers with desired mechanical and biochemical properties are very limited compared to nontransient counterparts.Here,we introduce a bioresorbable elastomer,poly(glycolide-co-ε-caprolactone)(PGCL),that contains excellent material properties including high elongation-at-break(<1300%),resilience and toughness,and tunable dissolution behaviors.Exploitation of PGCLs as polymer matrices,in combination with conducing polymers,yields stretchable,conductive composites for degradable interconnects,sensors,and actuators,which can reliably function under external strains.Integration of device components with wireless modules demonstrates elastic,transient electronic suture system with on-demand drug delivery for rapid recovery of postsurgical wounds in soft,time-dynamic tissues.

Recent progress and future research directions for electrochromic zinc-ion batteries

In recent times,future energy storage systems demand a multitude of functionalities beyond their traditional energy storage capabilities.In line with this technological shift,there is active research and development of electrochromic-energy storage systems designed to visualize electrochemical charging and discharging processes.The conventional electrochromic-energy storage devices primarily integrated supercapacitors,known for their high power density,to enable rapid color contrast.However,the low energy density of supercapacitors restricts overall energy storage capacity,acting as a significant barrier to expanding the application range of such systems.In this review,we introduce electrochromic zinc(Zn)-ion battery systems,which effectively overcome the limitation of low energy density,and provide illustrative examples of their applicability across diverse fields.Although many recent research works are present for electrochromic Zn-ion batteries,little review has so far taken place.Our objective is to discuss on the current progress and future directions for electrochromic Zn-ion batteries,which are applicable for wearable electronics applications and energy storage systems.This review provides an initial milestone for future researchers in electrochromic energy storage and zinc-ion batteries,which will lead to a stream of future works related to them.

Biomimetic Synthesized Conductive Copolymer EDOT-Pyrrole Electrodes for Electrocardiogram Recording in Humans

We report on electrodes fabricated with EDOT-Pyrrole copolymer through electrophoretic deposition and used for recording and sensing bio-electrical signals. We measured the electrical properties of the copolymer deposited on a stainless-steel substrate, and we performed Cyclic Voltammetry (CV) and Scanning Electron Microscopy (SEM) studies to characterize the morphological properties and copolymer distribution on the metal surface. We found that electrodes fabricated with EDOT-Pyrrole copolymer exhibit a high signal-to-noise ratio as well as an accurate and stable conductivity compared with other commonly used electroconductive polymers. Stainless-steel-coated EDOT-Pyrrole electrodes are suitable to record electrocardiograms in humans with high resolution comparable to standard silver-electrodes.

Breaking Through Bottlenecks for Thermally Conductive Polymer Composites:A Perspective for Intrinsic Thermal Conductivity,Interfacial Thermal Resistance and Theoretics

Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers,carbon nanomaterials,or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering,owing to the similar conductivity to human skin,good antioxidant and antibacterial activities,electrically controlled drug delivery,and photothermal effect.However,a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking.In this review,the design and fabrication methods of conductive biomaterials with various structural forms including film,nanofiber,membrane,hydrogel,sponge,foam,and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized.The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies(electrotherapy,wound dressing,and wound assessment)were reviewed.The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound(infected wound and diabetic wound)and for wound monitoring is discussed in detail.The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Mussel‑Inspired Redox‑Active and Hydrophilic Conductive Polymer Nanoparticles for Adhesive Hydrogel Bioelectronics

Conductive polymers(CPs)are generally insoluble,and developing hydrophilic CPs is significant to broaden the applications of CPs.In this work,a mussel-inspired strategy was proposed to construct hydrophilic CP nanoparticles(CP NPs),while endowing the CP NPs with redox activity and biocompatibility.This is a universal strategy applicable for a series of CPs,including polyaniline,polypyrrole,and poly(3,4-ethylenedioxythiophene).The catechol/quinone contained sulfonated lignin(LS)was doped into various CPs to form CP/LS NPs with hydrophilicity,conductivity,and redox activity.These CP/LS NPs were used as versatile nanofillers to prepare the conductive hydrogels with long-term adhesiveness.The CP/LS NPs-incorporated hydrogels have a good conductivity because of the uniform distribution of the hydrophilic NPs in the hydrogel network,forming a well-connected electric path.The hydrogel exhibits long-term adhesiveness,which is attributed to the mussel-inspired dynamic redox balance of catechol/quinone groups on the CP/LS NPs.This conductive and adhesive hydrogel shows good electroactivity and biocompatibility and therefore has broad applications in electrostimulation of tissue regeneration and implantable bioelectronics.

ELECTROACTIVE AND NANOSTRUCTURED POLYMERS AS SCAFFOLD MATERIALS FOR NEURONAL AND CARDIAC TISSUE ENGINEERING

Conducting polymer, polyaniline （PANI）, has been studied as a novel electroactive and electrically conductive material for tissue engineering applications. The biocompatibility of the conductive polymer can be improved by （i） covalently grafting various adhesive peptides onto the surface of prefabricated conducting polymer films or into the polymer structures during the synthesis, （ii） co-electrospinning or blending with natural proteins to form conducting nanofibers or films, and （iii） preparing conducting polymers using biopolymers, such as collagen, as templates. In this paper, we mainly describe and review the approaches of covalently attaching oligopeptides to PANI and electrospinning PANI-gelatin blend nanofibers. The employment of such modified conducting polymers as substrates for enhanced cell attachment, proliferation and differentiation has been investigated with neuronal PC-12 cells and H9c2 cardiac myoblasts. For the electrospun PANI- gelatin fibers, depending on the concentrations of PANI, H9c2 cells initially displayed different morphologies on the fibrous substrates, but after one week all cultures reached confluence of similar densities and morphologies. Furthermore, we observed, that conductive PANI, when maintained in an aqueous physiologic environment, retained a significant level of electrical conductivity for at least 100 h, even though this conductivity was decreasing over time. Preliminary data show that the application of micro-current stimulates the differentiation of PC-12 cells. All the results demonstrate the potential for using PANI as an electroactive polymer in the culture of excitable cells and open the possibility of using this material as an electroactive scaffold for cardiac and/or neuronal tissue engineering applications that require biocompatibility of conductive polymers.

A Novel Method for Preparing Polyurethane Based Conductive Composites with Low Percolation Threshold

A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise in carbon black concentration the insulator-conductor transition in the emulsion blended composites occurs at 0.8-1.4vol%. In contrast, the solution blended composites exhibit drastic increase in conductivity at conducting filler fraction as high as 12.3-13.3vol%. It is demonstrated that the composites microstructure rather than chemical structure of the matrix polymer predominantly determines the electrical conduction performance of the composites.

LOW POTENTIAL ELECTROPOLYMERIZATION OF ANISOTROPIC CONDUCTIVE POLYTHIOPHENE FILMS AND FABRICATION OF ELECTRICAL DEVICES

The Complexation of thiophene with a Lewis acid with moderate acidity as a solvent, such as BF3-ethyl ether (BFEE) remarkedly lowered the electrochemical polymerization potential. The positively charged metal surface of electrode in the process of electrochemical deposition enhanced the coordination interaction between pi-electrons of thiophene unit and the metal, which makes thiophene rings lie parallel to the surface of electrode, resulting in a highly ordered polymeric structure. Because of the large intra-chain transfer integrals, the transport of charge is believed to be principally along the conjugated chains, which is much greater than the inter-chain hopping. The specific electrical resistance across the polythiophene film thickness is more than 10(4) times than that along the surface plane of the film. In this paper we review the recent development of polymerization technique by low potential electrochemical method performed in our lab and several electrical devices in which the compact polythiophene films, such as anionic and cationic sieves, and laminate film junction of undoped polythiophene derivatives were used.

A review on electronically conducting polymers for lithium-sulfur battery and lithium-selenium battery:Progress and prospects

Lithium-sulfur(Li-S) batteries and lithium-selenium(Li-Se) batteries,as environmental protection energy storage systems with outstanding theoretical specific capacities and high energy densities,have become the hotspots of current researches.Besides,elemental S(Se) raw materials are widely sourced and their production costs are both low,which make them considered one of the new generations of high energy density electrochemical energy storage systems with the most potential for development.However,poor conductivity of elemental S/Se and the notorious "shuttle effect" of lithium polysulfides(polyselenides) severely hinder the commercialization of Li-S/Se batteries.Thanks to the excellent electrical conductivity and strong absorption of lithium polysulfide(polyselenide) about electronically conducting polymer,some of the above thorny problems have been effectively alleviated.The review presents the fundamental studies and current development trends of common electronically conducting polymers in various components of Li-S/Se batteries,which involves polyaniline(PANI) polypyrrole(PPy),and polythiophene(PTh) with its derivatives,e.g.polyethoxythiophene(PEDOT) and poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS).Finally,the review not only summarizes the research directions and challenges facing the application of electronically conducting polymers,but also looks forward to the development prospects of them,which will provide a way for the practical use of electronically conducting polymers in Li-S/Se batteries with outstanding electrochemical properties in the short run.

FERROFLUID CONTAINING SOLUBLE CONDUCTIVE POLYANILINE AND ITS FREESTANDING FILMS

Ferrofluid containing highly conductive polyaniline (PANI) was prepared, in which soluble PANI solutions dopedwith 10-camphorsulfonic acid (CSA) and dodecyl benzenesulfonic acid (DBSA) were used as the basic solution and Fe_3O_4nanoparticles (d = 10 nm) as the magnetic material. Moreover, the freestanding films of the resulting ferrofluid can beobtained by an evaporation method. The electrical and magnetic properties of the ferrofluid or its films can be adjustedthrough changing the content of PANI and Fe_3O_4. High saturated magnetization (≈ 30 emu/g) and high conductivity(≈ 250 S/cm) of the composite films can be achieved when the composite film contains 26.6 wt% of Fe_3O_4. In particular, itwas found that the composite films exhibit a super-paramagnetic behavior (Hc = 0) attributed to the size of Fe_3O_4 particles on the nanometer scale.

STUDIES ON ENHANCED CONDUCTIVITY OF STRETCHED CONDUCTING POLYMERS

A physical model of series of the conductivity on chain and the interchain conductivitybetween chains is proposed to explain enhanced conductivity of stretched conducting polymers.This model suggests that the enhanced conductivity for stretched conducting polymers might bedue to increasing of the interchain conductivity between chains along the elongation direction afterdrawing processes if the conductivity on chain is assumed much larger than that of the interchainconductivity between chains. According to this model, it is expected that the temperaturedependence of conductivity measured by four-probe method for stretched conducting polymers iscontrolled by a variation of the interchain conductivity between chains with temperature, whichcan be used to explain that a metallic temperature dependence of conductivity for stretchedconducting polymers is not observed although the conductivity along the elongation direction isenhanced by two or three orders of magnitude.

Spin Filter Effect in Organic Polymers in the Presence of Local Magnetic Field

Using a nonadiabatic evolution method, we investigate the spin filter effect in organic polymers in the presence of a local magnetic field. Through a spin-dependent magnetic field, polarons （charge carrier） with different spins will feel repulsive or attractive force determined by their spins. Our simulations show that in a single-site magnetic field （affecting electrons at a single site）, for example V150 = 0.35 eV, or V150 = 0.45 eV, a spin-up polaron accelerated to saturated velocity by an electric field can pass through the field while the spin-down polaron is trapped. When the local field extends over several sites （Vn～ exp[-（n - nc）2/nw^2]）, similar behaviour is also found. Simultaneously we find that it is more likely to realize the spin filter effect in a comparatively large field since the polaron which feels attractive force is easily trapped by a local magnetic field.