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Self-lubricating polyphenylene sulfide (PPS) composites were fabricated by constructing a segregated network structure using the co-deposition method. Both carboxyl-functionalized multi-walled carbon nanotubes (CNTs) and silicon carbide (SiC) were successfully coated on the surface of PPS powders with the aid of self-polymerization of dopamine (PDA) and co-polymerization between PDA and polyethyleneimine (PEI), thereby forming PPS@PDA-CNTs-SiC hierarchical reinforcing hybrids. Results showed that the thermal conductivity of PPS@PDA-CNTs-SiC (0.97 W/(m K)) is about 120% higher than that of PPS/CNTs/SiC. The friction coefficient (0.193) and specific wear rate (2.50 × 10−5 mm3/(N m)) of PPS@PDA-CNTs-SiC are 18.9% and 50% lower than those of PPS/CNTs/SiC, respectively. The enhanced thermal conductivity of PPS@PDA-CNTs-SiC contributes to rapid dissipation of frictional heat at the sliding interface which protects the polymer substrate from being destroyed or peeled, thereby improving the tribological performance. This work provides new insights into expanding the application of self-lubricating polymer composites in the fields where efficient heat dissipation is also a primary concern.

The last few years have seen a rapid increase in body-worn devices because these devices cover a broad spectrum of potential uses. Moreover, body-worn devices still require improvements in their flexibility, size, and weight that necessitate the development of flexible and miniature antennas. In this paper, we present a new flexible miniature antenna for body-worn devices. To ensure flexibility and comfort when the antenna is in contact with the human body, a substrate from natural rubber filled with TiO2 is developed. The miniaturization is achieved using the quadratic Koch curve. The antenna design, optimization, and characterization are performed on a human body model. The performance of the antenna is analyzed in two scenarios: (1) in- to on-body, and (2) on- to off-body wireless communications. The results show that the antenna realized the maximum telemetry range of more than 80 mm for in-body communications and more than 2 m for off-body communications. Moreover, the highest 10 g specific absorption rate value was 0.62 W/kg. These results, in addition to the antenna’s compact dimensions (12 mm × 26 mm × 2.5 mm) and the low manufacturing price, make the proposed antenna an ideal candidate for health telemetry applications.

Polydopamine (PDA)-based biomimetic materials have attracted much attention due to the outstanding adhesion and biocompatibility, etc. However, developing a generalized and simple approach for the patternable polymer coatings in a liquid environment and the secondary modification for high-resolution electrodes are challengeable. Herein, A high-performance flexible microelectrode arrays (fMEAs) for biomedical applications based on novel platinum nanowire (PtNW) was proposed using PDA as the bioinspired adhesive buffer layer between the polymer substrate and the nanowire layer. The PDA film was patternable and selectively grafted on the flexible PI substrate using the micro-contact printing ( $\mu $ CP) technique, followed by the reduction of PtNW on patterned PDA in chloroplatinic acid (H2PtCl6) by in situ electroless deposition. The as-fabricated PI-PDA/PtNW electrode has greatly reduced the electrochemical impedance at 1 kHz by 99.54% compared with that of PI-Ti/Pt using the conventional sputtering method, and also increased the charge storage capacity (CSCc) by 27 times. At the same time, the adhesion between the metal layer (PDA/PtNW or Ti/Pt) and the PI substrate was evaluated using both intense ultrasonic bath and torsion fatigue test. The results showed that PDA was very effective as the adhesive layer by significantly enhancing both mechanical adhesion and impedance stability when suffering mechanical stress. These achievements are of great interest for robust flexible electronics for implantable or wearable biomedical applications.

The ongoing demand for the development of intelligent devices has greatly inspired the development of metallic nanostructure incorporated composite electrospun mats. The astounding characteristics ...

Ductility of polymer-supported metal films is important for flexible electronic devices and it is strongly affected by the metal film, polymer substrate, and their interfacial properties. In this paper, the effect of interfacial adhesion and substrate thickness on the metal film ductility was investigated. Mechanical behavior of 500 nm-thick aluminum (Al) films deposited on polyethylene-terephthalate (PET) substrates with thickness of 12, 25, and 50 μm was studied by tensile testing with in-situ electrical resistance measurements and post-mortem scanning electron microscopy. In addition, plasma etching was applied to tailor the PET surface condition before Al film deposition. Subsequently, the Al/PET interfacial adhesion was quantitatively evaluated using the laser spallation approach. The tensile tests showed that plasma etching improved the ductility of the Al films, and that the apparent ductility of the Al film on the 50 μm-thick PET substrate was substantially lower than that on the 12 and 25 μm PET thickness. Laser spallation results revealed that the plasma etching increased the Al/PET interfacial adhesion. The influence of plasma etching and substrate thickness on the Al film ductility can be explained by the interface adhesion and shear lag theory. Plasma etching improves the interfacial adhesion by inducing both chemical and physical changes on the PET surface, and substrate thickness contributes to interface shear stress upon strain localization. The competing effect of the interfacial adhesion and the interfacial shear stress leads to a limiting substrate thickness for the desired ductility at a given tensile strain.

In this work, Linear Low Density Polyethylene (LLDPE)/graphite micro-composite coatings were deposited on an LLDPE substrate using the thermo-compression technique. The studied values of the mass f...

In order to solve the problem of wiring breakage in the conductive layer caused by a fold in the bending area of a flexible organic light-emitting diode (FOLED) and improve the conductive layer in the bending area of a FOLED, the conductive layer wiring scheme in its bending area is optimized. First, the polymer substrate FOLED samples are prepared, and the bending area structure is formed by stacking the resin, pin, metal wires and other layers. An equivalent working condition of the bending process is analyzed, and the three-dimensional finite element modeling of the bending area of the FOLED is completed. According to the simulation analysis results of the FOLED bending area, it is proposed that the optimal design of Resin ply thickness is as follows: the limiting conditions of material damage in the conductive layer should be fully considered, and the material damage mechanism should be studied to ensure that the cumulative plastic strain of A-A and B-B positions is smaller while being free from damage; the optimal wiring scheme design for the conductive layer is the following: using the square of optimal stress distribution to reduce the fracture angle, the routing scheme of crossing route type > full filling type > internal opening type should be adopted.

Metal oxide nanocomposites (MON) have gained significant attention in the literature for the possibility of improving the optical and electronic properties of the hybrid material, compared to its pristine constituent oxides. These superior properties have been observed for TiO2 — based MON, which exhibit improved structural stability and photoactivity in environmental decontamination processes. In addition, the use of polymer membrane-supported MON is preferable to prevent further aggregation of particles, increase the surface area of the semiconductor in contact with the contaminant, and enable material reuse without considerable efficiency loss. In this work, V5+-doped TiO2/WO3 MON nanostructures were prepared by the sintering process at 500 °C and supported in electrospun fiber membranes for application as photocatalyst devices. Microstructural characterization of the samples was performed by XRD, SEM, EDS, Raman, and DSC techniques. The reflectance spectra showed that the bandgap of the MON was progressively decreased (3.20 to 2.11 eV) with the V5+ ions doping level increase. The fiber-supported MON showed photoactivity for rhodamine B dye degradation using visible light. In addition, the highest photodegradation efficiency was noted for the systems with 5 wt% vanadium oxide dispersed in the fibers (92% dye degradation in 120 min of exposure to the light source), with recyclability of the composite material for use in new photocatalysis cycles. The best results are directly related to the microstructure, lower bandgap and aggregation of metal oxide nanocomposite in the electrospun membrane, compared to the support-free MON.

This paper examines the simulation, design, and fabrication of a nano-particle silver microheater. COMSOL Multiphysics is used to simulate the microheater of an area of 720 × 720 μm2. Different stages of the microheater fabrication process are discussed. The size of the cartridge used is 10 pL and the nozzle diameter was 50 μm. The drop spacing was chosen to be 45 μm after testing several different values. Controlled printing of Ag ink was reached by setting the tickle control frequency to 8 kHz and cartridge print height to 0.4 mm. The nozzle temperature was set at ambient temperature. The inkjet printed microheater is of same area and track and gap widths of 110 μm. The measured resistance of the microheater, 119 Ω, is approximately equal to the simulated resistance of 100 Ω. It was observed that the temperature at the center of the heater reaches up to 250 °C.

Previous research work shows that metal nanocomposite thin films fabricated by laser sintering of mixtures of metal nanoparticles (NPs) and carbon nanotubes (CNTs) on a polymer substrate have a great potential to help enhance reliability and durability of metal components in flexible electronic devices. To gain a good relevant fundamental understanding, it is important to know the material thermal history during laser sintering. However, an in-situ temperature measurement has been rarely reported in a paper in the literature for laser sintering of metal NP-CNT mixture thin films on a polymer substrate. Such temperature measurements are reported in this paper, which are performed using a two-color pyrometry system set up by the authors to overcome related technical challenges such as high spatial and temporal resolution requirements. The measurement method is non-contact, and by measuring thermal radiation in two wavelength ranges it does not require the value of the target surface emissivity. The electrical resistivities of composite material sintered with different laser scanning speeds are also measured. Under the conditions studied, it has been found that as the laser scanning speed increases significantly, the average melted material temperature in the measurement spot only slightly decreases, but the melting duration drops significantly. The average electrical resistivity of sintered composite material first decreases and then increases with the laser scanning speed. The measured material surface temperatures for laser sintering of CNT and silver NP mixtures are similar to those for laser sintering of silver NPs with the same laser scanning speed.

We employed imaging rotational fluorescence correlation microscopy to directly observe the segmental dynamics of the polymer near the polymer–substrate interface using a probe-tethered polymer brush buried in bulk polymer films. The probe-tethered polymers grafted onto the polymer–substrate interface provide spatial selectivity to probe only the segmental dynamics of polymer near the polymer–substrate interface. The perturbation caused by the grafted polymer chains on the segmental dynamics of the polymer film near the interface was minimized by reducing the molecular weight of the polymer brush compared with the critical entanglement molecular weight of the polymer and grafted with a low grafting density (≈0.1 chains/nm²) using a “grafting-to” method, which allows precisely controlled and fully characterized polymer brush structures. In addition, the molecular weight of the brush polymer was further controlled to ≈10 kg/mol with the root-mean-square end-to-end distance of ≈5 nm to probe dynamics within 10 nm of the polymer–substrate interface. Polystyrene and poly(methyl methacrylate) films carrying rather unfavorable and similar surface energies, respectively, with the silane-modified silicon wafer substrates were investigated. The polymer dynamics near the interface characterized by the degrees of non-Arrhenius temperature dependence and nonexponential relaxation were not altered in both systems compared with those of the bulk, suggesting that the polymer dynamics is not sensitive to moderate differences in enthalpic interaction between the polymer and the substrate.

Multifunctionality of all-in-one energy storage devices with the properties involving flexibility, interface stability, and wearability are urgently needed for portable electronic equipment. Here, we report a facile method based on interfacial cross-linking for preparing all-in-one energy storage devices, where the same polymer substrate is used in both electrode and electrolyte, while the electrolyte as the cross-linking agent to obtain more stable interface between the components of the all-in-one energy storage devices. This novel strategy endows the storage device small intrinsic impedance effect (RS=1.82 Ω) and mechanical stability; and more importantly it enables the supercapacitors to be used as public module to achieve arbitrary, designable, and multi-dimensional integration for the adaptation with complex power supply systems. The strategy is also successfully extended to aqueous Zn-MnO2 battery. Overall, the strategy provides a universal and simple path for the integrated design of the all-in-one energy storage device as a flexible and switchable power source.

A set of processing conditions for cold spray deposition of an embedded particle layer on a polymer substrate has been established using a dynamic impact model and verified experimentally. This research utilizes a three-network polymer model based on high strain-rate impact tests to capture the nonlinear and time-dependent response of polymer deformation during the cold spray impact with both rigid and deformable particles. The particle's material properties, particle velocity, and particle size were systematically studied to obtain the polymer deformation's various responses from finite element analysis. Particle impact velocity was experimentally measured with a double disk rotary system. The numerical results were mapped into diagrams and validated with the experimental results of cold spraying Cu and Al2O3 powders. This research contributes to quantifying the deposition window, which embeds but still exposes metallic/ceramic powders on a polymer substrate.

(K1−xNax)NbO3 (KNN)-based piezoelectric thin films have been extensively studied for application in micro-electromechanical systems. However, growing homogenous crystalline (K1−xNax)NbO3 (CKNN) films with good piezoelectric properties is difficult because Na2O and K2O evaporate during the growth process at high temperatures. Recently, amorphous (K1−xNax)NbO3 (AKNN) films containing KNN nanocrystals with good piezoelectric properties have been fabricated at low temperatures. Furthermore, [001]-oriented crystalline (K1−xNax)NbO3 (OCKNN) films with excellent piezoelectric properties have been grown at low temperatures (≤ 350 °C) using a metal-oxide nanosheet seed layer. This novel method is excellent for the growth of homogeneous KNN thin films. These films were deposited on a polymer substrate; thus, they can be utilized in future flexible electronic devices. In this study, the structural and piezoelectric properties of AKNN- and CKNN-based films fabricated at high temperatures, along with the growth process and application of OCKNN-based thin films at low temperatures, are reviewed.

A submicrometer-thick molecular sieve zeolite nanosheet laminated (ZNL) membrane has been synthesized on macroporous polyvinylidene fluoride (PVDF) substrate via the simplistic vacuum filtration-co...

A free-standing high boron-doped diamond nanosheet (BDDNS) has been fabricated for the development of a flexible BDDNS strain senor. High boron-doped diamond was initially grown on a tantalum substrate in a microwave plasma-assisted chemical vapor deposition method, and was then transferred to a Kapton polymer substrate to fabricate the flexible BDDNS/Kapton device. Before performing the transfer process, the thin BDDNS’s morphology and bonding structure on the top and bottom surfaces were investigated using scanning electron microscopy and Raman spectroscopy. The contact potential difference and work function values of the BDDNS top and bottom surfaces were measured using a Kelvin probe atomic force microscope. Significant electrical conducting properties were observed from the resistance mapping of the BDDNS foil, and the average resistance value of 31 Ω attained from the top surface of the BDDNS foil. The electrical response of the BDDNS/Kapton device was investigated using a custom-made measurement system and a positive residual resistance change with strain was observed. The developed BDDNS/Kapton device was able to sustain for measuring up to 0.55% of strain, which indicates it may have great potential to be utilized in low-strain sensor applications.

We demonstrate a facile one-step fabrication of flexible ridge waveguides by using the nanochannel-guided lithography (NCL) that enables continuous extrusion of a polymer that forms waveguiding core ridge on an undercladding polymer substrate. NCL utilizes a well-cleaved mold edge with microtrench patterns to slide continuously over a UV-curable liquid resin-coated substrate under conformal contact, where the resin and substrate can be chosen for suitable waveguide core and undercladding materials. The local heating of a trench mold can control the viscosity of liquid resin for optimal filling into the microchannels followed by smooth extrusion, which is subsequently UV-cured. Such a smoothly extruded resin core exhibits a very smooth surface potentially promising for the low-loss waveguiding operation which was experimentally confirmed by optical insertion loss characterization. The proposed technique may provide a practical route to the continuous and seamless fabrication of scalable waveguides and photonic elements.

Conductive elastomeric composites exhibit a great research potential in the intelligent materials and devices owing to their excellent mechanical and electrical properties. Herein, we reported a carbon nanotube (CNT)-coated conductive elastomer with electrical and near-infrared (NIR) light dual-stimulated shape memory and self-healing performance, which can also utilized in wearable sensing. The conductive elastomer composite, CNT-coated polymer substrate with shape memory and self-healing capacity (CNTs/CHSMPs), was first fabricated by graft copolymerization of tetrahydrofurfuryl methacrylate, lauryl acrylate (LA), and vinylimidazole on CNTs, subsequent supramolecular crosslinking, and CNT coating. Taking advantage of the remote controllability of NIR light and the rapid photothermal conversion by CNTs, the prepared composite can achieve accurate shape memory at a fixed point, and the shape recovery procedure can be completed within 30 s. The integrated conductive network throughout the polymer composite also endowed the material with unique electrical stimulated shape memory recovery performance, derived from the excellent electrothermal transition by CNTs. In addition, CNTs/CHSMPs also displayed self-healing characteristics for prolonging the service life of materials and strain sensitivity properties for the sensing of human motion, which contribute to their prodigious application potential in the field of wearable flexible electronic materials.

The poor environmental stability of natural anthocyanin hinders its usefulness in various functional applications. The objectives of the present study were to enhance the environmental stability of anthocyanin extracted from Lycium ruthenicum by mixing it with montmorillonite to form an organic/inorganic hybrid pigment, and then to synthesize allochroic biodegradable composite films by incorporating the hybrid pigment into sodium alginate and test them for potential applications in food testing and packaging. The results of X-ray diffraction, Fourier-transform infrared spectroscopy, and use of the Brunauer–Emmett–Teller method and zeta potential demonstrated that anthocyanin was both adsorbed on the surface and intercalated into the interlayer of montmorillonite via host–guest interaction, and the hybrid pigments obtained allowed good, reversible, acid/base behavior after exposure to HCl and NH3 atmospheres. The composite films containing hybrid pigments had good mechanical properties due to the uniform dispersion of the pigments in a sodium alginate substrate and the formation of hydrogen bonds between them. Interestingly, the composite films also exhibited reversible acidichromism. The as-prepared hybrid pigments in composite films could, therefore, serve simultaneously as a reinforced material and as a smart coloring agent for a polymer substrate.

The market for next-generation flexible displays is rapidly expanding with the launch of foldable electronic products. Consequently, the flexible electronic material and device industries are continuously growing. Specifically, the cover window used in foldable displays is a very important component that must have excellent optical, physical, and mechanical characteristics while withstanding high external stresses caused by the bending radius, unlike the existing rigid-type cover windows. Considerable research efforts have been dedicated toward improving their performance. In this study, a cover window substrate for a foldable display having high flexibility was developed. To this end, ultra-thin glass (UTG) with excellent flexibility and transparency was used to overcome the low surface hardness of the typical polymer substrate used in existing foldable substrates. In addition, for efficient stress control, the design of the multilayer structure was optimized by generating multiple neutral planes through the use of an optical clear adhesive (OCA) buffer layer. The structure of the cover window was designed using the finite element simulation technique, and actual samples of the cover window with the optimized structure were produced to evaluate their physical, mechanical, and optical characteristics. As a result, the optimized foldable cover window showed a surface hardness of 9 H and a light transmittance of 90 %; especially, it exhibited an excellent bending reliability with 200000 bending repetitions without failure at the small bending radius of 1.5 R.

The patterning of surface structures is a critical step for interfacial engineering applications that are based on soft lithography, casting, or imprinting techniques in general. However, photolithography and mold/die fabrication processes are expensive and time-consuming. To solve this problem, we developed a novel laser-based process that exploits the high stretchability of a polymer. In this study, continuous-wave laser-induced pyrolysis was conducted on a pre-stretched Ecoflex polymer substrate to obtain a controllable hydrophobic surface with functional structures at the micro/nanoscale, which were constructed via the facile removal of pyrolytic byproducts. Under the optimum strain rate and laser parameters, periodic wrinkle generation and a proportional channel pitch reduction were observed, which provided hierarchical micro/nanostructures and enlarged the air gaps between the target droplet and the hydrophobic structures. The processed surface exhibited improved hydrophobic properties (WCA ~ 135°) compared with a flat Ecoflex polymer surface (WCA ~ 105°). Thus, a facile manufacturing method for stretchable polymer substrates with hydrophobic patterned surfaces is proposed.

In this paper, we report the Co-metal organic frameworks (MOFs) were successfully synthesized with the aid of 2,6-pyridinedicarboxylic acid ammonium as an organic ligand in polylactic acid (PLA) as a biodegradable and biocompatibility polymer substrate through the ultrasonic-assisted electrospinning method. Co-MOFs/PLA nanofiber used as a new nanocomposite for design and construction of nanosensor based on the polymer prepared of the 4-aminobenzoic acid electrolytic molecule for measuring ciprofloxacin (CIP) drug class. The molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) sensors were studied by differential pulse voltammetry (DPV) to study changes in oxidation peaks and reduction of potassium ferricyanide. The calibration curve for ciprofloxacin was in the range of 0.5–150 μM also the detection limit was 0.017 μM and the standard deviation for five consecutive measurements at 60 μM concentration was calculated1.7% respectively. For characterizing the synthesized Co-MOF/PLA nanofiber we used X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDAX), Transmission electron microscopy (TEM) and Dynamic light scattering (DLS). In this study, we present new nanosensors with Co-MOF/PLA nanofiber as a biodegradable and bioactive composite for the first time in modified carbon paste electrode using the ultrasound-assisted direct micelle (UADM) method as the determination of ciprofloxacin drug.

Polymer-based nanocomposites with high dielectric constant have attracted the attention of many researchers, owing to their wide applications in advanced electronics. The experimental measurement of dielectric constant for every polymer-based nanocomposite system is not practically feasible, due to there being many polymer matrixes and nanofiller combinations. Therefore, there is rising interest in predicting the dielectric constant of polymer nanocomposites, using mathematical methods. In this study, we estimate the dielectric constant of polymer nanocomposites by considering astounding interphase properties. The Paletto model is modified, in order to predict the dielectric constant of a BaTiO3–polymer nanocomposite by properly assuming the interphase parameters, including the thickness of the interphase layer and the dielectric constant of the interphase region. Results from the modified Paletto model are verified by experimental data, indicating that the predicted values agree well with the experimentally determined dielectric constant, and thus the accuracy of the developed model. In addition, the particle concentration will significantly be underestimated if the influence of the interphase volume is ignored. Furthermore, the effects of different parameters, including the dielectric constant of polymer substrate, dielectric constant of particles, particle content, particle size, the thickness of the interphase layer as well as the dielectric constant of the interphase region on the dielectric constant of a BaTiO3–polymer nanocomposite are also investigated. The developed model provides a useful tool for predicting the dielectric constant of a BaTiO3–polymer nanocomposite, accompanied by interphase analysis.

ZnO is widely used as a semiconductor material in a variety of applications. Usually, ZnO is used as a thin film, which is composed of ZnO/intermediate layers/substrates. Recently we developed a rod-shaped ZnO crystal layer directly on a polyimide film without any intermediate layers by solution reaction coupled with surface treatments of the film. We studied the growth mechanism of ZnO crystal layers on the polyimide surface in the solution process. The physical and chemical effects of alkali, plasma, and heating treatments were clarified. The results indicated formation of homogeneous, fine irregularities on the polyimide surface and predominance of imide groups. The direct growth of ZnO crystals is attributed to the anchoring effect derived from gradual nuclei growth of Zn(OH)2 in the homogeneous, fine irregularities of the polyimide film. We also demonstrated a more facile approach for the preparation of ZnO crystal layers by physical roughening of the polyimide film to verify our proposed mechanism. Our findings provide new insights into the growth of ZnO crystals on polyimide and other polymer substrate surfaces without the use of any intermediate layer. This knowledge may be further used for mass production of ZnO crystals/polyimide thin films at low cost.

Control of structural transitions in flexible metal–organic frameworks (MOFs) on a substrate is crucial for controlling their properties for the development of MOF-based applications. In this study, we investigate the structural transition of directly formed flexible MOF crystals on a metal ion-doped polymer substrate. Utilizing hydrolyzed polymer substrates results in the formation of MOF crystals with no structural transition by the adsorption/desorption of guest molecules in their pores. Results suggest that the polymer chains of the substrate are entangled in the obtained MOF crystals, resulting in MOF crystals showing no structural transition by the adsorption/desorption of guest molecules in the pores. By controlling the temperature for the hydrolysis reaction of the polymer substrate, the number of polymer chains entangled with MOF crystals decreases, resulting in a dynamic structural transition of the resulting MOF crystals on the substrate. These results provide insights into the effect of the polymer substrate on the properties of MOF crystals on a two-dimensional substrate.

The applications of stretchable conductors, which spontaneously form microbuckles on flexible substrates in micro and nano manufacturing, flexible and stretchable electronic technology, medicine, and other fields, have attracted extensive attention. To demonstrate high-performance stretchable electrodes, a great deal of effort has been made in terms of high conductivity, high stretchable properties, and high durability. However, the application of stretchable electrodes remains challenging because the electrical conductivity degrades and is even lost when stretched due to induced mechanical tension and excessive deformation. This paper reports a highly stretchable and conductive electrode, fabricated using a polymer composite membrane (spun on the polymer substrate surface coated with a thin layer of Cu NWs and covered with a layer of chitosan), which is attached to the pre-draft elastomeric substrate and then releases the prestrain. The prepared electrode has excellent properties such as unchanged stretchable stability under 70% strain. In particular, the sheet resistance changes less than 13% at 175% strain and remains almost constant after 2500 stretchable cycles at the same strain. Finally, a stretchable heater based on the electrode was fabricated to verify the utility of the stretchable electrode, and the practicability of the stretchable conductor was confirmed through the circuit and human-wearable experiment.

Metal–organic framework (MOF) membranes with sub-nanometer channels have great potential in molecule selective transport, but the scalable and facile fabrication of flexible and thin membranes from stable MOF structures is difficult, which is the key to realizing practical applications. In this work, stable and ultra-small MOF nanoparticles act as “ordered porous monomers” and are interfacially polymerized with organic monomers into ultra-thin and flexible membranes. An ∼150 nm thin MOF active layer can be produced rapidly (

The capability to accurately monitor electrophysiological signals and instantly provide feedback to users is crucial for wearable healthcare. However, commercial gel electrodes suffer from drying out and irritation on skin with time, severely affecting signal quality for practical use. Toward a gel-free electrophysiology, epidermal electrodes that can accurately detect biosignals and simultaneously achieve the multifunctional properties of on-skin electronics needs are highly desirable. In this work, inspired by Lamellibranchia, which can adhere tightly to various surfaces using their extensible, adhesive and self-healing byssal threads, we developed a gel-free epidermal electrode to acquire high-quality electrophysiological signals based on a novel polymer substrate design. This polymer (STAR) features extreme stretchability (>2300% strain), high transparency (>90% transmittance at λ = 550 nm), gentle adhesion (adhesion strengths: tens of kPa), and rapid self-healing ability (95% healing efficiency in 10 min). Combined with silver nanowires as conductors, STAR was employed as a self-healing, stretchable and adhesive epidermal electrode for electrophysiological signal recording, showing a signal-to-noise ratio (SNR) even higher than that of commercial electrodes, and being able to control an artificial limb as an intermediate for human-machine interface. We believe our Lamellibranchia inspired STAR will pave a new way to design multifunctional polymers for epidermal electronics, accelerating the development of emerging wearable healthcare.

The synthesis method of transparent and flexible ZnO thin films is currently considered the most important factor for the fabrication of next generation wearable devices. To fabricate transparent and flexible devices by using sol–gel spin-coated ZnO thin films, an annealing step is necessary; however, annealing processes at high temperatures decompose polymer substrates due to their low melting temperature. It was found that sol–gel spin-coated ZnO thin films can be crystallized through the mobility difference of ZnO molecules placed at the surface of ZnO thin films. Especially, ZnO thin films can be annealed at high temperature (above 500 °C) by using a thermal dissipation annealing (TDA) method without the deformation of the polymer substrate. A transparent and flexible ultraviolet photodetector based on ZnO thin films annealed with the TDA method exhibited fast rise and decay time constants, a high on/off current ratio, and reproducible photocurrent characteristics. Thus, these results indicated that the TDA method is a feasible alternative route for the fabrication of next generation wearable devices.

The stability of polymer thin films is crucial to a broad range of technologies, including sensors, energy storage, filtration, and lithography. Recently, the demonstration of rapid deposition on solid substrates of ordered monolayers of polymer grafted nanoparticles (PGN) has increased potential for inks to additively manufacture such components. Herein, enhanced stability against dewetting of these self-assembled PGN films (gold nanoparticle functionalized with polystyrene (AuNP-PS)) is discussed in context to linear polystyrene (PS) analogues using high throughput surface gradients: surface energy (20–45 mN/m) and temperature (90–160 °C). PGNs exhibit a lower surface (γp) and interfacial (γsp) energy relative to linear polymers, which results in increased thermal and energetic stability by 10–25 °C and 5–15 mN/m, respectively. This enhanced wetting–dewetting transition is qualitatively consistent with the behavior of star macromolecules and depends on the architecture of the polymer canopy. Increased f...

The electro-mechanical behaviors of transparent conductive oxide film on polymer substrate are of great concern because they would greatly affect the stability and lifespan of the corresponding devices. In this paper, indium tin oxide (ITO) films with different thicknesses were deposited on a polycarbonate (PC) sheet; meanwhile, in situ electrical resistance, in situ scanning electron microscopy and profilometry were employed to record the electrical resistance, morphologies and residual stress in order to investigate the fracture behavior and electrical-mechanical properties of ITO films under uniaxial tension loading. The electrical resistance changes, crack initiation, crack propagation and crack density evolution of ITO films were systematically characterized by in situ tests. Three fracture stages of ITO films were summarized: Ⅰ crack initiation, Ⅱ crack propagation, Ⅲ crack saturation and delamination. The crack initiation and electrical failure in a thinner ITO film occurred at relatively higher applied tensile strain; namely, the ductility of the film decreased as the film thickness increased. Residual compressive stress was recorded in the ITO films deposited on PC at room temperature and increased as the film thickness increased. Intrinsic crack initiation strain (CIS*) showed an opposite thickness dependence to residual strain (εr); the increase in residual compressive strain was counteracted by the decrease of intrinsic cohesion, leading to an overall decrease in effective crack initiation strain (CIS) when the film thickness increased. In addition, integrated with a formulated mechanics model and the analysis of the three fracture stages under tension, the fracture toughness and interfacial shear strength were quantitatively determined. As the film thickness increased (in the range of 50~500 nm), the fracture toughness decreased and the films were more prone to crack, whereas the interfacial shear strength increased and the films were less likely to delaminate.

Laser manufacturing is a promising method for the design and preparation of high value-added materials. When the laser acts on the polymer precursors, some wonderful phenomena will always occur and accompanied by the generation of new substances. Herein, we report a top-down approach for the direct preparation of orange-yellow dye that is similar to psittacofulvins from commercial polymer resins by laser writing. Conjugated double bonds and micro-rough structures are formed simultaneously on laser-irradiated polymer substrate surfaces. The typical polyconjugated structures of psittacofulvin dyes were confirmed by micro-Raman and Raman imaging results. Temperature-dependent Fourier transform infrared and X-ray photoelectron spectroscopy further demonstrated the formation mechanism of laser-induced psittacofulvins dyes based on the chemical composition. Further, optical microscopy, laser confocal microscopy, and scanning electron microscopy were carried out to characterize the physical morphologies of laser-irradiated polymer substrates. A unique advantage of preparing psittacofulvins dye using laser writing is its simple steps, and the dye can be converted directly from the appropriate precursor substrate. Interestingly, the laser-irradiated polymer substrate surface undergoes color change. This laser-induced color patterning is attractive due to the characteristics of high precision, flexibility, and maskless; any patterns can be easily designed and produced on the polymer at desired positions.

A novel flexible polymer/fabric fractal monopole antenna with a wideband performance is presented. A thin sheet of highly conductive fabric and a natural rubber‐based composite have been used for conductive and non‐conductive parts of the antenna, which allow keeping the antenna as flexible and thin as possible. The proposed antenna has been simulated, prototyped and tested. Results show that the antenna has a simulated impedance bandwidth of 3.8 GHz (2.2–6.0 GHz) and a measured impedance bandwidth of 3.7 GHz (2.3–6.0 GHz) to cover the most commonly used standards in wireless communication systems. The radiation efficiency of the antenna reaches over 93% throughout the operating frequency band with satisfactory radiation patterns and gain.

Active silica nanorod (OPal) was prepared from natural palygorskite (RPal) using an updated acid leaching route, and then the effect of RPal and OPal as nano-filler on the network structure, mechanical, thermal and anti-aging properties of chitosan/polyvinylpyrrolidone (CS/PVP) films was studied comparatively. It was revealed that OPal had a better dispersibility than RPal in CS/PVP substrate, and its incorporation improved the mechanical properties and thermal stability of the films significantly. The optimal composite film containing OPal shows the maximum tensile strength of 27.53 MPa (only 14.87 MPa and 22.47 MPa for CS/PVP and CS/PVP/RPal films, respectively), resulting from the more uniform dispersion of OPal in polymer substrate and its stronger interaction with 3D polymer network. By a controllable acid-leaching process, the metal ions in octahedral sheets of RPal were dissolved out continuously, which is favorable to alleviate the adverse effects of variable metal ions on the film under UV light irradiation, and thus improve the aging-resistant ability of films. This study provides new ideas for improving the reinforcing ability of natural clay minerals towards biopolymer-based material, finds a new way to resolve the aging problem of polymer composites caused by incorporation of natural clay minerals.

Increasingly, copper nanopowders are commonly used in conductive inks due to their cost-efficiency compared to silver or gold and excellent electrical conductivity. One of the challenges associated with copper inks is oxidation and to address, we have developed a hybrid copper-based ink by removing the oxide layer of copper powders and coat the powders with a silver shell to protect from oxidation. Despite the advances, the inks are prone to fatigue failures when the ink films are repeatedly bent or stretched. In order to overcome this challenge, we proposed to integrate cellulose nanocrystals (CNC) with the copper-based ink on a polymer substrate and use a sintering process based on intense pulsed light in an argon atmosphere. Sintering in argon gas environment improved in electrical conductivity that may be the result of the partial carbonization of the CNC rather than combustion. It has also been experimentally determined that CNC improved adhesion strength of the copper ink film. Moreover, the addition of CNC also reduced the damage caused by bending and stretching. The ink film containing 10% CNC increased the electrical resistance by only 3.82 times after 600 bending cycles versus the resistance increased by 34.4 times without CNC. Under the 30% strain of stretching, the change in resistance of the ink film containing 10% CNC was 1.75 times lower than without CNC. It was observed through microscopy techniques that the presence of CNC reduced the formation of cracks by enhancing mechanical strength.

The exceptional high surface area and wide band gap ranges of semiconductor metal oxide nanostructures owe unique chemical, optical and physical properties that have grabbed their utilization for humidity sensing applications. In this framework, cost-effective sensors have been fabricated using a simple spray coating technique. Initially, the sonication was carried out for all the conductive inks such as carbon nanotubes (CNTs), zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) for 15 min in each case and then sprayed over conducting cellulose polymer substrate. Surface study demonstrated conducting networks of CNTs and cellulose polymer, and layers of ZnO and Ag NPs, as well. The analysis of elemental composition confirmed the required stoichiometric contents. Sensing measurement of CNTs/ZnO/Ag sample showed smaller resistance and enhanced current as compared to CNTs/ZnO sample. Hence, the device showed an efficient activity to sense humidity.

This paper aims to present the simulation work and obtain optimized parameters for the development of drop-on-demand electrohydrodynamic jet (DoD E-Jet) to print control and stable micro-structures on a flexible insulating substrate. In this work, the novel comparison of three types of combination needle structures was developed based on the multiphase flow (liquid–air) technique, in order to achieve optimal printing conditions for a flexible PET substrate. According to simulation results, steel-quartz needle combination provides very unique compensations in the controllability and stability of E-Jet. Printing on a flexible substrate was challenging, but parameters used in simulation validate the possibilities for DoD E-Jet printing method. Optimize working parameters were achieved by the numerical simulation executed to generate developed and stable E-Jet morphology. In addition, various stable and uniform microscale droplets and structures were directly printed on a flexible polymer substrate with the help of collective impact of electrical force, viscous force, and internal pressure force throughout DoD E-Jet printing process. The results of numerical simulation and experimental work exhibited an excellent and promising E-Jet printing tool for flexible electronic systems.

Patterns with periodically arranged dimples are fabricated by an inexpensive soft-imprint lithography technique on a flexible transparent polymer substrate. Excellent diffraction characteristics, with highly intense and fine features, are seen from these polymer layers in transmission, even though the effective refractive index variation across their thickness is very small. The diffraction is studied at two different feature sizes and at multiple wavelengths. The results from the experiment emphasize that the diffraction is a 2-D spatial Fourier transform of the object but with some important limitations. Numerical calculation based on rigorous coupled-wave analysis exactly reproduces the results and supports the features of the experiment such as unequal intensity distribution in the diffraction pattern.

As the demand for flexible devices has increased, polymers have become very promising materials for these applications because they have excellent flexibility, lightweight, and low cost. Vacuum kinetic spraying can be a good alternative technology for film fabrication on polymers as dense ceramic films can be fabricated even at room temperature without thermal degradation of the polymer substrate. However, there is a lack of understanding of the deposition process of ceramic films on a polymer substrate. In this regard, the deposition behavior and microstructural features were investigated by comparing Al2O3 particle deposition on glass and polycarbonate (PC) substrates by using simulations and experimental methods. Simulations demonstrated that hard particles were prone to penetrate or be only embedded in the soft substrate without sufficient fragmentation. This is attributed to the shock absorption effect of the substrate. Particle kinetic energy was transferred mostly to the internal energy of the soft substrate but not to particle internal energy (plasticity and/or failure), which prevents particle fragmentation. Consequently, unusual interface microstructural feature was attributed to insufficient particle fragmentation by the shock absorption of the soft substrate.

The performance of conjugated polymer (CP)-based electronic devices relies on optimal charge carrier mobilities, which are determined by monomeric architecture, degree of polymerization, chain conformation, and the nano- and mesoscale morphologies. With regard to the latter, we discuss two effects that have received limited attention in the literature, yet important for device performance optimization: (1) the role of morphological disorder and of CP/substrate interactions on the in-plane and out-of-plane carrier transport in CPs; (2) the impact of morphological disorder on charge transfer at the CP/substrate interface. The emergence of film thickness-dependent carrier mobilities, varying over two orders of magnitude within a length scale of 200 nm, and band-bending phenomena, extending tens of nanometers within the CP, are associated with these effects. These findings suggest areas for further research in order to enable widespread applications of next-generation CP-based devices. Graphical abstract

This paper presents the fabrication of novel flexible counter electrodes for use in dye-sensitized solar cells (DSSCs). The conductive electrodes are composites formed from a carbon film deposited on layered metal nanowire (NW) and polyacrylate polymer substrates. The metal NW materials consist of single-layer silver NWs (AgNWs) and copper NWs (CuNWs), in addition to double-layer AgNW/CuNW and CuNW/AgNW configurations. The carbon films are deposited using three different coating methods. Detailed analyses demonstrate that the photovoltaic performances of DSSCs based on the as-prepared carbon/metal nanowire/polymer composite counter electrodes are affected by the processing of both the carbon layer and the metal NW layer, as well as the metal NW layer configuration. A highest DSSC efficiency of 4.39% is achieved for the counter electrode prepared with the carbon layer deposited by drop casting on the AgNW/polymer substrate. A DSSC based on a counter electrode fabricated with a modified CuNW layer having improved uniformity, density, and smoothness achieves a cell efficiency of 4.01%. The developed electrodes have the advantages of facile preparation and low cost, and the DSSC efficiency can be increased by improving the preparation process of the counter electrode.

Organic materials have been widely used in photovoltaic solar applications because of their flexibility and low cost. Poly(3,4-ethylenedioxythiophene) (PEDOT) has been known to have good mechanical stability under stretching and bending and also has good electrical and optical properties. Unlike inorganic materials, PEDOT can withstand high strains. In flexible solar cells, modules are usually exposed to heating–cooling cycles during day and night. When the structure of a thin film on a flexible substrate is exposed to high temperatures, the film and the substrate will expand at different rates; this will produce a residual strain caused by the thermal mismatch between the two layers. In contrast, indium–tin oxide (ITO) is brittle, and its conductivity decreases significantly as the ITO films are exposed to stretching or bending strains, especially in flexible/foldable solar cell applications. Cracks in ITO appear at very low strains that might cause failure in the conductive layer because of the combination of a very thin film of brittle ceramic material applied to a polymer substrate. In this work, a comparison of the thermal stability was conducted between PEDOT and ITO on flexible polyethylene terephthalate (PET) substrate. The performances of the two candidates were assessed during thermal bending fatigue and accelerated thermal cycling experiments. This work was designed to study the behavior of ITO and PEDOT under thermal cycling and thermal bending fatigue.

We have demonstrated the concept of imprinting graphene on a polymer substrate via coextrusion of polypropylene/graphene (PP/G) composite and target polymers. First, we predicted by wetting coeffic...

Organic light-emitting diodes (OLEDs) are widely commercialized in the display market due to many advantages such as wide color gamut, outstanding flexibility, and high contrast ratio. However, the...

Metal nanoclusters (NCs) are nanomaterials of size of less than 2 nm that exhibit a set of unique physical, chemical, optical, and electronic properties. Because of recent interest in NCs, a great deal of effort is being made to develop synthetic routes that allow control over the NC size, shape, geometry, and properties. Direct laser writing is one of the few synthesis methods that allow the generation of photostable NCs with high quantum yield in a highly controlled fashion. A key advantage of laser-written NCs is the ability to create easy-to-use solid-state devices for a range of applications. This review will present necessary background and recent advances in laser writing of silver NCs and their applications in different solid-state matrixes such as glass, zeolites, and polymer substrate. This topic will be of interest to researchers in the fields of materials science, optics and photonics, chemistry, and biomedical sciences.

Flexible transparent electrodes are in significant demand in applications including solar cells, light-emitting diodes, and touch panels. The combination of high optical transparency and high electrical conductivity, however, sets a stringent requirement on electrodes based on metallic materials. To obtain practical sheet resistances, the visible transmittance of the electrodes in previous studies is typically lower than the transparent substrates the electrode structures are built on, namely, the transmittance relative to the substrate is, Designing flexible and transparent electrodes for high-performance optoelectronic devices remains a challenge. Here, the authors presented conductive and flexible dielectric-metal-dielectric multi-layers electrodes based on Cu-doped Ag film (thickness of 6.5 nm) with 100.3% relative transmittance.

The topic of interactions between plastic and natural communities is now more relevant than ever before. Gradual accumulation of artificial polymer products and their fragments in the natural environment has reached a level at which it is already impossible to ignore the affect of these materials on living organisms. First and foremost, microorganism colonies inhabiting different biotopes, both aquatic and terrestrial, have been affected. These species are at the front-end of interaction with plastic, including those present in marine ecosystems. Nevertheless, in order to understand these processes, it is necessary to take into account several aspects of such interactions: the impact of different types of plastic on microbial community through the release of their decomposed products into the environment, the forms of plastic usage by microorganisms themselves, including mechanisms for surface colonization, as well as possible biodegradation processes of polymers due to the actions of microorganisms. At the same time, types of plastic may differ not only in mechanical strength, but also in their resistance to biodegradation caused by microorganisms. Experiments with surface colonization of types of plastic, which are different in composition and mechanical strength, provide a wide range of results that are not just relevant for understanding modern natural processes involving plastic: these results are also important for application in certain areas of technology development (for example, when creating composite materials). In particular, researches into the forms and mechanisms of sustainable colonization of particularly strong polymers by diatoms from natural communities are of great interest. Due to the fouling of surface of particularly strong synthetic polymers by diatoms, it is possible to form a single diatom-polymeric composite with general properties being already substantially different from those of the polymer itself. For example, when a polymer is fouled with diatoms that are firmly held on its surface due to physiological mechanisms that ensure their reliable fixation, total surface area of the composite increases by 2–3 orders of magnitude compared with this of bare polymer. Such composites and their properties are formed due to mechanisms of substrate colonization used by diatoms from natural marine cenoses – during the transfer of these mechanisms to a new material being prospective for diatom settlement. The practical applications of these composites lie in the sphere of heat and sound insulation, as well as in the field of creating prosthetic tissues for bone operations. In our experiments, we tracked the sequence of development of a stable composite when diatoms colonized the surface of samples of a particularly strong synthetic polymer being resistant to corrosion. In this case, the sample population process took place on the basis of colonies formed in accumulative cultures from the natural marine environment. Samples of ultra-high molecular weight polyethylene (UHMWPE) with a smooth and porous surface structure (with an open cell, bulk porosity up to 80 %) were colonized by diatoms Karayevia amoena (Hust.) Bukht., 2006, Halamphora coffeaeformis (C. Agardh) Levkov, 2009, and Halamphora cymbifera (W. Greg.) Levkov, 2009. These laboratory experiments lasted for three weeks. Accumulative microphyte cultures, on the basis of which the experiments were conducted, were obtained from the Baltic Sea (Baltiysk area, Russia) and the Arabian Sea (Mumbai area, India). The types and stages of development of colonial settlements on various elements of the frontal surface microrelief and in the underlying caverns were studied using a scanning electron microscope on samples subjected to stepwise thermal drying. Individual cells of K. amoena, H. coffeaeformis, and H. cymbifera, their chain-like aggregates, and outstretched colonial settlements occupied varying in degree non-homogeneous microrelief surface elements, forming structures with a thickness of 1–2 layers with an average settlement height of 1–1.3 single specimen height. K. amoena cells were tightly fixed to the polymer substrate using the pore apparatus of the flap of the frustule. Observations using scanning electron microscope revealed shell imprints on the substrate, which were signs of a polymer substrate introduction into hypotheca areoles. The spread mechanisms of diatoms of three mentioned species on various elements of UHMWPE surface were explored, as well as the formation of the characteristic elements of colonial settlements, including for K. amoena – consecutively in the form of “pots” and spheres, by means of interaction with polymer surface and its extension with the increase in the number of tightly attached cells in the colonial settlement.

Transition metal dichalcogenides (TMDs) have attracted significant interest as one of the key materials in future electronics such as logic devices, optoelectrical devices, and wearable electronics. However, a complicated synthesis method and multistep processes for device fabrication pose major hurdles for their practical applications. Here, we introduce a direct and rapid method for layer-selective synthesis of MoS2 and WS2 structures in wafer-scale using a pulsed laser annealing system (λ = 1.06 μm, pulse duration ∼100 ps) in ambient conditions. The precursor layer of each TMD, which has at least 3 orders of magnitude higher absorption coefficient than those of neighboring layers, rigorously absorbed the incoming energy of the laser pulse and rapidly pyrolyzed in a few nanoseconds, enabling the generation of a MoS2 or WS2 layer without damaging the adjacent layers of SiO2 or polymer substrate. Through experimental and theoretical studies, we establish the underlying principles of selective synthesis and optimize the laser annealing conditions, such as laser wavelength, output power, and scribing speed, under ambient condition. As a result, individual homostructures of patterned MoS2 and WS2 layers were directly synthesized on a 4 in. wafer. Moreover, a consecutive synthesis of the second layer on top of the first synthesized layer realized a vertically stacked WS2/MoS2 heterojunction structure, which can be treated as a cornerstone of electronic devices. As a proof of concept, we demonstrated the behavior of a MoS2-based field-effect transistor, a skin-attachable motion sensor, and a MoS2/WS2-based heterojunction diode in this study. The ultrafast and selective synthesis of the TMDs suggests an approach to the large-area/mass production of functional heterostructure-based electronics.

A quantum dots optical fiber (QDOF) sensor is proposed for temperature sensing in this paper. The sensor is fabricated by the drop-on-demand inkjet printing technology. By controlling the diameter of droplet, the spacing between droplets and the number of printed layers, the QDOF is printed on the polymer substrate. The loss of QDOF is less than 0.35 dB·mm-1 at the fluorescence wavelength. The experimental results show that the temperature sensitivity of sensor is 109 pm/ °C. As far as we know, this is the first time that a QDOF sensor is manufactured by the inkjet printing technology to realize the temperature measurement.