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Highly oriented three-dimensional metal–organic framework (MOF) crystals with a pillared-layer structure were prepared on a metal ion-doped polymer substrate. This approach allowed the formation of MOF crystals with controlled crystalline orientation in a one-pot reaction facilitated by the control of the chemical interaction between the framework components and polymer substrate. Further, this approach provides a new concept for the one-pot synthesis of oriented MOF crystals and furthers the fundamental understanding of the crystal growth mechanism based on self-assembly processes on two-dimensional support substrates.

We investigate the interaction of carbon nanotubes (CNTs) embedded in a polymer matrix [poly(methyl methacrylate) (PMMA)] with Ar plasma, which results in the formation of PMMA nanostructures, as CNTs act as an etching mask. Because of the large differences in the Ar ion sputtering yields between CNTs and PMMA, PMMA lines with the width comparable to that of CNTs and as high as 20 nm (for single-walled CNTs) or 80 nm (for multiwalled CNTs) can be obtained after repeated exposure of CNT/PMMA films to Ar plasma. We also follow the etching process by investigating changes in the IV characteristics and Raman spectra of CNTs after each exposure to Ar plasma, which shows progressive defect generations in CNTs while they maintain structural integrity long enough to act as the etching mask for PMMA underneath. We demonstrate that the PMMA nanostructure patterns can be transferred to a different polymer substrate using nanoimprinting.

It is still a challenge to achieve the polymer replication of high aspect ratio micro-structured surface especially when the completed and unified replication quality is required. This paper shows a new method for the replication named ultrasonic vibration micro-injection mold (μUVIM) technology which combines the micro-injection mold (μIM) with ultrasonic vibration. An experimental mold that integrates micro-injection compression mold (μICM) and μUVIM has been designed. In this paper, the effect of important process parameters on the replication quality of microstructure was studied via μUVIM experiment, and the process parameters were optimized through the response surface method (RSM). Compared with replication methods based on μICM technology, the μUVIM technology discussed in this paper can increase the average height of the microstructure by 14.6% and increase the production efficiency by three times. Moreover, it has been found that the μUVIM technology is insensitive to the thickness of the polymer substrate, so it can widen the processing scope of microstructure with high aspect ratio.

Self-assembling polydopamine has shown great versatility as a multifunctional surface coating. This study investigates the adhesive properties of polydopamine used to bind electroless copper films to several polymer substrates widely used for commercial applications, including polyethylene (PE), polycarbonate (PC), poly(methyl methacrylate) (PMMA), and nylon 6,6. Each substrate was coated in a similar manner resulting in continuous copper films of 52 ± 12 nm in thickness. Transmission electron microscopy revealed a non-preferential polycrystalline microstructure of copper grains averaging 53 ± 17 nm in diameter with a range of 21 nm to 123 nm, indicating there is some overlap of grains in the film. Peel testing, tensile tests, and tribological oscillating wear tests were used to characterize the mechanical performance of the adhered copper films. The nylon substrate had the highest peel strength, 49 ± 5 mN/mm, while the remaining substrates ranged from 5 to 13 mN/mm on average. Coated substrates were strained up to 20% tensile strain to investigate film delamination, buckling, and rupture. Transverse buckling of the films relative to the direction of strain was observed due to Poisson's effect during tension. Films on nylon substrates resisted buckling and rupture up to 20% strain, whereas buckling, delamination, and rupture was observed in the other substrates below 20% strain. Tribological testing revealed that the coefficient of friction was governed by the polymer substrate and was not dependent upon the polydopamine or copper films. As a demonstration of the robust nature of this method, a nylon suture was coated with polydopamine-adhered copper film and tied in a knot to show a large complex deformation state without showing signs of delamination.

Growth of printed electronics has increased the interest in the nanoparticle inks. Research on flexible electronics has expanded not only due to inherent benefits of producing flexible products but also for its high-throughput manufacturability, such as roll-to-toll (R2R) process. Conventional sintering methods cause microcracks and voids in the sintered nanoink film, which lead to subpar performance, and are not suitable for the high-throughput R2R production. Furthermore, these methods are incompatible with many polymer substrates used in flexible electronics due to their low thermal budget. In this study, we present an alternative method utilizing an intense pulsed light (IPL) with a xenon flash lamp to sinter silver nanoink on a polymer substrate. The IPL method is capable of selectively sintering the silver nanoink in milliseconds without damaging the polymer substrates. The silver nanoink was stencil printed on a polydimethylsiloxane (PDMS) specimen. Samples were prepared using five different sintering conditions and tested under uniaxial strain. Three IPL sintering conditions were compared against a non-sintered (NS) and an oven-sintered (OS) conditions. The IPL-sintered samples show a significant improvement in tensile test over NS and OS samples. Samples sintered at 20 J/cm2 of flash energy density and 10 ms of duration were stretched up to 27% strain before losing electrical conductivity. Scanning electron microscopy (SEM) confirms these results showing a reduction in porosity of the sintered nanoink as compared to NS and OS samples.

Spectroscopic ellipsometry characterization of coatings on polymeric substrates can be challenging due to the substrate optical anisotropy. We compare four characterization strategies for thin coating layers on anisotropic polymeric substrates with regard to accuracy of the resulting layer thickness and coating optical constants. Each strategy differs in measured data type, model construction, implementation complexity, and inherent capabilities and sensitivity to the coating properties. Best practices and limitations are discussed for each strategy.

Iron nitride thin films of different compositions and thicknesses were deposited on flexible polymer substrate in Ar/N2 atmosphere by reactive magnetron sputtering under varying nitrogen flow rates. The nano structured films were characterized by X-ray diffraction, UV–visible spectrophotometer, electrochemical impedance (EIS), atomic force (AFM) and transmission electron microscopies. The dependence of their functional properties on coating and growth conditions was studied in detail. It was found that the thin films show a uniform permeability in the frequency range of 200 MHz to 1 Ghz and can be used in this range without appreciable changes. Decrease of nitrogen flow rate resulted in the smoother surfaces which in turn increase transmittance quality and corrosion resistance. Functional properties are dependent of nature, relative concentration of the iron nitride phases and film thickness. Surface integrity is excellent for180 nm thick sample because the films appear to be very dense and free from open pores. By keeping sputtering power stable at 110 W, nitrogen flow rate of 10 sccm was ideal to develop the ferromagnetic γʹFe4N phase at room temperature.

Transparent, conductive, and superhydrophobic nanocomposite coatings were fabricated on the polyethylene terephthalate substrate by a spray method. Different concentrations of multi-walled carbon nanotubes (MWCNTs) entwined with SiO 2 nanoparticles, which originated from the hydrolysis and condensation of tetraethyl orthosilicate, were sprayed to form MWCNTs/SiO 2 nanocomposite coatings. The coatings were characterized by scanning electron microscopy, contact angle measurements, and other analytical techniques. The surface morphology, hydrophobicity, transparency, and conductivity of the nanocomposite coating were found to be strongly dependent on the MWCNT concentration. With increasing MWCNT concentration, the hydrophobicity increased first and then decreased, and the optical transmittance and sheet resistance decreased. The enhanced hydrophobicity was associated with the surface microstructure and chemical composition of the coating. The decreased hydrophobicity resulted mainly from the decrease in the trapped air between the water droplet and the nanocomposite coating. Owing to the hierarchically porous 3-dimensional microstructure and opportune fluorinated MWCNT content, the nanocomposite coating with 0.2 wt% MWCNTs exhibited the best hydrophobicity with a contact angle of 156.7°, good transparency with 95.7% transmittance and relatively high conductivity with a sheet resistance of 3.2 × 10 4 Ω sq −1 .

In this work, we investigated how elastomeric mold properties could affect the final replication accuracy in hot roller embossing. Amorphous polyethylene terephthalate was used as the polymer substrate. It was discovered that for dense features, the elastomeric mold provided better replication results compared to a metal mold. The experimental results revealed that embossing with larger pitch sizes such as 300 and 400 µm achieved better replication accuracy than that with smaller pitch sizes such as 100 and 200 µm. The side-wall surface areas of the features on the mold affected the embossing process, resulting in different degrees of replication accuracy.

Cu2ZnSn(S1−xSex)4 solar cells are well suited for roll-to-roll mass production since they are formed mainly by non-toxic and earth-abundant elements. Polyimide (PI) has proved to be a promising roll-to-roll compatible substrate yielding very high efficiency devices for Cu(In,Ga)Se2. In this work, we demonstrate the feasibility of using PI as a low-weight and flexible alternative to soda-lime glass for Cu2ZnSnSe4 (CZTSe) solar cells. Two main concerns arise when working with PI. Firstly, its low thermal robustness limits process temperatures below 500°C. The second concern is the lack of alkali in PI in contrast to conventional soda-lime glass fundamental for high efficiency devices. This work tackles both issues. First, different alkali doping strategies are investigated for the incorporation of Na and K into CZTSe absorbers prepared on PI substrates by sequential precursor sputtering and selenization at 470°C: pre-absorber synthesis and post-deposition treatment. Post-deposition treatment does not lead to an improvement of performance. Pre-absorber synthesis effectively dopes the CZTSe absorbers increasing the solar cell performance and carrier concentration of the devices. Cu2ZnSnSe4 devices are then fabricated on glass and PI at different temperatures (450°C-490°C). A detrimental SnSe2 secondary phase is detected in most of these devices. The formation of this phase is proved to be strongly related to process temperature. Despite this, a 6.4% efficiency device is achieved at 490°C on glass. Finally, through further experimentation and the addition of a Ge nanolayer, we report a 4.9% efficiency flexible device on PI setting a new record for kesterite solar cells on a polymer substrate.

Combination of shrink induced nano-composites technique and layer-by-layer (LbL) self-assembled graphene challenges controlling surface morphology. Adjusting shrink temperature achieves tunability on graphene surface morphology on shape memory polymers, and it promises to be an alternative in fields of high-surface-area conductors and molecular detection. In this study, self-assembled graphene on a shrink polymer substrate exhibits nanowrinkles after heating. Induced nanowrinkles on graphene with different shrink temperature shows distinct surface roughness and wettability. As a result, it becomes more hydrophilic with higher shrink temperatures. The tunable wettability promises to be utilized in, for example, microfluidic devices. The graphene on shrink polymer also exhibits capability of being used in sensing applications for pH and alpha-fetoprotein (AFP) detection with advantages of label free and low cost, due to self-assembly technique, easy functionalization, and antigen-antibody reaction on graphene surface. The detection limit of AFP detection is down to 1 pg/mL, and therefore the sensor also has a significant potential for biosensing as it relies on low-cost self-assembly and label-free assay.

Polymer/metal/polymer and polymer/metal/inorganic trilayer-structured transparent electrodes with fluorocarbon plasma polymer thin film heaters have been proposed. The polymer/metal/polymer and polymer/metal/inorganic transparent conducting thin films fabricated on a large-area flexible polymer substrate using a continuous roll-to-roll sputtering process show excellent electrical properties and visible-light transmittance. They also exhibit water-repelling surfaces to prevent wetting and to remove contamination. In addition, the adoption of a fluorocarbon/metal/fluorocarbon film permits an outer bending radius as small as 3 mm. These films have a sheet resistance of less than 5 Ω sq–1, sufficient to drive light-emitting diode circuits. The thin film heater with the fluorocarbon/Ag/SiNx structure exhibits excellent heating characteristics, with a temperature reaching 180 °C under the driving voltage of 13 V. Therefore, the proposed polymer/metal/polymer and polymer/metal/inorganic transparent conducting el...

The preparation of composite transparent electrodes of poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate/single-wall carbon nanotubes by the spray method is described. The influence of the successive treatment of each functional layer in acid media with different activities on the optical and electric film characteristics is considered. The composite with the surface resistance of 89 Ω/sq at the transparency of 85.3% (550 nm) on a polymer substrate is obtained.

This paper demonstrates a mm-wave high-gain antenna design that is printed on a flexible polymer substrate using silver nanoparticles ranging from 50 to 200 nm in inkjet printing technology. Specifically, it shows that inkjet technology can leverage to fully fabricated antennas with this technology, where it provides both the characterization and preparation of an antenna. The initial fabrication problem addressed via ink formulation for printing a homogeneous layer with an excellent electrical conductivity. A planar series fed antenna array was analyzed by using the Transmission Line Model with tapering feed line structure. The excitation coefficients in both E and H planes follow a uniform aperture distribution. The realized antenna has 24 dBi gain, the side-lobe level of elevation direction at the center frequency is lower than −15dB. In combination with the planar antenna structure, polymer substrate, and inkjet printing enables the production of structures with high gain that are widely applicable for mm-wave wireless sensors and portable communication devices.

Cross stacking of nanopatterned conductive polymer film was explored using a sacrificial soft template made of nanopatterned polystyrene (PS) film as a guide for nanopatterned conductive polymer film. For use as a conductive film, the PS pattern was filled with poly(3,4-ethylenedioxythiophene) (PEDOT), and then completely removed, to generate single-patterned PEDOT (SPDOT) film having a conductivity of 1079 S/cm, which was comparable to the pristine unpatterned PEDOT (UPDOT) film on a glass slide. SPDOT layers were stacked across each other to form double-layered (DPDOT) and multiple-layered patterned PEDOT film on a glass slide or polymeric substrate. The patterned PEDOT film showed enhanced optical and electrochemical activity; specifically as compared to the UPDOT film on a glass slide, the DPDOT film showed an increase in reflectance and an enhanced electrochemically active surface by 23.4% and 32.8%, respectively. The patterned PEDOT film on a polymer substrate showed high bendability up to being completely folded and maintained its conductivity for over 10 000 cycles of bending. The patterned PEDOT layers were applied to dye-sensitized solar cells (DSSCs) as a transparent conductive oxide (TCO)-free counter electrode. An N719-based DSSC with a DPDOT film recorded a photoconversion efficiency of 7.54%, which is one of the highest values among the TCO-free DSSCs based on a PEDOT counter electrode.

The crystallization behaviors of three types of polymer systems grafted on a flat solid substrate with different grafting densities were investigated by dynamic Monte Carlo simulations. For both of the systems with low and medium grafting densities, nucleation induction period becomes shorter with the increasing polymer-substrate interactions. However, the nucleation mechanisms are different. For the systems with low grafting density, the increase of the attractive interactions results in the enhancement of heterogeneous nucleation process of grafted polymers. For the systems with medium grafting density, the attractive interactions can compensate for the conformational entropy loss induced by the restriction of the substrate, resulting in the increase of local segment density near substrate surface and the improvement of nucleation ability. Meanwhile, nucleation mode changes from intermolecular fringed-micelle nucleation to intramolecular chain-folding nucleation with the increasing interactions. For the systems with high grafting density, crystallization behaviors are almost not affected by polymer-substrate interactions. These findings are helpful to reveal the microscopic mechanism of crystallization behaviors of polymer nanocomposites and the corresponding reinforcement mechanism.

Plasma treatment processing is a ubiquitous and necessary processing step in the manufacturing of electronic components. In the semiconductor industry, this processing step is utilized to clean the polymer substrates prior to soldering and applying epoxy underfill resins in flip-chip technology. In this paper, two polymers, polystyrene and polyimide, were protected with a cover and exposed to various plasmas, to simulate the plasma processing steps found within the microelectronics industry. The industrial step that is modeled is when the silicon die and polymer substrate are connected via solder bumps (flip-chip) and the region in between is exposed to plasma prior to the underfill dispensing step, during the assembly process. Two optical techniques, sum-frequency generation (SFG) vibrational spectroscopy and Fourier transform infrared (FT-IR) spectroscopy, were utilized to investigate the polymer surface and bulk structures, respectively. It was demonstrated that the middle and edge regions of the covered polymer surface behaved differently when exposed to various plasmas. Specifically, the polymer surface, as measured by SFG spectroscopy, changes drastically at the edge, and negligible or much smaller changes are detected at the middle position after the plasma treatment. The FT-IR spectroscopic measurements showed that both the edge and the middle positions of the bulk polymer film are generally unaffected by the plasma treatment, which demonstrates that the changes detected by SFG spectroscopy only occur on the polymer surface. The surface structural changes induced by the plasma treatment include the changes of surface functional group orientation and ordering (or orientation distribution). A better understanding of how plasma processing affects polymer surfaces while covered is of utmost importance to the microelectronics industry and is paramount to improved adhesion and quality in semiconductor devices.

The Ga doped ZnO (GZO) film was deposited on the polymer substrate at room temperature by magnetron sputtering. The resistivity is 8.9×10 −4 Ω cm. The average transmittance in the visible region is over 85%. According to the resistivity and transmittance in the visible light, it is obtained that the film exhibits excellent electrical and optical properties, which satisfies the application for optoelectronic devices. However, the adhesion between the film and the polymer substrate is very weak. In order to figure out the reason of the weak adhesion, we study the adhesive mechanism between the GZO film and the polymer substrate through using depth profiling XPS method, residual stress test, and SIMS method for the first time. The residual stress of the film is a compressive stress. According to the SIMS results, an element diffusion exists at the interface. However, according to the depth profiling XPS results, there is no chemical bonding between the GZO film and the polymer substrate.

As it has outstanding electrical and mechanical properties, like high conductivity, durability, and flexibility, graphene may be an interesting material also for conformal and wearable antennas. Whereas mono-atomic graphene layers have been proven to perform inadequately at microwave frequencies, in this article the performance of multilayered graphene-based sheets (GBS) fabricated onto a polymer substrate is assessed when used as flexible planar and conformal antennas. This is accomplished through studying a simple microstrip antenna topology. Challenges related to the fabrication process of these antennas are discussed, for example adhesion issues and the occurrence of air gaps on the substrate layer. The graphene-based technology is compared to a classical technology involving copper as metal. Bending of the antennas is also discussed. The main conclusion is that multilayered graphene does perform adequately as conductor in antennas at microwave frequencies, with the possibility of providing a slightly higher gain than copper.

Perovskite solar cells are promising for realizing high power conversion efficiency (PCE) with low manufacturing costs, but efficient coating methods are needed for commercialization. Here, a gas blowing method was used to fabricate perovskite solar cells and was found to create a smooth perovskite layer and to prevent voids in large-area cells, when organic materials were used as scaffolds for forming the perovskite. A PCE of 13% in a 1 cm2 active area is achieved by tuning the band-gap energy of MAPbX3 via substitution of Br for I ions in X sites. Incorporation of a poly(3,4-ethylenedioxythiophene) hole transport layer with a higher work function increased the open circuit voltage of the solar cells. All layers of the cells were fabricated at low temperatures (

The electromechanical characteristics of chemical vapor deposited graphene transferred onto a polymeric substrate were investigated by conducting tensile tests in combination with electrical resistance measurement inside a scanning electron microscope. Our results showed that the unique interfacial adhesion character of the graphene/polymer substrate, where the graphene adheres to the substrate by weak van der Waals forces, gives rise to interfacial sliding in the region around the crack edge during tensile straining, causing a reduction in strain transfer from the substrate to the graphene, and this retards or restricts the growth of preformed cracks and promotes the nucleation of new cracks. Such a fracture mechanism (i.e., cracking mechanism) was closely associated with the electromechanical behavior, leading to a distinct three–stage feature, i.e., the stage I flat region, the stage II superlinear region and the stage III linear region, in the electrical resistance−strain curve. We demonstrated the validity of the suggested fracture mechanism and its correlation with the electromechanical characteristics by combining statistical analysis of the evolution of crack size distribution with strain, frictional force measurement and coupled thermal–electrical finite element analysis.

When thin metallic multilayers deposited on a compliant polymer substrate are subjected to stretching, a “brick wall” fracture pattern arises that is associated with a non-uniform two-dimensional stress-strain state evolving as a function of the underlying substrate stretch. The present study is devoted to in situ mechanical microscopy of strain states in a copper/tungsten 18/6 nm multilayer using the combination of synchrotron Scanning X-Ray Diffraction Microscopy (SXDM) and Scanning Electron Microscopy (SEM), coupled with Digital Image Correlation (DIC). We demonstrate that these methods allow spatial variation of the coating strain to be mapped and compared with theoretical predictions based on shear lag theory, allowing the fracture properties of the multilayer to be extracted.

We report the effect of the outgassed moisture depending on main roll temperature from polymer substrate on the electrical and optical properties of indium tin oxide (ITO) films prepared with roll-to-roll sputtering for use as transparent electrodes. The ITO films deposited with a high main roll temperature of 80 °C were found to exhibit an amorphous structure and the post-annealing process did not improve their electrical conductivity or optical transmittance. After the outgassing process was performed 6 times in the roll-to-roll sputtering chamber, the optimized sheet resistance of the ITO thin film was improved from 95 Ω/□ to 78 Ω/□. We found that the structural and electrical properties of the ITO films are strongly dependent on the outgassed moisture during deposition.

In this study, the influence of an externally applied elastic strain on the electrochemical activity of metal film catalysts during the oxygen reduction reaction (ORR) was examined. A novel three-layer specimen, composed of a 10 nm-thick Pt or Pd surface film on a 20 nm-thick Pd70Zr30 metallic glass film that was first deposited on a polymer substrate was used. The intermediate metallic glass layer is instrumental in allowing the top-layer catalytic film to be elastically deformed to a large elastic strain, (up to 2%), enabling a strain effect to be clearly observed. The results consistently show that an applied compressive strain improves the ORR catalytic activity of the Pd and Pt surface layer, while a tensile strain degrades it. These experimental findings are consistent with the prediction of the d-band model, and provide an opportunity to improve the catalytic response during ORR.

Generally, Pd membranes used for H2 purification are deposited on porous stainless steel (SS) or porous ceramics. These membranes are thick ( > 5 μm) because of the large pore size of the support used; hence, such thick membranes are not cost-effective. In this study, cost-effective, viable ultrathin Pd membranes, which were deposited on a polymer substrate, e.g., polybenzimidazole-4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (PBI–HFA), with a thickness less than 700 nm, were prepared by vacuum electroless plating (VELP). The estimated thickness and effective permeation area of the Pd/PBI–HFA membranes were 130–656 nm and 8.3 cm2, respectively. An optimum Pd/PBI–HFA membrane was deposited after two times activation (A2). Because of the adequate grain size of Pd crystals and thickness, Pd/PBI–HFA exhibited better hydrogen permselectivity than the samples prepared by one and three times activation. Furthermore, the polymer surface treated by the CO2 plasma (CO2) and oxidation by H2O2 (H) leads to the enhanced selectivity performance of the final Pd/PBI–HFA membrane, caused by the enhanced adhesion between Pd and PBI–HFA. Gas permeation properties of H2, N2, CO2, and CO were evaluated between 35 and 200 °C and pressure differences between 4 and 8 bar. Pd films fabricated by A2-CO2 methods exhibited superior performance, as well as excellent α H 2 / N 2 and α H 2 / CO 2 permselectivities of 41.4 and 22.3, respectively, at 150 °C and 8 bar, and proved to be impermeable to carbon monoxide (CO). It is a 48% increase in the α H 2 / N 2 permselectivity and fourfold increase in the α H 2 / CO 2 permselectivity from bare PBI-HFA membrane. In this study, an effective Pd layer was deposited on PBI–HFA under optimum Pd electroless plating conditions by controlling the interface adhesion strength and distribution of Pd seeds on the substrate.

This paper discusses metallization of polymers using a low-pressure cold spray (Dymet 413). Three commercial copper powders: i) spherical and ii) dendritic were deposited on thermoplastic polymer - polyamide 6 (PA6). It was difficult to successfully apply a copper coating directly on the polymer substrate, therefore interlayers were applied. Additionally, the copper powder was pre-treated in hydrogen atmosphere to remove the oxide layer and reduce its critical velocity. Finally, the adhesion strength, electrical conductivity, oxygen content and microstructure of resulting coatings were determined. Coatings were characterized by one order of magnitude of lower conductivity than the bulk material and bond strength of 3.6 MPa. The powder shape turned out to have a decisive effect on the possibility on coatings formation.

This article proposes a rapid fabrication method for the production of various molds for the replication of polymer lens arrays. The method involves ultrasonic vibration embossing with a polymer substrate and small steel ball array. Only one embossing step is required in which a concave lens array pattern is directly fabricated onto the polymer substrate. The total processing cycle time is less than 20 s. The polymer substrate with a concave lens array pattern can then be used as a mold for the replication of a polymer lens array through a polydimethylsiloxane casting process. In addition, the diameter and depth of the concave lens array pattern on the surface of the polymer substrate can be changed and controlled by adjusting the processing conditions of the ultrasonic vibration embossing process. Hence, various molds with different concave lens array patterns and thus polymer lens arrays, can be effectively fabricated at very low cost and with high throughput. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Electronics, which functions for a designed time period and then degrades or destructs, holds promise in medical implants, reconfigurable electronic devices and/or temporary functional systems. Here we report a thermally triggered mechanically destructive device, which is constructed with an ultra-thin electronic components supported by an electrospun poly(ε-caprolactone) nanofibrous polymer substrate. Upon heated over the melting temperature of the polymer, the pores of the nanofibers collapse due to the nanofibers’ microscopic polymer chain relaxing and packing. As a result, the polymer substrate exhibits approximately 97.5% area reduction. Ultra-thin electronic components can therefore be destructed concurrently. Furthermore, by integrating a thin resistive heater as the thermal trigger of Joule heating, the device is able to on-demand destruct. The experiment and analytical results illustrate the essential aspects and theoretical understanding for the thermally triggered mechanical destructive devices. The strategy suggests a viable route for designing destructive electronics.

In this work, Zeoliticimidazolate framework-8 (ZIF-8)-based hybrid nanofibrous films were successfully fabricated by a simple strategy of in situ loading on a polymer substrate. In addition, the hybrid film was confirmed by scanning electron microscopy and X-ray diffraction. This hybrid-structure nanofibrous web was applied in heavy metal treatment by combining the unique properties of microporous material as active sizes for heavy metal adsorption with a high surface area of electrospun polyacrylonitrile (PAN) film as the porous substrate. This structure performed with a high permeation flux of 180 L/(m 2 ·h·psi), and the capacity of heavy metal removal from water increased more than three times compared with pure electrospun PAN film. Moreover, the capacity of heavy metal removal was maintained after several recycling processes, which is a significant characteristic of the hybrid electrospun film as a filtering membrane. The hybrid electrospun film is suitable for heavy metal removal from water.

This paper describes a modified dry peel-off process for the fabrication of gold micro heaters embedded in polydimethylsiloxane (PDMS), the characterization of the micro heaters, and the comparison of the measured results with simulated data. The modified dry peel-off process utilizes the difference in molecular adhesion between gold, amine (NH2), and thiol (SH). Three kinds of self-assembled monolayers (SAMs) were implemented in the process for controlling the adhesion between gold electrodes and crystalline silicon as well as between gold electrodes and PDMS. In this work, especially, the different affinities of 3-aminopropyl-triethoxysilane (APTES) and 3-mercaptopropyl-trimethoxysilane (MPTMS) to gold were exploited for the reliable transfer of three different shapes of gold micro heaters to new substrates. Octadecyltrichlorosilane (OTS) reduced the surface energy of silicon and enabled PDMS to easily detach from the silicon. Finally, a simple straight micro heater was characterized by using an infrared (IR) thermal microscopy, and its resistivity and temperature coefficient of resistance (TCR) were estimated to be 48nm and 0.0029K1, respectively, from a temperature-resistance plot. Display Omitted Gold micro heaters were transferred on PDMS substrate through different affinities of thiol (-SH) and amine (-NH2) groups.The resistivity of the gold micro heater was 48nm, and the temperature coefficient of resistance was 0.0029K1.The micro heater was stably heated up during 10cycles in the repeatability test.

Techniques for large-area pattern formation on polymeric substrates are important for fabricating a large variety of functional devices, such as flexible electronics, tunable optical devices, adhesives, and so on. The present study demonstrates a method for pattern formation on poly(dimethylsiloxane) that involves grafting methacrylate polymers through photo-initiated polymerization. The influence of substrate stiffness and monomers type on pattern formation was investigated. Firstly, the stiffness of the substrate was found to affect the topology of the patterns produced. The gap width of convex regions of the pattern was enlarged with decreasing stiffness. It was found that the gap width trended in a manner that was consistent with previous reports, but in this study, relatively large gap widths were observed compared with those from previous studies. Secondly, it was revealed that the solubility of the monomer in the poly(dimethylsiloxane) precursor was the dominant factor in determining whether or not pattern formation occurred. When using insoluble monomers (glycidyl methacrylate and benzyl methacrylate), characteristic patterns were observed. It is speculated that intermolecular attractive forces between the grafted polymers induce lateral aggregation on the substrate, resulting in buckling instability of the grafted polymer layer caused by a mismatch in the equilibrium between the grafted polymer layer and the substrate. Copyright © 2017 John Wiley & Sons, Ltd.

Understanding mechanisms of catalyst–substrate interactions is of essential importance for the design and development of novel catalysts with superior performances. In the present density functional theory study, selective hydrogenation of styrene on a polyacetylene (PA)-supported Pd4 catalyst (Pd4/PA) was employed as a model system to address how catalyst–substrate interactions affect the charge state of Pd, which subsequently influences catalytic activity. It was found that the Pd cluster can be anchored strongly on the C═C bond of the polymer substrate through the π–d interaction, which further leads to charge rearrangement on the Pd4 cluster with the top two Pd atoms being more negatively charged. By comparing the calculated minimum energy profiles of styrene hydrogenation on surfaces of both pure Pd4 and Pd4/PA, the mechanism that dictates the catalytic process on Pd4/PA was identified. Charge analysis reveals that the enhanced catalytic activity of Pd4/PA is largely attributed to the negative charge...

Broadband absorbers are essential components of many light detection, energy harvesting, and camouflage schemes. Current designs are either bulky or use planar films that cause problems in cracking and delamination during flexing or heating. In addition, transferring planar materials to flexible, thin, or low-cost substrates poses a significant challenge. On the other hand, particle-based materials are highly flexible and can be transferred and assembled onto a more desirable substrate but have not shown high performance as an absorber in a standalone system. Here, we introduce a class of particle absorbers called transferable hyperbolic metamaterial particles (THMMP) that display selective, omnidirectional, tunable, broadband absorption when closely packed. This is demonstrated with vertically aligned hyperbolic nanotube (HNT) arrays composed of alternating layers of aluminum-doped zinc oxide and zinc oxide. The broadband absorption measures >87% from 1,200 nm to over 2,200 nm with a maximum absorption of 98.1% at 1,550 nm and remains large for high angles. Furthermore, we show the advantages of particle-based absorbers by transferring the HNTs to a polymer substrate that shows excellent mechanical flexibility and visible transparency while maintaining near-perfect absorption in the telecommunications region. In addition, other material systems and geometries are proposed for a wider range of applications.

In this work we present a novel route to produce a graphene-based film on a polymer substrate. A transparent graphite colloidal suspension was applied to a slat of poly(methyl methacrylate) (PMMA). The good adhesion to the PMMA surface, combined with the shear stress, allows a uniform and continuous spreading of the graphite nanocrystals, resulting in a very uniform graphene multilayer coating on the substrate surface. The fabrication process is simple and yields thin coatings characterized by high optical transparency and large electrical piezoresitivity. Such properties envisage potential applications of this polymer-supported coating for use in strain sensing. The electrical and mechanical properties of these PMMA/graphene coatings were characterized by bending tests. The electrical transport was investigated as a function of the applied stress. The structural and strain properties of the polymer composite material were studied under stress by infrared thermography and micro-Raman spectroscopy.

Herein, we demonstrated direct-write flexible micro-supercapacitors prepared by the near-field electrospinning of polypyrrole (PPy) nanofibers on a patterned metal electrode deposited on a flexible polymer substrate. The continuous porous nanofiber network with a pseudocapacitance effect greatly increases the capacitance and facilitates ion transport in the electrodes. The prototype based on the lab-synthesized PPy nanofibers shows a high capacitance of 0.48 mF cm−2 when the total area of both electrodes and electrolyte is considered, and the performance is not affected when it is bent to different extents. The micro-supercapacitors were experimentally proved to be highly flexible with excellent electrochemical performance and cycling stability. Our approach is simple, versatile, and compatible with different substrates for the direct integration of energy storage devices in flexible microsystems.

This work describes the use of inkjet printing technology to fabricate a flexible microstrip antenna. The antenna is printed on a flexible PET foil (Polyethylene terephthalate) using silver nanoparticles. Silver nanoparticles were synthetized by the solvothermal precipitation technique. The diameter of the prepared silver nanoparticles ranges from 20 to 200 nm measured with the help of the SEM analysis. In addition, the ink formulation for printing of a homogenous and electrically conductive layer was further prepared using silver nanoparticles. The printed antenna operates in two frequency bands of 2.02 GHz (-16.02 db) and 2.3 GHz (-19.33 db). The antenna is flexible and weigh is only 0.208 g and is suitable for electronic devices of a very low weight, such as wearable electronic devices. © 2017 Elsevier Ltd., Ministry of Education, Youth and Sports of the Czech Republic - National Sustainability Program NPU I [LO1504]; Operational Program Research and Development for Innovations; European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409]

We have successfully synthesized an ABA tri-block co-polymer of poly(methacrylic acid)-block-poly(2-hydroxyethyl methacrylate)-block-poly(methacrylic acid), having Mw = 100k and 272k where we were able to insert RDG or RGD peptide sequences using thiol-acrylate Michael addition. A soft silicone stamp was then used to imprint a 0.4-micron wide grating of the copolymer with a period of 10 microns. The samples were then examined with atomic force microscopy after application of an external electric field and the pattern was observed to stretch by a factor of five. Cells plated onto these substrates showed clear preference for the striped patterns formed under the influence of the external field, and no preferential attachment to the patterns formed in the absence of the field. Cell migration experiments, using the agarose droplet method, performed on spun cast copolymer films showed minimal migration and adhesion on the substrates without peptides or those with only with the RDG peptide, while good adhesion and significant outward migration was observed for cells plated on the copolymers with the RGD sequence. Taken together these results confirmed our hypothesis that a smart biomimetic polymer substrate could be constructed where functional domains could be revealed selectively allowing us to mimic the natural design of engineered tissue constructs.

High dielectric constant ceramic-polymer composite materials have been produced by thermal-treatment in the range of 160 to 200 °C. Here, we introduce a room temperature process of generating flexible high dielectric constant nanocomposite films on a polymer substrate by combining a printing technique with a UV-curing process. The composite structure is based on nanoscale BaTiO3 and Ag particles dispersed in a UV-cured polymer matrix. Dielectric characteristics of the nanocomposite thick films depended on the volume fraction and particle size of BaTiO3 as well as the content of Ag. As an optimal result, a dielectric constant of ∼300 and a dielectric loss of 0.08 were achieved when ∼81 nm BaTiO3 and ∼34 nm Ag particles were used in a total volume fraction of 56.2%, which are very competitive for flexible capacitive devices. Current–voltage behavior of the nanocomposite films depended largely on the content of Ag content as related to the percolative transition of electrical conduction.

A magnetodielectric substrate is firstly proposed for implantable antennas in medical implant communication service (MICS) band. Ba 3 Co 2 Fe 24 O 41 (Co 2 Z), Z-type hexaferrite flakes synthesized by molten-salt method were incorporated with a polymer matrix, having a real permeability of 2.88 and a magnetic loss of 0.029 at 402 MHz. A spiral antenna with the magnetodielectric substrate has a bandwidth 70% and 50% broader than that with a commercial dielectric substrate, Rogers 3210, in a 2/3-phantom model and a multi-layered body model, respectively. The band broadening retains the bandwidth to be overlapped after implant positions change, leading to an enhancement in insensitivity to the implant position.

Flexible negative refractive index metamaterials (NIMs), composed of two conductive metallic layers separated by a 0.75 mm thick polyimide film, are fabricated using a simple and effective screen printing method. Benefiting from the ultra-high conductivity of the 3 μm silver (Ag) layers, the NIMs exhibit negative refraction on a wide frequency range of 3 GHz, whereas the thickness is only 0.756 mm. The NIMs show excellent flexibility with a minimum bending diameter of 20 mm without degradation of Ag layer, because of the strong adhesion between the Ag and the polymer substrate. Furthermore, these flexible NIMs show amazing stability at a temperature of 25 °C and a relative humidity of 30% for 10 months.