Search

Polyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C. [ABSTRACT FROM AUTHOR]

Thin films of polyimide (PI) and graphene oxide (GO) were exposed to the accelerated Cu-ions with an energy of 1500 keV at different ion fluences (3.75 × 1012; 3.75 × 1014; 1 × 1016) cm−2. The reason for Cu-ion irradiation lies in the modification of thin PI and GO layers and their subsequent use in electronics, photo-catalysis and humidity sensing. It was expected that three ways would primarily carry out modification: i) interaction of the accelerated ions with atoms and electrons of the irradiated films, ii) implantation of Cu ions inside the matrices and their attachment to the structures in the form of CuO, and iii) formation of C and Cu aggregates and Cu nanoparticles in the subsurface layer to form an electrically conductive network. The effects of the interactions of energetic Cu-ions on the PI and GO matrices, including the prediction of the depth of Cu ion penetration, were simulated by SRIM software. Elemental changes, including the depth profiles of implanted Cu-ions, were investigated by Rutherford backscattering spectrometry (RBS) and Elastic recoil detection analysis (ERDA). Changes in the chemical bonding on the PI and GO surfaces were studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The effect of energetic Cu-ions on the surface morphology was analyzed by Atomic force microscopy (AFM). For the possible application of PI and GO composites in electronics and sensory, the sheet resistivity were measured by the two- point method and the effect of air humidity on electrical properties was studied. Furthermore, the degradation of Rhodamine B solution in the presence of prepared composites under UV-light irradiation was measured for possible use in photo-catalysis. It was found that the interaction of Cu- ions with the matrix leads to the release of oxygen and hydrogen, resulting in an increase in carbon concentration. The increase in carbon concentration leads to an increase in the electrical conductivity of both materials. The irradiation with Cu ion fluence of 1 × 1016 cm−2 probably formed in PI a subsurface conducting network that reduced the sheet resistivity by almost eleven orders of magnitude. The ion irradiation by Cu ion with fluences below 1 × 1016 cm−2 enhances the photo- catalytic properties of both used materials and the best result was achieved in the case of PI irradiated by the ion fluence of 3.75 × 1014 cm−2. [ABSTRACT FROM AUTHOR]

Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 µm to 25 µm, and the effect of aggregation structure on thermal expansion behavior along different directions was studied. Both in-plane and out-of-plane linear thermal expansion (CTF// and CTF⊥) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method. Volumetric and anisotropic behavior of thermal expansion were also investigated. With increasing film thickness, CTF// gradually increased from 32.2 ppm/°C to 46.1 ppm/°C while CTF⊥ decreased from 149.7 ppm/°C to 128.2 ppm/°C. Volumetric thermal expansion of polyimide films was less sensitive to the varied thickness, but anisotropy of thermal expansion was reduced. Polyimide film of 5 µm thickness showed large birefringence, indicating more considerable in-plane chain orientation anisotropy. Besides, molecular chains were more densely packed along in-plane direction when film thickness increased, while became loosely stacked in the out-of-plane direction. In contrast to the enhanced lateral chain packing for thicker films, higher vertical chain packing order was found in thinner films. The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD. It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing, whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing. The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing, which is associated with both chemistry and morphological structure of polyimide. [ABSTRACT FROM AUTHOR]

Piezoelectric nanogenerators (PENGs) composed of inorganic ceramic nanoparticles and polymer matrix have received extensive attention from scientific researchers. In this article, PENG based on BaTiO3-Bi/Polyimide (BTO-Bi/PI) composite thin films were prepared. The influence of the doping amount of Bi2O3 on the electrical properties of BaTiO3 and the power generation performance of composite thin films were studied in detail. BaTiO3 doped with 0.1 mol% Bi2O3 achieve optimal piezoelectric properties with d33 of 246 pC/N and d33* of 856 pm/V. The flexible BTO-Bi/PI PENG device demonstrates short-circuit current of 365 nA and open-circuit voltage of 17 V, which shows great capability of capturing mechanical energy; it also can be used as sensors under lower mechanical stress and has a wide operating temperature range. [ABSTRACT FROM AUTHOR]

Polyimide thin films with high thermal stability and resistance will contribute to the development of flexible energy devices, which could be compatible with their high temperature fabrication process. Thus, we have prepared poly(amic acid) solutions with bisbenzimidazole and bisbenzoxazole based diamines and finally fabricated polyimide thin films. After comparing with commercial type polyimides, the polyimides containing bisbenzimidazole and bisbenzoxazole segments showed excellent thermal decomposition temperatures (of 581 and 584 °C, respectively), outstanding mechanical properties (with a tensile strength of 218 and 192 MPa, respectively), and relatively low water absorption percentages (of 0.68% and 0.63%, respectively). The superior properties should be ascribed to the rigid molecular chain skeleton, strong inter- and intra-molecular-chain forces, and hydrogen bonds. [ABSTRACT FROM AUTHOR]

This paper presents the surface modification and charge transportation mechanism of thin polyimide films. Here, we demonstrate that the surface modification of these films, by using the fluorine gas-phase, improves the charges mitigation and, thereafter, suppress the space charges. The experimental results indicate that the thermal step current for fluorine coated films reduce significantly in comparison to pure polyimide films. The thin layer of fluorine coating helps to release the surface charge, reduce the charge injection from the electrode, provide hindrance for charges to penetrate into the bulk of the films and the higher degree of charge disappearing helps to reduce the space charge growth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Quantification of thin film adhesion to their substrates is crucial to ascertain reliable multi-material components, which are typically encountered in technologically relevant structures such as microelectronic devices. Metal-polymer interfaces have gained increased attention in the past since they open a new research field towards developing flexible electronic devices, yet their quantification is often experimentally challenging since standard routes to assess adhesion such as nanoindentation-based techniques or four-point bending may not be applicable due to lack of rigidity. In the present study interface adhesion of nominally 150 nm thin WTi films sputtered onto polyimide, part of a multi-material stack consisting of brittle and compliant materials, was determined experimentally. Upon contactless removal of the bilayer by etching a sacrificial layer, originally part of the multilayer stack, the WTi film showed cracks and buckles, which could be characterized by atomic force and confocal laser scanning microscopy. Hence, two models to quantify adhesion were compared: the model of tensile induced delamination – typically employed for metal films on compliant substrates – and the model of Hutchinson and Suo, which is usually applied on spontaneously formed, straight buckles. The first model reveals adhesion values for the native WTi-polyimide interface of 2.4 ± 0.8 J/m2 and the latter model 4.7 ± 2.3 J/m2. The slight difference in adhesion results, which are both rooted in the same theory, could be rationalized by the fact that the model for tensile induced delamination gives a measure of the lower bound of the adhesion energy. The overall rather lower adhesion values could be explained by additional transmission electron microscopy investigations conducted on the cross section of the interface, which reveals no interlinking morphology and a flat interface. [Display omitted] • Adhesion of unconditioned WTi-PI interface was determined with spontaneous buckles. • Two adhesion models based on Euler theory were compared on same buckles. • WTi-PI adhesion compares to other native metal-polymer interfaces (2.4–4.7 J/m2). • Sharp interface structure and film chemistry were evaluated with TEM. • Interface structure and chemistry feasibly control adhesion energy. [ABSTRACT FROM AUTHOR]

In this study, we deposited a series of Ag and N co-doped ZnO thin films (ZnAgO:N) with different Ag atomic percentage (at. %) ratios on flexible polyimide (PI) substrates to realize p-type ZnO-based thin films for wearable thermoelectric applications by in situ co-sputtering of ZnO and Ag by RF and DC magnetron sputtering in a mixture of Ar and N2O gases. To evaluate the thermoelectric performance of these ZnAgO:N thin films, we measured the Seebeck coefficient S and electrical conductivity σ of the thin films with various Ag at. % ratios and calculated the power factor S2σ. These measurements confirmed that the co-doping of Ag and N into ZnO is an effective method for fabricating p-type ZnAgO:N thin films with σ in the range of about 105–3.3 × 106 S/m, as a function of Ag at. % ratio on the flexible PI substrates. In addition, the presence of an optimal Ag at. % ratio that leads to a maximum S2σ for the p-type ZnAgO:N thin films was observed. Raman spectroscopy and x-ray photoelectron spectroscopy revealed that the p-type conductivity in ZnAgO:N thin films originates from the acceptors AgZn and NO formed by the co-dopants Ag and N. As a result, the S and σ of the p-type ZnAgO:N thin films were investigated to be affected significantly by the acceptors and defects formed by the Ag and N co-dopants in the thin films. The influence of AgZn and NO on the appearance of the p-type conductivity in ZnAgO:N thin films and S and σ of the thin films was intensively studied. [ABSTRACT FROM AUTHOR]

We present a combined experimental and analytical approach to study the formation of creases in tightly folded Kapton polyimide films. In the experiments, we have developed a robust procedure to create creases with repeatable residual fold angle by compressing initially bent coupons. We then use it to explore the influence of different control parameters, such as the force applied, and the time the film is being pressed. The experimental results are compared with a simplified one-dimensional elastica model, as well as a high fidelity finite element model; both models take into account the elasto-plastic behavior of the film. The models are able to predict the force required to create the crease, as well as the trend in the residual angle of the fold once the force is removed. We non-dimensionalize our results to rationalize the effect of plasticity, and we find robust scalings that extend our findings to other geometries and material properties. [ABSTRACT FROM AUTHOR]

Schematic of growing ZnO nanoarrays on flexible PI substrates. • ZnO nanoarrays were prepared on polyimide by a novel method. • Partially imidized polyimide films have significantly larger surface roughness. • Seed particles of ZnO can be embedded to polyimide during its growth process. • ZnO nanoarrays on partially imidized ZnO-seeded membranes show excellent properties. ZnO seed and nanoarrays were effectively integrated on polyimide (PI) substrates by depositing the ZnO seed during thermal imination of PI. The surface roughness of PI films with different imidization degrees was different; the maximum root-mean square-value was achieved when the imidization degree was 80%. The prepared wurtzite-type ZnO seed and nanorods showed preferential c-axis orientation and offered good adhesion to flexible PI substrates. The light transmittance of the functionalized film, which mainly depends on PI, was sufficiently large in the visible region. Therefore, the proposed methodology is a novel route for synthesizing a variety of nanostructures on PI films at a low cost. [ABSTRACT FROM AUTHOR]

We report the anisotropic field-effect hole mobility of 30 nm-thick pentacene films deposited on 1.6 nm-thick polyimide photo-alignment layers with different in-plane anisotropy. To induce different in-plane anisotropy, the light exposure was varied up to 16 J/cm2. In this light exposure range, the long molecular axis of pentacene was standing with respect to the substrate surface (c*-axis oriented 'thin film phase'), and the pentacene molecular plane was oriented on average parallel to the average alignment direction of the underlying polyimide backbone structures. For light exposures of 6 and 11 J/cm2, the field-effect mobility for the current flow direction parallel (perpendicular) to the alignment direction of pentacene molecular plane was enhanced (suppressed) compared to that of the pentacene film deposited on non-aligned polyimide film. This field-effect mobility enhancement shows a positive effect of the in-plane alignment control of pentacene molecules. However, the field-effect mobility decreased at a light exposure of 16 J/cm2, even though the in-plane orientation order of the pentacene molecular plane slightly increased. The causes for the mobility enhancement at 6 and 11 J/cm2 and the mobility decrease at 16 J/cm2 were discussed. [ABSTRACT FROM AUTHOR]

The development of flexible film/substrate composite systems has emerged as a promising strategy to enhance the functionality of sub-micron NiTi (Nickel–Titanium) thin films. Among potential substrates, polyimide foils offer many advantages as they are lightweight, flexible, and durable. However, the properties and behavior of NiTi films deposited on polyimides remain poorly understood compared to films on traditional substrates. In this work, NiTi films were sputter-deposited simultaneously onto polyimide foils (Kapton) and Si wafers under various conditions. The films' composition, crystalline nature, and morphology were analyzed and compared. The films deposited on polyimide exhibited distinct differences in Ni content (1.0 -4.4 at.% lower), thickness, grain morphology, and crystal structure compared to those deposited on Si. The differences in properties between polyimides and Si (e.g., surface energy, thermal conductivity) induced noticeable effects on NiTi film growth and final structure. These discrepancies can lead to different optical, wetting, superelastic, and shape memory behavior, as demonstrated by the pseudo-two-way shape memory effect observed in only one of the NiTi/Kapton actuators. Our findings highlight the need for further investigations of the interactions between NiTi films and polyimide substrates, which will facilitate the development of sub-micron NiTi-based applications such as wearable electronics. [Display omitted] • Sub-micron Nickel–Titanium films were sputtered on polyimide foils and Si wafers. • NiTi films' Ni content on polymide were 1.0 - 4.4 at.% lower than on the Si wafers. • The films on polyimide were 63–123% of the thickness of films on Si. • Films on polyimide were morphologically and structurally different than films on Si. [ABSTRACT FROM AUTHOR]

• A low-cost and simple non-solvent induced phase separation was adopted. • With coagulation bath content varying, two kinds of pore structure were got. • The prepared PI porous films showed excellent properties in many aspects. Polyimide (PI) porous films were prepared by non-solvent induced phase separation with low-cost and simple method. A low-cost and environmentally friendly solution of water and ethanol was selected as non-solvent coagulation bath and effects of water and ethanol content on microstructure and properties was studied. The prepared films showed high mechanical property at high temperature, excellent dielectric property and thermal stability. Thus there are excellent application prospects in fields of flexible electronics and microelectronics industry. [ABSTRACT FROM AUTHOR]

Vertically aligned (VA), fully aromatic polyimide (PI) thin films were successfully prepared from a lyotropic smectic liquid-crystalline precursor of poly(amic ester) (PAE) containing perfluorooctyl (R f) terminal groups using a "push-coating" method. Because the repeating units of PAE form the smectic layer, the main chains of PAE are oriented perpendicular to the layer. A homeotropically aligned smectic structure is induced by the step-by-step stacking growth of the layer from the monolayer of the R f groups self-organized on the hydrophobic interfaces (interfaces between the PAE solution and air or a surface-modified substrate), leading to a vertically aligned PAE. By optimizing the preparation conditions, the values of the orientational order parameter (S) of the push-coated PAE film exceeded 0.7. The homeotropically aligned PAE films were imidized by heating to 300 °C, and the high S values were maintained in the subsequent imidization to give VA PI films. Despite the large standard deviation in the temperature variation of the optical path length of the VA PI films, the small and reversible variations in S confirmed that the vertical orientation of the PI films was thermodynamically stable. [Display omitted] • A series of s BPDA-based fully aromatic poly(amic ester)s, BP m , is exhibit a lyotropic smectic liquid-crystal (LSm). • Vertically-aligned polyimide (PI) thin films were successfully prepared from LSm of BP m with perfluorinated termini (R f). • Smectic layer consisting of the repeating unit of BP m grows from surface-organized monolayer of R f in gradual stacking manner. • Main-chains of BP m are vertically aligned to the smectic layer and the surface, resulting in VA. • Vertical alignment induced in the LSm phase of BP m remains during imidization, resulting in thermodynamically-stable VA PI. [ABSTRACT FROM AUTHOR]

• Two fluorinated polyimide films crosslinked by TAPP or TAPc were prepared. • The PI/TAPP and PI/TAPc films showed higher dielectric constant than neat PI. • The PI/TAPP and PI/TAPc exhibited smaller charge decay than neat PI in LS-TENGs. • The PI/TAPP and PI/TAPc showed higher friction coefficient stability than neat PI. In order to improve the charge retention, anti-decay ability and durability of traditional triboelectric materials in lateral sliding-mode triboelectric nanogenerators (LS-TENGs), two fluorinated polyimide films crosslinked by porphyrin tetra-amino phenyl porphyrin (TAPP) and tetra-amine phthalocyanine (TAPc) were synthesized, and their contact angles, dielectric properties, output performances and tribological properties were studied in detail. The results showed that the polyimide films crosslinked by TAPP (PI/TAPP) and TAPc (PI/TAPc) with lower surface energies had higher dielectric constants compared with neat PI and Kapton. In addition, TAPP and TAPc not only improved the electrical output with a small decay of charge density, but also reduced the wear of PI films during the whole triboelectrification process, which is attributed to the high permittivity and the crosslinked effect of PI with TAPP or TAPc. Thus, PI films with TAPP and TAPc hold great promise for dielectric research and LS-TENG applications. [ABSTRACT FROM AUTHOR]

• Low-temperature prepared BiFe 0.95 Co 0.05 O 3 films exhibited excellent characteristics. • A solution-based seeded photocatalytic precursor method has been developed. • The physical mechanism of the low-temperature prepared films is explained. Multiferroic memory exhibits unusual physical properties due to the electrical writing and magnetic reading of data to achieve low power consumption and efficient data processing. The flexibility of the multiferroic memory can realize its application in portable and wearable smart electronic products. The main challenge of integrating multiferroic oxides onto flexible substrates is to lower their processing temperature below the degradation temperature of plastic substrates. In this paper, the bendable inorganic BiFe 0.95 Co 0.05 O 3 polycrystalline thin films were prepared directly on flexible polyimide substrates with Pt electrode at only 350 ℃ by solution-based seeded photocatalytic precursor method. The flexible multiferroic element could bend safely to a small bending radius of 3 mm and exhibited excellent ferroelectricity, ferromagnetic, and magnetoelectric coupling characteristics at room temperature. Its remanent polarization was as high as 36 μC/cm2, remanent magnetization up to 4110 A/m, and magnetoelectric coupling coefficient up to 0.0135 V/A. The polarization did not deteriorate significantly during 103 bending-release cycles, 107 fatigue cycles, and 104 s data retention.These results prove the concept of integrating single-phase multiferroic thin films and flexible plastic substrates with low temperature by seeded photocatalytic precursor method and demonstrate the application potential of single-phase multiferroic films prepared at low temperature in the next generation of flexible multiferroic memory. [ABSTRACT FROM AUTHOR]

CaCu3Ti4O12 (CCTO) and Zr-doped CaCu3Ti3.95Zr0.05O12 (CCTZO) particles with a giant dielectric permittivity were used as filler to prepare Polyimide (PI)-based composites, respectively. Dielectric properties of CCTO/PI and CCTZO/PI composite films have been investigated comparatively. It is found that the dielectric properties of two kinds of composite films with low concentration filler loading have independence on frequency and temperature, while the dielectric permittivity of two kinds of composite films increases remarkably with increasing concentration of filler loading(>20%) and temperature. The dielectric permittivity of CCTZO/PI composite film with a 40% filler loading reaches up to 70 at 10 Hz, which is higher than that (43) of CCTO/PI composite film with the same concentration filler loading. It is also found that the dielectric permittivity of CCTZO/PI composite film can reach about 260 at 150 ° when the concentration of CCTZO loading is 40 vol%. The conductive properties of two kinds of composite films increase with increasing frequency, temperature and concentration of filler loading. The study indicates that dielectric and conductive properties are closely related to the polarization between filler and PI matrix and semiconductive network supported by the percolation theory. [ABSTRACT FROM AUTHOR]

Polyimide/TiO2 (PI/TiO2) composite films were fabricated by in-situ polymerization and are reported in this paper. The effect of interface (PI-TiO2) on dielectric and breakdown properties was investigated via conductivity, photo-stimulated discharge (PSD), permittivity, thermo-gravimetric analysis (TGA) and breakdown characteristic. The results show that interface between PI and TiO2 in composites contains deep charge traps with density proportional to TiO2 doping concentration. Interface enhances space-charge polarization to increase conductivity and loss tangent at low frequency. The pinning influence of interface on PI molecular chain motion is reflected in the downtrend of permittivity (0%-4% nano-TiO2 doping concentration) and increasing decomposition temperature (TPI

Flexible devices have recently been actively investigated for various purposes. Sb-based materials particularly attractive for medical applications. We grew InSb and dilute nitride InSbN thin films on polyimide (PI) films and on quartz substrates by reactive radio frequency magnetron sputtering. By comparing the properties of thin films grown on PI films with those on quartz substrates, we revealed that InSb/PI contains large amount of native defects which originate from Sb clusters and Sb vacancies (V Sb). Although the properties of the thin films grown on quartz substrates did not improve by nitridation, dilute nitride InSbN/PI showed superior properties to InSb/PI. These changes in thin film properties suggest that nitridation generates the substitution of V Sb for N and the suppression of native defect formation. Consequently, dilute nitride InSbN/PI is potentially useful in electronic device applications. Furthermore, we evaluated the skin absorption of dilute nitride InSbN/PI. As a result, both In and Sb hardly permeated and were retained inside the skin. We conclude that the flexible dilute nitride InSbN/PI can be applied to epidermal optoelectronics. • Flexible InSb/PI and InSbN/PI were prepared by reactive RF magnetron sputtering. • Crystallinity of InSb/PI is improved by substituting Sb vacancies for N. • Dilute nitride InSbN/PI shows properties useful for electronic device applications. • Permeated amounts of In and Sb are small and are retained inside skin. • Flexible dilute nitride InSbN/PI can potentially be used in E-skin devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti 3 C 2 T x MXene was synthesized successfully. • A novel nanomaterial hybrid of Ti 3 C 2 T x -AuNP was synthesized. • Transducing bioreceptor base of Polyimide/ Ti 3 C 2 T x -AuNP was synthesized. • A thin film of the same was used for biosensing of CEA successfully. •Limit of detection was obtained at 0.001 ng/mL. Ti 3 C 2 T x MXene was synthesized and the 2D layers were hybridized with Au nanoparticle (AuNP) through the in-situ method. The study was successfully prepared MXene 2D layer and the same was TEM captured as well. Polyimide/MXene-AuNP (PI/Mxene-AuNP) transducing conducting nanocomposite thin film was synthesized and evaluated the new material's capability to use as a transducing thin film for biosensing application. The bioreceptor was prepared on the delay line area of the SAW device by covalently immobilizing mouse monoclonal antibody of carcinoembryonic antigen (CEA) through the thioglycolic acid arm linker mechanism. Immunoassay analysis has suggested that the biosensor responds linearly with the increase in the concentration of the CEA sample. The limit of detection was observed at 0.001 ng/mL. The insertion loss of the bioreceptor was recorded at 10 dB, which also mattered in the high sensitivity of the biosensor. The biosensor has shown excellent selectivity within the environment of other common tumour markers and was stable for 75 days under periodical testing conditions. Clinical serum samples were analyzed successfully and the results were compared with values obtained through the ELISA method. [ABSTRACT FROM AUTHOR]

This paper reports the fabrication and the characterization of an optical waveguide from a 6FDA/MPDA polyimide in order to realize the interconnection of systems of communication. The emergence of such systems is conditioned by the performances that the material must present (with low optical losses) and its resistance to high temperatures (>300 °C).We present the optical characterizations of monomode guiding structures in rib-waveguide configuration; propagation loss measurements are made by the “cut-back” method and at the wavelength of 1.3 and 1.55 μm in polarized light. In the best case, we obtain propagation losses of about 0.55 dB/cm for the TE mode at a wavelength of 1.3 μm. [Copyright &y& Elsevier]

Results of in situ measurements of the thermomechanical properties of polyimides used in the microelectronic packaging industry are presented. During the formation of polymer layers and their subsequent use, there are several thermomechanical effects which can affect the electronic packages performance. Specifically, thermal loading of the structure results in elastic and inelastic effects such as relaxation. The time and temperature dependent relaxation behavior of polyimides in multilayer structures were investigated to determine their thermomechanical properties. Both a numerical model and experimental analysis were used to determine the curvature change of multilayer structures during manufacturing. The numerical model, which is based on Maxwell's model, characterizes the stress relaxation behavior of thermoplastics. The changes in stress over time for quartz-polyimide-aluminum and quartz-polyimide-germanium heterostructures were obtained. From these observations, the relaxation time constant, activation energy, and viscosity-to-shear-modulus ratio were determined for the polyimide [ABSTRACT FROM PUBLISHER]

Porous polyimide (PI) thin films have been fabricated successfully by using silica microparticles (MPs) with different particle sizes as a template, and the three dimensional porous structure has been observed clearly by mean of transmission electron microtomography. The measured values of dielectric constant (ε) decreased remarkably by introducing a porous structure, compared with ordinary PI thin films. Especially, the porosity evidently increased (ca. 10%) by suitably employing silica MPs having different particle sizes, and then the value of ε was further reduced. Bruggeman model could reproduce nearly the relationship between the value of ε and porosity. Image 1 • Porous polyimide thin films fabricated by using silica microparticles as a template. • Increase in porosity by employing silica microparticles with different particle sizes. • Transmission electron microtomography images of three-dimensional porous structure. • Reduction of dielectric constants with the porosity on the basis of Bruggeman model. [ABSTRACT FROM AUTHOR]

• AZO electrode on transparent PI are fabricated with ex-situ low temperature ALD. • Tribological properties of AZO electrode by nanoscratch test were characterized. • Cracking characteristics of AZO electrode for various tensile strain is investigated. • Sheet resistance and electrical properties of the AZO electrode were studied. Fabrication of Al 2 O 3 doped ZnO (AZO) thin films on transparent polyimide substrates using ex-situ oxygen plasma-assisted atomic layer deposition (ALD) is studied. The alumina composition is controlled by adjusting the ALD cycle ratio in the reaction sequence from 9:1 to 49:1 (diethylzinc/H2O:trimethylaluminum/H2O). Nanoscratch and electromechanical tensile tests are performed to evaluate the mechanical reliability of the AZO thin films fabricated under various processing conditions. Conventionally deposited AZO shows the lowest sheet resistance of 294 Ω/sq at a doping ratio of 19:1 at 150 ℃. However, the resistance of AZO grown on a polymer surface modified by plasma is higher at 429 Ω/sq. Nanoscratch results reveal that the first critical load could be increased by surface hardening and strong adherence as a function of the process temperature and plasma treatment. Under a tensile strain, doping of alumina delayed the strain (%) at crack initiation from 0.58 to 0.82%. The initial elastic modulus of the AZO/transparent polyimide composites showed a transient decrease with an increase in the alumina content from 2.7 to 3.8 at.%. These results demonstrating the mechanical characteristics of thin films as a function of the processing conditions are significant for flexible display manufacturing. [ABSTRACT FROM AUTHOR]

This study focuses on a detailed comparative investigation of the changes inflicted by the UV irradiation of some polyimide films. In this regard, three aromatic polyimides were synthesized via conventional, high-temperature, polycondensation reactions in solution, followed by conventional casting towards polyimide thin films. The obtained materials were subjected to 10 h of UV irradiation and various techniques were used to assess the chemical and topographical changes it produced. The FT–IR evaluation provided evidence of the breakage of the imide cycle. Variations in the water contact angle values suggested a shift in the occurrence of hydrophobic and hydrophilic groups on the surface of the polyimide films. SEM analysis showed no major changes in films' morphology after UV irradiation, while EDX measurements emphasized the connections between the structure of each polyimide and the changes in its surface chemistry. Cell behavior was closely related to the surfaces' wettability and revealed that UV irradiation enhances cell proliferation on polyimide films. It was assumed that the hydrophobicity induced by certain structural elements led to a different exposure of the imide cycle to UV irradiation through distinct polymer chains orientation. Image 1 • Functionalization of polyimide films via UV irradiation. • Assessment of the chemical and topographical changes via multiple investigation tools. • Cell behavior was closely related to the surface wettability properties due to UV irradiation. [ABSTRACT FROM AUTHOR]

This paper theoretically and experimentally studies an innovative laser lift-off (LLO) technique that utilizes a line-shaped laser to scan the interfacial polyimide (PI) film through the transparent substrate to peel off the thin-film electronics. A comprehensive illustration of the mechanism of the occurrence of wrinkles in ultrathin PI films is provided, based on which the LLO process for ultrathin flexible electronics is optimized. A mechanical model is established to describe the deformation of the laser-induced blister and validated by experimental results. The results show that the wrinkles are due to the plastic deformation inside the film, which is caused by the instantaneous pressure of gas products generated by laser ablation. By measuring the instantaneous pressure through piezoelectric sensors, the maximum allowable laser fluence without inducing plastic deformation has been found, which decreases linearly with the film thickness. Accordingly, the process window of the traditional single-pass LLO has been obtained, which confirms that the wrinkles in ultrathin PI films (<5 μm) are inevitable through traditional LLO process. To obtain non-wrinkled ultrathin films, two optimization approaches are proposed, which are also verified through the tests of strain sensors. Unlabelled Image • Wrinkles result from plastic deformation of ultrathin PI film caused by gas pressure. • A high stress level of the ultrathin PI film due to its large-deflection deformation • A linear relationship between the film thickness and the allowable laser fluence • Minimum thickness of peelable, nonwrinkled PI film of traditional LLO is over 5 μm. • Two strategies can peel ultrathin flexible devices without plastic deformation. [ABSTRACT FROM AUTHOR]

• Enhanced flexible room temperature ammonia sensor based on FeCl 3 -PEDOT: PSS films. • Inkjet printing gas sensing films with controlled film thickness and additive level. • FeCl 3 additive plays two key role in response to NH 3. • A simple and effective method to find new sensing material with inkjet printing method. Herein we report improved ammonia (NH 3) gas sensing properties based on poly (3,4-ethylene-dioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) thin films with ferric chloride (FeCl 3) as additives, which were prepared by inkjet printing the PEDOT: PSS solution and FeCl 3 aqueous solution onto the flexible polyimide films in sequence. PEDOT: PSS based gas sensing films with different thickness and different content of FeCl 3 were formed. The morphologies and electrical properties of these films were investigated by scanning electron microscope, X-ray photoelectron spectroscopy and an instrument designed to measure the gas sensing abilities of the films. The results showed that the addition of FeCl 3 to the PEDOT: PSS (FeCl 3 -PEDOT: PSS) thin film improved the NH 3 sensing performance of the sensor significantly. The response value was increased tenfold to approximately 44%, and the response time was reduced by 30 times to 20 s than those of the pure PEDOT: PSS film for detecting 50 ppm NH 3 at 20 °C. Furthermore, the lower detectable NH 3 concentration of the FeCl 3 -PEDOT: PSS thin film sensor was 0.5 ppm at room temperature with the response value of 7.6%. Additionally, the FeCl 3 -PEDOT: PSS thin film sensor presented excellent flexible stability, showing only minor response value changes with different bending angles. The results reveal the potential application of flexible based sensor for monitoring NH 3 gas under ambient conditions and show that ink-jet printing is a simple and low-cost method to prepare flexible gas sensing films with controlled film thickness and additive level. [ABSTRACT FROM AUTHOR]

Flexible charge‐trap memory thin‐film transistors (CTM‐TFTs) are fabricated and characterized for next‐generation highly functional consumer electronics. Poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and 1.2‐µm‐thick polyimide (PI) films are introduced as source/drain electrodes and plastic substrates, respectively, to realize highly flexible CTM‐TFTs with conducting polymers. A uniquely structured sacrificial layer is suggested for the lithography‐compatible transfer and patterning processes of PEDOT:PSS on inorganic Al2O3 barrier layers are prepared on the PI substrates. The CTM‐TFTs show significantly improved device performance compared with those of the previous proto‐type devices, including a memory window (MW) of 16.8 V and program speed of 100 µs at a program pulse amplitude of ±20 V. Furthermore, the MWs and on/off current ratio do not shown remarkable degradation, and total variations within a range of less than 7.5% are observed even under harsh bending strains with a curvature radius of 1 mm. Additionally, the mechanical robustness of the fabricated CTM‐TFTs is quantitatively discussed based on the contributions of the conducting polymer electrode and the ultrathin PI film to further improve device performance of the flexible CTM‐TFTs. [ABSTRACT FROM AUTHOR]

The authors report on thermally‐evaporated MoO3/Ag/MoO3 multilayer films as a flexible and transparent electrode for high performance flexible thin film heaters (TFHs). Using thermal evaporation, the authors obtain highly flexible MoO3/Ag/MoO3 multilayer films on colorless polyimide substrate without plasma damage. To optimize the thickness of the Ag interlayer, the authors investigate the electrical, optical, morphological, and mechanical properties of MoO3/Ag/MoO3 multilayers as a function of Ag interlayer thickness. Based on a figure of merit value, the authors obtain an optimal MoO3/Ag/MoO3 electrode with a low sheet resistance of 3.17 Ohm/square, a high optical transmittance of 77.85%, and critical bending radius of 1 mm, which are acceptable for fabrication of TFHs. The flexible TFHs (25 × 25 mm2) fabricated on a thermally evaporated MoO3/Ag/MoO3 electrode shows a high saturation temperature of 118 °C even at a low input power of 2.5 W (input voltage 2.5 V) due to very low sheet resistance. Successful operation of the flexible TFHs indicate that the thermally‐evaporated MoO3/Ag/MoO3 film is a promising alternative transparent electrode to substitute sputtered Sn‐doped In2O3 (ITO) films for highly transparent and flexible TFHs. A flexible and transparent thin film heater (TFH) is fabricated on a thermally‐evaporated MoO3/Ag/MoO3 multilayer electrode on a 50‐µm‐thick CPI substrate. The TFH shows better performance than conventional ITO‐based thin film heaters due to the low resistance and outstanding flexibility of the MoO3/Ag/MoO3 multilayer. [ABSTRACT FROM AUTHOR]