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The World Health Statistics 2023, as presented by the World Health Organization (WHO), underscores a significant global health concern: 73% of global mortality is attributed to chronic diseases. Within the domain of medical diagnostics, serum bilirubin levels serve as a critical biomarker for identifying several prevalent chronic conditions in adult and geriatric populations. In this study, a polymer composite fiber-optic Fabry–Pérot interferometer is prepared, wherein the reflective surfaces are, respectively, constituted by polyurethane (PU), with characteristics marked by high thermal responsiveness and rapid thermal transfer rates, and a single-mode fiber. Subsequently, the outer surface of the PU reflective end undergoes deposition with Ti 3 C 2 T X MXene material, which has the capability to enhance the adsorption of bilirubin molecules. This work proposes a detection method using the photothermal effect of bilirubin. When the sensor is operational, bilirubin generates a thermal effect under 405 nm laser irradiation. The Fabry–Pérot air cavity rapidly expands with the increased heat absorption, leading to shifts in the interference spectrum, which enables the effective detection of low concentrations of bilirubin within the serum. The experimental results indicate that the sensor exhibits a sensitivity of 7.51 [nm/(μmol/L)] and a detection limit of a mere 0.002 19 μmol/L within the linear dynamic range of 1–10 μmol/L. Furthermore, a tenfold improvement is observed when compared to the previously reported lowest detection limit. The sensor delineated herein is characterized by heightened sensitivity, minimal detection limit, rapid response time, and substantial robustness, rendering it suitable for potential applications in the early diagnosis and prognosis of chronic diseases such as Alzheimer's disease. [ABSTRACT FROM AUTHOR]

The proliferation of polymer optical fibers (POFs) has opened multiple avenues of optical-based networks and sensing applications in the visible spectral range. However, the lack of efficient amplifiers significantly hinders their utilization in practical scenarios. As emerging gain media, halide perovskites have attracted considerable attention in exploring their practical applications. In this Letter, we investigated the optical gain properties of cesium lead bromide quantum dots (CsPbBr3 QDs), and by facet dip-coating, we realized a polymer optical fiber amplifier. Under a 400-nm, 163-fs Ti:Sapphire laser pumping, the amplified spontaneous emission (ASE) thresholds of 1.6 and 20.1 μJ/cm2 were achieved through stripe pumping of a QDs-thin-film and end-pumping of a polymer-fiber facet dip-coated with the QDs, respectively. A gain coefficient of 232.2 ± 22.8 cm−1 was obtained using the variable stripe length method. By coupling a broadband continuous-wave light source into the POF as the signal, the optical gain behavior was studied with varying pump fluence and signal power density. More than 20 dB optical gain was achieved within the ASE wavelength region of 530–540 nm with a predicted theoretical maximum gain of 33.6 dB. The research verifies the feasibility of amplifying continuous-wave signals in the visible spectrum and potentially closing the research gap in visible-light optical-to-optical amplifiers. This opens the avenue for further research and innovations in practical polymer-based optical amplification for a plethora of applications, including all optical processing chips and short-range interconnects, as well as visible-light and underwater communications. [ABSTRACT FROM AUTHOR]

Polymers are extensively employed in diverse industries, including electrical equipment and electronic devices. Recent technological advancements have intensified the demand for dielectric polymers with both high insulation resistance and high thermal conductivity. We employed molecular dynamics simulations to clarify the intricate relationship between molecular structures, thermal conductivity, and ionic mobility from an atomistic point of view. Examined polymers include polyethylene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyoxymethylene, and polyethylene oxide. Based on the elucidated correlations among force field parameters, we found that the parameters can be clustered into four groups: group 1 (atomic and bond parameters and force constant of the bond angle), group 2 (equilibrium angle and force constant of dihedral angle), and group 3 (side chain atom charges). Thermal conductivity showed relationships with parameters in group 1, with correlation coefficients mostly exceeding 0.7 in the absolute value. Considering the correlations between the parameters, we systematically altered the parameters within each group and computed thermal conductivity and ionic mobility. When altering the force field parameters of groups 1 and group 2, a trade-off relationship between thermal conductivity and ionic mobility becomes evident. Conversely, altering the force field parameters in group 3 increased thermal conductivity while decreasing ionic mobility, breaking the trade-off relationship. The proposed clustered-parameter variation method can predict the changes in the electrical and thermal conductivity of polymers through molecular structure modifications. The method, being a general and first-principles approach, is likely to have significant advantages in the molecular design across a diverse range of polymers. [ABSTRACT FROM AUTHOR]

Electroactivity of polymers used in energetic materials may result in charge separation that could result in safety concerns (unintentional ignition) or be exploited for multifunctional applications. We measured the flexoelectric properties of several polymers and energetic composites including poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)], nanosized aluminum (nAl)/P(VDF-TrFE), poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)], micron aluminum (μAl)/P(VDF-HFP), hydroxyl-terminated polybutadiene (HTPB), ammonium perchlorate (AP)/HTPB, μAl/AP/HTPB, polytetrafluoroethylene (PTFE), and polydimethylsiloxane (PDMS). The presence of flexoelectricity in PTFE (Teflon®) and the relatively high flexoelectric coefficient of P(VDF-HFP) (Viton®) measured in this work may help explain accidents involving the production and use of Magnesium-Teflon-Viton (MTV) that in many instances have been attributed to electro-static discharge. The addition of aluminum nanopowders to the P(VDF-TrFE) increased the flexoelectric coefficient by ∼30%. However, the addition of aluminum micrometer particles (10 wt. %) to P(VDF-HFP) decreased the effective flexoelectric coefficient, while an increase was observed when the aluminum loading was increased from 10 to 20 wt. %. The effective flexoelectric coefficient of HTPB and two propellant compositions (AP/HTPB and μAl/AP/HTPB) were measured to be in the same range as each other. The effect of particle addition (nAl, μAl, and AP) on flexoelectricity was different depending on the binder, further illustrating the complexity of flexoelectric properties in composite energetics. This may be somewhat explained by competing effects where particle additions (nAl, μAl, and AP) create additional strain gradients that contribute to flexoelectricity, but the particle additions also replace the mass of flexoelectric polymer binders (P(VDF-TrFE, P(VDF-HFP), and HTPB) with particles (nAl, μAl, and AP) that are less flexoelectric. [ABSTRACT FROM AUTHOR]

Conductive polymers have attracted attention for wearable and implantable thermoelectric devices due to their lightweight, flexibility, and solubility. With the development of microsystems, thermoelectric power generation devices are trending toward miniaturization, flexibility, high integration, and lightweight thin films. Therefore, the study of the thickness of thermoelectric materials has become increasingly important. In this study, we prepared ultrathin polymer thermoelectric (TE) films with different thicknesses (14–52 nm) by modifying the substrate with self-assembled monolayers (SAMs). The thickness-dependent thermoelectric performances on SAMs are investigated. It is found that SAMs regulate the carrier concentration in polymer ultrathin TE films, and a smoother surface contributes to the improvement of carrier mobility, thus optimizing the thermoelectric performance. The maximum modulation of thermoelectric performance is observed at a film thickness of approximately 35 nm, which contains nine molecular layers. [ABSTRACT FROM AUTHOR]

Polarization-sensitive organic photodetectors (OPDs) are increasingly paid attention for their broad application prospect. However, it is extremely difficult to achieve highly sensitive detection of polarized light for most organic semiconductor polymers with intrinsic isotropic amorphous behavior. In this study, the performance-enhanced intrinsic anisotropic all-polymer bulk heterojunctions (BHJs) are obtained by constructing molecular fluorination engineering in the fused-ring backbone of the acceptor polymer. The molecular orientation, alignment, and packing can be effectively optimized during the floating-film formation process without using any additives and post-treatments. The outstanding intrinsic polarization-sensitive photodetection performance with a very high photocurrent dichroic ratio of 3.73, a specific detectivity of 1.3 × 1011 Jones at 0 V, and a broad linear dynamic range of 120 dB is achieved for the optimum-fluorine-content self-assembly all-polymer organic BHJ film. The superiorities of self-powered capability, fast response, and high-contrast imaging demonstrate that the backbone fluorination for acceptor polymers is conducive to achieving excellent structural regularity and can endow the intrinsic polarization-sensitive all-polymer OPDs with more demanding polarized-light detection ability. [ABSTRACT FROM AUTHOR]

Polymer passivation has been leveraged to improve photodetection in two-dimensional transition metal dichalcogenide field-effect transistors. The relative passivation effects of common polymers, however, are not well understood. In this work, the interface of monolayer MoS2 and three common polymers, parylene N (Pa-N), polymethyl methacrylate (PMMA), and polyvinylidene difluoride trifluoroethylene (PVDF-TrFE), is assessed with multiple spectroscopic methods. Raman and photoluminescence spectroscopy demonstrate that Pa-N and PMMA provide an n doping effect, which increases photoconductivity and photogenerated charge in terahertz domain and time-resolved spectroscopy. Terahertz time-resolved spectroscopy shows significantly longer carrier lifetime for MoS2 coated with PVDF-TrFE compared to other polymers. These results suggest that PVDF-TrFE provides a unique benefit for photodetection applications. [ABSTRACT FROM AUTHOR]

The development of silicon nitride (SiN) waveguide platforms has enabled the realization of photonic circuits with unprecedented performance. Despite the exciting progress, SiN suffers from intrinsic material properties that block it for high-speed electro-optic (EO) modulators. Here, we present an approach to heterogeneously integrate organic EO polymer on SiN for high-performance modulators. We utilize the high resistivity of SiN to achieving a strong overlap between the optical and electrical field. Furthermore, sol–gel SiO2 side-claddings inserted in waveguides shorten the inter-electrode distance and increase the EO activity to a much higher level. As a result, the fabricated micro-ring modulator exhibits an electrical tunability of 10 pm/V, corresponding to an in-device EO coefficient as 60 pm/V. High frequency tests in the device show a 3-dB bandwidth of 32 GHz and a data rate of 40 Gbps. The proposed approach will enable efficient mass-production of the micro-footprint modulators and promote the development of integrated SiN photonics. [ABSTRACT FROM AUTHOR]

Terahertz electromodulation spectroscopy is used to investigate charge transport in the semiconducting polymer poly-diketopyrrolopyrrole-terthiophene (PDPP3T). Both electrons and holes show band transport with a preferential conduction along the polymer chain. In devices with oriented thin-films, mobilities of 2.0 and 12.8 cm2/V s are measured for electrons and holes, respectively. Temperature-resolved and long-time measurements suggest that only a fraction of the injected charge carriers participate in band transport. Carrier trapping into localized states is identified as the major factor that limits the overall mobilities. According to the Ioffe–Regel criterion, the material's inherent mobilities are expected to significantly exceed the observed values. [ABSTRACT FROM AUTHOR]

Organic photodetectors have attracted increasing attention in the scenario of low-cost imaging, health monitoring, and near-infrared sensing. However, relatively high dark current and trap density block the sensitivity for organic photodetectors. In this manuscript, a simple yet effective strategy is proposed to enhance the detectivity of organic photodetectors by incorporating a non-conjugated polymer additive of polystyrene into the functional layers. Systematic morphological investigation reveals that this strategy can not only enable suppressed amorphous phase but also effectively tune the phase separation in the bulk heterojunction blends. Electrical results suggest the suppressed trap density in optimized organic photodetectors. Consequently, a dark current density of 5.06 × 10−10 A cm−2 is achieved for PM6:Y6-BO-based organic photodetectors, showing a peak detectivity of 6.38 × 1013 cm Hz1/2 W−1 at 850 nm. This strategy is also applicable in various representative organic-semiconductor systems, including PTB7-Th:PC71BM and P3HT:PC61BM blends, superior to other optimization techniques. [ABSTRACT FROM AUTHOR]

Refractive index (RI) of polymers plays a crucial role in the design of optoelectronic devices, including displays and image sensors. We have developed a framework for (1) high-throughput computation of RI values for computationally synthesized amorphous polymer structures based on a generalized polarizable reactive force-field (ReaxPQ+) model, which is orders-of-magnitude faster than quantum-mechanical methods; (2) prediction of composition–structure–RI relationships based on a machine-learning model based on graph attention neural network; and (3) computation of frequency-dependent RI combining ReaxPQ+ and Lorentz-oscillator models. The framework has been tested on a computational database of amorphous polymers. [ABSTRACT FROM AUTHOR]

A waveguide Bragg grating (WBG) can facilitate an adaptable method for glucose monitoring according to the optical properties of polymer materials. We propose the design and fabrication of a WBG for glucose monitoring. By exploiting glucose oxidase as the upper cladding, polydimethylsiloxane was used as the substrate, and polymethyl methacrylate was used as the core layer. We investigated the effects of the diffraction order, waveguide structure, and grating period on the reflected spectrum of the WBG. Finally, process reproducibility after long-term storage and the capability to eliminate background solution interference (to achieve more specific glucose detection) were evaluated. The experimental results showed that when the glucose concentration was in the range of [0, 3.6] mg/ml, as the glucose concentration increased, the wavelength decreased approximately linearly, with a sensitivity of approximately 242.9 pm/(mg/ml) in the range of 0–2.7 mg/ml, while maintaining good selectivity and stability. The WBG for glucose monitoring has the advantages of a large measurement range and high sensitivity. This approach facilitates the application potential of such polymer material-based WBG photonic sensors in wearable technology and realizes the measurement of human blood glucose. [ABSTRACT FROM AUTHOR]

Endowing bulk electrocaloric polymers with excellent thermal conductivity is a superior solution to the high-efficient and precise management of tremendous heat from high-power-density electronic devices. Semi-crystalline polymer P(VDF-TrFE-CFE), i.e., poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), has a predominant amorphous phase of randomly entangled chains and abundant interface, leading to localized behavior in phonon heat conduction and thereby low thermal conductivity. To enhance the thermal transport performance, electrocaloric polymer films were mechanically stretched or fabricated by electrospun to achieve highly aligned molecular chains. Chain orientation brought about a 2.4- and 1.6-times increase in the thermal diffusion coefficient of the stretched and electrospun films, respectively. Interestingly, after mechanical stretching, the thermal conductivity of the film was increased by a factor of two. In contrast, the electrospun film had a slightly lower thermal conductivity than that of the unoriented one. A remarkable discrepancy in the electrocaloric properties was observed, where the stretched polymer film reached a much higher adiabatic temperature change under an applied electric field than that of the electrospun film. Our strategy provides a perspective on designing a promising thermal management system through the integration of active refrigeration and passive heat dissipation in bulk electrocaloric polymers. [ABSTRACT FROM AUTHOR]

N-type organic field-effect transistors have suffered from poor environmental instability. Here, we report that, by using nickel (Ni) instead of the commonly used gold (Au) as contact electrodes, n-type polymer transistors showed much improved stability upon annealing in nitrogen and exposure to air. In particular, Au-contacted devices exhibited pronounced ambipolar conduction whereas Ni-contacted devices retained fairly good unipolar properties. The results are important to build stable n-type polymer transistors at low cost. [ABSTRACT FROM AUTHOR]

Intrinsic polarization-sensitive photodetectors (IPPDs) have attracted considerable attention in recent years due to their simplicity in configuration, making them ideal candidates for compact and integrated polarization-sensitive sensing and imaging systems. Photoactive films with intrinsic optical anisotropy are necessary for IPPDs. This study reports an achievement of photoactive films based on all-polymer heterojunction films with in-plane optical anisotropy using a simple bottom-up self-assembly method. Both the donor (TQ1) and acceptor (N2200) polymers have the same spatial orientation with distinct anisotropy, approaching a dichroic ratio (DR) of 8. Polarization-sensitive light absorption is due to the uniaxially oriented polymer chains, which are dominated by lamellar packing with edge-on orientation. For IPPDs based on this anisotropic all-polymer heterojunction film, a photocurrent anisotropy was found with a polarized photocurrent ratio of 2.6. The detectivity of these IPPDs was found to be 1.9 × 1011 Jones (@ ∼600 nm, 0 V bias). Our work shows that oriented polymer donor–acceptor films fabricated using bottom-up self-assembly have great potential in applications, such as polarization detection. [ABSTRACT FROM AUTHOR]

A high-performance ultraviolet photodetector based on a thin layer DPPT-TT organic material is experimentally demonstrated. The high absorption of DPPT-TT in the ultraviolet band is attributed to the foundation for a high-performance ultraviolet detector. The device's responsivity can be improved by adequately designing the hole-blocking layer HfO2 and the stepped structure at the bottom contact. Due to the self-filtering and optical trapping structure, the device achieves external quantum efficiency above 100%, even with a thin absorption layer (around 50 nm). The maximum spectral responsivity of the device is 383 A/W, and the corresponding maximum specific detection rate is about 2.79 × 1012 at a bias voltage of 0.5 V. Our results advocate that the thin organic ultraviolet photodetector promises excellent potential in low-cost ultraviolet-visible light detection and imaging applications. [ABSTRACT FROM AUTHOR]

Solid-state batteries (SSBs) are an ideal next-generation energy storage system due to their safety and high energy density. However, many interfacial problems, such as high interfacial resistance and poor compatibility between electrodes and electrolytes, limit the development of SSBs. In this study, an ultrathin interfacial layer composed of poly(ethylene oxide) (PEO) and ethylene carbonate (EC) are in situ fabricated on the surface of electrodes, integrating ceramic/polymer composite electrolyte and electrodes and reducing the interfacial impedance. Meanwhile, the excellent chemical compatibility between PEO and lithium metal effectively improves the interfacial stability. Also, the modification of the interfacial layer leads to more F- participation in the formation of solid electrolyte interphase (SEI), and the relative content of LiF, Li3N, and other by-products increases, which facilitates the formation of dense and stable SEI, thus inhibiting the growth of dendritic lithium and improving the ionic conductivity. With the interfacial layer, a highly stable interface against Li is maintained for more than 1400 h at a current density of 0.1 mA cm−2. A solid-state battery with LiNi0.5Co0.2Mn0.3O2 (NCM523) as the cathode delivers a capacity of 153.4 mAh g−1 and a capacity retention of 92.1% after 100 cycles. This study shows that the interfacial layer PEO-EC is an effective way to improve the performance of SSBs. [ABSTRACT FROM AUTHOR]

This paper presents a hierarchically designed polymer nanocomposite approach in which nanofillers at ultralow volume loading generate large dielectric enhancement in blends of high temperature dielectric polymers with tailored nanostructures. We blend poly(1,4-phenylenen ether sulfone) (PES) with polymers, such as polyetherimide (PEI), that possess more coiled chain conformations to tailor polymer nano-morphologies. Making use of such blends as the matrix, dilute nanocomposites with 0.65 vol. % loading of alumina nanoparticles (20 nm size) generate a marked enhancement in dielectric performance, i.e., raising the dielectric constant K from PES K = 3.9 (and PEI K = 3.2) to the dilute nanocomposites K = 7.6, a much higher enhancement compared with the dilute nanocomposites employing neat polymers as the matrix. The results show that polymer blends with tailored nano-morphologies as the matrix can lead to higher dielectric enhancement in dilute nanocomposites compared with neat polymers as the matrix. [ABSTRACT FROM AUTHOR]

Polishing techniques have been used since antiquity but remain important in high-value manufacturing processes in optics and semiconductor fields. State-of-the-art polishing enables the production of atomically flat surfaces of even advanced materials, such as diamond, SiC, and GaN, by exploiting the exceptional chemical characteristics of particle surfaces, fluid solutions, and pad surfaces. Although various effective chemical reactions are employed, chemical reactivities of organic polymer surfaces have not been thoroughly explored. We demonstrate a water-only and slurry-less polishing technique using an acrylic polymer plate. We investigated the possibility of glass processing with several polymer materials and found that normal acrylic polymers have remarkable properties for polishing. Glass and silicon surfaces with atomic-level flatness can be produced using only an acrylic polymer plate and water. We believe that the developed polishing methods will become popular in the future because they are simple and cost-effective processes. [ABSTRACT FROM AUTHOR]

Polymer composite dielectrics have been actively developed for electrical power and electronic applications. The latest advances in dielectric polymer composites with ultralow (<1 vol. %) filler loadings have overcome many of the significant drawbacks of polymer composites. Such composites now offer opportunities of gleaning insights into the impact of interfaces on dielectric behaviors and developing dielectric mathematical theories and models with the interface contributions. In this Perspective, we review key developments in the dielectric polymer composites with ultralow contents of small-sized fillers. We highlight the filler–polymer interface characterizations and the current understandings of the underlying mechanisms and examine the dielectric models in order to fit the dielectric data over a wide range of filler contents. We also discuss challenges and opportunities for the polymer composites with ultralow filler loadings in the development of scalable high-energy-density dielectrics. [ABSTRACT FROM AUTHOR]

As a promising strategy, strain engineering has been employed on different semiconductor materials, aiming to modulate their photoelectric properties, thus innovate device applications. An interesting experimental result is the directional exciton migration induced by creating some local nonuniform strains in materials, such as "exciton funneling." In this Letter, to clarify the dynamical mechanism and the impacting factors, we theoretically investigate the migration dynamics of excitons/biexcitons along organic polymers induced by a funnel-like nonuniform compression strain. First, the migration dynamics of an exciton/biexciton are separately demonstrated right after the strain created. It is found that both of them will migrate toward the strain center with the speeds up to 7–10 nm/ps, comparable with the experimental observations in a bending ZnO microwire, where the difference between the exciton and biexciton migration dynamics is also emphasized. We attribute the present exciton/biexciton migration mechanism to the strain-induced gradient of the exciton/biexciton creation energy along polymers. Furthermore, some typical factors impacting the exciton migration dynamics are considered, such as the strain gradient, the initial ratio of the exciton located in the strain region, the electron-lattice interaction, etc. Finally, based on these findings, we briefly discuss the possible results about the strain-modulated luminescence of organic polymers. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study, implementation, and numerical simulation of the transmissivity of a polymer waveguide covered by a GST225 thin film with various phase states. The paper considers an optical synapse prototype based on the interface between the waveguide and an optically controlled GST225 film. We demonstrate the fundamental possibility of controlling an optical signal in the telecommunication C-range as it passes through the synaptic interface via the action of an external laser on an optically active GST225 film. Experimentally, 40% single- and multi-level modulations of the optical signal intensity are achieved. The numerical simulation results are in line with the experimental data. Based on this principle, next-generation all-optical storage and computing devices that simulate the properties of biological synapses and neurons can be developed. [ABSTRACT FROM AUTHOR]

Comprehensively understanding the main differences exhibited in the ignition stage of high-intensity shock and low-intensity impact initiation processes of polymer bonded explosives (PBXs), including defect-related hotspot formation, ignition threshold, and sensitization or desensitization, is necessary for the safety evaluation of PBXs. The roles of shear-crack and void-collapse hotspots in the ignition for single-impacted PBXs are first studied using a physically based thermomechanical model. The variations of sensitivity for pre-impacted PBXs are further reported. Results show that a crack hotspot dominates in a low pressure range (90–200 MPa) with a relatively long ramp time (∼1.0 μs). High pressure will cause a friction-locked crack, while low pressure will lead to the insufficient frictional heating, thus resulting in a slight increase in hotspot temperature. Moreover, a long duration (∼10.0 μs) is required for satisfying the hotspot temperature-size criterion of ignition. The void hotspot dominates in high pressure (≥350 MPa) with a short ramp time (<0.1 μs). The dominant range of crack hotspots is extended (70–240 MPa) after a pre-impact load, while that of the void hotspot reduces (≥550 MPa). If the secondary loading is high-intensity shock, the explosives are desensitized due to the pre-elimination of voids. In contrast, if the secondary loading is low-intensity impact, the explosives are sensitized due to the pre-increase in crack-related damage. [ABSTRACT FROM AUTHOR]

The luminescent solar concentrator (LSC) has attracted worldwide attention as a sunlight manager for harvesting solar energy in building integrated photovoltaic structures. However, until now the relatively low optical efficiency (ηopt) still severely hinders the advancement of the LSCs. In this work, we report the perovskite quantum dots (QDs) integrated into the thiol-ene polymer for LSC applications. After encapsulated by the thiol-ene polymer, the CsPbBr3 QDs exhibit a slight blue-shift of the PL peak position and increasing FWHM because of the dielectric screen effect. With the different QDs' concentrations from 8.3 × 10−3 to 2.5 × 10−2 mg/ml, the LSC performance is evaluated by the direct optical characterization and the indirect photo-electrical measurement in detail. After coupling the PV cells, the as-fabricated LSC shows the optimal optical efficiency of 2.11% and the power conversion efficiency of 1.06%. [ABSTRACT FROM AUTHOR]

We designed a high-performance polymer electret material using a deep-learning-based de novo molecule generator. By statistically analyzing the enrichment of the functional groups of the generated molecules, the hydroxyl group was determined to be crucial for enhancing the electron gain energy. Incorporating such acquired knowledge, we designed a molecule using cyclic transparent optical polymer (CYTOP; perfluoro-3-butenyl-vinyl ether). The molecule was synthesized, and its surface potential for a 15-μm-thick film is kept at −3 kV for more than 800 h. Its performance was significantly better than all commercialized CYTOP polymer electrets, indicating great potential for its application in vibration-based energy harvesting. Our results demonstrate the application of machine learning in polymer electret design and confirm the combination of molecule generation and functional group enrichment analysis to be a promising chemical discovery method achieved via human–artificial intelligence collaboration. [ABSTRACT FROM AUTHOR]

The relative optical gains at three near infrared wavelengths (1550 nm, 1064 nm, and 980 nm) were achieved in NaYF4: Er3+, Yb3+ nanoparticle-doped SU-8 waveguides when using two low-cost light-emitting diodes (LEDs) instead of traditional 980 nm semiconductor laser as pump source. The polymer waveguides were fabricated by one-step photolithography process. The fluorescence bands around 1550 nm and 1000 nm wavelengths due to the 4I13/2 → 4I15/2 transition of Er3+ ions and 2F5/2 → 2F7/2 transition of Yb3+ ions were observed under the excitation of 405 nm and 520 nm LEDs. By using the vertical top pumping mode of LEDs, the relative gains of 4.2 dB, 1.7 dB, and 2.1 dB at 1550 nm, 1064 nm, and 980 nm wavelengths were achieved, respectively, on a 10-mm-long waveguide. [ABSTRACT FROM AUTHOR]

Solid-state humidity sensors are generally AC powered as they sense the fluctuations in the dielectric polarization and/or ionic conductance of the water layer formed by Kelvin condensation on the effective surface of their hydrophilic sensing elements. DC-powered, printable, and bendable hygrometers, however, are demanded for battery-driven wearable electronics. Here, we demonstrate that the electronic (as opposed to ionic) conduction in the polymer composite poly(3,4-ethylenedioxythiophene–poly(styrenesulfonate) (PEDOT:PSS) thin films constantly decreases with increasing relative humidity (RH) in the surrounding atmosphere and use this property for the fabrication of a DC-powered solid state hygrometer. PEDOT, the conductive component of this composite, is hydrophobic, and the hydrogen bonding of the airborne H2O to the surface available sulfonic acid groups of the non-conductive component, PSS, is verified as the main cause of sensitivity. This hydrogen bonding deters the doping action involving H+ transfer from the sulfonic acid groups to the thiophene groups on the PEDOT chain and decreases the bulk conductivity of the sensing element. As predicted by this model, the electrical resistance measurements carried out by applying DC and AC electric fields lead to different RH dependences; the former demonstrates the positive RH dependence in the full RH range, while the latter results in strongly nonlinear RH sensitivity crossing zero around RH 60%. Our model assists better understanding of the charge conduction mechanisms in PEDOT:PSS. The described sensing mechanism is anticipated to initiate research on many two-component organic composites for the fabrication of varieties of gas and humidity sensors. [ABSTRACT FROM AUTHOR]

Polymers with electrically charged internal air cavities (ferroelectrets) reveal a pronounced piezoelectric response and are regarded as soft electroactive multi-functional materials. This work presents preliminary results on the preparation and piezoelectric effect of ferroelectrets based on the polylactic acid (PLA) polymer. A distinctive feature of the manufactured films is that they are biodegradable. After a microstructure modification of carbon dioxide (CO2) foamed PLA sheets by hot-pressing treatment and corona polarization, these cellular films reveal large piezoelectric d 33 and d 31 responses in both quasi-static and dynamic modes. For freshly charged films, the maximum quasi-static piezoelectric coefficients are about 600 pC/N ( d 33 ) and 44 pC/N ( d 31 ) for a relatively thick film of 360 μm and a nominal porosity of about 60%. During the first 20 days after polarization, the piezoelectric activity decreases by half compared to the primary value, but then remains almost unchanged for a long time. Due to an already established inherent biocompatibility of PLA polymers, these eco-friendly ferroelectrets can be potentially used in various biological applications such as biosensors and microenergy harvesters embedded in tissue and artificial muscles. [ABSTRACT FROM AUTHOR]

We report the fabrication of large-area highly aligned films of a naphthalene dicarboximide-based copolymer P(NDI2OD-T2) via solvent vapor annealing of as-spun films under a high magnetic field. Structural characterization reveals that the incorporation of a small amount of graphene nanosheets via solution mixing remarkably improves the degree of chain alignment and ordering of the semiconducting polymers. Field-effect transistors based on the magnetically aligned polymer/graphene composites exhibit a dramatic enhancement of electron mobility as well as extraordinarily high mobility anisotropy of 81, compared to pristine P(NDI2OD-T2)-based devices. We further proposed a mechanism to explain the enhancement of molecular orientation and charge transport, which is based on the assembling of polymer aggregates on the π-plane of graphene to facilitate magnetic alignment. [ABSTRACT FROM AUTHOR]

A dye immersed in a polymer matrix represents a promising material class for organic polariton lasers. While polariton condensation has been established for boron-dipyrromethene blends, it has yet to be extended to other small dye blends. Here, we demonstrate polariton lasing in a molecularly isolated perylene diimide immersed in polystyrene. The emission exhibits threshold behavior, strong directionality, and slight blueshifting of organic polariton systems. We expect that continuous exploration of new dyes will allow improved performance in organic polariton lasing. [ABSTRACT FROM AUTHOR]

Even though the fundamental benefits of the staggered bottom-gate top-contact geometry in organic thin-film transistors (TFTs) have been fully demonstrated for enhancing the charge injection efficiency, most printed organic TFTs with inkjet-printed source/drain electrodes have only been fabricated in bottom-contact configurations, probably due to the difficulty of printing with metal-nanoparticle ink on soluble organic semiconductor (OSC) without film deformation/dissolution. Here, we present the printing process and the electrical characteristics of inkjet-printed top contact OSC in bottom-gate TFTs. We first fabricated polymer bottom-gate TFTs by printing in two different top- and bottom-contact configurations. The physical carrier mobility of the two TFTs was extracted from a gated-contact organic TFT model to exclude the effect of geometric contact resistance RC. When compared to assess the OSC film damage from the printing metallization, the two mobility values were almost identical. This result indicates that the metal nanoparticle ink used in this work formed a top metal contact on the OSC film without significant chemical damage. Furthermore, the printed top-contact TFT exhibited I-V characteristics almost identical to those of a thermally evaporated Ag top-contact TFT. This study suggests the possibility of inkjet-printed top metal contacts for organic thin-film devices such as transistors, solar cells, and diodes. [ABSTRACT FROM AUTHOR]

In this work, the frictional properties of various polymer binders were studied using atomic force microscopy to enhance the mechanical integrity of the silicon (Si) anode for lithium-ion batteries (LIBs). The binders used include polyacrylic acid (PAA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and polyvinylidene fluoride. The interfacial shear strength of the polymer binder was determined against Si to understand the contact shearing and sliding behaviors. The results showed that due to electrolyte immersion, the intrinsic interfacial shear strengths and pressure coefficients decreased by factors of 1.3–7.5 and 1.6–23.7, respectively. Decreases in mechanical and adhesion properties in the electrolyte may be responsible for the decrease in the frictional properties. The results also showed that topography-induced friction fluctuation became significant in the electrolyte due to an increase in the slope of the surface asperities, which is associated with polymer swelling. The Si anodes of LIBs containing polymer binders with relatively large intrinsic interfacial shear strengths and pressure coefficients in the electrolyte (PAA, PAN, PVA, and CMC) had high capacity retention. Given that a polymer binder with high interfacial shear strength helps maintain the mechanical integrity of the Si anode, PAA with high intrinsic interfacial shear strength may be preferred when the stress level is low during lithiation, while PVA with a large pressure coefficient may be advantageous when the stress level is high during lithiation. The outcome of this work suggests that the interfacial shear strength is a better polymer binder performance indicator than just considering mechanical and adhesion properties. [ABSTRACT FROM AUTHOR]

The curing process of polymer materials and structures has a crucial influence on their final properties. However, existing methods are only capable of characterizing their time-resolved information. To comprehensively reveal curing behaviors inside polymers, we report a method that combines optical coherence tomography and quantitative phase imaging for visualizing time- and space-resolved curing degree (or curing rate) distributions. For validation, the curing process of a polymer droplet was monitored by using the proposed method, which not only revealed that the curing rate of the polymer surface is faster than that of the interior but also discovered the depth-dependent gelation process. The experimental results indicate that the proposed method can effectively reveal curing behaviors inside polymers, which opens new possibilities for better understanding curing kinetics. [ABSTRACT FROM AUTHOR]

Experimental determination of the isothermal high-pressure equation of state (EOS) of composites is not feasible by using conventional diffraction techniques. To overcome this issue in the case of polymer bonded explosives (PBXs), composites made of an energetic material and a polymeric binder, we have expanded the applicability of the optical microscopy and interferometry technique previously developed in our group. To accommodate representative samples of a PBX with large grains, we modified the diamond culets of a diamond anvil cell to include etched micrometer-scale pits. This enabled us to measure the isothermal EOS of a PBX, namely, LX-17, up to 8 GPa. The results are compared with the EOSs of the constituent materials and previously published shock measurements. The technique employed in this study is not limited to PBXs and could be potentially used for the EOS determination of other materials ranging from composites to alloys and granular materials. [ABSTRACT FROM AUTHOR]

Here, we report the fabrication of electrostatic fractional capacitors based on two-dimensional Ti3C2 MXene/vinylidene fluoride–trifluoroethylene–chlorofluoroethylene terpolymer [P(VDF-TrFE-CFE)] composites. The bandwidth of MXene-based fractional capacitors varies between 200 kHz and 2 MHz, while the phase angle varies less than ±2°. Additionally, the constant phase angle of the MXene/P(VDF-TrFE-CFE) can be precisely tuned from −67° to −34° by varying the volume ratio of MXene nanosheets in the polymer matrix. The results presented in this work demonstrate the potential of MXene/P(VDF-TrFE-CFE) composites as solid-state electrostatic fractional capacitors. [ABSTRACT FROM AUTHOR]

Traditional molding and casting processes in optical manufacturing require sophisticated and expensive molds and molding equipment. In this work, magnetic liquid droplets were used as soft and deformable molds. The magnetic drop within an immiscible polymeric resin forms a conical shape at the interface due to the equilibrium of magnetostatic force and surface tension, which results in a plano–concave lens after curing. An apparatus was assembled to control the amplitude and gradient of the magnetic field. A Shack-Hartmann sensor was employed to measure the focal length of the formed polydimethylsiloxane lenses. The effects of magnetic field intensity, gradient of the magnetic field, and magnetic susceptibility were investigated. This technique is low cost, rapid, and straightforward and can be used for forming lenses with different sizes and shapes. [ABSTRACT FROM AUTHOR]

The ability to control the bulk and interfacial polarization of dielectric polymers is important to their application in organic electronics. We examine the effect of the trifluoromethyl substituent on poly(3-trifluoromethylstyrene) (P3TFMS) as compared to unsubstituted polystyrene (PS) on the I-V relationships of pentacene-based organic field-effect transistors (OFETs). Single- and double-layered films of these polymers were used, with lower layers crosslinked through vinylbenzocyclobutene comonomers before deposition of upper layers. Control experiments verified that the electronic effect of the crosslinking was negligible. We found that the TFM substituent markedly and independently affected both the initial threshold voltage Vth and the nonvolatile, shifted Vth observed after the application of static gate voltage, depending on its position adjacent or apart from the pentacene. The trifluoromethyl-bearing polymers exhibited significantly lower magnitude initial threshold voltages ( V t h , i of ca. −17 V for P3TFMS compared to −35 V for PS), large threshold voltage shifts after charging by the application of static electric fields (Δ V t h of ca. 32 V for P3TFMS and 17 V for PS), and greater stability of the Δ V t h under repeated charge/discharge cycles. These results are consistent with P3TFMS having fewer interfacial trap states but more stable bulk trap states. The results are applicable to organo-electronic systems such as piezoelectrics for energy harvesting and nonvolatile OFETs such as memory, sensing, and logic elements. [ABSTRACT FROM AUTHOR]

We investigate local heat generation by molecules at the apex of polymer-embedded vertical antennas excited at resonant mid-infrared wavelengths, exploiting the surface enhanced infrared absorption effect. The embedding of vertical nanoantennas in a non-absorbing polymer creates thermal isolation between the apical hotspot and the heat sink represented by the substrate. Vibrational mid-infrared absorption by strongly absorbing molecules located at the antenna apex then generates nanoscale temperature gradients at the surface. We imaged the thermal gradients by using a nano-photothermal expansion microscope, and we found values up to 10 K/μm in conditions where the radiation wavelength resonates with both the molecule vibrations and the plasmonic mode of the antennas. Values up to 1000 K/μm can be foreseen at maximum quantum cascade laser power. The presented system provides a promising thermoplasmonic platform for antenna-assisted thermophoresis and resonant mid-infrared photocatalysis. [ABSTRACT FROM AUTHOR]

Gold nanoparticle (AuNP)-polymer composites have emerged as promising candidates for flexible electronics due to their super-high stretchability and metal-like conductivity. Their percolation threshold is, however, much higher than that of 1D carbon nanotubes or silver nanowires. A practical and appealing solution is to assemble AuNPs into 1D quasi-nanowires via the van der Waals interaction. In this letter, electron tunneling is incorporated into the theory of traditional composites to explore the percolation of these nanocomposites. The geometries of AuNP-chains are found to play a key role in determining the effect of electron tunneling and thus the overall percolation behavior. Small and/or short AuNP-chains yield the substantial tunneling effect, leading to the rapid growth in conductivity across a transition zone where the conductivity mechanism transfers from electron tunneling to contact conductance. This unique feature agrees with experimental observation but cannot be characterized directly by existing theories. [ABSTRACT FROM AUTHOR]

Polymer nanofibers, with their specific set of material properties, are favorable for many applications in biomedical engineering (scaffold, stent, or tissue engineering). This application, however, requires the ability to control the manufacturing process together with organization and orientation of the deposited fiber. Electrospinning device parameters leading to a stable fiber extrusion were already found, together with the influence of the individual working parameters on the fiber properties. It was also found that fiber steering via the external electrostatic field, created by auxiliary electrodes, has very limited steering capabilities. In this article, electrodynamic steering of the electrospun polymer nanofiber is discussed, with focus on the macroscopic fiber deposition pattern and microscopic fiber alignment and straightness. Different electric field distributions are examined, and the corresponding fiber collection patterns are demonstrated on a series of experiments. Finally, a mathematical model of a discretized fiber is created. Matching the simulation and experimental results allows for the determination of unknown fiber properties, like the structural damping coefficient or Stokes drag coefficient. [ABSTRACT FROM AUTHOR]

Recent advances in the electrospinning technique offer significant opportunities for improved fiber reinforced polymer composites of interest for capacitor applications. Classical effective medium approximation may fail to reach exact solutions due to the intricately inhomogeneous distribution of the depolarizing field in fibers with arbitrary orientation degrees. In this work, a three-dimensional finite element method (FEM) model has been developed to in-depth study the effects of fiber alignment on the dielectric response in fiber/polymer composites. A quantitative relationship between the effective permittivity of composites and the alignment degree of fiber has been initially established. Furthermore, we define a parameter of the effective angle which has the equivalent contribution on the effective permittivity with the actually distributed multiple alignment angles of fibers in practical composite materials. The calculation results with FEM show good agreement with the experiment measurements delivered recently. [ABSTRACT FROM AUTHOR]

Open-cell foams of polyvinylidene fluoride (PVDF) homopolymer were fabricated with the content of polar phase being changed by thermal treatment, and their airborne acoustic absorption performance properties were measured comparably in an acoustic tube. The experimental results showed that the sample with the more polar phase and hence a stronger local piezoelectric effect exhibited a significantly larger acoustic absorption coefficient. In addition to the conventional visco-inertial, thermal and materials damping effects, our analysis indicated that the thin and polar struts of PVDF foams with the polar phase and the local piezoelectric effect may further enhance the mechanical damping by converting the excited mechanical vibration to electricity through the local piezoelectric effect and increasing the friction and viscous loss at the fluid-solid interface in the presence of electrical charges. The open-cell polymer foams with high content of the polar phase and the local piezoelectric effect have great potential for passive airborne noise mitigation applications. [ABSTRACT FROM AUTHOR]

Contact-resonance atomic force microscopy (CR-AFM) has been used to measure the viscoelastic loss tangent of soft materials such as polymers. Usually, the damping is attributed to the dissipation in the contact volume due to internal friction and air damping of the cantilever. However, partial slip or even full sliding can exist in the contact zone under tangential loading, and thus, the accompanying energy dissipation must be taken into account when measuring the damping constant Q l o c − 1 . Here, the stick-to-sliding transition of the tip-sample contact in CR-AFM was studied. Amplitude drops were observed in the resonance curves caused by such stick-to-sliding transitions. The results show that the stick-to-sliding transition arises under small contact forces and large excitation amplitudes. Extra energy loss from full sliding induces large contact damping. The critical lateral displacement needed for the stick-to-sliding transition varies linearly with the contact radius. [ABSTRACT FROM AUTHOR]

Fabrication of thermal interface materials (TIMs) from sustainable resources is a very challenging task but at the same time of great importance due to the continuously growing problem of electronic waste management. A variety of TIMs comprising synthetic polymers loaded with metallic wires or ceramic nanofillers are commercially available; however, they are usually frail and difficult to recycle. In this letter, we report a simple fabrication process for sustainable bio-based TIMs using regenerated cellulose and graphene nanoplatelets (GnPs). The process relies on forming conductive inks by dissolving post-consumer cotton fabrics and dispersing GnPs in a common solvent, followed by solution casting/drying. The TIM pads become electrically conductive (30 S/m) at 25 wt. % GnP concentrations. Their cross-plane thermal conductivity (k) was estimated to be 5.50 W/mK using infrared thermal measurements on a chip-stack setup. Additionally, the surface or in-plane 2D thermal conductivity was found to be approximately 800 W/mK. In the case of damage, the TIMs can be recycled by re-dispersing in the solvent. [ABSTRACT FROM AUTHOR]

Microlasers are involved in a broad range of devices for numerous research applications. However, the mode structures of three-dimensional microlasers without rotational symmetry are largely unexplored. Previous studies of such cavities revealed lasing modes exclusively localized on periodic orbits in the plane parallel to the substrate, which is to say that the associated momentum vectors are concentrated in the plane. In this paper, we characterize three-dimensional, polymer-based Fabry-Perot (i.e., ribbon-shaped) microcavities and demonstrate that such cavities exhibit modes with momentum vectors out of the substrate plane. These results constitute a proof-of-principle and motivate follow-up studies with more complex three-dimensional geometries. [ABSTRACT FROM AUTHOR]

The advancement of 3D-printing opens up a new way of constructing affordable custom terahertz (THz) components due to suitable printing resolution and THz transparency of polymer materials. We present a way of calculating, designing, and fabricating a THz waveplate that phase-modulates an incident THz beam (λ0 = 2.14 mm) in order to create a predefined intensity profile of the optical wavefront on a distant image plane. Our calculations were performed for two distinct target intensities with the use of a modified Gerchberg-Saxton algorithm. The resulting phase-modulating profiles were used to model the polylactide elements, which were printed out with a commercially available 3D-printer. The results were tested in a THz experimental setup equipped with a scanning option, and they showed good agreement with theoretical predictions. [ABSTRACT FROM AUTHOR]

Biodegradable polymer scaffolds for tissue engineering is a promising technology for therapies of patients suffering from the loss of tissue or its function including cardiac tissues. However, limitations such as hydrophobicity of polymers prevent cell attachment, cell conductivity, and endothelialization. Plasma modification of polymers allows producing materials for an impressive range of applications due to their unique properties. Here, we demonstrate the possibility of bioresorbable electrospun polycaprolacton (PCL) scaffold surface modification by reactive magnetron sputtering of the titanium target in a nitrogen atmosphere. The influence of the plasma treatment time on the structure and properties of electrospun PCL scaffolds was studied. We show that the plasma treatment does not change the physico-mechanical properties of electrospun PCL scaffolds, leads to an increase in PCL scaffold biocompatibility, and, simultaneously, increases their hydrophilicity. In conclusion, this modification method opens a route to producing scaffolds with enhanced biocompatibility for tissue engineered vascular grafts. [ABSTRACT FROM AUTHOR]

The facile sorting of highly pure semiconducting single-walled carbon nanotubes (s-SWNTs) is still one of the challenging issues for the next-generation wearable electronic devices such as various opto-electric devices and field-effect transistors (FETs). Herein, we demonstrate the selective dispersion of high-purity s-SWNTs using indacenodithiophene-co-benzothiadiazole (IDT-BT), which is a state-of-the-art high-mobility conjugated polymer. By the selective wrapping of the IDT-BT copolymer, SWNTs of chiral indices (6, 5), (7, 5), (7, 6), (8, 4), (9, 4), (8, 6), (8, 7), (10, 5), (9, 7), (10, 6), (11, 1), and (13, 3) are sorted. Finally, the networked s-SWNT film formed by spin-coating is applied as an active layer of FETs that exhibited ambipolar characteristics with an average mobility of 2.28 cm2/V s in the p-channel and 2.10 cm2/V s in the n-channel. The ON/OFF ratios in both p- and n-channels are approximately 105, which supports the high purity separation of s-SWNTs wrapped by IDT-BT. [ABSTRACT FROM AUTHOR]

We show that graphene supported on a hydrophobic and flat polymer surface results in flakes with extremely low doping and strain as assessed by their Raman spectroscopic characteristics. We exemplify this technique by micromechanical exfoliation of graphene on flat poly(methylmethacrylate) layers and demonstrate Raman peak intensity ratios I(2D)/I(G) approaching 10, similar to pristine freestanding graphene. We verify that these features are not an artifact of optical interference effects occurring at the substrate: they are similarly observed when varying the substrate thickness and are maintained when the environment of the graphene flake is completely changed, by encapsulating preselected flakes between hexagonal boron nitride layers. The exfoliation of clean, pristine graphene layers directly on flat polymer substrates enables high performance, supported, and non-encapsulated graphene devices for flexible and transparent optoelectronic studies. We additionally show that the access to a clean and supported graphene source leads to high-quality van der Waals heterostructures and devices with reproducible carrier mobilities exceeding 50000 cm2 V-1 s-1 at room temperature. [ABSTRACT FROM AUTHOR]

In order to obtain polymer-based composites with a high dielectric constant and suppressed dielectric loss, polyvinylidene fluoride (PVDF)/silver (Ag) multi-layer structured composites were fabricated via vacuum evaporation and hot-press methods. The dielectric constant of the PVDF/ Ag(5/4) composite (including five PVDF layers and four Ag layers) is up to 31, and dielectric loss can be suppressed below 0.02 (smaller than that of pure PVDF) at 1 kHz. The enhanced interfacial polarization in multi-layer structured composites is determined via temperature dependence of electrical modulus, which is regarded as the origin of dielectric constant enhancement. The suppressed dielectric loss at low frequency is attributed to the difficulty in the formation of a percolation conductive network in this multi-layer system. This promising multi-layer strategy could be generalized to a variety of polymers to develop polymer-based composites with a high dielectric constant and low dielectric loss. [ABSTRACT FROM AUTHOR]