Low Dielectric Constant Research Articles

Superior Capacitive Energy Storage Enabled by Molecularly Interpenetrating Interfaces in Layered Polymers.

Polymer dielectrics are essential for advanced electronics and electrical power systems, yet they suffer from low energy density (Ue) due to their low dielectric constant (K) and the inverse relationship between K and breakdown stength (Eb). Here a scalable approach utilizing the designed molecularly interpenetrating interfaces is presented to achieve all-organic dielectric polymers with high Ue and charge-dischage efficiency (η). Distinctive intermolecular interactions and microstructural changes, as demonstrated experimentally and theoretically, are introduced by the molecularly interpenetrating interfaces, resulting in simultaneous improvements in dielectric responses and mechanical strength while inhibiting electrical conduction - outcomes unattainable in conventional layered polymers. Consequently, exceptional improvments in both K and Eb are achieved, yielding a very high Ue of 22.89Jcm-3 with η ≥ 90%, outperforming current layered polymer dielectrics. The bilayers can be easily fabricated into large-area films with high uniformity and outstanding capacitive stability (>500 000 cycles), offering a practical route to scalable high-Ue polymer dielectrics for electrical energy storage.

Textured-piezoelectric-ceramic-based focused intravascular ultrasonic transducer with improved image quality and uniformity

Intravascular ultrasound (IVUS) imaging is a minimally invasive medical technology that plays a critical role in diagnosis, treatment guidance, and post-treatment assessment of coronary artery diseases. As a crucial component of the IVUS system, conventional IVUS transducers are designed to be planar and unfocused to adequately cover the region of interest. However, this design comes at the cost of spatial resolution. Here, we developed a high-performance focused IVUS transducer using Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 (PIN-PSN-PT) textured ceramics with both high electromechanical performance (thickness-mode electromechanical coupling factor kt: ∼60%) and high Curie temperature (TC: ∼250 °C). Benefiting from the relatively low clamped dielectric constant (ε33S/ε0: ∼450) of PIN-PSN-PT-textured ceramics in contrast to currently used soft piezoelectric ceramics (>1000), we designed a relatively large aperture for the focused IVUS transducer, with a goal of enhancing lateral resolution across a larger depth of field, ranging from 1 to 5 mm. The developed focused IVUS transducer operates at 42 MHz with an −6 dB bandwidth of 72%, featuring a 0.6 × 0.6 mm2 aperture while maintaining an electrical impedance of approximately 40–60 Ω. The axial and lateral resolutions characterized by wire phantom imaging are 45 and 208 μm, respectively. The acoustic pressure generated by the focused IVUS transducer is 1.4 times higher than that of its planar counterpart. Ex vivo porcine coronary artery imaging demonstrates that our focused IVUS transducer offers improved image quality and uniformity for the visualization of intravascular structures. Our work shows great potential of PIN-PSN-PT-textured ceramics for creating high-frequency miniaturized focused transducers.

Preparation of modified epoxy resin with high hydrophobicity, low dielectric constant, toughness, and flame retardant by epoxy-functionalized siloxanes

A series of α, ω-dimethylglycidoxypropyl-terminated PDMS oligomer (PDMS-GE) oligomers with different polymerization degrees were synthesized and used to modify the bisphenol-A diglycidyl ether E51 (DGEBA) / 4,4-diaminodiphenylmethane (DDM) epoxy resin, resulting in epoxy resins with high hydrophobicity, low dielectric constant, good impact toughness, low combustion heat release rate, and low total heat release. The combustion heat release rate and total heat release of the material decreased with the increase in the loadings of PDMS-GE. Relative to pure epoxy resin, the composite E51/D30–10, which using DGEBA as the matrix, PDMS-GE with a degree of polymerization of 30 as the modifier in an amount of 10 phr relative to the mass sum of DGEBA, PDMS-GE and DDM, exhibited the best comprehensive performance with a water contact angle of 102.42°, a dielectric strength of 6.49 kV/mm, a dielectric constant of 2.93 at 14.2 GHz, the peak rate of heat release (PRHR) and total heat release (THR) are of 378.3 kW/m2 and 134.4 MJ/m2, respectively. These comprehensive performances underscore the potential of PDMS-GE oligomers in significantly improving epoxy resin properties. When the loadings of PDMS-GE oligomers are less than 5 wt%, PDMS-GE with a lower degree of polymerization can improve the toughness of epoxy resins. The impact strength of the composite E51/D24–5, which uses DGEBA as the matrix, PDMS-GE with a degree of polymerization of 24 as the modifier in an amount of 5 phr relative to the mass sum of DGEBA, PDMS-GE, and DDM, reaches 98.1 kJ/m2, which is about 28.9 % higher than that of pure epoxy resin. The results also indicated that the degree of polymerization of PDMS-GE oligomers has less influence on the dielectric properties and mechanical properties of composite materials.

Evaluation the influence of different chemical bond on microwave dielectric properties of YbMgGaO4 ceramics with low dielectric constant

Evaluation the influence of different chemical bond on microwave dielectric properties of YbMgGaO4 ceramics with low dielectric constant

High dielectric energy storage properties of chitin matrix composites regulated by SiO2.

High-performance polymer-based dielectric materials have attracted much attention in the field of energy storage due to high breakdown field strength and low cost. However, partial polymer-based materials are derived from traditional fossil energy derivatives, which are characterized by non-renewable and low dielectric constants, which are not conducive to the improvement of energy storage. In this paper, dissolved chitin through alkali/urea system is composited with SiO2 prepared by electrostatic spinning. The maximum discharge energy density of the fiber composite film reaches 4.34 J cm-3, which is 1.6 times higher than that of the micron particle composite film (2.8 J cm-3) and 1.9 times higher than that of the pure chitin film. The high aspect ratio and low concentration of silica filler effectively improved the breakdown field strength. In addition, the thermal stability was improved. This study paves the way for the application of bio-based materials in high-performance dielectrics.

Design of Microstrip Antenna Array for Autonomous Vehicles

The utilization of Autonomous vehicles has been rapidly increasing in both civilian and military applications. This is primarily due to their exceptional communication capabilities with ground clients, as well as their inherent properties such as adaptability, mobility, and flexibility. To effectively monitor and control the deployment of Autonomous vehicles, a 5G wireless network can be utilized alongside other devices as user equipment (UE). Through the utilization of a highly directive microstrip patch antenna (MPA) functioning within a dedicated frequency band, the Autonomous vehicle is able to establish effective long-range communication, overcoming signal degradation and minimizing interference from other channels within a confined area. The adoption of MPA is especially advised for Unmanned Aerial Vehicles (UAVs) due to its characteristics such as being lightweight, cost-efficient, small in size, and having a flat structure. This study details the development and simulation of a highly directive single-band 1x2 and 1x4 antenna array designed to operate at a 5.8 GHz frequency specifically tailored for Autonomous vehicle use. To enhance directivity and ensure structural robustness, the Roger RT5880 material has been utilized as a substrate, known for its lower dielectric constant.. The results demonstrate a high gain of 9.16 dBi and 11.4 dBi for the 1x2 and 1x4 antenna arrays respectively, while maintaining a compact size. The simulated 1x4 antenna array was fabricated using the Roger RT5880 material, and this array was tested in the microwave communication's laboratory at College of Engineering, Al-Nahrain University. The antenna presents good results by means of return losses (-26.672 dB) which equivalent to VSWR of 1.098.

Tailoring Dielectric Properties and Dimensional Stability of Poly(Phenylene Ether) Using Bismaleimide Crosslinkers for High-Frequency PCB Applications.

With the increasing demand for high-performance printed circuit boards (PCBs) in the 6G communication era, dielectric substrate materials must exhibit a low dielectric constant (Dk), low dielectric loss (Df), and high dimensional stability. In this study, a series of bismaleimide-incorporated poly(phenylene ether) resins (PPE-BMI) with varying bismaleimide (BMI) crosslinker contents is developed, exhibiting significantly enhanced dielectric properties and dimensional stability, owing to the restricted polymer chain mobility and increased crosslinking density. Dielectric property measurements reveal that the PPE-BMI resins exhibit low Dk and Df values at frequencies above 100GHz, while maintaining an excellent dielectric performance even after an 85 °C/85% relative humidity reliability test. A significant reduction in the coefficient of thermal expansion is observed with an increase in the BMI content. Molecular dynamics simulations are employed to clarify the role of BMI crosslinkers in reducing the free volume, enhancing the crosslinking in the PPE (poly(phenylene ether)) matrix, and influencing the thermophysical properties of PPE-BMI. The infiltration of PPE-BMI into glass fabrics and liquid crystal fabrics highlights their potential for practical use in advanced PCB applications operating at high frequencies.

Macromolecular Architecture in the Synthesis of Micro- and Mesoporous Polymers.

Polymers with micro- and mesoporous structure are promising as materials for gas storage and separation, encapsulating agents for controlled drug release, carriers for catalysts and sensors, precursors of nanostructured carbon materials, carriers for biomolecular immobilization and cellular scaffolds, as materials with a low dielectric constant, filtering/separating membranes, proton exchange membranes, templates for replicating structures, and as electrode materials for energy storage. Sol-gel technologies, track etching, and template synthesis are used for their production, including in micelles of surfactants and microemulsions and sublimation drying. The listed methods make it possible to obtain pores with variable shapes and sizes of 5-50 nm and achieve a narrow pore size distribution. However, all these methods are technologically multi-stage and require the use of consumables. This paper presents a review of the use of macromolecular architecture in the synthesis of micro- and mesoporous polymers with extremely high surface area and hierarchical porous polymers. The synthesis of porous polymer frameworks with individual functional capabilities, the required chemical structure, and pore surface sizes is based on the unique possibilities of developing the architecture of the polymer matrix.

Effect of Al doping on structural and electrical properties of HfO2/ZrO2 layered structures for high-k applications

ZrO2 films with ultrathin Al2O3 layers have effectively contributed to the miniaturization of dynamic random access memory (DRAM) capacitors for many years. However, as memory devices continue to shrink, higher dielectric constants are required to maintain cell capacitance. To address this challenge, research has explored the use of tetragonal HfO2 layers, which theoretically possess a higher dielectric constant than ZrO2, as dielectrics. However, the thermodynamically stable phase of HfO2 is monoclinic with a lower dielectric constant, necessitating a phase transition to the tetragonal form for DRAM capacitor applications. Although attempts have been made to induce this phase transition to achieve high dielectric constants by applying an HfO2/ZrO2 layered structure or doping HfO2 with elements such as Zr, Al, and Si, significant challenges remain in completely eliminating the monoclinic phase or implementing a pure tetragonal phase of HfO2. In this study, we systematically investigated the crystallinity changes and improved the electrical properties of HfO2/ZrO2 layered structures with Al doping in the HfO2 layers. Our findings demonstrate that optimizing the partitioning of the ZrO2 and HfO2 layers, combined with Al doping, effectively achieves equivalent oxide thickness scaling.

Enhanced Dielectric Properties and Antibacterial Activity of Natural Rubber by Modification with Poly(Acrylic Acid-Co-Acrylamide) Incorporating Silver Nanoparticles and Titanium Dioxide.

This work aims to enhance natural rubber's dielectric properties and antibacterial activity by incorporating silver nanoparticles and titanium dioxide. Deproteinized natural rubber (DPNR) was modified through the graft copolymerization of acrylic acid and acrylamide using N', N'-Methylenebisacrylamide as a crosslinking agent, resulting in poly(acrylic acid-co-acrylamide)-modified, deproteinized natural rubber (MDPNR). This modification facilitated coordination with silver ions and interaction with titanium dioxide. Silver nanoparticles were generated under heat and pressure. Modified natural rubber composites containing silver nanoparticles and titanium dioxide (MDPNR/Ag-TiO2) were prepared. Scanning electron microscopy (SEM) revealed well-distributed silver in the modified natural rubber matrix, while agglomeration of titanium dioxide was observed at a high loading. Both MDPNR and MDPNR/Ag-TiO2 showed high thermal stability compared to DPNR. The MDPNR/Ag-TiO2 composites exhibited higher Tg and lower tan δ, indicating higher stiffness due to the restriction of chain movement compared to that in MDPNR. DPNR exhibited a low dielectric constant, enhanced by poly(acrylic acid-co-acrylamide) modification and silver nanoparticle/titanium dioxide incorporation. Incorporating 0.5 phr of AgNO3 and 2.5 phr of TiO2 in the composites increased the dielectric constant by 1.33 times compared to that of MDPNR. MDPNR showed no antibacterial activity, while the MDPNR/Ag-TiO2 composites exhibited promising antibacterial activity against Staphylococcus aureus and Escherichia coli.

Investigation On Barrier Layers Of PT/BaTiO3/PT Based Thin Film Capacitors

AbstractBarium titanate is a ferroelectric material used as a dielectric in thin film capacitors owing to its high dielectric constant. Barrier layers are utilized in these capacitors to improve the capacitors’ performance by controlling the microstructure and creating thin resistive films. In this paper, the effect of barrier layers in Pt/BT/Pt capacitors is studied using zinc oxide and aluminium oxide. The performance parameters such as capacitance density, leakage current, equivalent series resistance, dielectric loss and dielectric strength of Pt/BT/Pt thin film capacitors with barrier layers of different sizes are simulated using COMSOL Multiphysics modeling software. 2 nm thick aluminum oxide as Pt ‐ BT barrier layer gives optimal performance. The leakage current, dielectric loss, capacitance density, equivalent series resistance and dielectric strength of Pt/BT/Pt capacitor are found to be 0.519 mA, 9.62×10−12, 172.8 fF/μm2, 9.62 kΩ, 108 V/m respectively whereas that of Pt/ALO/BT/ALO/Pt capacitor are found to be 1.56×10−18 A, 7.81×10−18, 11.6 fF/μm2, 9.01×1015 Ω, 5.05×109 V/m respectively. The low capacitance in Pt/ALO/BT/ALO/Pt capacitor is due to the low dielectric constant of aluminium dioxide barrier layer. The reduced leakage current and increased equivalent series resistance is due to the low conductivity of the aluminium oxide barrier layer. The use of aluminium oxide barrier layer between the conductive surfaces can reduce the electric field and increase the breakdown voltage, leading to improved dielectric strength and reduced dielectric loss.

Achieving enhanced thermal conductivity and low dielectric constants using double-oriented fluorinated graphene skeleton in silicone gel composites

The dielectric properties and thermal conductivity of composites are often contradictory. To improve the thermal conductivity, the filler content needs to be increased, which often contributes to the high dielectric constant of the material. Inspired by the layout of community buildings, in this study, silicone gel/double-oriented fluorinated graphene skeleton composites were prepared, which solved the difficulty in assembling fluorinated graphene in situ into a three-dimensional continuous network structure. This greatly improved the thermal conductivity and reduced the dielectric constant of the silicone gel while maintaining a low filler content and the insulating properties. In addition, based on the reconstruction of a real three-dimensional body, the mechanism by which the skeleton improved the material performance was analyzed using finite element simulation. The vertical and horizontal thermal conductivity of the silicone gel/double-oriented fluorinated graphene skeleton composites reached 3.34 W/(m·K) and 2.65 W/(m·K), respectively, and the dielectric constant dropped to 80 % of that of pure silicone gel. This provided a new way to synergistically improve the dielectric properties and thermal conductivity of insulating materials, and has great application potential as a thermal interface material in next-generation electronic devices.

Crosslinked silsesquioxane with high thermal stability and low dielectric constant by the autopolymerization of Q-type H-POSS

A novel method was developed for constructing cross-linked silsesquioxane, utilizing Q-type H-POSS as a precursor. The Piers-Rubinsztajn (P–R) like reaction of Q-type H-POSS was catalyzed by B(C6F5)3, resulting in the production of a prepolymer containing partial Si–H. Upon heating at high temperature in air, the prepolymer transformed into an insoluble and infusible cross-linked polymer, named Cured poly(H-POSS). This polymer exhibited high thermostability, with a 5 % weight loss temperature (T5d) of 709 °C and a residue of 92 % at 800 °C. Additionally, Cured poly(H-POSS) exhibited high transparency, with a transmittance of 90 % in the 400–800 nm wavelength range, and favorable dielectric properties, with a dielectric constant (Dk) of 2.88 at 14 GHz.

Investigation of Charge Transfer Mechanism and Dielectric Relaxation in CsCdCl3 Perovskite

ABSTRACTThe exceptional optoelectronic capabilities of all‐inorganic metal halide perovskite semiconductor components open up a multitude of possible applications. Among all the metal halides, the chloride of cesium cadmium has not been investigated in great detail. Here, we describe a straightforward method for creating CsCdCl3 perovskite single crystals using the slow evaporation solution growth approach. These were investigated by utilizing X‐ray powder diffraction, and optical and impedance spectroscopies. The creation of a single‐phase with a hexagonal‐type structure was verified by the X‐ray powder diffraction (XRPD) data. The compound's semiconductor characteristics were verified by the optical measurement, indicating a direct band‐gap value of about 3.16 eV. The absorption and reflectance spectrum was also used to calculate and explain the optical extinction coefficient, Urbach energy, and skin depth as functions of the input photon's wavelength. Besides, the impedance spectroscopy technique was employed to investigate the characteristics of this component, across a frequency range of 10−1 Hz to 106 Hz and at temperatures ranging from 313 K to 453 K. The frequency behavior of the AC conductivity, σac, was analyzed using the universal Jonscher law. The outcomes of the charge transport investigation on CsCdCl3 imply that the perovskite material possessed a quantum mechanical tunneling (QMT) model for T < 363 K and a large polaron tunneling (OLPT) paradigm for T > 363 K. A correlation between the ionic conductivity and the crystal structure was established and discussed. Ultimately, the low dielectric loss and high dielectric constant of CsCdCl3 make it a promising material for energy harvesting devices.

Cellulose nanocrystal dispersion-ability in polylactides with various molecular weights prepared in dichloromethane/dimethyl sulfoxide solvents for electrospinning applications

In this study, effects of polylactide molecular weight, i.e., high (HPLA), medium (MPLA), low (LPLA), and dichloromethane (DCM)/dimethyl sulfoxide (DMSO) blend ratio on cellulose nanocrystal (CNC) dispersion quality in solution casted PLA/CNC nanocomposites were investigated via small amplitude oscillatory shear rheological analysis, while crystallization behavior, thermal degradation, morphological structure of the nanocomposites were also reported. Due to its low dielectric constant, none of the nanocomposites with 100DCM indicated a change in their complex viscosity as a result of poor CNC dispersion. This is while the increase in DMSO content (50%vv−1) improved CNC dispersion. The superior CNC dispersion-ability in PLAs with lower molecular weight was confirmed. The poorer CNC dispersion in HPLA attributes to hindering effect of higher molecular weight on solvent and nanoparticle diffusion. The better dispersed CNCs influenced crystal nucleation behavior of PLAs and increased crystallinity degree. In addition, the impact of well-dispersed CNCs on fiber formation quality of nanocomposites was reported. Introducing finely dispersed CNCs (1 wt%) in LPLA refined fiber diameters around 1200 nm with more homogenous structure. Besides, the use of 100DCM and the use of DMSO at high contents (50%vv−1) deteriorated fiber formation, respectively, due to low conductivity of DCM and high boiling temperature of DMSO.

Partitioning of an Enzyme-Polymer Surfactant Nanocomplex into Lipid-Rich Cellular Compartments Drives In Situ Hydrolysis of Organophosphates.

Most organophosphates (OPs) are hydrophobic, and after exposure, can sequester into lipophilic regions within the body, such as adipose tissue, resulting in long term chronic effects. Consequently, there is an urgent need for therapeutic agents that can decontaminate OPs in these hydrophobic regions. Accordingly, an enzyme-polymer surfactant nanocomplex is designed and tested comprising chemically supercharged phosphotriesterase (Agrobacterium radiobacter; arPTE) electrostatically conjugated to amphiphilic polymer surfactant chains ([cat.arPTE][S-]). Experimentally-derived structural data are combined with molecular dynamics (MD) simulations to provide atomic level detail on conformational ensembles of the nanocomplex using dielectric constants relevant to aqueous and lipidic microenvironments. These show the formation of a compact admicelle pseudophase surfactant corona under aqueous conditions, which reconfigures to yield an extended conformation at a low dielectric constant, providing insight into the mechanism underpinning cell membrane binding. Significantly, it demonstrated that [cat.arPTE][S-] spontaneously binds to human mesenchymal stem cell membranes (hMSCs), resulting in on-cell OP hydrolysis. Moreover, the nanoconstruct can endocytose and partition into the intracellular fatty vacuoles of adipocytes and hydrolyze sequestered OP.

Crystal structure, bond characteristics, and microwave dielectric properties of novel low-εr LiRE(PO3)4 (RE = Pr, Nd) ceramics

The rapid advancement of Internet of Things poses significant challenges to signal latency. To address this issue, novel low dielectric constant (εr) lightweight LiRE(PO3)4 (RE = Pr, Nd) ceramics were synthesized by solid-state method. Accompanied by densification of the microstructure, the exceptional microwave dielectric properties can be obtained in the LiPr(PO3)4 ceramics sintered at 910 °C, with a low εr value of 5.25, a high-quality factor (Q·f) value of 42,939 GHz and a temperature coefficient of resonant frequency (τf) of −14.17 ppm/°C. Meanwhile, the LiNd(PO3)4 ceramics sintered at 940 °C demonstrate high performance, with εr of 5.23, a Q·f of 65,718 GHz and a τf of −34.28 ppm/°C. The low εr is mainly influenced by the strong covalency and bond susceptibility contribution of [PO4] tetrahedron, and the underestimated εr is subjected to the cation “compression” effect through the bond valence theory. The analysis via Phillips–Van Vechten–Levine (P-V-L) theory indicates that the enhancement of Q·f value in LiNd(PO3)4 ceramics can be attributed to the enhanced total lattice energy and packing fraction value. In addition, the 5 GHz Wi-Fi microstrip patch antennas utilizing LiNd(PO3)4 ceramics were fabricated. The outstanding antenna’s performance was tested in the microwave anechoic chamber, with a gain of 6.34 dB and a broad bandwidth of 276 MHz at 5.49 GHz, confirming the promising application prospects of LiNd(PO3)4 ceramics for an indoor Wi-Fi antenna.

Effects of phase transition on the structure and microwave dielectric properties of (1-x)CeO2-0.5xSm2O3 (x=0–0.9) ceramics

(1-x)CeO2-0.5xSm2O3 (x = 0–0.9) microwave dielectric ceramics are synthesized by the conventional solid-phase reaction method, with the effects of phase transition on structure and microwave dielectric properties being investigated in detail. The phase transition process is analyzed using the ionicity and lattice energy of (1-x)CeO2-0.5xSm2O3 ceramics, which is related to the coordination number and effective valence electron charge. With the increase of Sm3+ content, there are three phase regions: the cubic fluorite phase (0 ≤ x ≤ 0.4), the rare-earth C-type phase (0.4 < x ≤ 0.8) and the mixed phase (0.8 < x < 1.0). With the phase transition, the microstructures of (1-x)CeO2-0.5xSm2O3 (x = 0–0.9) ceramics show a quasi-periodic change, where x = 0.4 and x = 0.8 are the critical points with similar grain size and distribution. When the phase transition occurs, the polarization, Q × ƒ values and the resonant frequency temperature coefficients (τƒ) of (1-x)CeO2-0.5xSm2O3 (x = 0–0.8) ceramics are all mutated, which is due to the change of bond ionicity and effective valence electron charge caused by the phase transition. The microwave dielectric properties in each pure phase region vary regularly with bond ionicity and valence. Compared with the cubic fluorite phase (0 ≤ x ≤ 0.4), (1-x)CeO2-0.5xSm2O3 ceramics with rare-earth C-type phase (0.4 < x ≤ 0.8) have lower dielectric constant, with better Q × ƒ values and τƒ values.

Enhanced mechanical and dielectric properties of Si3N4−BN composite ceramics fabricated via reaction re-sinteirng process

Dense Si3N4−BN composite ceramics were synthesized using reaction re-sintering method which involved an in-situ reactive sintering followed by a re-sintering process, employing Si3N4 and SiB6 powders as raw materials. Initially, SiB6 underwent nitridation to form Si3N4 and BN during the in suit reactive sintering. Subsequently, the pores between the Si3N4 and BN grains were significantly removed during the re-sintering stage, facilitating the strong integration of Si3N4 and BN grains within the composite ceramics. The re-sintering process significantly enhanced both the density and mechanical properties of the composite ceramics. The generated BN grains were uniformly distributed throughout the Si3N4 matrix, thereby improving both the machinability and dielectric properties. The composite ceramics with 20 wt.% BN demonstrated excellent mechanical and dielectric properties, characterized by a low apparent porosity of 3.8%, a high flexural strength of 315.6 MPa, a Vickers hardness of 5.0 GPa, a low dielectric constant of 5.02, and a loss tangent ranging from 1× 10-3 to 2.5 × 10-3 at frequencies between 8.2 and 12.4 GHz.

Fluorine polyimide nanofibrous composites with outstanding piezoelectric property for human motion monitoring

The limited high-temperature resistance of conventional piezoelectric polymers remains an extremely arduous obstacle to fabricate a flexible sensor that meets the practical application in extreme environments. In this paper, the fluorine-containing polyimide (FPI) nanofiber membrane was prepared by electrospinning and further encapsulated with FPI resin into a flexible and wearable piezoelectric sensor. The influence of fluorine-containing monomer content on the mechanical properties, heat resistance, and piezoelectric properties of FPI nanofiber composite membranes was systematically investigated. The fabricated samples show outstanding thermal stability with Tg of 247℃-262℃ and Td5% of 570℃. The composite also displays a low dielectric constant (2.25–3.5) and dielectric loss (0.004–0.01), respectively. It is particularly noteworthy that the prepared fluorine-containing PI nanofiber membrane exhibits excellent piezoelectric properties. The output voltage of CPI-100 can reach up to 7 V with fast response / recovery time (16 ms / 7 ms) and exceptional durability (10,000 cycles). Moreover, the prepared CPI nanofiber composite membrane sensor can effectively detect bending and pressuresignals, which can be applied to motion and pressure monitoring. We found a new kind of substrate with outstanding piezoelectric and provided a novel strategy for developing high-temperature resistant flexible self-powered piezoelectric sensors in wearable electronics.