This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu₃Ti₄O₁₂(CCTO)/Ag nanoparticles (CCTO@Ag).

Matching the acoustic impedance of high-frequency (≥100 MHz) ultrasound transducers to an aqueous loading medium remains a challenge for fabricating high-frequency transducers. The traditional matching layer design has been problematic to establish high matching performance given requirements on both specific acoustic impedance and precise thickness. Based on both mass-spring scheme and microwave matching network analysis, we interfaced metal-polymer layers for the matching effects. Both methods hold promises for guiding the metal-polymer matching layer design. A 100 MHz LiNbO₃ transducer was fabricated to validate the performance of the both matching layer designs. In the pulse-echo experiment, the transducer echo amplitude increased by 84.4% and its −6dB bandwidth increased from 30.2% to 58.3% comparing to the non-matched condition, demonstrating that the matching layer design method is effective for developing high-frequency ultrasonic transducers.

This work reports the high dielectric permittivity of polyimide (PI) embedded with CaCu₃Ti₄O₁₂ (CCTO) nanoparticles. The dielectric behavior has been investigated over a frequency of 100 Hz-1 MHz. High dielectric permittivity (ε = 171) and low dielectric loss (tan δ = 0.45) at 100 Hz have been observed near the percolation threshold. The experimental results fit well with the Percolation theory. We suggest that the high dielectric permittivity originates from the large interface area and the remarkable Maxwell-Wagner-Sillars effect at percolation in which nomadic charge carriers are blocked at internal interfaces between CCTO nanoparticles and the polyimide matrix.

Spintronics exhibits significant potential for a neuromorphic computing system with high speed, high integration density, and low dissipation. In this article, we propose an ultralow-dissipation skyrmion-based nanodevice composed of a synthetic antiferromagnet (SAF) and a piezoelectric substrate for neuromorphic computing. Skyrmions/skyrmion bubbles can be generated in the upper layer of an SAF with a weak anisotropy energy (E_a). Applying a weak electric field on the heterostructure, interlayer antiferromagnetic coupling can be manipulated, giving rise to a continuous transition between a large skyrmion bubble and a small skyrmion. This thus induces a variation of the resistance of a magnetic tunneling junction that can mimic the potentiation/depression of a synapse and the leaky-integral-and-fire function of a neuron at a cost of a very low energy consumption of 0.3 fJ. These results pave a way to ultralow power neuromorphic computing applications.

P-type Sb₂Te₃/poly(3,4-ethylenedioxythiophene) (PEDOT) thermoelectric composites are fabricated by embedding PEDOT into Sb₂Te₃ matrix. The grains of Sb₂Te₃ in the composites are found to be in micron degree and keep plate-like shapes. The measurements of thermoelectric properties show that the thermal conductivity κ of the composites is about 0.14 W m⁻¹ K⁻¹ in the temperature range of 300–523 K, much lower than that of Sb₂Te₃ compounds. The maximum of dimensionless figure of merit of the composites reaches to 1.18 at 523 K, which is the highest value for the reported Sb₂Te₃/organic composites. It is suggested that the plate-like Sb₂Te₃ grains and the embedded PEDOTs may play a significant role in decreasing the thermal conductivity. Furthermore, results of the thermal cycling between the room temperature and 523 K for 50 cycles show that the composites are stable with κ remaining a low value.