The rapid advancement of 5G/6G communication technologies imposes ever-increasing demands on microwave dielectric ceramics (MWDCs). However, it remains challenging to simultaneously achieve good temperature stability and high Q×f values. Metamaterials with artificially designed structures exhibit extraordinary properties, and metamaterialogy holds great potential for advancing conventional materials. Inspired by this paradigm, an artificial core-shell cofired architecture was designed to realize high-performance MWDCs. The architecture employed the Zn_1.01Nb₂O₆ (ZNO) matrix as the shell and positive-τ_f compensators, including TiO₂ (TO), CaTiO₃ (CTO), or SrTiO₃ (STO), in either green or pre-sintered states, as cores. The τ_f values of all the core-shell samples were effectively tuned to near zero while high Q×f values were retained. Specifically, the ZNO-TO core-shell ceramic with a 1.43 wt% pre-sintered TO core exhibited εᵣ ~ 25.32, Q×f ~ 119,100 GHz, and τ_f ~ -4.8 ppm/°C, while the temperature-stable counterparts using the CTO or STO cores retained Q×f ≥ 67,800 GHz. Furthermore, HFSS simulation of a cylindrical dielectric resonator antenna (CDRA) based on the optimized ZNO-TO core-shell ceramic predicted favorable impedance matching (VSWR ~ 1.015), radiation efficiency above 90%, and a peak realized gain of 6.13 dBi at 4.31 GHz. It preliminarily demonstrates the feasibility of CDRA applications. The artificial core-shell architecture provides a general strategy for synergistically optimizing microwave dielectric properties by tailoring the electric-field participation and confining heterogeneous interfacial reactions, which is beneficial to developing high-performance MWDCs required for next-generation communication technologies.

Bi₂Te₃-based materials were prepared by direct ink writing (DIW) 3D printing and their microstructure and thermoelectric properties were investigated with an emphasis on the effect of the content of DMF and Te/Se addition. As the mass ratio of DMF in the composition increased from 6.5% to 8.0% (in mass), the electrical conductivity deteriorated because of the corresponding increased porosity and organic remains in the samples. However, the volatilization of DMF would reduce the fluidity of the slurry. Thus, thermoelectric slurry with 7.0% DMF is the most suitable mass ratio for 3D printing. Additionally, adding Te in the p-type Bi_0.4Sb_1.6Te₃ and adding Se in the n-type Bi₂Te_2.6Se_0.4 have significantly improved their electrical conductivity due to the increased carrier concentration and mobility. Combining with the moderate Seebeck coefficient (~200 μV/K), high power factors with ~802 μW·m⁻¹·K⁻² and 1266 μW·m⁻¹·K⁻² were obtained for the n-type Bi₂Te_2.6Se_0.4+10%Se and p-type Bi_0.4Sb_1.6Te₃+7%Te, respectively, which result in the final relatively high zT values of 0.68 at 573 K and 0.56 at 330 K for n-type and p-type 3D-printed samples.

All-nanofiber self-powered device was fabricated using simple, low-cost, safe, and scalable solution blow spinning (SBS) technology for real-time respiratory monitor and timely identification of respiratory obstruction clinically. Polytetrafluoroethylene (PTFE) and polyamide-66 (PA66) nanofibers were selected as triboelectric pairs, owing to strong ability to gain electrons of PTFE and supply electrons of PA66. Poly (ethylene oxide) (PEO) was added to regulate spinning solution viscosity and prepare PTFE/PEO nanofibers, and the morphology and diameter distribution of nanofibers were discussed. PTFE nanofiber film was obtained after the decomposition of PEO in PTFE/PEO nanofiber and melt flow of PTFE pellets in a limited region, and possessed a tensile strength of 1.05 MPa and elongation at a break of 288.58%. Later, PTFE/PA66 all-nanofiber self-powered device was constructed containing PA66 nanofibers, and Au deposition film was used as electrodes by magnetron sputtering. The as-obtained device showed robust electrical performance with an open circuit voltage of ~ 110 V at a loading force of 10 N, a short-circuit current of ~ 5 uA at a loading force of 10 N and a frequency of 4 Hz, a maximum power density of 562 mW·m^–2, and a current of 3.1 uA at a loading resistance of 30 MΩ. Based on the triboelectric mechanism, the device possessed stable response and effective sensibility for stimuli, was used to monitor human breathing conditions, prevent suffocation, and distinguish slow, normal, and fast breathing, with an output voltage of ~ 0.08 V perceived in one normal respiratory circle.