Boosting Conductive Loss and Magnetic Coupling Based on "Size Modulation Engineering" toward Lower-Frequency Microwave Absorption.

The rational design of absorber size is a promising strategy for obtaining excellent electromagnetic wave (EMW) absorption performance. However, achieving controllable tuning of the material size through simple methods is challenging and the associated EMW attenuation mechanisms are still unclear. In this study, the sizes of metal-organic frameworks (MOFs) are successfully tailored by changing the growth time and the molar ratio of iron (Fe)/organic ligands. The lateral and vertical lengths of MOFs vary in the range of 200 nm to 2 µm and 100 nm to 1 µm, respectively. Both experiments and simulations confirm that the decrease of MOF size favors the formation of more conductive networks, which is beneficial for improving the conductivity loss. Meanwhile, the micromagnetic simulation reveals that the magnetic coupling can be effectively enhanced by the decrease of MOF size, which is conducive to the improvement of magnetic loss, especially in low-frequency range. The reflection loss of Fe-based MOFs with optimized size reaches -46.4 dB at 6.2 GHz with an effective absorption bandwidth of 3.1 GHz. This work illustrates the important role of size effect in EMW dissipation and provides an effective strategy for enhancing the low-frequency EMW absorption performance.

Fabrication and Conductive Mechanism Analysis of Stretchable Electrodes Based on PDMS-Ag Nanosheet Composite with Low Resistance, Stability, and Durability.

A flexible and stretchable electrode based on polydimethylsiloxane (PDMS)-Ag nanosheet composite with low resistance and stable properties has been investigated. Under the synergistic effect of the excellent flexibility and stretchability of PDMS and the excellent electrical conductivity of Ag nanosheets, the electrode possesses a resistivity as low as 4.28 Ωm, a low resistance variation in the 0-50% strain range, a stable electrical conductivity over 1000 cycles, and a rapid recovery ability after failure caused by destructive large stretching. Moreover, the conductive mechanism of the flexible electrode during stretching is explained by combining experimental tests, theoretical models of contact point-tunneling effect, and finite element simulation. This research provides a simple and effective solution for the structure design and material selection of flexible electrodes, and an analytical method for the conductive mechanism of stretchable electrodes, which has potential for applications in flexible electronic devices, smart sensing, wearable devices, and other fields.