Investigation of flexible warp-knitted metal meshes for electromagnetic interference shielding

Abstract

This paper develops four novel warp-knitted structures with two bars of the one-in one-out threading mode and describes the investigation of electromagnetic interference (EMI) shielding metal meshes composed of contiguous ultra-fine metal wires fabricated using warp-knitting technology. The mechanical properties, electrical conductivity, and microwave shielding effectiveness (SE) of the flexible meshes are assessed in terms of the mesh structure, mesh material, and warp run-in parameter. The results reveal that the metal mesh has a flexible and stable mechanical property, good electrical conductivity, and optimal EMI performance when the mesh structure is open lap atlas. The gold-coated molybdenum mesh exhibits the lowest electrical resistivity (5.18 × 10−5 ohm/sq) and optimal average EMI SE (–21.04 dB), making it a candidate for EMI shields for intelligent wearable electronic devices. The warp run-in can adjust the EMI SE, and the optimum average EMI SE (–25.52 dB) can be obtained when the warp run-in is set at the 2580 rack. Moreover, the warp-knitted metal meshes show desirable EMI shielding efficiency persisting at >70% even at large strain deformations and under cyclic bending and twisting deformations. Conductive warp-knitted meshes with a millimeter period and micron-scale wire diameter exhibit an adequately large scale, satisfactory mechanical stability, excellent flexibility, permanent conductivity, and strong microwave reflection, simultaneously. Moreover, the EMI SE of warp-knitted metal mesh reaches the protection level (–20 dB) prescribed by standard electronic devices. Therefore, the warp-knitted metal meshes show great potential in flexible and wearable EMI shielding devices.

Flexible Warp-Knitted Metal Mesh-Based Composites: An Effective EMI Shielding Material with Efficient Joule Heating

“…Generally, the structural parameters of the textile substrate, i.e., pore size and yarn diameter, significantly influence the electrical conductivity and EMI shielding property of composites. The structural parameters of the warp-knitted metal mesh in this paper are the optimized parameters in the previous fundamental investigation …”

“…The structural parameters of the warp-knitted metal mesh in this paper are the optimized parameters in the previous fundamental investigation. 32 From Figure 2e, the CNT nanofillers are observed as a tubeshaped structure with ∼0.03 μm in diameter and ∼2 μm in length. It should be mentioned here that the CNTs are easy to agglomerate and entangle with each other owing to the high interfacial strength between CNTs, such as the strong van der Waals and Coulomb forces.…”