Shulin Ji

Increasing electromagnetic interference (EMI) issues make shielding materials urgent in need. However, designing a thin/lightweight material with high shielding effectiveness (SE over 100 dB) by facile and scalable technologies with high production accuracy is still challenging. Herein, excellent shielding composite films are successfully prepared through sequential scalable positive pressure filtration, accurate inkjet printing, and facile transferring. From mass ratio optimization of 1D silver nanowires to 2D MXene, a skeleton with maximum inner free space and fast electron and phonon transport channels through cross-dimensional percolation is produced for internal multiple reflection absorption. To further increase EMI SE, graphene-based mesh metamaterials are theoretically calculated and accurately printed with controlled conductivity for impedance matching as the top layer. Facile inkjet printing succeeds in balancing print accuracy and conductivity control by advanced ink formulation. Finally, under multiple attenuation mechanisms verified through complex permittivity analysis in both frequency domain and real space (conductive loss, dipole polarization, and various interfacial polarizations), EMI SE of 102.31 dB in X-band is achieved. Integrating different attenuation technologies in a single material system of multidimensions inspires further designing shielding materials with increasingly strict requirements like multiband compatibility with special frequency enhancement.

In electromagnetic interference (EMI) shielding applications, high shielding effectiveness and good mechanical properties are extensively required considering conformal or foldable use. However, the natural brittleness of efficient shielding materials like layered structure hinders their widespread application and mechanisms behind these fragile films need in-depth study. Herein, silver nanowire-transition metal carbide nanosheet composite films with 63.93 dB under 4.02 μm are first prepared through mass ratio optimization. Polymers incorporated into the brittle nanowire-nanosheet system are designed through simultaneous positive pressure filtration with nanowires and nanosheets. It further increases the shielding effectiveness owing to impedance matching through conductivity adjustment; more importantly, the flexibility and property stability of films are significantly enhanced to withstand 3000 bending cycles, maintaining values of 58.81 and 63.00 dB for nanowire-nanosheet/poly(vinyl alcohol) and nanowire-nanosheet/waterborne polyurethane, respectively. Next, mechanisms of interface strengthening through polymer incorporation are thoroughly investigated through in-depth Fourier transform infrared and X-ray photoelectron spectroscopy analysis, cross-link density tests, as well as microstructure characterization. Polymers synergistically strengthen the microscopic interface through hydrogen-bond network formation and chain segment motion, providing elastic recovery properties. This work provides a viable strategy to design and fabricate flexible, lightweight, and high-performance shielding materials for many advanced fields.

Conductive textiles, as an important platform for developing wearable electronic devices, often face challenges related to washing to remove dirt while retaining conductivity. It is still a great challenge to manufacture textiles with high conductivity, washability and uniformity in an efficient and economical way. Polyvinyl alcohol (PVA) containing numerous hydroxyl groups allowing easy modification and crosslinking is a promising candidate for conductive textile construction. Herein, a stable composite ink with PVA as the matrix and silver nanowires (AgNWs) as the conductive filler for screen printing on textile surfaces is proposed. The composite conductive network endows the fabric with the highest conductivity up to 2087 S cm⁻¹ and a low percolation threshold of 0.025 mg cm⁻² for AgNW mass loading. The printed conductive pattern shows high uniformity even for a line width as small as 500 μm on fabric. The resistance change of conductive textiles washed at 60 °C for 1 h is reduced from 500 000% to 40%, thanks to the cooperation of a physically and chemically dually crosslinked polymer network with a conductive AgNW network. The prepared outperforming conductive textiles and their potential for mass production of patterned fabric electrodes provide a basis for further development of smart fabrics and wearable electronics.

Process microminiaturization is in need not only in chip field, but also in sensor‐related industries. Touch panel sensors as an example have their man‐machine interactive performance in high relation with the circuit resolution. Traditional etchings by yellow light or laser encounter their resolution limit of ≈50 µm; moreover, former pollution using chemical etchants and latter damage to flexible substrates are inevitable. This paper demonstrates an efficient and green patterning technology for flexible silver nanowire (AgNW) transparent and conductive films, which can enable complicated patterns on various types of substrates with high resolution of a 30 µm line width and 40 µm line spacing. The approach uses a water‐soluble photosensitive polymer as the selective protection layer to facilitate the removal of unwanted AgNWs through simple water washing. Due to its good water resistance and mechanical properties, the patterned electrodes exhibit excellent flexibility and environmental stability. As a proof of concept, a capacitive proximity sensor is designed using the patterned AgNW electrodes of the micro feature size, which exhibits excellent proximity sensing performance. The developed patterning technology paves the way to miniaturized feature sizes of different optoelectronic devices for wide applications in fields like new‐style displays, man‐machine interaction, IoT sensing and intelligent robots.

Silver nanowires synthesized by the most commonly used polyol method are typically accompanied by nanoparticles and nanorods, which have a negative impact on the performance of silver nanowire-based devices. Herein, we report a reproducible and easy method for preparing silver nanowires with yields exceeding 70% by optimizing the heterogeneous nucleation of silver from silver chloride precursors and regulating the reduction in ethylene glycol. The yield of silver nanowires depended on the morphology and concentration of silver chloride and the decomposition time of ethylene glycol. The Raman spectra were used to study the effect of the decomposition time of ethylene glycol on the concentration of acetaldehyde in solution, which influenced the reduction rate of silver ions. Then, the reaction time of silver nanowires was further reduced from 24 min to 10 min by increasing the reaction temperature from 160 °C to 170 °C. On the basis, the silver nanowire based capacitive screen with a good capacitive response and anti-aging performance was further fabricated. This method provides a new way for the macro preparation of silver nanowires with high yields.

Silver nanowire films have a wide application prospect in flexible electronics, while it is a noticeable problem that the silver nanowires break due to the shear force under the mass production film cutting or extreme service conditions. In this paper, the shear fracture behaviour of silver nanowire films with different structural parameters was studied under the extreme shear failure tests. The load–displacement curve was obtained from the nano-indentation test, while the hardness H , the elastic modulus E and the plastic properties represented by the ratio of H ³ / E ² of silver nanowire films with different diameters and thicknesses were calculated. On the other hand, based on the load–displacement curve, the stress–strain curve can be obtained through the finite element method simulation. The plastic properties can also be judged by the lower limit of yield strength from simulated stress–strain curve. Combined with characteristic crack propagation range, the relationship between plasticity and shear fracture was found, which was further disclosed by in-depth microstructure analysis. The results show that the better the plasticity of silver nanowire films, the stronger the resistance to shear fracture.