As electromagnetic (EM) pollution continues to increase, electromagnetic interference (EMI) shielding materials have been intensively evaluated in terms of two main shielding mechanisms of reflection and absorption. Since the shielding effectiveness (SE) is represented in the logarithmic scale and in a coupled way of transmission (SE T ), absorption (SE A ), and reflection (SE R ), often there is a misinterpretation that the EM wave reflectors are regarded as EM wave-absorbing materials. Surprisingly, we found that many materials reported as an EM wave absorber in the literature provide, in fact, less than 50% of EM wave-absorbing capability, i.e., over 50% of EM wave-reflecting feature. According to the theory and definition of EMI SE, the absorption-dominant EMI shielding materials should have the ratio of absorption to incident energy (A) as A > 0.5, which corresponds to a necessary condition that SE R < 3.01 dB. The SE R subsequently gives SE A in relation to SE T . Using this criterion, we classified the EMI shielding materials with their shielding mechanism. The proposed methodology provides significant insight into the evaluation and development of EMI shielding materials.

Next-generation electromagnetic interference (EMI) shielding technology requires a frequency-selective capability, which can enable shielding and/or passing electromagnetic (EM) waves of a certain frequency range. Herein, we propose a novel composite...

Electroadhesion device allows one to pick up almost all of the objects regardless of their shape or type of materials by means of the electrostatic Maxwell force, which is developed due to the dielectric-induced polarization on the subject surface. In this study, we propose the modeling methodology and its experimental verification that could maximize the lifting shear force of the electroadhesive device to reach well over the human-finger grip force, say, ca. 8.9 kPa, which has not been achieved yet in this device system. In this study, we maximized the lifting force up to 33.05 kPa for paper objects by scaling down the electrode pitches in the scale of micrometers while avoiding the voltage breakdown using the boundary-edge-length modeling methodology [ChoiK. Choi, K. ACS Omega2019479948000 The developed model equation expressed adhesion lifting force as a function of the boundary edge length, applied voltage, and impedance, demonstrating that the model equation agreed well with the experimental output of our device and allowed the lifting force well over the human-finger grip. The in situ charge-transfer resistance measurement value of the impedance analysis (R CT), indicating the amount of polarization, was decreased in the order of paper and glass, and it was clearly related to the enhanced lifting force of the two types of objects (23.9 and 50.0 kPa, respectively). Hence, the impedance analysis could quantify the magnitude of polarizations and the amount of induced charges of objects while in contact with the device.

No abstract

Although the typical antioxidant, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), ensures high durability and long lifespan for rubber compounds, it generates a highly toxic quinone in water, causing serious environmental pollution. Herein, as an alternative material of 6PPD, we newly introduce ecofriendly amine-functionalized lignin (AL) to be incorporated in rubber, which can provide excellent combinatorial antiaging properties of thermal stability and ozone/fatigue resistances through radical scavenging effect. The heterolytic ring-opening reaction of AL and sulfur can accelerate curing and improve the cross-link density by 28% (v, 4.107 × 10 −4 mol/cm 3 ), consequently reducing the ozone vulnerable areas of the matrix and further improving the aging resistance. Notably, AL allows its rubber compound to exhibit superior anti-ozone performance after ozone aging, with the arithmetic surface roughness (Sa) of 2.077 μm, which should be compared to that of 6PPD (4.737 μm). The developed chemically modified lignin and the methodology have enormous potential as a promising additive for future eco-friendly rubber compounds. The eco-friendly lignin-based antioxidant manufactured by amination reaction has the potential to reduce environmental pollution for the future rubber industry.