The millimeter wave (mmWave)‐enabled 5G wireless networks can meet the increasing demands of data rates and mobile subscriptions. However, the mmWave wireless networks require directional beamforming to overcome the propagation and penetration losses. The directional communication in turn increases the user equipment's (UE) energy expenses, as it has to perform beam searching to identify the best beam pair. Discontinuous reception (DRX) is a popular mechanism for energy saving in LTE/LTE‐A networks. The DRX mechanism when applied to mmWave‐5G networks, would also be required to incorporate the beam searching procedure making it less effective. In this article, we propose signaling‐based DRX to improve UE's energy saving in 5G networks by reducing the impediments of beam searching. Though the frequent requirement of beam searching in 5G cannot be avoided, the time in the beam searching can be curtailed if data/paging is absent. We propose to use power saving indication (PSI) that can be applied to both, connected‐ and idle‐state DRX. We employed semi‐Markov model to obtain the probabilistic estimation of power saving and delay for the proposed mechanism. The performance analysis shows that signaling can be used to improve energy saving in 5G DRX by limiting beam searching when not necessary.

The electrical manipulation of graphene oxide (GO) alignment in aqueous dispersions is a useful technique with various applications. In particular, the electrical switching of GO particles can be used to devise optical birefringent liquid crystal displays. However, the electric switching of aqueous GO dispersions with a high ionic concentration requires driving voltages with high frequencies (∼10 kHz), which is a challenging limitation. We demonstrate that stable electro-optical switching can be achieved at low frequencies (100 Hz) using GO dispersions in organic solvents instead of water. The hydrodynamic flow of the solvent and the electrophoretic drift of the GO particles are hindered in the GO dispersions in organic solvents with lower dielectric constants. Moreover, the electro-optical performance of these GO dispersions is similar to the aqueous GO dispersions, despite the lower magnitude of the ionization ratio for the GO particle functional groups. These results are crucial for developing a liquid crystal display device using GO dispersions.

Even though a graphene-oxide (GO) dispersion is attractive for electro-optical switching devices because of its high Kerr coefficient, it has several limitations such as chemical instability and optical loss due to absorption at visible wavelengths. Here we introduce the use of tetrabutylammonium-tethered α-zirconium phosphate (TBA-ZrP) colloid in various solvents for electro-optical switching devices; the TBA-ZrP colloid is chemically stable and optically transparent. We find that the electrical switching behavior of TBA-ZrP is sensitively dependent on the type of solvent. The TBA-ZrP colloid in acetone exhibits the highest effective Kerr coefficient and the fastest switching time, which is related to the unusual behavior of the viscosity of the TBA-ZrP colloid in acetone. Its viscosity is relatively low and less sensitive to concentration compared to ZrP in other solvents. This indicates that the motion of individual nanoparticles is relatively less restricted in acetone. These findings may be useful in developing electro-optical devices using lyotropic liquid crystal colloids.

Although the large Kerr coefficient of aqueous graphene oxide (GO) dispersions is quite attractive for electro-optical applications with low power consumption, the maximum birefringence of GO dispersions is not sufficiently high for actual display applications. Here we report that adding a small amount of larger GO particles (about 4 μm) into a high-concentration dispersion of small GO (about 0.2 μm) can improve the electro-optical sensitivity to an electric field and also the maximum birefringence. Large GOs induce the ordering of small particles and enhance the electro-optical switching. Large GOs have higher polarizability and are easily driven under an applied electric field, and the rotational motion of large GO particles leads to switching of surrounding small GO particles, improving the electro-optical performance. The binary mixture can overcome the limitations of pure dispersions of large GO or small GO particles; the former has high interparticle interaction, and the latter has low sensitivity to an electric field.

The structural color in 2D nanoparticle colloid photonic crystal can be switched by using both electrohydrodynamic flow and Maxwell–Wagner polarization.