The chemistry underlying the storage phenomena in batteries and supercapacitors has been known to mankind for quite some time now. Nonetheless, a holistic apprehension of their rudimentary characteristics throughout their lifetime and beyond is imperative to accentuate their maximum potential. Although numerous reviews have addressed many of the facts individually, a consolidated report on the associated history, challenges, and environmental aspects considering the cutting‐edge advancements in this field is missing. This review gives a comprehensive insight into the two technologies by drawing a detailed comparison between their governing attributes and potential challenges. First, a brief history of batteries and supercapacitors along with their classifications based on materials and corresponding working mechanisms are delineated. Thereafter, some of the inexorable losses restricting the performance of these systems from reaching their theoretical limits are outlined. A picture of the significance of theoretical modeling of batteries and supercapacitors highlighting the associated challenges in the same is drawn. Furthermore, their fates after retirement as well as their scopes in the future based on their current trends are reported in the ensuing sections. Alongside detailed tutorial background of energy storage literature, this review compares different energy storage devices and the latest developments in this field.

Chemical pattern directed spin-dewetting of a macroscopic droplet composed of a dilute organic solution of liquid crystal (LC) formed an ordered array of micro- and nanoscale LC droplets. Controlled evaporation of the spin-dewetted droplets through vacuum drying could further miniaturize the size to the level of ∼90 nm. The size, periodicity, and spacing of these mesoscale droplets could be tuned with the variations in the initial loading of LC in the organic solution, the strength of the centripetal force on the droplet, and the duration of the evaporation. A simple theoretical model was developed to predict the spacing between the spin-dewetted droplets. The patterned LC droplets showed a reversible phase transition from nematic to isotropic and vice versa with the periodic exposure of a solvent vapor and its removal. A similar phase transition behavior was also observed with the periodic increase or reduction of temperature, suggesting their usefulness as vapor or temperature sensors. Interestingly, when the spin-dewetted droplets were confined between a pair of electrodes and an external electric field was applied, the droplets situated at the hydrophobic patches showed light-reflecting properties under the polarization microscopy highlighting their importance in the development of micro- or nanoscale LC displays. The digitized LC droplets, which were stationary otherwise, showed dielectrophoretic locomotion under the guidance of the external electric field beyond a threshold intensity of the field. Remarkably, the motion of these droplets could be restricted to the hydrophilic zones, which were confined between the hydrophobic patches of the chemically patterned surface. The findings could significantly contribute in the development of futuristic vapor or temperature sensors, light reflectors, and self-propellers using the micro- or nanoscale digitized LC droplets.

We explore the salient features of electroosmotic flow inside patterned and deformable microchannels. A computational fluid dynamic simulator is developed to solve the coupled Poisson's equation for electrolyte, Laplace equation for external electric field, and continuity and momentum equations for fluid flow, with appropriate boundary conditions. The simulations reveal existence of some exceptional flow profiles with the variations in normalized Debye length, dimensions, and locations of heterogeneities, strength of external field, and deformability of walls. The surface heterogeneities are found to facilitate the variation in ζ-potential, which in turn locally modulate the flow rate to cause intermixing of layers. The extent of mixing due to the deformability and heterogeneity of the walls have been analyzed to identify the conditions for augmented micromixing in laminar electroosmotic flows. The variations of current densities along the walls with surface patterns have been explored for the probable application in differentiating the ζ-potentials of biosurfaces.

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