Solar energy storage is an emerging technology which can promote the solar energy as the primary source of electricity. Recent development of laser scribed graphene electrodes exhibiting a high electrical conductivity have enabled a green technology platform for supercapacitor-based energy storage, resulting in cost-effective, environment-friendly features, and consequent readiness for on-chip integration. Due to the limitation of the ion-accessible active porous surface area, the energy densities of these supercapacitors are restricted below ~3 × 10−3 Whcm−3. In this paper, we demonstrate a new design of biomimetic laser scribed graphene electrodes for solar energy storage, which embraces the structure of Fern leaves characterized by the geometric family of space filling curves of fractals. This new conceptual design removes the limit of the conventional planar supercapacitors by significantly increasing the ratio of active surface area to volume of the new electrodes and reducing the electrolyte ionic path. The attained energy density is thus significantly increased to ~10−1 Whcm−3- more than 30 times higher than that achievable by the planar electrodes with ~95% coulombic efficiency of the solar energy storage. The energy storages with these novel electrodes open the prospects of efficient self-powered and solar-powered wearable, flexible and portable applications.

Textile integrable large-scale on-chip energy storages and solar energy storages take a significant role in the realization of next-generation primary wearable devices for sensing, wireless communication, and health tracking. In general, these energy storages require major features like mechanical robustness, environmental friendliness, high-temperature tolerance, inexplosive nature, and long-term storage duration. Here we report on large-scale laser-printed graphene supercapacitors of dimension 100 cm 2 fabricated in 3 minutes on textiles with excellent water stability, an areal capacitance, 49 mF cm −2 , energy density, 6.73 mWh/cm −2 , power density, 2.5 mW/cm −2 , and stretchability up to 200%. Further, a demonstration is given for the textile integrated solar energy storage with stable performance for up to 20 days to reach half of the maximum output potential. These cost-effective self-reliant on-chip charging units can become an integral part for the future electronic and optoelectronic textiles.

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Reflectionless potentials (RPs) represent a class of potentials that offer total transmission in the context of one dimensional scattering. An optical realization of RP can exhibit a truly broadband omni-directional antireflection. We report our experimental observations confirming the reflectionless behavior. Stratified media conforming to RP's are designed and fabricated using Al(2)O(3) and TiO(2) heterolayers. They showed < 0.5% reflection over the broad wavelength range of 350 nm to 2500 nm for angles of incidence 0 - 50 degrees. These RPs can be designed on substrates and are thus interesting for optical instrumentation as broadband, omni-directional antireflection coatings.

Direct laser writing with an ultrashort laser beam pulses has emerged as a cost-effective single step technology for realizing high spatial resolution features of three-dimensional structures in confined footprints with potential for large area fabrication. Here we present the two-photon direct laser writing technology to develop high-performance stretchable biomimetic three-dimensional micro-supercapacitors with the fractal electrode distance down to 1 µm. With multilayered graphene oxide films, we show the charge transfer capability enhanced by order of 102 while the energy storage density exceeds the results in current lithium-ion batteries. The stretchability and the volumetric capacitance are increased to 150% and 86 mF/cm3 (0.181 mF/cm2), respectively. This additive nanofabrication method is highly desirable for the development of self-sustainable stretchable energy storage integrated with wearable technologies. The flexible and stretchable energy storage with a high energy density opens the new opportunity for on-chip sensing, imaging, and monitoring.

Supercapacitors have surfaced as a promising technology to store electrical energy and bridge the gap between a conventional capacitor and a battery. This chapter reviews various fabrication practices deployed in the development of supercapacitor electrodes and devices. A broader insight is given on the numerous electrode fabrication techniques that include a detailed introduction, principles, pros and cons, and their specific applications to provide a holistic view. Key performance parameters of an energy storage device are explained in detail. A further discussion comprises several electrochemical measurement procedures that are used for the supercapacitor performance evaluation. The performance characterization section helps to determine the correct approach that should be utilized for supercapacitor device performance measurement and assessment.

Direct laser writing is a single-step fabrication technique for the micro and nanostructures even below the sub-diffraction limits. In recent times, the technique is adapted to the fabrication of on-chip energy storages with additional features of flexibility and stretchability. The major category of the energy storages taken into consideration for laser writing belongs to the family of supercapacitors which is known for the high rate of charge transfer, longer life spans and lesser charging times in comparison with traditional batteries. The technology explores the possibilities of non-explosive all solid-state energy storage integration with portable and wearable applications. These features can enable the development of self-powered autonomous devices, vehicles and self-reliant infrastructures. In this chapter, we discuss the progress, challenges and perspectives of micro-supercapacitors fabricated using direct laser writing.

Laser beam‐induced graphene oxides (GOs) with excellent tunable properties have to find attention in various applications. But, the understanding of the complex mechanics involved in this reduction process is incomplete, most primarily the reduction using ultrashort laser beam pulses. Herein, the influence of laser beam‐induced acoustic waves on the photoreduction as well as the generation of a reversible phase in the GOs using photoacoustic studies is presented. However, these waves influence the phase transition in GOs. These observations find aspiring applications for next‐generation optical technologies, such as data storage and neural chips.