Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO2, single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS2, graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications.

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Muscle-based biohybrid actuators have generated significant interest as the future of biorobotics but so far they move without having much control over their actuation behavior. Integration of microelectrodes into the backbone of these systems may enable guidance during their motion and allow precise control over these actuators with specific activation patterns. Here, we addressed this challenge by developing aligned CNT forest microelectrode arrays and incorporated them into scaffolds for stimulating the cells. Aligned CNTs were successfully embedded into flexible and biocompatible hydrogel exhibiting excellent anisotropic electrical conductivity. Bioactuators were then engineered by culturing cardiomyocytes on the CNT microelectrode-integrated hydrogel constructs. The resulting cardiac tissue showed homogeneous cell organization with improved cell-to-cell coupling and maturation, which was directly related to the contractile force of muscle tissue. This centimeter-scale bioactuator has excellent mechanical integrity, embedded microelectrodes and is capable of spontaneous actuation behavior. Furthermore, we demonstrated that a biohybrid machine can be controlled by an external electrical field provided by the integrated CNT microelectrode arrays. In addition, due to the anisotropic electrical conductivity of the electrodes provided from aligned CNTs, significantly different excitation thresholds were observed in different configurations such as the ones in parallel vs. perpendicular direction to the CNT alignment.

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

Highly porous metal nanowire aerosponges are produced by direct assembly of the Cu nanowire in situ during their synthesis. Such a method offers not only great simplicity, but also excellent properties such as extremely low densities, high electrical conductivities, and remarkable mechanical properties. Furthermore, these Cu aerosponges exhibit excellent wicking behavior, suggesting their potential for heat-exchange applications in heat pipes.

The design and optimization of 3D graphene nanostructures are critically important since the properties of electrochemical energy storages such as supercapacitors can be dramatically enhanced by tunable porous channels. In this work, we have developed porous graphene aerogels from graphene suspensions obtained via electrochemical exfoliation and explored their application as supercapacitor electrodes. By adjusting the content of the electrolyte in the exfoliation process, the aspect ratio of graphene sheets and the porosity of the graphene network can be optimized. Furthermore, the freezing temperature in the freeze drying step is also found to play a critical role in the resulting pore size distributions of the porous networks. The optimized conditions lead to meso- and macroporous graphene aerogels with a high specific surface area, extremely low densities and superior electrical properties. As a result, the graphene aerogel supercapacitors exhibit a specific capacitance of 325 F g(-1) at 1 A g(-1) and an energy density of 45 Wh kg(-1) in a 0.5 M H2SO4 aqueous electrolyte with high electrochemical stability and electrode uniformity required for practical usage. This research provides a practical method for lightweight, high-performance and low-cost materials in the effective use of energy storage systems.

Creating inorganic nanowire hydrogels/aerogels using various materials and inexpensive means remains an outstanding challenge despite their importance for many applications. Here, we present a facile methodology to enable highly porous inorganic nanowire hydrogel/aerogel production on a large scale and at low cost. The hydrogels/aerogels are obtained from in situ hydrothermal synthesis of onedimensional (1D) nanowires that directly form a cross-linking network during the synthesis process. Such a method not only offers great simplicity but also allows the interconnecting nanowires to have much longer length. The longer length offers aerogels with remarkable porosity and surface area extremely low densities (as low as 2.9 mg/cm 3 ), are mechanically robust, and can have superelasticity by tuning the synthesis conditions. The nanowires in the hydrogels/aerogels serve both as structural support and active sites, for example, for catalysis or absorption. In this work, we have found that the as-grown hydrogels can be used directly as water filters to remove pollutants such as heavy metal ions and toxic organic contents. Our studies indicate that this method for nanowire hydrogels/aerogels production is not only economical but greatly augmented their applications in environmental, catalysis, sensing, absorption, energy storage, and beyond. KEYWORDS: Inorganic nanowires, hydrogels, aerogels, superelasticity, water purification filters P orous inorganic nanowire hydrogels/aerogels are highly attractive in applications for energy generation and storage, sensing, catalytic conversion, selective absorption and removal, or thermal insulation, and so forth.1−4 General syntheses of the inorganic nanowire aerogels have been demonstrated with template-assisted deposition followed by a template removal step such as metal electrodeposition onto a polymer template, 5 or atomic layer deposition of a metal oxide onto nanocellulose 6 or a copolymer 7 template. However, these methods are complicated and are limited in terms of porosity 8 without collapsing of the three-dimensional (3D) network during the template removal process. Because the pore geometry and pore size play a critical role in the properties and performance of these porous materials, 9 this hampers their utilization for various applications.Previously, we demonstrated that highly porous inorganic nanowire hydrogels/aerogels can be obtained by assembling the nanowires into a cross-linking network from their colloidal suspensions at the transition from semidilute to isotropic concentrated regimes without using templates or supporting materials. 10 The synthesized nanowires were initially dispersed with/without surfactant in ethanol using ultrasonication at a dilute concentration, and then the suspension was transformed into a nanowire gel by evaporating the solvent to reach the gel formation concentration (φ gel = a r −1, where a r is the nanowire aspect ratio, a r = L/d, and L is the nanowire length and d is the diameter).10 For this method, in the case of bri...

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