Selective thermal emission in a useful range of energies from a material operating at high temperatures is required for effective solar thermophotovoltaic energy conversion. Three-dimensional metallic photonic crystals can exhibit spectral emissivity that is modified compared with the emissivity of unstructured metals, resulting in an emission spectrum useful for solar thermophotovoltaics. However, retention of the three-dimensional mesostructure at high temperatures remains a significant challenge. Here we utilize self-assembled templates to fabricate high-quality tungsten photonic crystals that demonstrate unprecedented thermal stability up to at least 1,400°C and modified thermal emission at solar thermophotovoltaic operating temperatures. We also obtain comparable thermal and optical results using a photonic crystal comprising a previously unstudied material, hafnium diboride, suggesting that refractory metallic ceramic materials are viable candidates for photonic crystal-based solar thermophotovoltaic devices and should be more extensively studied.

As sensors, wireless communication devices, personal health monitoring systems, and autonomous microelectromechanical systems (MEMS) become distributed and smaller, there is an increasing demand for miniaturized integrated power sources. Although thinfilm batteries are well-suited for on-chip integration, their energy and power per unit area are limited. Three-dimensional electrode designs have potential to offer much greater power and energy per unit area; however, efforts to date to realize 3D microbatteries have led to prototypes with solid electrodes (and therefore low power) or mesostructured electrodes not compatible with manufacturing or on-chip integration. Here, we demonstrate an on-chip compatible method to fabricate high energy density (6.5 μWh cm −2 ·μm −1 ) 3D mesostructured Li-ion microbatteries based on LiMnO 2 cathodes, and NiSn anodes that possess supercapacitor-like power (3,600 μW cm −2 ·μm −1 peak). The mesostructured electrodes are fabricated by combining 3D holographic lithography with conventional photolithography, enabling deterministic control of both the internal electrode mesostructure and the spatial distribution of the electrodes on the substrate. The resultant full cells exhibit impressive performances, for example a conventional light-emitting diode (LED) is driven with a 500-μA peak current (600-C discharge) from a 10-μm-thick microbattery with an area of 4 mm 2 for 200 cycles with only 12% capacity fade. A combined experimental and modeling study where the structural parameters of the battery are modulated illustrates the unique design flexibility enabled by 3D holographic lithography and provides guidance for optimization for a given application.energy storage | microelectronics | miniature batteries | lithium-ion batteries | interference lithography M icroscale devices typically use power supplied off-chip because of difficulties in miniaturizing energy storage technologies (1, 2). However, a miniaturized on-chip battery would be highly desirable for applications including autonomous microelectromechanical systems (MEMS)-based actuators, microscale wireless sensors, distributed monitors, and portable and implantable medical devices (3-8). For many of the applications, high energy density, high power density (charge and/or discharge), or some combination of high energy and power densities is required, all characteristics which can be difficult to achieve in a microbattery due to size and footprint restrictions, and process compatibilities with the other steps required for device fabrication. Although 2D thin-film microbatteries (typical thickness of a few micrometers) can deliver high power, they require large (often cm 2 ) footprints to provide reasonable energies (9). Making the electrodes thicker boosts the theoretical areal energy density but the resultant increases in electron and ion diffusion lengths reduce the effective power and energy densities. Efforts to improve microbattery performance have focused on increasing the electrode surface area and active material loading...

Electrodeposition of lithium-ion battery cathodes enables ultraflexible, ultrathick, and high-power rechargeable batteries.

We present a micromanufacturing method for constructing microsystems, which we term 'micro-masonry' based on individual manipulation, influenced by strategies for deterministic materials assembly using advanced forms of transfer printing. Analogous to masonry in construction sites, micro-masonry consists of the preparation, manipulation, and binding of microscale units to assemble microcomponents and microsystems. In this paper, for the purpose of demonstration, we used microtipped elastomeric stamps as manipulators and built three dimensional silicon microstructures. Silicon units of varied shapes were fabricated in a suspended format on donors, retrieved, delivered, and placed on a target location on a receiver using microtipped stamps. Annealing of the assembled silicon units permanently bound them and completed the micro-masonry procedure.

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Internet connected devices are limited by the performance of microbatteries that power them. In this issue of Joule, Hur et al. develop microbatteries with tall 3D electrodes that have high areal energy densities. These microbatteries were fabricated on a silicon wafer using silicon and polymer processing that are compatible with microelectronics, paving the way for future microbattery and microelectronics integration.

Porous liquids (PLs), an emerging type of flowing liquid materials that combine the merits of porous solids and flowing liquids, have garnered immense attention since the concept of PLs was proposed in 2007. Meanwhile, PLs have witnessed growing success in versatile synthesis strategies and emerging applications, especially since 2017. Given the lack of a timely comprehensive review, developing a prompt summary with a comprehensive understanding is undoubtedly urgent. Thus, this critical review offers a comprehensive summary of the progress in fundamental chemistry, developmental history, synthetic strategies, and emerging applications of PLs. First, the fundamental chemistry and developmental history are reviewed. Then, the synthesis strategies of PLs are highlighted. Additionally, crosscutting studies of pure theoretical simulations are reviewed. Meanwhile, the daunting characterization issues of PLs are analyzed. Next, the state-of-the-art of PLs applications is reviewed in detail. In the end, perspectives regarding the remaining challenges and future directions for PLs are presented. It is speculated that this critical comprehensive review of PLs could inspire scientific communities who focus on the taskspecific materials for various applications, such as gas sorption, membrane separation, catalytic conversion, chiral separation, thermal management and electrolyte, and so on.

Porous liquids (PLs), an emerging kind of liquid materials with permanent porosity, have attracted increasing attention in gas capture. However, directly turning metal−organic frameworks (MOFs) into PLs via a covalent linkage surface engineering strategy has not been reported. Additionally, challenges including reducing the cost and simplifying the preparation process are daunting. Herein, we proposed a general method to transform Universitetet i Oslo (UiO)-66-OH MOFs into PLs by surface engineering with organosilane (OS) and oligomer species via covalent bonding linkage. The oligomer species endow UiO-66-OH with superior fluidity at room temperature. Meanwhile, the resulting PLs showed great potential in both CO 2 adsorption and CO 2 /N 2 selective separation. The residual porosity of PLs was verified by diverse characterizations and molecular simulations. Besides, CO 2 selective capture sites were determined by grand canonical Monte Carlo (GCMC) simulation. Furthermore, the universality of the covalent linkage surface engineering strategy was confirmed using different classes of oligomer species and another MOF (ZIF-8-bearing amino groups). Notably, this strategy can be extended to construct other PLs by taking advantages of the rich library of oligomer species, thus making PLs promising candidates for further applications in energy and environment-related fields, such as gas capture, separation, and catalysis.