Photothermal modulated dielectric elastomer actuator for resilient soft robots.

Soft robots need to be resilient to extend their operation under unpredictable environments. While utilizing elastomers that are tough and healable is promising to achieve this, mechanical enhancements often lead to higher stiffness that deteriorates actuation strains. This work introduces liquid metal nanoparticles into carboxyl polyurethane elastomer to sensitize a dielectric elastomer actuator (DEA) with responsiveness to electric fields and NIR light. The nanocomposite can be healed under NIR illumination to retain high toughness (55 MJ m-3) and can be recycled at lower temperatures and shorter durations due to nanoparticle-elastomer interactions that minimize energy barriers. During co-stimulation, photothermal effects modulate the elastomer moduli to lower driving electric fields of DEAs. Bilayer configurations display synergistic actuation under co-stimulation to improve energy densities, and enable a DEA crawler to achieve longer strides. This work paves the way for a generation of soft robots that achieves both resilience and high actuation performance.

Electropolymerized 1D Growth Coordination Polymer for Hybrid Electrochromic Aqueous Zinc Battery.

Organic materials are always viewed as promising electrochromic (EC) materials due to their synthetic versatility, color tunability, ready processability, and derivability from sustainable feedstocks. Most organic materials, however, are prone to undesirable redox side reactions in the presence of oxygen and water. As such, redox-active organic layers are often used in tandem with organic electrolytes to preserve their electrochemical stability. With the growing interest in electronics that are environmentally sustainable and biologically safe, developing aqueous-compatible organic materials is gaining growing interest. Herein, a rationally designed iron terpyridyl coordination polymer (CP) is prepared by controlled electropolymerization for realization of aqueous compatible EC and energy storage applications. Detailed analysis is established, showing that the CP grows in a 1D fashion and exhibits a predominant capacitive behavior which is reflected from its rapid charge-transfer kinetics. Taking this as an advantage, an integrated hybrid electrochromic zinc battery device is demonstrated with high color contrast, fast response time, and good endurance.

Optimization design for edge-lateral support of a medium-aperture lightweight primary mirror.

Lightweight primary mirrors are increasingly applied both in ground-based and space-based telescopes. Because the absolute stiffness of the lightweight mirror is much lower than that of the solid one, the design of lateral support becomes more difficult. Based on parallel push-pull support, we have proposed a multi-class variable F-θ optimization approach (MVFOA), where F denotes the magnitude of the support force and θ denotes the support position. Compared with conventional optimization approaches, which only have one class of design variables, F or θ, MVFOA considers the impact of F and θ simultaneously. In addition, we also study push-pull-shear lateral support and propose an unequal-angle push-pull-shear support optimization approach (UPSOA). To verify the advancement of above approaches, by means of finite element calculation, the lateral support optimization of a 2.5 m ultra-low expansion honeycomb sandwich mirror is performed in this paper. For parallel push-pull support with 24 forces, three optimization approaches with different variables, including single-class variable F, single-class variable θ, and multi-class variable F-θ, are compared, and the RMSs of surface deformations are 17.60 nm, 15.93 nm, and 14.81 nm, respectively. For push-pull-shear support with 24 forces, the optimal result by UPSOA occurs when ß equals to 0.84 and the RMS of surface deformations is 10.83 nm. UPSOA also solves the problem that the forces in the region x≈±R are much larger than the ones in the region x≈0 in the equal-angle push-pull-shear support optimization approach (EPSOA). Through the analysis of results, we find that optimal ß of the honeycomb sandwich mirror is greater than that of the meniscus mirror in push-pull-shear support. In addition, both in parallel push-pull support and push-pull-shear support, it also can be concluded that the position and the magnitude of optimal lateral support forces depend on the stiffness distribution of the mirror along the altitude axis rather than the mass distribution.

Encapsulation of MnS Nanocrystals into N, S-Co-doped Carbon as Anode Material for Full Cell Sodium-Ion Capacitors.

Sodium-ion capacitors (SICs) have received increasing interest for grid stationary energy storage application due to their affordability, high power, and energy densities. The major challenge for SICs is to overcome the kinetics imbalance between faradaic anode and non-faradaic cathode. To boost the Na+ reaction kinetics, the present work demonstrated a high-rate MnS-based anode by embedding the MnS nanocrystals into the N, S-co-doped carbon matrix (MnS@NSC). Benefiting from the fast pseudocapacitive Na+ storage behavior, the resulting composite exhibits extraordinary rate capability (205.6 mAh g-1 at 10 A g-1) and outstanding cycling stability without notable degradation after 2000 cycles. A prototype SIC was demonstrated using MnS@NSC anode and N-doped porous carbon (NC) cathode; the obtained hybrid SIC device can display a high energy density of 139.8 Wh kg-1 and high power density of 11,500 W kg-1, as well as excellent cyclability with 84.5% capacitance retention after 3000 cycles. The superior electrochemical performance is contributed to downsizing of MnS and encapsulation of conductive N, S-co-doped carbon matrix, which not only promote the Na+ and electrons transport, but also buffer the volume variations and maintain the structure integrity during Na+ insertion/extraction, enabling its comparable fast reaction kinetics and cyclability with NC cathode.

A Nonpresodiate Sodium-Ion Capacitor with High Performance.

Sodium-ion capacitors (SICs) have received intensive attention due to their high energy density, high power density, long cycle life, and low cost of sodium. However, the lack of high-performance anode materials and the tedious presodiation process hinders the practical applications of SICs. A simple and effective strategy is reported to fabricate a high-performance SIC using Fe1- x S as the anode material and an ether-based electrolyte. The Fe1- x S electrode is found to undergo a reversible intercalation reaction after the first cycle, resulting in fast kinetics and excellent reversibility. The Fe1- x S electrode delivers a high capacity of 340 mAh g-1 at 0.05 A g-1 , 179 mAh g-1 at high current of 5 A g-1 and an ultralong cycling performance with 95% capacity retention after 7000 cycles. Coupled with a carbon-based cathode, a high-performance SIC without the presodiation process is successfully fabricated. The hybrid device demonstrates an excellent energy density of 88 Wh kg-1 and superior power density of 11 500 W kg-1 , as well as an ultralong lifetime of 9000 cycles with over 93% capacity retention. An innovative and efficient way to fabricate SICs with both high energy and power density utilizing ether-based electrolytes can be realized to eliminate the presodiation process.

A fiber asymmetric supercapacitor based on FeOOH/PPy on carbon fibers as an anode electrode with high volumetric energy density for wearable applications.

Fiber supercapacitors are promising energy storage devices for wearable applications. However, the fiber supercapacitors are currently limited by the mediocre capacitance performances due to the use of typical carbon materials as the anode, sacrificing the volumetric energy density of the whole device. In addition, the inability to undergo washable cycles and poor self-discharge rate prevents the fiber-shaped supercapacitors from being a true energy textile and affects their practicability. Hence, the porous anode electrode FeOOH/PPy@CF has been firstly prepared with a high volumetric capacitance of 30.17 F cm-3, contributing to a high volumetric energy density of 2 mWh cm-3 (based on the whole encapsulated device) for a fiber asymmetric supercapacitor MnO2@CF//FeOOH/PPy@CF in PVA/LiCl. Good flexibility could be exhibited when it was woven into a glove. Desired working voltage and capacity output could be easily obtained when connecting devices in series and parallel. The encapsulated device could work stably even after it was dipped for multiple cycles in different solutions and with intensive stirring in water that simulates washing cycles. The self-discharge rate could be mitigated when an ionogel electrolyte ([EMIM][TFSI]/FS) was incorporated and this further enhanced the energy density to 3.7 mWh cm-3. The outstanding properties of our assembled asymmetric fiber supercapacitor device render it a good candidate for practical wearable energy storage devices.

A High-Performance Lithium-Ion Capacitor Based on 2D Nanosheet Materials.

Lithium-ion capacitors (LICs) are promising electrical energy storage systems for mid-to-large-scale applications due to the high energy and large power output without sacrificing long cycle stability. However, due to the different energy storage mechanisms between anode and cathode, the energy densities of LICs often degrade noticeably at high power density, because of the sluggish kinetics limitation at the battery-type anode side. Herein, a high-performance LIC by well-defined ZnMn2 O4 -graphene hybrid nanosheets anode and N-doped carbon nanosheets cathode is presented. The 2D nanomaterials offer high specific surface areas in favor of a fast ion transport and storage with shortened ion diffusion length, enabling fast charge and discharge. The fabricated LIC delivers a high specific energy of 202.8 Wh kg-1 at specific power of 180 W kg-1 , and the specific energy remains 98 Wh kg-1 even when the specific power achieves as high as 21 kW kg-1 .