Energy Harvesting‐Storage Bracelet Incorporating Electrochemical Microsupercapacitors Self‐Charged from a Single Hand Gesture

The development of wearable electronics and sensing networks has increased the demand for wearable power modules that have steady output, high energy density, and long cycle life. Current power modules, such as batteries, suffer from low energy density due to their limited storage capacity. One solution to avoid the issue is to build a hybrid device consisting of both energy harvesting elements that continuously harvest ambient mechanical energy, and electrochemical energy storage units to store the harvested energy. Here, a hybrid energy harvesting bracelet, which combines a dual electromagnetic and triboelectric nanogenerator to harvest wrist motions, is reported. The bracelet is able to charge the RuO₂‐based microsupercapacitor to 2 V with a single shake of human wrist, which allows the supercapacitor to power most electronic devices for minutes, such as a calculator, relative humidity, and temperature sensors.     

MXene‐on‐Paper Coplanar Microsupercapacitors

A simple and scalable direct laser machining process to fabricate MXene‐on‐paper coplanar microsupercapacitors is reported. Commercially available printing paper is employed as a platform in order to coat either hydrofluoric acid‐etched or clay‐like 2D Ti₃C₂ MXene sheets, followed by laser machining to fabricate thick‐film MXene coplanar electrodes over a large area. The size, morphology, and conductivity of the 2D MXene sheets are found to strongly affect the electrochemical performance due to the efficiency of the ion‐electron kinetics within the layered MXene sheets. The areal performance metrics of Ti₃C₂ MXene‐on‐paper microsupercapacitors show very competitive power‐energy densities, comparable to the reported state‐of‐the‐art paper‐based microsupercapacitors. Various device architectures are fabricated using the MXene‐on‐paper electrodes and successfully demonstrated as a micropower source for light emitting diodes. The MXene‐on‐paper electrodes show promise for flexible on‐paper energy storage devices.     

Energy metabolism of Bdellovibrio bacteriovorus. I. Energy production, ATP pool, energy charge.

Bdellovibrio bacteriovorus, strain Bd. 109 Sa, generates ATP mainly by oxidative phosphorylation during electron transport. During exponential growth the ATP pool is constant (9 mmoles/100 mugN) indicating that energy-producing and energy-consuming reactions are well balanced. The ratio of substrate respiration/endogenous respiration is approx. 2.5/1. Energy charge is constant both in endogenous and substrate respiration at values of 0.62 to 0.64. During endogenous respiration (starvation) the ATP pool oscillates at regular intervals. ATP over-production is started after the ATP pool has decreased to a minimum level of 6 nmoles/100 mug N. The alternating over- and under-production of ATP is interpreted as a special regulation which enables the organism to make economic use of its own cellular materials. Addition of substrate (glutamate) to starving cells does not influence the type of ATP pool oscillation as observed in endogenous respiration. The parasitic strain Bd. 109 Pa exhibits the same periodicity of ATP overproduction as does it saprophytic derivative, Bd. 109 Sa. Decrease of viability during starvation is paralleled by a decrease of the ATP pool.     

Information Technology and U.S. Energy Consumption: Energy Hog,Productivity Tool,or Both?

A significant debate has emerged with respect to the energy requirements of the Internet. The popular literature has echoed a misleading study that incorrectly suggests the growth of the information economy will require huge amounts of new energy resources. Even correcting the misleading assumptions in that study, discussion on this topic tends to result in a highly limited and unsatisfactory review of many larger issues. Although the evidence suggests a relatively small amount of energy is required to power today's information needs—;about 3% of total electricity consumption in the United States—;the complexity and connectivity of the Internet, and, more generally, the information economy, yield a deep uncertainty about the eventual long-term impact on energy consumption. Although we may not yet be able to generalize about the future long-term energy needs associated with the information economy, the evidence points to continuing technical changes and the growing substitution of knowledge for material resources. These interrelated trends will likely generate small decreases in energy intensity and reduce subsequent environmental impacts relative to many baseline projections. Despite these trends, a number of questions need to be addressed before any solid long-term conclusions might be forthcoming. The article reviews some of the dimensions of these possible changes and suggests further directions for research that may help answer these important questions.     

On‐Chip MXene Microsupercapacitors for AC‐Line Filtering Applications

Microsupercapacitors (MSCs) with high energy densities offer viable miniaturized alternatives to bulky electrolytic capacitors if the former can respond at the kilo Hertz (kHz) or higher frequencies. Moreover, MSCs fabricated on a chip can be integrated into thin‐film electronics in a compatible manner, serving the function of ripple filtering units or harvesters of energy from high‐frequency sources. In this work, wafer‐scale fabrication is demonstrated of MXene microsupercapacitors with controlled flake sizes and engineered device designs to achieve excellent frequency filtering performance. Specifically, the devices (100 nm thick electrodes and 10 µm interspace) deliver high volumetric capacitance (30 F cm^?3 at 120 Hz), high rate capability (300 V s^?1), and a very short relaxation time constant (τ₀ = 0.45 ms), surpassing conventional electrolytic capacitors (τ₀ = 0.8 ms). As a result, the devices are capable of filtering 120 Hz ripples produced by AC line power at a frequency of 60 Hz. This study opens new avenues for exploring miniaturized MXene MSCs as replacements for bulky electrolytic capacitors.     

Lignin Laser Lithography: A Direct‐Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

In this work, a simple lignin‐based laser lithography technique is developed and used to fabricate on‐chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser‐scribed graphene (LSG) electrodes by a simple one‐step CO₂ laser irradiation. This step is followed by a water lift‐off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm^?1), and have a high specific surface area (338.3 m² g^?1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm^?2), high volumetric energy density (≈1 mWh cm^?3), and high volumetric power density (≈2 W cm^?3). The versatility of lignin laser lithography opens up the opportunity in applications such as on‐chip microsupercapacitors, sensors, and flexible electronics at large‐scale production.     

Conductive Metal–Organic Frameworks Selectively Grown on Laser‐Scribed Graphene for Electrochemical Microsupercapacitors

Conductive 2D metal–organic frameworks (MOFs) have merits beyond traditional MOFs for electrochemical applications, but reports on using MOFs as electrodes for electrochemical microsupercapacitors (MSCs) are practically non‐existent. In this work, a Ni‐catecholate‐based MOF (Ni‐CAT MOF) having good conductivity and exhibiting redox chemistry in the positive and negative voltage windows is developed. A novel process is developed to selectively grow the conductive Ni‐CAT MOF on 3D laser scribed graphene (LSG). The LSG with its superior wettability serves as a functional matrix‐current collector for the hybridization of conductive Ni‐CAT MOF nanocrystals. Impressively, MSCs fabricated using the hybrid LSG/Ni‐CAT MOF show significant improvement compared with MOF‐free LSG electrodes. Specifically, the LSG/Ni‐CAT MOF electrodes can deliver MSCs with a wide operating voltage (1.4 V), high areal capacitance (15.2 mF cm^?2), energy density (4.1 µWh cm^?2), power density (7 mW cm^?2), good rate performance, and decent cycling stability. This work opens up an avenue for developing electrochemical microsupercapacitors using conductive MOF electrodes.     

Energy, Life, and ATP

The mechanism by which ATP is synthesized during oxidative and photophosphorylation has been elucidated by oxygen exchange and other studies: a novel form of catalysis--termed rotary catalysis--is involved.     

落叶松人工林群落能量积累,分配,固定和转化的研究

生态系统中的能流测定是生产力研究中一项重要因素,这需要测定组成群落主要种类的热值或者是构成群落各成分的热值。能量值的测定比干物质能更好地评价物质在生态系统