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Contact electrification (CE) has been utilized in various energy conversion systems in recent years. This work presents a constant electric energy output that was generated based on the CE at the water–metal interface. When a grounded Pt mesh is placed in water that is heated to boil, a continuous flow of electrons between the Pt mesh and the ground is generated. A possible mechanism for the generation of such electric current is based on the CE between the surface of the Pt mesh and water molecules. The local high-pressure thin liquid film regions between vapor bubbles and surface of Pt mesh promote this CE process. The constant water evaporation and bubble detachment enable the continuous electric current output. In this work, the impact of the heating temperature and the bias voltages on the generation of the current was also studied. This work provides an alternative approach to generate unidirectional current on the basis of CE at the water–metal interface, and it also offers new insights in the design of CE-based systems for the generation of electricity. [ABSTRACT FROM AUTHOR]

This work explores an alternative vapor sensing mechanism through analyzing dynamic desorption process from butterfly wings for the differentiation of both individual and mixed vapors quantitatively. Morpho butterfly wings have been used in differentiating individual vapors, but it is challenging to use them for the differentiation of mixed vapor quantitatively. This paper demonstrates the use of Morpho butterfly wings for the sensitive and selective detection of closely related vapors in mixtures. Principal components analysis (PCA) is used to process the reflectance spectra of the wing scales during dynamic desorption of different vapors. With the desorption-based detection mechanism, individual vapors with different concentrations and mixed vapors with different mixing ratios can be differentiated using the butterfly wing based sensors. Both the original butterfly wings and butterfly wings with surface modification show the capability in distinguishing vapors in mixtures, which may offer a guideline for further improving selectivity and sensitivity of bioinspired sensors. [ABSTRACT FROM AUTHOR]

The development of high performance uncooled infrared (IR) detection and imaging systems will greatly expand the application of IR technology in broad areas such as transportation, environmental monitoring, and medical care. Inspired by the superior IR detection capability of beetle Melanophila acuminata, we explored the potential use of hydrogel nanoparticles (NPs) in uncooled IR detection system. In the system, the absorption of the incoming IR radiation by the temperature-sensitive hydrogel NPs, together with water, induces the volume change of the hydrogel NPs, similar to the volume change of the biofluid inside the sensillae receptors in M. acuminata caused by the IR radiation. This volume change results in the change of optical readout (transmittance in this study) in visible range and provides the sensitive detection of the IR radiation. In this work, poly(N-isopropylacrylamide-co-acrylic acid) (poly(NIPAM- co-AAc)) copolymer NPs with different sizes were synthesized and their IR sensing performances were studied in detail. The correlation between the NP size and concentration and the IR sensing property was also discussed in the paper. This work helps enhance the understanding of the response of hydrogel NPs under IR radiation, and offers a potential material system for uncooled IR detection that is inspired by M. acuminata. The direct use of transmittance of the NP solution as the readout for IR detection also provides a simple and sensitive IR detection approach for low cost and portable industrial applications. [ABSTRACT FROM AUTHOR]