The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002. However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity (κ) and thermopower (S) of single CNT bundles that encapsulate C , Gd@C and Er @C. Encapsulation causes 35-55% suppression in κ and approximately 40% enhancement in S compared with the properties of hollow CNTs at room temperature. Measurements of temperature dependence from 40 to 320 K demonstrate a shift of the peak in the κ to lower temperature. The data are consistent with simulations accounting for the interaction between CNTs and encapsulated fullerenes.

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Efficient multifunctional materials informatics enables the design of optimal graphene thermoelectrics.

Carbon nanotubes (CNTs) have recently attracted attention as materials for flexible thermoelectric devices. To provide theoretical guideline of how defects influence the thermoelectric performance of CNTs, we theoretically studied the effects of defects (vacancies and Stone-Wales defects) on its thermoelectric properties; thermal conductance, electrical conductance, and Seebeck coefficient. The results revealed that the defects mostly strongly suppresses the electron conductance, and deteriorates the thermoelectric performance of a CNT. By plugging in the results and the intertube-junction properties into the network model, we further show that the defects with realistic concentrations can significantly degrade the thermoelectric performance of CNT-based networks. Our findings indicate the importance of the purification of CNTs for improving CNT-based thermoelectrics.

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Interface-induced reduction of thermal conductivity has attracted great interest from both engineering and science points of view. While nanostructures can enhance phonon scattering, the multiscale nature of phonon transport (length scales ranging from 1 nm to 10 µm) inhibits precise tuning of thermal conductivity. Here, we introduce recent advances toward ultimate impedance of phonon transport with nanostructures and their interfaces. We start by reviewing the progress in realizing extremely low thermal conductivity by ultimate use of boundary scattering. There, phonon relaxation times of polycrystalline structures with single-nanometer grains reach the minimum scenario. We then highlight the newly developed approaches to gain further designability of interface nanostructures by combining informatics and materials science. The optimization technique has revealed that aperiodic nanostructures can effectively reduce thermal conductivity and consequently improve thermoelectric performance. Finally, in the course of discussing future perspective toward ultimate low thermal conductivity, we introduce recent attempts to realize phonon strain-engineering using soft interfaces. Induced-strain in carbon nanomaterials can lead to zone-folding of coherent phonons that can significantly alter thermal transport.

SUMMARYWireless access networks of the future could provide a variety of context-aware services with the use of sensor information in order to solve regional social problems and improve the quality of residents' lives as a part of the regional infrastructure. NerveNet is a conceptual regional wireless access platform in which multiple service providers provide their own services with shared use of the network and sensors, enabling a range of context-aware services. The platform acts like a human nervous system. Densely located, interconnected access points with databases and data processing units will provide mobility to terminals without a location server and enable secure sensor data transport on a highly reliable, managed mesh network. This paper introduces the motivations, concept, architecture, system configuration, and preliminary performance results of NerveNet. key words: network platform, regional network, sensor and actuator network, context-aware

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