For an electrodeposited bismuth telluride $\left({\mathrm{Bi}}_x{\mathrm{Te}}_{1-x}\right)$ nanowire from one batch with $x$ found to be about 0.46, the Seebeck coefficient $\left(S\right)$ was measured to be 15%–60% larger than the bulk values at temperature $300\mathrm{K}$ . For four other nanowires from a different batch with $x\approx 0.54$ , $S$ was much smaller than the bulk values. The electrical conductivity of the nanowires showed unusually weak temperature dependence and the values at $300\mathrm{K}$ were close to the bulk values. Below $300\mathrm{K}$ , phonon-boundary scattering dominated phonon-phonon Umklapp scattering in the nanowires, reducing the lattice thermal conductivity.

The thermal conductivity enhancement of neat poly(vinyl alcohol) and poly(vinyl alcohol) (PVA)/cellulose nanocrystal (CNC) composite was attempted via electrospinning. The suspended microdevice technique was applied to measure the thermal conductivity of electrospun nanofibers (NFs). Neat PVA NFs and PVA/CNC NFs with a diameter of approximately 200 nm showed thermal conductivities of 1.23 and 0.74 W/m-K, respectively, at room temperature, which are higher than that of bulk PVA by factors of 6 and 3.5, respectively. Material characterization by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis confirmed that the thermal conductivity of the PVA/CNC NFs was enhanced by the reinforcement of their backbone rigidity, while that of the neat PVA NFs was attributed to the increase in their crystallinity that occurred during the electrospinning.

The thermal conductivity (k) of poly(acrylic acid) (PAA) nanofibers, which were electrospun at various electrospinning voltages, was measured using suspended microdevices. While the thermal conductivities of the as-spun PAA nanofibers varied depending on the electrospinning voltages, the most pronounced 3.1-fold increase in thermal conductivity in comparison to that of bulk PAA was observed at the electrospinning voltage of 14 kV. On the other hand, a reduction in the thermal conductivity of the nanofibers was observed when the as-spun nanofibers were either thermally annealed at the glass transition temperature of PAA or thermally crosslinked. It is notable that the thermal conductivity of crosslinked PAA nanofibers was comparable to that of crosslinked bulk PAA. Polarized Raman spectroscopy and Fourier transform infrared spectroscopy verified that the k enhancement via electrospinning and the k reduction by the thermal treatments could be attributed to the conformational changes between gauche and trans states, which may be further related to the orientation of molecular chains. In contrast, hydrogen bonds did not contribute significantly to the k enhancement. Additionally, the suppression of k observed for the crosslinked PAA nanofibers might result from the shortening of single molecular chains via crosslinking.

Terahertz polarimetric imaging, capable of capturing not only intensity profiles but also the polarization states of the incident pattern, is an essential technique with promising applications such as security scans and medical diagnoses. Recently, a novel approach for terahertz imaging has been proposed using a metasurface absorber that converts terahertz light into a temperature profile. However, polarization remains indistinguishable in the imaging process due to the isotropic geometry of the metasurface. To address this issue, this study introduces an all-dielectric, polarization-sensitive metasurface absorber and showcases its suitability for terahertz polarimetric imaging. Optical and thermal simulations confirm that the polarization dependence of our metasurface is translated into the thermal domain, allowing us to distinguish both intensity and polarization states in the incoming image. Additionally, we demonstrate that polarimetric imaging under general, elliptical polarization is attainable. This metasurface facilitates terahertz polarimetric imaging, eliminating the need for complex setups or bulky components, thereby reducing the form factor and enabling widespread use.