Development of a cornea-equivalent phantom in the terahertz frequency region for 3D temperature rise assessment

As the next generation of mobile communication systems (Beyond 5G/6G) is expected to extend into the terahertz (THz) frequency region, it is essential to ensure human safety from electromagnetic waves. For this purpose, the evaluation of the temperature rise caused by the electromagnetic wave energy absorbed by the human body is required. However, there have been no reports on the development of phantoms with dielectric properties equivalent to biological tissues that can be used to measure temperature rise in the THz frequency region by experimental methods. Therefore, in this study, a glycerin-based semisolid phantom was developed to match the dielectric properties of the cornea between 0.1 and 0.6 THz; the cornea is one of the most important tissues for exposure assessment in the THz frequency region. In addition, fluorescent thermoprobes were included in the phantom to measure the temperature rise induced by the absorption of THz waves. The results show that temperature measurements using confocal laser microscopy can be used to obtain temperature distributions in the phantom with a high spatial resolution [2 µm in the transverse direction (xy) and 20 µm in the axial direction (z)] and a high-temperature resolution (0.04 °C).