Investigating the Propagation of 0.1 - 2.5 THz Radiation Through a Phantom Ear Model: Implications for Wireless Network-Biological Tissue Interaction.

This research focuses on the investigation of the propagation of frequencies between 0.1 and 2.5 THz through a phantom ear model using terahertz (THz) time-domain spectroscopy (TDS). While the use of THz frequencies between 0.1 to 0.3 THz in fifth and sixth generation cellular networks has gained significant attention, there is also a growing interest in utilising higher frequencies, such as 1 THz and above, for various applications, including the Internet of Things (IoT), autonomous vehicles, smart sensors, and smart cities. Despite the limited absorption coefficient of soft tissues at 5G and 6G frequencies (0.2-0.4 mm), the effect of higher frequencies on deeper regions of the ear, such as the tympanic membrane (with a thickness of 0.1 mm), has not been extensively studied. The study aims to determine the optimal conditions for THz transmission through the ear canal and to investigate the interaction between wireless networks and biological tissues. The results show that when parallel to the ear canal, the average power flux density within the central region of the tympanic membrane is 97% of the incident excitation. However, the outer ear structures are highly protective, with less than 0.4% of the power flux density directed towards them reaching the same region. Due to the sensitivity of the tympanic membrane to mechanical changes, in-vivo assessments are necessary to evaluate the penetration of THz frequencies into the ear canal, assess the suitability of current radiation safety limits, and evaluate the implications of devices that emit these frequencies. The study highlights the importance of understanding the interaction between THz radiation and biological tissues, particularly in the context of emerging wireless technologies, and the need for further research to ensure their safety and effectiveness.