The attenuated total reflection (ATR) apparatus, with an added partial reflection/partial transmission mode, was used to demonstrate a novel way of characterizing water-based substances at 0.7 to 10.0 THz at the Australian Synchrotron THz-far infrared beamline. The technique utilized a diamond-crystal-equipped ATR to track temperature-dependent changes in reflectance. A “crossover flare” feature in the spectral scan was noted, which appeared to be a characteristic of water and water-dominated compounds. A “quiet zone” feature was also seen, where no temperature-dependent variation in reflectance exists. The variation in these spectral features can be used as a signature for the presence of bound and bulk water. The method can also potentially identify the presence of fats and oils in a biological specimen. The technique requires minimal sample preparation and is non-destructive. The presented method has the promise to provide a novel, real-time, low-preparation, analytical method for investigating biological material, which offers avenues for rapid medical diagnosis and industrial analysis.

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.

Research has shown that exposure to high power THz radiation can cause thermal damage to the ear, leading to hearing loss and damage to the tympanic membrane. However, more research is needed to fully understand the effects of low intensity THz radiation on the ear and to determine safe exposure levels. This study investigates the transmission of 0.1 to 2.5 THz electromagnetic waves through porcine tympanic membrane samples. Similar to human tympanic membrane, porcine ear drum is a thin layer of tissue that separates the external ear from the middle ear and plays a crucial role in the process of hearing. Using THz time-domain spectroscopy, transmission of THz waves through ex vivo porcine tympanic membrane samples was measured. Results indicate that transmission of THz waves through the tympanic membrane is frequency dependent, with higher transmission observed at lower frequencies (0.1 to 0.5 THz) and lower transmission observed at higher frequencies (2 to 2.5 THz). This study provides new insights into the transmission of THz waves through the tympanic membrane and has potential to examine potential bioeffects as a result of THz interaction.

The attenuated total reflection (ATR) setup, equipped with a diamond crystal and operating in a mixed reflection/transmission mode, demonstrated a superior and efficient capacity for investigating temperature-related interactions of biological materials at the THz-far infrared beamline at the Australian Synchrotron. This methodology was employed explicitly to investigate the temperature-driven variations in reflectance of biological tissues, such as the tympanic membrane, skeletal muscle, and brain samples, in addition to the interaction of water with THz radiation. Uniquely, the technique detected a characteristic ‘crossover flare’ feature in the spectral scan, a trait inherent to water and water-based compounds. It also identified a ‘quiet zone’ feature, a region exhibiting no temperature-dependent reflectance variation at higher frequencies. Remarkably, this approach required minimum sample preparation and was non-destructive, enabling the investigation of a range of tissue temperatures to ascertain the influence of temperature on the reflection and absorption dynamics of THz radiation.