Exploring Non-Contact Ultrasound Technology Based on Terahertz Photoacoustic Effect

We review our recent exploration of non-contact ultrasound technology based on the terahertz photoacoustic effect. Since terahertz waves are highly attenuated in water, irradiating the surface of a water-containing object with modulated terahertz waves can generate ultrasound without physical contact. Hence, by delivering terahertz waves to the skin, ultrasound is generated inside the body. Although this approach still requires a significant increase in acoustic pressure to become fully practical, it has the potential to make ultrasound technology contactless. Unlike conventional in-vivo ultrasound applications, which require a transducer to be in close contact with the skin, this method could expand application opportunities. While ultrasound applications are often confined to controlled environments such as laboratories and hospitals, the proposed approach could make them as easy and versatile as the wireless technology, expanding potential applications in health monitoring, sports training, and brain science and engineering.