Recently, China has achieved a major breakthrough in the field of needle-free diagnosis. Professor Tian Zhen's team from the School of Precision Instrument and Optoelectronics Engineering at Tianjin University has successfully developed a new terahertz photoacoustic system, providing a new technical means for biomedical detection. The research results have been recently published in the international academic journal *Optica*. ### Research Background Terahertz waves lie between millimeter waves and infrared rays in the electromagnetic spectrum and possess unique physical properties. Their low-energy characteristic means they do not cause ionizing damage to biological tissues, and this tissue harmlessness gives them a natural advantage in biomedical detection. Additionally, their weak scattering property allows them to clearly reflect changes in biological structures and functions to a certain extent. These characteristics make terahertz waves a highly promising tool in biomedical detection, regarded by many researchers as an ideal choice. However, the application of terahertz waves in biomedicine is not without challenges. Water, a key component in organisms, strongly absorbs terahertz waves, posing two severe challenges in practical applications: - **First challenge**: Eliminating interference from water molecules in complex samples. Biological samples are usually compositionally complex, with water molecules widely present. When terahertz waves interact with water molecules, their signals change significantly, masking the information about biological structures and functions that need to be detected. This makes it difficult for researchers to accurately extract valid information from the disturbed signals, seriously affecting the accuracy and reliability of terahertz wave detection. - **Second challenge**: Penetrating thick biological tissues for in vivo detection. Biological tissues have a certain thickness, and as terahertz waves pass through thick tissues, their energy is continuously attenuated due to absorption by water. If terahertz waves cannot penetrate to a sufficient depth, they cannot effectively detect biological structures and functions in vivo, limiting their application in early disease diagnosis and other fields. ### Technical Breakthroughs To address these issues, researchers have continuously explored solutions, and the new terahertz photoacoustic system developed by Professor Tian Zhen's team represents a significant breakthrough. The system innovatively combines photoacoustic detection with terahertz spectroscopy. Terahertz spectroscopy can sensitively capture changes in biological structures and functions using terahertz waves, while photoacoustic detection provides an effective way to solve the problem of water absorption of terahertz waves. The combination leverages the advantages of both technologies, opening up new possibilities for biomedical detection. In its specific working process, the system emits terahertz waves to excite vibrations in sodium ions in the blood. Sodium ions are widely present in blood, a vital component of organisms. When terahertz waves interact with sodium ions, they cause the ions to vibrate, which in turn generates ultrasonic waves—an ingenious conversion of terahertz wave energy. The generated ultrasonic waves are captured by an ultrasonic transducer, which has high sensitivity to accurately detect weak ultrasonic signals. By analyzing and processing these signals, relevant information about biological structures and functions in vivo can be obtained. The key advantage of this photoacoustic detection technology is that it effectively overcomes the strong absorption interference of water molecules on terahertz waves. By converting absorbed terahertz energy into sound waves, it bypasses water molecule interference and enables long-term monitoring without labels. This not only improves detection accuracy and reliability but also provides a more convenient and efficient method for biomedical detection. ### Application Prospects In the experimental phase, researchers first used the system to perform real-time measurements of blood sodium concentration in living mice. The system operated stably, accurately capturing and reflecting dynamic changes in the mice's blood sodium levels. Subsequent trials on human volunteers also yielded positive results. These experimental data initially verify the potential and feasibility of the system for clinical application, laying a solid foundation for its further promotion. Accurate measurement of blood sodium is of great significance in the medical field. Conditions such as dehydration, kidney diseases, and some neurological and endocrine disorders are closely related to abnormal blood sodium concentrations. Precise blood sodium data helps doctors make timely diagnoses and develop treatment plans. The system enables long-term non-invasive monitoring of blood sodium levels, avoiding the pain and inconvenience caused by traditional detection methods, and can continuously provide reliable data support for medical diagnosis. The system has extremely broad development prospects. Associate Professor Li Jiao, a team member, noted that the system's functions will not be limited to blood sodium detection in the future. Terahertz waves have unique spectral characteristics, and different ions and biomolecules have characteristic absorption spectra in the terahertz band. By identifying these spectra, the system is expected to detect other ions such as potassium and calcium. Beyond ion detection, the system can also identify various biomolecules such as carbohydrates, proteins, and enzymes. These biomolecules play key roles in human physiological processes, and their detection helps deepen understanding of human health and disease mechanisms. As technology continues to develop and improve, the new terahertz photoacoustic system is expected to become an important tool in biomedical detection, providing more comprehensive and accurate information for early disease diagnosis, treatment, and prevention, and driving the biomedical detection industry to new heights.