Instead of asking friends "How do you feel?" or doctors examining patients, one day such queries and examinations may be replaced by tiny radio antennas implanted under the skin to act as remote sensors of humans' emotional, physiological state. Scientists at the Hebrew University's applied physics department have discovered a method for remote sensing of people's physiological and emotional state. Their initial results were published last week in the prestigious scientific journal The Physical Review Letters and have aroused much results in physicians and scientists. Their invention has been patented and commercialized by Yissum, HU's technology transfer company. The researchers - Profs. Yuri Feldman and Aharon Agranat with Dr. Alexander Puzenko, Dr. Andreas Caduff and doctoral student Paul Ben-Ishai - believe the discovery theoretically could help help monitor medical patients from afar, evaluate athletic performance, diagnose disease and remotely sense stress levels - which could have significant implications for technology in the biomedical engineering, anti-terror and security technology fields. The key is in the surprising shape of human sweat ducts. The researchers discovered that human skin is structured as an array of minute antennas that operate in the "sub-terahertz" frequency range. This discovery is based on investigations of the internal layers of the skin that were undertaken using a new imaging technique called "optical coherent tomography." Images produced by this technique revealed that the sweat ducts - tubes that lead the sweat from the sweat gland to the surface of the skin - are shaped as tiny coils. Similar helical structures with much larger dimensions have been used widely in as antennas in wireless communication systems. This led the investigators to consider the possibility that sweat ducts could behave like tiny helical antennas as well. In a series of experiments, the team measured the electromagnetic radiation reflected from the palm skin at the frequency range between 75GHz and 110GHz. It was found that the level of the reflected intensity depends strongly on the level of activity of the perspiration system. In particular, it was found that the reflected signal is very different if measured in a subject that was relaxed and if measured in a subject following intense physical activity. In a second set of measurements, they found that during the period of return to the relaxed state, the reflected signal was strongly correlated with changes in the blood pressure and the pulse rate that were measured simultaneously. The researchers emphasize however, that the research is still in its initial stages, and as they "sail in unsheltered water," it will take some time before the full significance of the research is understood and its technological potential is fully evaluated.