Researches from Duke University develop a new motion sensor based on meta-materials that is sensitive enough to monitor a person’s breathing.
The researchers from Duke University and Institut Langevin, France, revealed that radio wave patterns can be used as effective sensors to detect the presence of a person and determine location anywhere inside a room. The paper on the new motion-sensing technology was published in Scientific Reports on August 6, 2018.
The researchers utilized patterns created by radio waves bouncing around a room and interfering with themselves. It was observed that the unique patterns change with the slightest perturbation of the room’s objects. The change is detected by a sensitive antenna when something moves in or enters the room. Furthermore, cyclical movements can be detected by comparing the change in these patterns over the time. The researchers trained the demonstration system for the pattern of radio waves scattered by a triangular block placed in 23 different positions on a floor. Such calibration is capable of distinguishing between the learned 23 scenarios. Furthermore, it distinguished the positions of three identical blocks placed in any one of 1,771 possible configurations.
The technology is based on the behavior of radio waves in an enclosed room as the radio waves have the ability to continuously reflect off multiple surfaces that create complex interference patterns throughout a room. This complexity has been an obstacle for systems trying to locate the origin of a signal in previous experiments. However, the same complexity is capable of detecting movement and locate objects within a room when tapped. The large number of antennas installed in many places around a room to take multiple measurements would be costly and inconvenient. Therefore, the researchers used meta-materials— artificial materials that manipulate waves like light and sound through properties of their structure, to dynamically control the shape of the waves. The technology that is energy- efficient and capable of counting the number of people in a room, distinguish body positions and monitor breathing patterns has potential applications in security, healthcare and gaming.