Researchers at the Massachusetts Institute of Technology have developed an aerosolisable spray containing 2-D circuits, which could be used in a number of environmental and health applications where limited access and space prevents larger sensors being used.
The polymer circuit, which contains a sensor element, a photodiode to supply power and a memory element to store recorded information, is fabricated on a 100 µm-square, 1 µm thick substrate of SU-8 photoepoxy, and then dispersed in suspension and atomised. A range of circuits can be built to test for different gas and particle constituents along the flow path of the generated aerosol spray. They can then be passed, for example, through gas lines normally inaccessible to measurement, and here were tested to determine the presence of ammonia and soot particles. They are also small enough that they could be used, in suspension, within the human body e.g. in circulatory or digestive system tests, with delivery via injection, ingestion or nasal spray.
At present, the sensors must be interrogated after spraying to determine whether they were exposed to the test chemical, but future versions could include a transmitter to relay this information immediately upon sensing the test material.