In-situ instrumentation enables better prediction of the aging of structures than the commonly used visual inspections and “just-in-time” prevention of accidents linked to failures. To reach its full development, this science is in dire need for cheap wireless micro (or even nano) sensors immersed by the thousands in the concrete of every new structure. Demonstrating than such micro-sensors are actually embeddable into cementitous materials and can provide the user with valuable information on the material under test will be a major breakthrough. A step toward this long-term goal, we describe in this paper an innovative high frequency capacitive micromachined transducer (cMUT) based on a membrane of aligned carbon nanotubes. To this day, we have realized potentially suitable membranes. They are being characterized. By modeling, we have determined that such device, used in water from about 50 MHz to 5 GHz, could measure pores in the 10 nm to 10μm range.