Wireless Miniature Dosimeters for In-Situ Radiation Measurement

Purdue University, West Lafayette IN

Investigators

Abstract

Intellectual Merit: This sensor proposal focuses on the development of a novel microtransponder for wireless in-situ radiation dosimetry. The proposed sensor is totally passive, i.e., do not require an on board power source, and thus avoid problems associated with radiation damage to active electronics (transistors, etc). The transponder is based on a novel device structure combining the quasi-permanent electric field produced by an electret with silicon micromachining. The micromachined LC dosimeter incorporates an array of cantilever beams deflected by the electric field produced by an electret. This array is connected to an on-chip spiral coil, thereby forming a passive LC resonant circuit. Upon exposure to the ionizing radiation, the surface charge of the electret is reduced hence decreasing the force on the cantilever beams (and therefore decreasing their deflection). This decreases the capacitance between the beams and the bottom electrode of the electret, which can be detected remotely by monitoring the resonant frequency of the LC transponder. Broader Impact: The ability to use wireless techniques for radiation measurement in conjunction with a miniature dosimeter will provide a valuable tool in many areas such as radiation therapy, personnel, and environmental monitoring. The out come of this research will lead to a family of cost effective, small sized wireless in-situ radiation sensors. The techniques developed during the course of this project will also have a broad impact on many applications and devices that require the integration of electrets with MEMS microstructures (e.g., electromechanical transducers, particle filters, and infrared sensors).