Investigation of a flexible printed circuit board MEMS electrostatic field sensor

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Hill, Brandon
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This thesis details a novel variation on a previous MEMS electrostatic field sensor by the application of a new material and fabrication method. Electrostatic field sensors are required that can operate in industrial or outdoor environments where they are subject to damage and contamination. Current MEMS electrostatic field sensors provide a range of benefits, but are extremely delicate. Polymer MEMS are an alternative to conventional silicon micromachined MEMS. The fabrication of a MEMS electrostatic field sensor from a polyimide polymer substrate using a low‐cost commercial flexible printed circuit board (Flex‐PCB) process is explored in this thesis. Also included is the design of a silicon based device which is similar in geometry to the polyimide device. Both the silicon and the polyimide devices are tested to characterize them, and their performances are compared to demonstrate the equivalence and suitability of polymer devices to replace silicon devices. The polyimide sensor achieved a sensitivity of 440 μV/(V/m) and a resolution of 15(V/m)/√Hz, which is similar to the silicon design, as well as to many other published electrostatic field sensors. This performance demonstrates the viability of the polyimide sensor in place of silicon designs. The application of this type of sensor as a non‐contact printed circuit voltage probe is demonstrated, and the influence of surrounding structure on the performance of the sensor in various configurations is examined. Also included is the design of a miniaturized electronic system to record measurements and drive the sensors developed, and some theoretical analysis of the sensor function.
electrostatic force, electric field sensor, flex PCB, polymer MEMS, polyimide, silicon MEMS