Fabrication methods for creating flexible polymer substrate sensor tags

Abstract

Articles you may be interested inA wireless demodulation system for passive surface acoustic wave torque sensor Rev. Sci. Instrum. 85, 125001 (2014); 10.1063/1.4902180 Local oscillator phase noise limitation on the resolution of acoustic delay line wireless passive sensor measurement Rev. Sci. Instrum. 85, 065001 (2014); 10.1063/1.4880455 Surface acoustic wave devices as passive buried sensorsThe authors describe the design, fabrication, and testing of a passive wireless sensor platform utilizing low-cost commercial surface acoustic wave ͑SAW͒ filters and sensors. Polyimide and polyethylene terephthalate sheets are used as substrates to create a flexible sensor tag that can be applied to curved surfaces. A microfabricated antenna is integrated on the substrate in order to create a compact form factor. The sensor tags are fabricated using 315 MHz SAW filters and photodiodes and tested with the aid of a fiber-coupled tungsten lamp. Microwave energy transmitted from a network analyzer is used to interrogate the sensor tag. Due to an electrical impedance mismatch at the SAW filter and sensor, energy is reflected at the sensor load and reradiated from the integrated antenna. By selecting sensors that change electrical impedance based on environmental conditions, the sensor state can be inferred through measurement of the reflected energy profile. Testing has shown that a calibrated system utilizing this type of sensor tag can detect distinct light levels wireless and passively. The authors also demonstrate simultaneous operation of two tags with different center passbands that detects light. Ranging tests show that the sensor tags can operate at a distance of at least 3.6 m.

A multi-sensing reconfigurable platform for gas applications

“…The use of external battery limits the lifetime and cost of the active RFID sensor tag [1], as can be observed in [7,8]. However, in case of passive RFID tags with no battery, the power is harvested by the incoming RF signal which in turn limits the current budget for the whole tag to be as low as few micro Amperes.…”