Wireless Passive Radiation Sensor Using SAW Devices
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Solution Overview
Problem
Existing radiation detectors are not portable, inexpensive, or capable of providing immediate real-time radiation dose warnings, often requiring laboratory analysis and being fragile or costly.
Innovation Solution
A wireless passive radiation sensor using a piezoelectric substrate with interdigital transducers and a radiation-sensitive film that changes impedance upon exposure to radiation, allowing for remote detection via surface acoustic waves without the need for batteries or wires, enabling immediate and cost-effective radiation monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional radiation detectors are used, then radiation detection capability is achieved, but the detectors require laboratory analysis, are fragile, costly, and cannot provide immediate real-time warnings
Solution Approach 1:
The patent replaces traditional mechanical/electronic radiation detector systems with a wireless surface acoustic wave (SAW) based system. The SAW device uses acoustic waves propagating through a piezoelectric substrate to sense radiation, eliminating the need for complex electronic readout circuits and laboratory equipment. The radiation-sensitive film modulates the acoustic wave properties, which are then wirelessly transmitted for remote detection, providing immediate real-time monitoring without fragile components.
Solution Approach 2:
The SAW device is designed as a self-powered, passive sensor that harvests energy from the acoustic waves themselves. The radiation-sensitive film directly modulates the acoustic wave impedance upon radiation exposure, enabling self-diagnosis and automatic signal transmission without requiring external power sources, batteries, or complex processing electronics at the sensor location.
2Adaptability or versatility
If unique photo-lithographically patterned bit sequences are fabricated on each SAW device for identification, then self-identification capability is achieved, but fabrication cost increases due to unique photo-masks and tracking requirements
Solution Approach 1:
Instead of using unique photo-lithographically patterned bit sequences requiring separate photo-masks for each device, the patent encodes identification information by varying physical parameters of the SAW device such as the acoustic path length, transducer finger spacing, or resonance frequency. These parameter variations can be achieved through standard fabrication process adjustments without requiring unique photo-masks, significantly reducing manufacturing costs while maintaining unique identification capability for each sensor.
3Measurement precision
If network analyzers are used to monitor phase angle of reflected signals for sensor response, then pressure, strain, and torque monitoring is achieved, but the readout hardware is expensive and not portable
Solution Approach 1:
The patent replaces expensive network analyzer-based electronic measurement systems with a wireless acoustic wave-based detection system. The SAW device propagates acoustic waves through the piezoelectric substrate, and radiation exposure modifies the acoustic wave impedance through the radiation-sensitive film. These acoustic wave changes are detected wirelessly using simple RF equipment, eliminating the need for complex network analyzers and providing portable, low-cost monitoring capability with maintained measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor provides immediate, real-time radiation detection with a robust, portable, and inexpensive solution that does not require batteries or wires, allowing for remote sensing and simultaneous identification of multiple sensors using a single antenna and data acquisition system.
Implementation Method 1
a launch interdigital transducer, disposed on the surface of the piezoelectric substrate and adapted to launch a surface acoustic wave at a resonance frequency in the piezoelectric substrate when an RF electric field is applied across the launch interdigital transducer
Implementation Method 2
The sensor is triggered by ionizing radiation e.g., gamma or neutron radiation. On exposure to a given level of radiation, the radiation-sensitive film can switch from high resistance (e.g., >105Ω) to low resistance (e.g., 2Ω). The radiation-sensitive film forms catalytic sites when electrons are ionized from the molecules due to a radiation event
Data Source
AI summary
A novel measurement technique is employed using surface acoustic wave (SAW) devices, passive RF, and radiation-sensitive films to provide a wireless passive radiation sensor that requires no batteries, outside wiring, or regular maintenance. The sensor is small (<1 cm2), physically robust, and will operate unattended for decades. In addition, the sensor can be insensitive to measurement position and read distance due to a novel self-referencing technique eliminating the need to measure absolute responses that are dependent on RF transmitter location and power.