Passive Wireless Sensor Using Interdigitated Capacitor for Analyte Detection
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Solution Overview
Problem
Current chemical-biological sensors face challenges with specificity and interference issues, requiring inexpensive, compact, and reliable solutions for detecting chemical and biological agents, especially in real-time monitoring applications such as homeland security and environmental monitoring.
Innovation Solution
The development of passive wireless sensors using a relaxation oscillator circuit with an interdigitated capacitor coated with a functional material, which changes its dielectric constant upon exposure to analytes, altering the response-pulse frequency for detection without the need for probes or batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive wireless sensors are used, then device complexity and power requirements are reduced, but measurement precision and detection sensitivity may be compromised
Solution Approach 1:
The patent replaces active electronic sensing mechanisms with a passive dielectric-based sensing mechanism. The interdigitated capacitor's dielectric layer interacts with analytes through physical/chemical binding, and the resulting dielectric constant changes are detected wirelessly through impedance measurements, eliminating complex active electronics while maintaining detection capability
Solution Approach 2:
The patent utilizes changes in the dielectric constant of the functional material layer as the sensing mechanism. When analytes bind to the dielectric layer, the dielectric constant changes, which directly alters the impedance characteristics of the interdigitated capacitor, providing a measurable signal for analyte detection without requiring complex active components
2Measurement precision
If functional materials with high analyte affinity are used, then detection sensitivity is improved, but specificity may be reduced due to interference from other substances
Solution Approach 1:
The patent employs different functional materials with specific affinities for different analyte types in different sensing zones or layers. This allows the sensor to be tuned for specific analyte detection while maintaining high sensitivity, as each functional material layer can be optimized for its target analyte
Solution Approach 2:
The dielectric layer acts as an intermediary between the analyte and the sensing mechanism. The functional material within the dielectric layer selectively binds to target analytes, and this binding event is transduced into an electrical signal through dielectric constant changes, providing both sensitivity and specificity
3Speed
If real-time monitoring capability is implemented, then response time is reduced, but energy consumption increases
Solution Approach 1:
The patent implements periodic interrogation of the sensor by the external reader, rather than continuous operation. The passive sensor only consumes energy when interrogated, and the dielectric-based sensing mechanism provides immediate response to analyte binding events, achieving real-time monitoring capability with minimal energy consumption
Solution Approach 2:
The sensor utilizes the electromagnetic field from the external reader to both power itself and transmit sensing data. The passive sensor harvests energy from the interrogating field and modulates the reflected field based on analyte detection, eliminating the need for an independent power source while maintaining real-time detection capability
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
These sensors provide high sensitivity and specificity, are environmentally independent, and can be used in various environments, offering a cost-effective and portable solution for detecting chemical and biological agents.
Implementation Method 1
the functional material having a detection-layer dielectric constant that defines an IDC dielectric constant of the interdigitated capacitor. The detection-layer dielectric constant may then change when the functional material is exposed to the analyte, thereby changing the response-pulse frequency
Implementation Method 2
a relaxation oscillator circuit electrically coupled to the DC converter... The relaxation oscillator circuit may include a capacitance element that defines a response-pulse frequency of the wireless sensor
Implementation Method 3
a sensor receiving antenna configured to receive interrogation pulses having an interrogation frequency
Implementation Method 4
a sensor transmitting antenna electrically coupled to the relaxation oscillator circuit. The sensor transmitting antenna may be configured to receive response pulses from the relaxation oscillator circuit and to transmit the response pulses at the response-pulse frequency
Data Source
AI summary
Wireless sensors for detection of an analyte may include a sensor receiving antenna configured to receive interrogation pulses having an interrogation frequency, a DC converter, a relaxation oscillator circuit electrically, and a sensor transmitting antenna. The relaxation oscillator circuit may include a capacitance element that defines a response-pulse frequency of the wireless sensor. The capacitance element may include an interdigitated capacitor coated with a detection layer of a functional material having a dielectric constant that defines the dielectric constant of the interdigitated capacitor. This dielectric constant changes when the functional material is exposed to the analyte, thereby changing the response-pulse frequency of the relaxation oscillator circuit to an analyte-exposure frequency indicative of the exposure of the functional material to the analyte. Wireless systems for detecting an analyte may include a wireless sensor that communicates with an interrogation module.