Replicating Spectral Baseline for Unambiguous Frequency Locking in Resonant Sensors

Area of Science:

• Microelectromechanical Systems (MEMS)
• Sensor Technology
• Nanotechnology

Background:

• Electrothermal piezoresistive resonant cantilever sensors utilize embedded heating and piezoresistive elements for actuation and sensing.
• Close proximity of these elements causes thermal parasitic effects, leading to asymmetric amplitude and reversing phase spectral responses.
• These spectral distortions impede accurate resonant frequency determination and phase-locked loop (PLL) based resonance tracking.

Purpose of the Study:

• To develop and validate a method for mitigating the thermal parasitic effect in electrothermal resonant cantilever sensors.
• To improve the accuracy of resonant frequency tracking for sensor applications.
• To enable reliable real-time resonance tracking using phase-locked loop techniques.

Main Methods:

• Fabrication of electrothermal piezoresistive resonant cantilever sensors with integrated Wheatstone bridge.
• Development of a replica spectral subtraction technique to mathematically remove thermal parasitic effects.
• Simulation and experimental assessment using cigarette smoke particles for spectral response optimization.

Main Results:

• The replica spectral subtraction method effectively removed thermal parasitic effects from sensor resonance spectra.
• Optimized spectral responses exhibited symmetrical amplitude and monotonic phase transitions.
• Successful real-time PLL-based frequency tracking was demonstrated, validated by particle detection.

Conclusions:

• The proposed replica spectral subtraction technique accurately compensates for thermal parasitic effects in resonant sensors.
• This method significantly enhances the precision of resonant frequency determination and enables robust PLL-based tracking.
• The findings pave the way for more reliable and accurate sensor systems in various environmental and industrial monitoring applications.