研究目的
Investigating the use of thermo-responsive shape memory polymers as highly sensitive uncooled infrared detectors.
研究成果
The study demonstrates the highest temperature coefficient of frequency (TCF) reported for resonant infrared detectors, with a direct temperature detection sensitivity of 63 μK for SMP resonators and 28 μK for SiNx/SMP resonators. The noise equivalent temperature difference (NETD) was as low as 22 mK in vacuum and 112 mK in air, with further improvement to 6 mK in vacuum using SiNx/SMP resonators. The high performance in air suggests potential for flexible, non-hermetically sealed infrared sensors. Future improvements could focus on optimizing IR radiation collection efficiency and absorption to achieve sub-mK NETD levels.
研究不足
The study highlights the trade-off between the quality factor (Q-factor) and the temperature coefficient of frequency (TCF) in SMP resonators, especially near the glass transition temperature. The intrinsic material loss near Tglass limits the Q-factor, affecting frequency stability. Additionally, the response time of the sensor is proportional to the heat capacity and inversely proportional to the thermal conductance, suggesting a need for optimization in resonator dimensions for faster response.
1：Experimental Design and Method Selection:
The study involves the design of resonant infrared sensors using thermo-responsive shape memory polymers (SMPs) as the transduction mechanism. The theoretical model involves the relationship between the temperature change and the mechanical resonance frequency shift of the SMP resonators.
2：Sample Selection and Data Sources:
Commercial MM4520 SMP material was used, characterized by dynamic mechanical analysis (DMA) to determine its Young’s modulus and quality factor as a function of temperature.
3：List of Experimental Equipment and Materials:
Equipment includes a laser Doppler vibrometer (LDV) for displacement measurement, a Fourier transform infrared (FTIR) spectrometer for absorbance measurements, and a vacuum chamber for testing under different pressure conditions. Materials include SMP pellets, silicon nitride membranes, and piezo-disk actuators.
4：Experimental Procedures and Operational Workflow:
The SMP resonators were fabricated and characterized in terms of resonance frequency and Q-factor as a function of temperature. The IR response was measured by modulating IR radiation from a black resistive heater and tracking the resonance frequency shift.
5：Data Analysis Methods:
The Allan deviation was used to measure frequency stability, and the noise equivalent temperature difference (NETD) was calculated to evaluate sensor sensitivity.
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ZnSe Optical Window
ZNSEP50-3
Crystran LTD
Allowing transmission of both the IR radiation and the red laser light for displacement readout
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IR ZnSe Lenses
LA7656-G-?1"-f = 25.4 mm and LA7542-G-?1"-f = 50.1 mm
Thorlabs
Producing a controllable irradiance that is independent of source-target distance
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Rotating Chopper
SR540
Stanford Research Systems
Modulating the IR radiation from the IR target
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Lock-in Amplifier
SR550
Stanford Research Systems
Driving the piezo-disk actuator at the fixed driving frequency and tracking the phase difference between the actuation signal and the sensor output
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Oscilloscope
MSO9104A
Agilent Technologies
Collecting the phase and amplitude data from the lock-in amplifier
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Laser Doppler Vibrometer
MSV 400
Polytec
Measuring the magnitude and the phase of the frequency response of the SMP resonators
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Fourier Transform Infrared Spectrometer
Nicolet 8700
THERMO
Measuring the absorbance spectrum of the SMP samples
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Piezo-disk Actuator
PA4FEW
Thorlabs
Actuating the SMP resonators
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PID Temperature Controller
TEC-1091
Meerstetter Engineering GmbH
Adjusting the operation temperature of the resonators
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Piezo-disk Actuator
NAC 2014
Noliac
Actuating the SMP resonators
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Thermal Adhesive
WLFT 404 23 × 23
Fischer Elektronik
Bonding the SMP resonators on piezo-disk actuators
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Peltier Element
MCPE-127-10-25
Multicomp
Controlling the operation temperature of the resonators
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PT-100 Temperature Sensor
Measuring the temperature on the PMMA substrate
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Resistive Heater
HP04?1/04-24
DBK
Used as an IR source
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IR Thermometer
PeakTech 4950
Calibrating the IR target to define the temperature difference of the target with the ambient
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Lock-in Amplifier
UHFLI
Zurich Instruments
Measuring the frequency tracking directly by means of a phase-locked loop (PLL)
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