Shape Memory Polymer Resonators as Highly Sensitive Uncooled Infrared Detectors

Abstract

Uncooled InfraRed (IR) detectors have enabled the rapid growth of thermal imaging applications. These detectors are predominantly bolometers, where the heating of pixel from incoming IR radiation is read out as a resistance change. Another uncooled sensing method is to transduce the IR radiation into the frequency shift of a mechanical resonator. We present here a highly sensitive, simple to fabricate resonant IR sensor, based on thermo-responsive Shape Memory Polymers (SMPs). By exploiting the phase-change polymer as the transduction mechanism, our approach provides 2 orders of magnitude improvement of the temperature coefficient of frequency (TCF). The SMP has very good absorption in IR wavelengths, obviating the need for an absorber layer. A Noise Equivalent Temperature Difference (NETD) of 22 mK in vacuum and 112 mK in air are obtained using f/2 optics. Such high performance in air eliminates the need for vacuum packaging, paving a path towards flexible IR sensors.