# Shape Memory Polymer Resonators as Highly Sensitive Uncooled Infrared Detectors

## TL;DR

This paper introduces a highly sensitive uncooled IR detector using shape memory polymers that transduce IR radiation into frequency shifts, achieving significant improvements in sensitivity and enabling flexible, vacuum-free operation.

## Contribution

The study presents a novel resonant IR sensor based on thermo-responsive shape memory polymers, offering two orders of magnitude better temperature coefficient of frequency and eliminating the need for absorber layers.

## Key findings

- Achieved NETD of 22 mK in vacuum and 112 mK in air.
- Provided a simple fabrication process for flexible IR sensors.
- Demonstrated high sensitivity without vacuum packaging.

## 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.

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Source: https://tomesphere.com/paper/1904.01453