Bioinspired infrared detection using thermoresponsive hydrogel nanoparticles.

The development of high performance uncooled infrared (IR) detection and imaging systems will greatly expand the application of IR technology in broad areas such as transportation, environmental monitoring, and medical care. Inspired by the superior IR detection capability of beetle Melanophila acuminata, we explored the potential use of hydrogel nanoparticles (NPs) in uncooled IR detection system. In the system, the absorption of the incoming IR radiation by the temperature-sensitive hydrogel NPs, together with water, induces the volume change of the hydrogel NPs, similar to the volume change of the biofluid inside the sensillae receptors in M. acuminata caused by the IR radiation. This volume change results in the change of optical readout (transmittance in this study) in visible range and provides the sensitive detection of the IR radiation. In this work, poly(N-isopropylacrylamide-co-acrylic acid) (poly(NIPAM- co-AAc)) copolymer NPs with different sizes were synthesized and their IR sensing performances were studied in detail. The correlation between the NP size and concentration and the IR sensing property was also discussed in the paper. This work helps enhance the understanding of the response of hydrogel NPs under IR radiation, and offers a potential material system for uncooled IR detection that is inspired by M. acuminata. The direct use of transmittance of the NP solution as the readout for IR detection also provides a simple and sensitive IR detection approach for low cost and portable industrial applications. [ABSTRACT FROM AUTHOR]