Infrared Detection Based On Localized Modification Of Morpho Butterfly Wings

Infrared(IR)radiation is one kind of electromagnetic wave whose wavelength is between visible light and microwave.Due to the non-invasive nature of infrared radiation and the unique information it reveals,IR detection plays an important tool for a broad range of applications,such as,industrial process monitoring,medical diagnostics,and military applications.Generally,there are two kinds of IR detection: IR thermal detection and IR photon detection.IR thermal detection is based on the change of material physical properties induced by the thermal effect of IR;IR photon detection converts the invisible IR into electric signal through the interaction between the absorbed IR photons and the electrons.Although IR photon detection systems are superior to the thermal detection systems in temperature sensitivity,response speed,and spatial resolution,the photon detection systems require cryogenic or thermoelectric cooling to ensure the performance.Such requirement not only makes photon detection devices bulky and expensive,but also limits their application range.Bioinspired engineering provides a new perspective to realize IR detection.In the first chapter of this thesis,we will briefly introduce some new IR detection approaches inspired by biological species,such as fire beetles,snakes,and Morpho butterflies.Morpho butterflies have attracted extensive attention in recent years due to their colorful wings with complex hierarchical nanostructures.Taking advantage of the highly sensitive reflectance response of butterfly wings,various research groups have utilized butterfly wings for the development of high performance sensors,including chemical sensors,infrared sensors,thermal sensors,magnetic sensors,and pH sensors.The second chapter of this thesis involves the investigation of subtractive modification of butterfly wings.Based on the nanostructure of Morpho butterfly wings,for the first time,we achieved controlled subtractive structural modification of butterfly wings using oxygen plasma etching.The structure and optical property change of butterfly wings with different duration of oxygen plasma etching were studied in detail.Such study not only extends our ability to modify biological structures,but also improves our understanding of optical properties of the butterfly wings.In the third chapter of this thesis,we will introduce our study of IR detection through selective modification of butterfly wing structures using physical vapor deposition,a layer of gold(Au)coating was selectively deposited on the nanostructure of butterfly wings and formed a 3D bimaterial nanostructure.Due to the differences in thermal expansion for the Au coating and the original butterfly wing,the local deformation of butterfly wings is induced upon IR exposure,which enables highly sensitive IR detection.A temperature sensitivity(TS)of ~ 32 mK and a response speed of 5 Hz were demonstrated in this study.We further simulated the optical property changes for this local bending effect on the gold-modified butterfly wings.The simulation results correlated well with the experiment data,which also supported the proposed IR detection mechanism.The study in this thesis not only provides us with a promising approach for the development of uncooled IR detection systems,but also offers a potential route for the development of multi-layered 3D bimaterial nanostructures as detection platforms for various high-performance sensing applications.