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Lessons from Nature - Surface Characterisation by means of Nanotechnology
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Engineering Design and Materials.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

There is still much to learn from nature. Springtails (collembola), a small arthropod that live in soil and decaying material, have through evolution developed extremely effective anti-wetting skin patterns. The hexagonal structure on the cuticle of some species distinguishes them from other anti-wetting surfaces and makes them an interesting study. In this thesis, two different methods of surface characterization were utilized. In the end there was an evaluation on which method that was the best. Method one consisted of analysing images taken with a Focused Ion Beam (FIB). A dual-FIB was utilized, which consists of both a FIB and a Scanning Electron Microscope (SEM). This made it possible to cut in to the surface structure on a nanoscale. The samples were then tilted, so one could view the cross-section and take SEM images. The images was then analysed and height values of the selected species extracted. A 3D image was also possible to obtain from the SEM images from the FIB. This was done by powerful image analytic software. The program analysed hundreds of SEM pictures taken only a few nm apart, sliced by the FIB. This produced a 3D image. The method was called "slice and view". The second method consisted of the use of a nanoindenter. A nanoindenter performed a Nanoindenter-"Atomic Force Measurement" scan, or NI-AFM scan, which produced a 3D image of the surface of the scanned sample. The height data was then relatively easy extracted from the images. In addition some mechanical properties of the specie \textit{F. quadrioculata} were measured. This was performed by nanoindenting. Nanoindenting consists of performing an indent on the surface and extract data of the forces used and how the material behaved. The data were then analysed and evaluated. The reduced Young's modulus and hardness were the material properties that were extracted. A total of five different species of springtails were tested with both methods. One deemed unscannable by the NI-AFM, but produced a beautiful 3D image by the ``slice and view'' method. The resulting four species was evaluated. To conclude, the springtail cuticles with the lowest surface structures, I. prasis and F. quadrioculata, was best fitted for the NI-AFM scans and hardest to analyse from the images of the cross sections. The indentation of F. quadrioculata confirmed some of the mechanical properties we know. The granules and bridges between the granules are harder than the skin between them. Nanoindentation of soft materials is a field increasing in scope. More material testing of the cuticles of springtails are reccomended.

Place, publisher, year, edition, pages
Institutt for produktutvikling og materialer , 2013. , 53 p.
URN: urn:nbn:no:ntnu:diva-20667Local ID: ntnudaim:8596OAI: diva2:616127
Available from: 2013-04-15 Created: 2013-04-15 Last updated: 2013-06-22Bibliographically approved

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