Three-dimensional imaging of Morpho butterfly wing nanostructures using FIB-SEM techniques

Accurate three-dimensional imaging of natural nanostructures is critical to obtain a full understanding of how they produce their remarkable optical properties. In this study, we developed scanning electron microscopy techniques, using a focused ion beam, to reconstruct models of the nanostructures found on both the cover and ground scales of the Morpho didius butterfly. By using the electron beam to deposit Pt and encase the scale structure beneath the top surface, we were able to determine the butterfly material in the plane of the 2D focused ion beam cross sections, preventing any shine-through effect affecting image segmentation and enabling the segmentation process to be undertaken using a semi-automated, non-machine-learning-based approach. The 3D models this method produced allowed us to quantitatively explore features of the nanostructures, such as thickness ripples in their trunks, with sizes as small as 40 nm.