Optical coherence tomography as a tool for characterization of complex biological surfaces

The advent of scanning electron microscopy has facilitated our understanding of the biology in relation to surface microstructure of many invertebrates. In recent years, interest in biomimetics and bio-inspired materials has further propelled the search for novel microstructures from natural surfaces. As this search widens in diversity to nurture deeper understanding of form and function, the need often arises to examine rare specimens. Unfortunately, most methods for characterization of the microtopography of natural surfaces are sacrificial, and as such, place limiting constraints on research progress in situations where only a few rare specimens are known, such as the rich resources lodged in natural history museum collections. In this paper, we introduce the use of optical coherence tomography (OCT) as a noninvasive tool for bioimaging surface microtopography of crab shells. The technique enables the capture of microstructures down to micron level using low coherence near-infrared light source. OCT has allowed surface microtopography imaging on crab shells to be carried out rapidly and in a nondestructive manner, compared to the scanning electron microscope technique. The microtopography of four preserved crab specimens from Acanthodromia margarita, Ranina ranina, Conchoecetes intermedius and Dromia dormia imaged using OCT were similar to images obtained from scanning electron microscope, showing that OCT imaging retains the overall morphological form during the scanning process. By comparing the physical lengths of the spinal structures from images obtained from OCT and scanning electron microscope, the results showed that dimensional integrity of the images captured from OCT was also maintained.