Image contrast immersion method for measuring refractive index applied to spider silks

Douglas J. Little*, D. M. Kane

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
26 Downloads (Pure)


A technique for measuring the refractive index of micron sized fibers using a series of immersion index matching oils, and image contrast measurements is proposed and demonstrated. It has been applied to radial silks of the orb web weaving spider Plebs eburnus. These have widths of ∼1-2 microns. Values about 1.5500 are obtained, with birefringence values between 0.0000 and 0.0133 for individual silks. An uncertainty in the range ± 5 × 10 -4 to ± 2 × 10-3 is achieved for these challenging samples. This accuracy is about a twenty times improvement on previously reported measurements for spider silks using other techniques. The technique is used to obtain measurements of the refractive index of spider silks as a function of wavelength, for the first time. An Abbe number for the radial silks of Plebs eburnus of ∼32 is found.

Original languageEnglish
Pages (from-to)19182-19189
Number of pages8
JournalOptics Express
Issue number20
Publication statusPublished - 26 Sept 2011

Bibliographical note

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.


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