Optical nanotomography of anisotropic fluids


Nature Physics, VOL 4 (2008)

A. De Luca, V. Barna, T. J. Atherton, G. Carbone, M. E. Sousa and C. Rosenblatt

1 - CNR-INFM LiCryL, Cemif.Cal, c/o Physics Department, University of Calabria, 87036 Rende (CS), Italy
2 - Faculty of Physics, University of Bucharest, PO Box Mg-11, 077125, Bucharest, Magurele, Romania
3 - Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
4 - 3M Corporation, St. Paul, Minnesota 55144, USA



The physical properties of anisotropic fluids can be manipulated on very short length scales of 100nm or less by appropriate treatment of the confining substrate(s). This facilitates the use of ordered fluids in a variety of scientific endeavours and applications. Although future advances will require a complete understanding of their structure at the nanoscale level, high-resolution three-dimensional optical imaging of the fluid’s molecular orientation profile is beyond the reach of extant techniques3.Here, we report a powerful imaging approach based on the collection of transmitted light in the far field that is emitted from a light source with a subwavelength aperture.We acquire high-resolution images by raster-scanning, at multiple heights, an optical fibre immersed inside a thin layer of anisotropic fluid, thereby facilitating the visualization of the fluid’s structure with a resolvable volume about 1/500 of that attainable by current methods. This novel technique offers the intriguing possibility of three-dimensional nanoscale reconstruction of a variety of soft materials, here the first direct visualization and measurement of the liquid-crystal molecular orientation relaxation length.