Squid Skin Cell-Inspired Refractive Index Mapping of Cells, Vesicles, and Nanostructures.

The fascination with the optical properties of naturally occurring systems has been driven in part by nature's ability to produce a diverse palette of vibrant colors from a relatively small number of common structural motifs. Within this context, some cephalopod species have evolved skin cells called iridophores and leucophores whose constituent ultrastructures reflect light in different ways but are composed of the same high refractive index material─a protein called reflectin. Although such natural optical systems have attracted much research interest, measuring the refractive indices of biomaterial-based structures across multiple different environments and establishing theoretical frameworks for accurately describing the obtained refractive index values has proven challenging. Herein, we employ a synergistic combination of experimental and computational methodologies to systematically map the three-dimensional refractive index distributions of model self-assembled reflectin-based structures both in vivo and in vitro. When considered together, our findings may improve understanding of squid skin cell functionality, augment existing methods for characterizing protein-based optical materials, and expand the utility of emerging holotomographic microscopy techniques.

Selectively Electron-Transparent Microstamping Toward Concurrent Digital Image Correlation and High-Angular Resolution Electron Backscatter Diffraction (EBSD) Analysis.

Digital image correlation (DIC) in a scanning electron microscope and high-angular resolution electron backscatter diffraction (HREBSD) provide valuable and complementary data concerning local deformation at the microscale. However, standard surface preparation techniques are mutually exclusive, which makes combining these techniques in situ impossible. This paper introduces a new method of applying surface patterning for DIC, namely a urethane microstamp, that provides a pattern with enough contrast for DIC at low accelerating voltages, but is virtually transparent at the higher voltages necessary for HREBSD and conventional EBSD analysis. Furthermore, microstamping is inexpensive and repeatable, and is more suitable to the analysis of patterns from complex surface geometries and larger surface areas than other patterning techniques.

Polymer cell culture substrates with micropatterned carbon nanotubes.

This article presents study of the interactions between cells and micropatterned carbon nanotubes on a polymer cell culture substrate. The polymer substrates with patterned carbon nanotubes were fabricated using an imprint process, whereby the nanotubes were pressed into a polymer layer at high temperature. The patterned substrates featured 28 different nanotube patterns of microscale lanes and circles, where the feature sizes ranged from 9 to 76 microm. Osteoblast-like cells were seeded on the substrates and cell alignment was quantified via fluorescent and electron microscopy. Many patterns were fabricated on each polymer substrate, allowing 28 different experiments on each cell culture substrate, which were tested over 10,000 cells. The cell response to the patterned nanotubes showed a maximum alignment to the microlane patterns of 55 +/- 6% and no significant alignment to microcircle patterns. This work enables the study of cell response to a wider range of patterns featuring both the micro and nano length scales.