The need for periodic metallic nanoparticle arrays is driven by a wide variety of applications including plasmonic waveguides, nanoscale lenses, and catalyzing the growth of ordered carbon nanotubes.  Current methods to form such organized, periodic structures usually suffer from high cost or poor quality structures.  Researchers Yadavali et al. from Oak Ridge National Labs and Univ of Tennessee reveal a new way to spontaneously make low cost, high quality periodic arrangements of gold nanoparticles.   

Laser interferences processes are known to induce periodic surface structures where a pattern forms due to the interference phenomenon between incident light and scattered light. The interference pattern produces periodic thermal gradients that induces mass transport and rearrangement. However, these types of patters often poor quality with defects. 

This work describes a new method involving irradiation of the surface by a single laser beam while apply a DC electric field to the underlying substrate.   When an electric field parallel to the laser polarization is applied, single-crystal like periodic ordering was formed covering a large area and with very low defect density.  In addition to high resolution studies by SEM, a Nanonics Multiview 1000 was used to analyze the topography and quality of the resulting patterns.  The resulting AFM images below show the gold periodic structures at difference conditions of a) no E field  b) E field perpendicular to the polarization and c) E field parallel to the polarization.











Published: Yadavali et al., Nanotechnology 25 (2014) p. 465301

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Published in Publication Highlights
Tuesday, 03 February 2015 20:13

Force spectroscopy on macrophages

A Multiview 1000 was used to probe the elasticity  of fixed macrophage cells with force spectroscopy.  Force spectroscopy was conducted on various cells with measurements performed around the nucleus.  A 3D image of a sample cell is shown below, with the force curves conducted at designated points on top of the cell.  Sneddon’s model was used to characterize the individual force curves to measure the elastic indentation of the cells; the Young’s modulus can then be calculated  by fitting the Hertz model to the data.  The authors find that the modulus of the macrophage cells increased significantly with adhesion to the ECM, showing that cellular adhesion plays a significant role in cytoskeleton and membrane softness.

Published:  Souza et al., European Biophysics Journal, 2014 DOI 10.1007/s00249-014-0988-3

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Published in Publication Highlights

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