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Published May 7, 2015 | Published + Supplemental Material
Journal Article Open

Motion-based threat detection using microrods: experiments and numerical simulations

Abstract

Motion-based chemical sensing using microscale particles has attracted considerable recent attention. In this paper, we report on new experiments and Brownian dynamics simulations that cast light on the dynamics of both passive and active microrods (gold wires and gold–platinum micromotors) in a silver ion gradient. We demonstrate that such microrods can be used for threat detection in the form of a silver ion source, allowing for the determination of both the location of the source and concentration of silver. This threat detection strategy relies on the diffusiophoretic motion of both passive and active microrods in the ionic gradient and on the speed acceleration of the Au–Pt micromotors in the presence of silver ions. A Langevin model describing the microrod dynamics and accounting for all of these effects is presented, and key model parameters are extracted from the experimental data, thereby providing a reliable estimate for the full spatiotemporal distribution of the silver ions in the vicinity of the source.

Additional Information

© 2015 The Royal Society of Chemistry. Received 21st October 2014, Accepted 23rd March 2015. This project received support from the Defense Threat Reduction Agency-Joint Science and Technology Office for Chemical and Biological Defense (Grant no. HDTRA1-13-1-0002). D. S. acknowledges support from NSF grant CBET-1151590. W. G. is a HHMI International Student Research fellow. R. D. acknowledges financial support from the China Scholarship Council (CSC). B. J.-S. acknowledges support from the People Programme (Marie Curie Actions) of the EU 7th Framework Programme (FP7 2007-2013) under REA Grant PIOF-GA-2012-326476. The authors greatly thank Mr Yuri Fedorak for assistance with the preparation of figures.

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