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Remotely powered self-propelling particles and micropumps based on miniature diodes

Abstract

Microsensors and micromachines that are capable of self-propulsion through fluids could revolutionize many aspects of technology. Few principles to propel such devices and supply them with energy are known. Here, we show that various types of miniature semiconductor diodes floating in water act as self-propelling particles when powered by an external alternating electric field. The millimetre-sized diodes rectify the voltage induced between their electrodes. The resulting particle-localized electro-osmotic flow propels them in the direction of either the cathode or the anode, depending on their surface charge. These rudimentary self-propelling devices can emit light or respond to light and could be controlled by internal logic. Diodes embedded in the walls of microfluidic channels provide locally distributed pumping or mixing functions powered by a global external field. The combined application of a.c. and d.c. fields in such devices allows decoupling of the velocity of the particles and the liquid and could be used for on-chip separations.

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Figure 1: Schematic diagrams of the experiments for measuring floating-diode velocity and diode pumping rate in a model microfluidic device.
Figure 2: Optical micrographs of self-propelling semiconductor ‘particles’.
Figure 3: Dependence of the diode velocity on the parameters controlling the electro-osmotic propellant force.
Figure 4: Flow of particle suspension in a microfluidic channel generated by two diodes embedded in the top and bottom sides of the channel, as observed from above.
Figure 5: Particle velocities at the centre of the long channel without diodes as a function of the magnitude of the a.c. and d.c. components of the external field.

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Acknowledgements

We acknowledge the Defense Advanced Research Projects Agency (DARPA/AFSOR) and NSF-CAREER (NCSU), NSF/NIRT and NSF/PREM DMR (UNM) and the EPSCR (UK) for support of this study.

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Correspondence to Orlin D. Velev.

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Supplementary information

Supplementary Information

Supplementary movie 1 - zoom moving diode (WMV 518 kb)

Supplementary Information

Supplementary movie 2 - diode small (WMV 753 kb)

Supplementary Information

Supplementary movie 3 - LED up down (WMV 596 kb)

Supplementary Information

Supplementary movie 4 - diode gear (WMV 1252 kb)

Supplementary Information

Supplementary movie 5 - LED gear (WMV 276 kb)

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Supplementary movie 6 - photodiode light control (WMV 1915 kb)

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Supplementary movie 7 - AC DC decoupling (WMV 1693 kb)

Supplementary Information

Movie details, supplementary figures and additional data (PDF 373 kb)

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Chang, S., Paunov, V., Petsev, D. et al. Remotely powered self-propelling particles and micropumps based on miniature diodes. Nature Mater 6, 235–240 (2007). https://doi.org/10.1038/nmat1843

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