Electronic desalting for controlling the ionic environment in droplet-based biosensing platforms

Vikhram Vilasur Swaminathan, Piyush Dak, Bobby Reddy, Eric Salm, Carlos Duarte-Guevara, Yu Zhong, Andrew Fischer, Yi Shao Liu, Muhammad A. Alam, Rashid Bashir

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Abstract

The ability to control the ionic environment in saline waters and aqueous electrolytes is useful for desalination as well as electronic biosensing. We demonstrate a method of electronic desalting at micro-scale through on-chip micro electrodes. We show that, while desalting is limited in bulk solutions with unlimited availability of salts, significant desalting of ≥1 mM solutions can be achieved in sub-nanoliter volume droplets with diameters of ∼250 μm. Within these droplets, by using platinum-black microelectrodes and electrochemical surface treatments, we can enhance the electrode surface area to achieve >99% and 41% salt removal in 1 mM and 10 mM salt concentrations, respectively. Through self-consistent simulations and experimental measurements, we demonstrate that conventional double-layer theory over-predicts the desalting capacity and, hence, cannot be used to model systems that are mass limited or undergoing significant salt removal from the bulk. Our results will provide a better understanding of capacitive desalination, as well as a method for salt manipulation in high-throughput droplet-based microfluidic sensing platforms.

Original languageEnglish (US)
Article number053105
JournalApplied Physics Letters
Volume106
Issue number5
DOIs
StatePublished - Feb 2 2015

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Swaminathan, V. V., Dak, P., Reddy, B., Salm, E., Duarte-Guevara, C., Zhong, Y., Fischer, A., Liu, Y. S., Alam, M. A., & Bashir, R. (2015). Electronic desalting for controlling the ionic environment in droplet-based biosensing platforms. Applied Physics Letters, 106(5), [053105]. https://doi.org/10.1063/1.4907351