(161e) Controlling Ionic and Water Transport Through Nanopores: Ionic Diodes, Ionic Transistors and Water Valves

Transport through nanopores has attracted scientific interest of researchers from various fields. Nanopores play a major role in contemporary biotechnology, because many separation and sensing processes require pores with nanometer-sized openings. Transport through pores and channels exists in virtually all biological cells and is important in such things as the regulation of heart function, nerve signals, and delivery of nutrients to the cell. My scientific interests have been focused on fabricating synthetic nanopores as small as 2 nm in diameter in order to elucidate interactions of ions and molecules with the pore structure. By increasing our understanding of these interactions we are able to develop a wide range of applications in ionic electronics for nanofluidic, lab-on-the-chip, and sensing systems. We apply these nanopores as (i) devices for controlling the flow of ions and molecules in a solution e.g. ionic diodes and transistors [1,2,3], (ii) biosensors, and (iii) valves for water [4]. Ionic diodes that we prepare consist of nanopores containing a junction between a zone with positive surface charges and a zone with negative surface charges, and offer rectification degrees of several hundreds [1,3]. Comparison of ionic diodes with pn junctions will be presented as well. Water valves use hydrophobic interactions on the nanoscale and the effect of reversible evaporation and condensation of water in hydrophobic nanopores [4].

1. I. Vlassiouk, Z. Siwy, Nanofluidic diode. Nano Letters 7, 552-556 (2007).
2. E. Kalman, I. Vlassiouk, Z. Siwy. Nanofluidic bipolar transistor. Advanced Materials 20, 293-297 (2008).
3. Z.S. Siwy, S. Howorka. Engineered Voltage-Responsive Nanopores. Chemical Society Reviews. 39, 1115-1132 (2010).
4. M.R. Powell, L. Cleary, M. Davenport, K.J. Shea, Z.S. Siwy. Electric-field-induced wetting and dewetting in single hydrophobic nanopores. Nature Nanotechnology 6, 798-802 (2011).