CBES Investigators

Igal Szleifer

Rikkert Nap

Research Assistant Professor
Biomedical Engineering

Luis Gonzalo Lopez

Postdoctoral Fellow
Chemistry

Research Overview

The Szleifer group is interested in understanding and designing transport of molecules and ions through synthetic nanopores and nanochannels. For this purpose, we seek inspiration in biological ion channels, ion pumps and nuclear pore complexes. These bionanomachines have attained, through millions of years of evolution, transport selectivities that are unrivalled by man-made devices. In order to mimic biology and improve transport selectivity, directionality and responsiveness, we propose to modify synthetic solid-state nanopores and nanochannels by stimuli-responsive functional soft materials. We theoretically study these nanochannels and nanopores, develop new theories to describe ion transport through them and collaborate with experimental groups to test our predictions and implement our designs, thus achieving the synergistic experimental-theoretical approach that is required by the complexity of the problem.

The image shows a schematic of a nanopore connecting two reservoirs. The inner surfaces of the nanopore are modified by positively charged polymer chains (orange chains). The positive charges on this polymer chain repel positive ions from the pore and attract negative ions into the pore. The pore of the figure, therefore, selectively transports the negative ions and blocks the positive ones.

Our current CBES effort is focused on electrochemically-gated nanochannels and nanopores. We aim to design nanochannels where the flow of ions can be controlled by switching the redox state of molecules grafted to the inner walls of the channel. This design is advantageous since the redox state can be externally controlled by applying a potential to the nanochannel membrane. The redox state of the molecules affects transport because molecules in different oxidation states have different charge and hydrophobicity, which affect differently the flow of ions through the channel.  In a second stage, we want to analyze the situation where the electrochemical switching of the redox molecules is performed very fast, which will lead to interesting out-of-equilibrium transport effects, such as ion ratcheting.