Collaborative Research: Electrokinetic Transport and Separation in MEMS-fabricated Nanofluidic Channels

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1402736Pennathur/GillespieUCSB/Rush Pres St Luke Med CtrThis project aims to investigate novel separation mechanisms that exist in nanofluidic devices. In such nanochannels, a sample of solution is moved down a slit with two walls that are 10 to 100 nanometers apart. In nanoscale electrokinetic channels, molecules not only interact with each other, but also with the charged walls of the device, to the point that these solid/liquid interface interactions dominate the performance of the device. This project tests whether specially-fabricated nanochannels and novel buffer electrolyte solutions can greatly enhance separation of two similar analyte ions. Specifically, this project aims to embed electrodes in the walls to directly manipulate the wall charge and therefore the relative speed of the analytes. The fabrication technique embeds electrodes into the walls and can produce slit heights of 10 nm. The novel buffer ions will vary in size from small to large and charge from +1 to +3. This project aims to investigate new separation techniques based on nanofluidic ion transport at high surface charge, high ion valence, and confining channels using a synergistic collaboration between theory and experiment. Specifically, experiments will be used to validate a model based on classical (not quantum) density functional theory of fluids. Then, the model will be used to predict new separation mechanisms because exploring the large parameter set by numerical modeling is orders of magnitude faster than using hardware in the lab. Potential mechanisms discovered will be then be validated in the lab and the theory used to understand the physics of separation. This project has the potential to show the full range of what is possible for nanochannel-based separations. Specifically, the fundamental properties of the nanofluidic channels will be explored to define how the electrical double layer can be harnessed for ion transport and analyte separation. If successful, this project will, for the first time, systematically measure how changing surface charge and ion properties like size and valence define the double layer and transport/separation properties. This new basic knowledge will not only be applicable to separation science and engineering, but to any area of physics, chemistry, and biology where electrical double layers play a role. For example, the new physical insights can be applied to heavy metal processing, environmental monitoring, energy conversion, desalination, batteries, and electrochemical supercapacitors to increase their efficiency and possibly lead to new designs. Proposed outreach activities include development of course materials, international activities and high school student outreach. All are well described and appear achievable.