CHEMICALLY-DRIVEN TRANSPORT OF COLLOIDAL PARTICLES AND MOLECULES

Restricted (Penn State Only)
Author:
Guha, Rajarshi
Graduate Program:
Chemical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 13, 2017
Committee Members:
  • Darrell Velegol, Dissertation Advisor
  • Darrell Velegol, Committee Chair
  • Manish Kumar, Committee Member
  • Michael Anthony Hickner, Committee Member
  • Ayusman Sen, Outside Member
Keywords:
  • Chemically-driven transport
  • Diffusiophoresis
  • Diffusioosmosis
  • Reverse Osmosis
  • Membrane fouling
  • Catalytic Membrane
  • Metal oxide nanoparticles
  • Coffee ring
  • Surface patterning
  • Dye-sensitized solar cells
  • Methylated DNA detection
  • Molecular chemotaxis
  • Binding-unbinding
  • Molecular dyes
  • polymer gradients
  • microchannel
  • COMSOL modeling
  • Droplet evaporation modeling
  • Coffee ring number
  • Polystyrene particles
  • Chemotaxis index
Abstract:
Chemically-driven transports are ubiquitous in nature and govern the working principles of several biochemical processes. Understading the mechanisms involved in such transport processes would enable us to answer and potentially solve many problems in separation, diagnostics, energy, electronics and communications. In this dissertation, I primarily addressed chemically-driven transports which arise from artificial and natural concentration gradients. The two major chemically-driven transports discussed in this dissertation are electrokinetic transport and molecular chemotaxis. Diffusiophoresis and diffusioosmosis are electrokinetic flows of colloidal particles and fluids respectively, which result from interaction of ionic concentration gradients with charged surfaces. Molecular chemotaxis, on the other hand, is solely driven by chemical potential gradients and dictated by the binding affinity between two molecules. High pressure reverse osmosis membrane separation peocesses are limited by fouling phenomena which limit the process efficiency and result in frequent shutdowns. This problem was addressed first by identifying diffusiophoresis as one of the leading mechnaisms of colloidal fouling in reverse osmosis systems and then a scalable solution was proposed by modifying the membrane surface with catalytic activity. Diffusiophoresis and diffusioosmosis mechanisms were also found to exist in an evaporating droplet with salt and colloidal particles, which result in spatio-temporal modulation of deposited patterns. These electrokinetic mechasims associated with droplet evaporation were successfully used to develop novel particle separation, cancer diagnosis and energy efficient solar cell fabrication. Finally, molecular chemotaxis mechanism of dyes in concentration gradients of neutral polymers was investigated. It was found that hydropobic attraction and charge-dipole interaction between dye and polymer molecules were active mechanism responsible for chemotaxis in microfluidics and dialysis systems. Understanding this phenomenon would enable us to develop novel molecular separation techniques and to build programmable devises implementing chemotactic logic gates.