Adaptive pores in next generation membranes

In this thesis a novel class of polymeric membranes known as slippery liquid-infused membranes are studied. In these membranes pores are filled with an infusion liquid which is typically an oil. The chemical compatibility between the oil and the membrane material is a requisite to ensure high affinity between these two. Once this criteria is satisfied, the infusion liquid spontaneously infiltrates the surface structure/pores and forms a smooth lubrication layer on the surface. This lubrication layer gives important features to these materials such as, low water contact angle hysteresis, self-healing and repelling a variety of liquids. Liquid-infused pores act like a gate that can open and close in response to the system pressure, thus called “Adaptive pores”. Once appropriate pressure is applied, certain species can be transferred through the pores while others are being retained. This is called gating capability which can be used for efficient sorting of immiscible fluids from a mixture in separation applications. After a general introduction in chapter 1, characterization, fabrication and gating mechanism of these membrane are studied in chapter 2. The oil retention inside the pores at high flux of permeating fluid (water) is investigated in chapter 3. Chapter 4 covers the application of these membrane for oil permeation from oil-in-water emulsions which requires movement of oil droplets towards the membrane. This is achieved here by gravity-driven creaming in dead-end filtration mode. The anti-biofouling performance is further studied in chapter 5 via long-term cross flow filtration. As an alternative technique for movement of oil droplets towards the membrane surface, an external field such as acoustic can be applied. The behavior of oil droplets in such field is investigated through a microfluidic study in chapter 6. Permeability is an important transport property of any porous media, including membranes. Numerical prediction of permeability suggest a universal scaling power-law for normalized permeability. This is experimentally validated via microfluidic experiments in chapter 7. The overall overview to the work together with reflections and perspectives are presented in chapter 8. The idea of gravity-driven oil permeation through the membranes is discussed in crossflow filtration mode at low oil concentrations.

Original promotion date was May 20, 2020 (COVID-19)