(109c) Control of Microscopic Liquid Flow with Amphiphilic Fabrics

Abstract

Large-scale liquid–liquid extractions are used commonly during crude oil refinement, pharmaceutical production, and wastewater treatment.  The efficiency of these extractions is determined by the size of the contact area between two immiscible liquid phases (larger is better), as well as the diffusion of solute from the bulk of each liquid to the liquid-liquid interface (faster diffusion being the goal). Industrially, costly liquid contacting columns are integrated with dispersion devices (e.g. sieve trays, mixer paddles, rotating disks) to achieve efficient extractions. Additionally, large solvent volumes are required. However, the factors needed to provide for efficient liquid-liquid extractions can also be met by microfluidic flow. Unfortunately, current microfluidic structures can only be manufactured on small scales. This research suggests that fabrics provide channels for fluid flow with the same micron-sized length scales as microfluidic structures, but they have the distinct advantage that textile manufacturing processes are not limited to small scales. By using fabrics to carry out chemical processes, the benefits of microfluidic devices (i.e. high surface-area-to-volume ratios, strong substrate-fluid interactions for control over bulk motion of fluids, and dominant diffusive forces) can be extended to large-scale liquid-liquid extractions.  Wicking fluids into fabrics with amphiphilic surface properties could allow for microfluidic flow between two immiscible phases throughout the large surface area of the fabric. Thus, faster, more efficient extractions using smaller hazardous waste reagent volumes could potentially be achieved. Fabric samples were carefully designed with systematically varied patterns of yarns with hydrophilic and hydrophobic surface chemistries, in order to investigate the mechanisms of fluid flow.  Results show that simultaneous wicking of organic and aqueous liquids into these fabrics promotes parallel flow of immiscible phases. These amphiphilic fabrics can selectively transport water along their hydrophilic channels and water flow paths can be controlled through fabric design. The ultimate goal of this work is to quantify parallel flow of aqueous and organic liquids in amphiphilic fabrics and then use these fabrics as microfluidic contactors for improved efficiency and reduction of solvent volumes in large-scale liquid-liquid extractions.