(84e) A MEMS Investigation of Osmotic Pressure-Driven Flows

Pore-scale transport is ubiquitous in contexts both technological (e.g., reverse osmosis, pervaperation, dialysis) and biological (e.g., transport across lipid bilayers and through transmembrane proteins). The pores of biological membranes (e.g., aquaporins) demonstrate the level of specificity, control, complexity and elegance that can be obtained through micro-scale engineering of the size, shape, and chemistry of pores. Though man-made membranes are becoming a successful and widely-used technology, methods for the rational design of transport at the pore-scale remain elusive. Hoping to discover methods of pore-scale engineering, I present a new silicon-based sensor – the microtensiometer – as a tool for elucidating principles of pore-scale engineering. This membrane-based, biomimetic microelectromechanical system (MEMS) is uniquely suited to aide in understanding pore-scale membrane transport due to its small size and rigid porous silicon membrane with known surface modification chemistries. I will give an overview of the design of the microtensiometer as well as relevant pore-scale theory. I will present in detail a first study into the response of the sensor to binary mixtures of non-charged solutes and water. I will discuss the microtensiometer’s unprecedented transient osmotic response and the useful information that can be extracted from these transients. This study represents a first step towards developing rational design techniques for tuning pore-scale transport.