Brownian Ratchets for Fractionation

During the past decade, membrane processes exist for most of the fluid separations encountered in industry. They are used for the purification, concentration, and fractionation of fluid mixtures. These processes can be classified based on the separation property of the process and on the membrane pore size.  The design of membrane separation processes, like all other processes, requires quantitative expressions relating material properties to separation performance but for high flux membranes, a fast accumulation and high concentration of non-permeating species near the membrane surface may seriously restrict the permeation and separation performance of the membrane and should be avoided.
In recent year, there has been increasing interest in the separation processes of various particles to fractionate macromolecules, DNA, proteins, etc such as Asymmetric Pinched Flow Fractionation, Field-Flow Fractionation, SPLITT-flow thin fractionation, Optical Tweezers ,Electrophoresis,  Deterministic Ratchet, etc.

The aim of this research project is to fractionate suspensions and colloidal solution by combining some of these methods. The principle of the ratchets is that geometric asymmetry in the ratchets is translated into asymmetry of the particle displacement. We expect that particles will be separated by Brownian motion, diffusion, hydrodynamic diffusion or deterministic lateral displacement (with possible addition of external electric field).

Fig.1 Simple device for separating small particles from a sample containing particles of various sizes.

Financial support by the Royal Thai Government and cooperation with MicroNed