Maximally efficient exchange in thin flow cells using density gradients

Published

October 25, 2024

Author(s)

Megan Mitchell, Charles Majkrzak, David Hoogerheide

Abstract

Flow cells are ubiquitous in laboratories and automated instrumentation and are crucial for ease of sample preparation, analyte addition, and buffer exchange. Often, the assumption that the fluids have exchanged completely in a flow cell is crucial to data interpretation. We describe the buoyancy effects on exchange of fluids with differing densities or viscosities in thin, circular flow cells. Depending on the direction of flow, fluid exchange varies from extremely efficient to drastically incomplete even after a large excess of exchange volume. Numerical solutions to the Navier-Stokes and Cahn-Hilliard equations match well to experimental observations, leading to quantitative predictions of the conditions under which buoyancy forces in thin flow cells are significant. We introduce a novel method for exchanging fluid cells by accounting for and utilizing buoyancy and viscosity effects that can be essential to obtain accurate results from measurements performed within closed-volume fluid environments.

Citation

Journal of Applied Crystallography

Volume

57

Issue

Part 5

Pub Type

Journals

Download Paper

https://doi.org/10.1107/S1600576724007283

Local Download

Keywords

neutron reflectometry, automated liquid handling, fluid flow, flow cell

Citation

Mitchell, M. , Majkrzak, C. and Hoogerheide, D. (2024), Maximally efficient exchange in thin flow cells using density gradients, Journal of Applied Crystallography, [online], https://doi.org/10.1107/S1600576724007283, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958029 (Accessed October 27, 2025)