# Hydraulic Permeability

The hydraulic permeability of a membrane is the inverse of the fluid resistance normalized to the membrane area.

Experimentally it is found with

# $latex \epsilon = \frac{Q}{\Delta P \, A_m}$

Where Q is the measured flow rate, $latex \Delta P$ is the pressure drop across the membrane and $latex A_m$ is the membrane area.

It can be calculated from membrane properties with

# $latex \epsilon = \frac{\phi }{A_p \, R_f }$

Where $latex R_f$ is the fluid resistance of a pore (Hagen Pousille or Dagen), $latex A_p$ is the area of a pore and $latex \phi$ is the porosity.

About

Professor McGrath holds a BS degree in Mechanical Engineering from Arizona State and a MS degree in Mechanical Engineering from MIT. He earned a PhD in Biological Engineering from Harvard/MIT's Division of Health Sciences and Technology. He then trained as a Distinguished Post-doctoral Fellow in the Department of Biomedical Engineering at the Johns Hopkins University. Professor McGrath has been on the Biomedical Engineering faculty at the University of Rochester since 2001 where he also serves as the director of the graduate program BME and associate director of the URNano microfab and metrology core. McGrath's research was focused on the phenomena of cell migration until 2007 when he founded the interdisciplinary Nanomembrane Research Group to development and apply silicon membrane technologies. Professor McGrath is also a co-founder and past president of SiMPore Inc., a company founded to commercially manufacture silicon membranes and related technologies.