A new methodology has been developed to measure the mechanical integrity of a bilayer lipid membrane (BLM) formed over porous substrates. A custom test fixture was fabricated in which a stepper motor linear actuator drives a piston in order to apply pressure to a BLM in very fine increments. The pressure, monitored with a pressure transducer, is observed to increase until the BLM reaches its failure pressure, and then drop. This experiment was performed on 1-Stearoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine (SOPC) lipid bilayers formed over porous polycarbonate substrates with various pore sizes ranging from 0.05 - 10 &mgr;m in diameter. A trend of increasing failure pressure with decreasing pore size was observed. The same set of experiments was repeated for BLMs that were formed from a mixture of SOPC and cholesterol (CHOL) at a cholesterol concentration of 50 mol%. The presence of cholesterol was found to increase the failure pressure of the BLMs by 1.5 times on average. A model of the characteristic pressure curve from this experiment was developed based on an initially closed fluid system in which pressure increases as it is loaded by a moving piston, and which upon reaching a critical failure pressure allows pressure to decrease as fluid escapes through a porous medium. Since the BLM is formed over many pores, this model assumes that the failure pressure for each micro-BLM follows a normal distribution over all pores. The model is able to accurately predict the major trends in the pressurization curves by curve-fitting a few statistical parameters.

Date Published: 25 April 2007
PDF: 12 pages
Proc. SPIE 6526, Behavior and Mechanics of Multifunctional and Composite Materials 2007, 652611 (25 April 2007); doi: 10.1117/12.715643

Published in SPIE Proceedings Vol. 6526:
Behavior and Mechanics of Multifunctional and Composite Materials 2007
Marcelo J. Dapino, Editor(s)