A capillary method to measure water transmission through polyurethane membranes

Area of Science:

• Biomaterials Science
• Medical Device Engineering
• Polymer Science

Background:

• Polyurethane membranes are crucial components in artificial heart ventricles.
• Accurate measurement of water transmission is vital for device performance and longevity.
• Existing methods may not fully capture the nuances of water transport in these membranes.

Purpose of the Study:

• To develop and validate a novel capillary method for quantifying water transmission rates through polyurethane membranes.
• To investigate the relationship between membrane thickness and water vapor transmission.
• To understand the dominant transport mechanism (diffusion vs. convection) of water through these membranes.

Main Methods:

• A leak-proof sample chamber system was designed to contain water.
• A glass capillary flow meter was employed to monitor water volume loss.
• Continuous dry air ventilation in the receiver compartment ensured controlled conditions.
• Water vapor transmission rates were measured across a range of polyurethane membrane thicknesses.

Main Results:

• The developed capillary method successfully measured water transmission rates.
• Water transmission rate was found to be inversely proportional to membrane thickness.
• Measured water vapor transmission rates varied from 7.53 x 10(-8) to 2.76 x 10(-8) mol/s cm2 for thicknesses of 0.09 mm to 0.34 mm.
• Water vapor concentration in the receiver had a minimal effect within a 50-200 mmHg pressure range.

Conclusions:

• The developed capillary method provides a reliable means to assess water transmission in polyurethane membranes.
• Water transport through these membranes is primarily governed by diffusion, not bulk convection.
• These findings have implications for the design and optimization of artificial heart devices.