Wetting the membrane is an important first step in preparing your filter. Wetting the membrane pores eliminates dry pathways where contaminants, like particles, gels, or bubbles could pass through, resulting in high defect levels in your process. Polymer membranes are natively hydrophobic or hydrophilic.
- Hydrophobic – having a natural aversion to water
- Hydrophilic – having a natural affinity to water
If a membrane is hydrophobic, it is difficult to wet with water. This results in a high contact angle, or a very round bead of water sitting on top of the membrane. If a membrane is hydrophilic, it is easily wet with water, and the water will penetrate the pores of the membrane.
This phenomenon directly relates to the surface tension of the liquid and the surface energy of the membrane. In the case of hydrophobic membranes, the surface tension of water is much higher than the surface energy of the membrane. To overcome this phenomenon, a lower surface tension fluid, like IPA (isopropyl alcohol), can be used to wet the membrane.
Watch as Dr. Aiwen Wu, senior applications engineer, demonstrates the different wettability of various polymer membranes when exposed to DI (deionized) water and IPA. He also explains how the use of surface modification technology can alter wettability to enhance liquid filtration performance in specific applications.
Keep an eye out for the next blog where Dr. Wu describes how filter membranes can maintain wettability, even when confronted by outgassing chemistries.
Related: The Lithographer's Toolkit
