Making Slides Hydrophobic and Dust Repellent

Coating with HMDS to make slides hydrophobic and dust repellent.

Silanisation of glass microscope slides using hexamethyldisil Azane (HMDS) can make slides hydrophobic dust repellent. Simply place the separated slides in a container like a wide mouth glass jar with an aluminium or Teflon lined cap. Add a few drops of HMDS and it will vaporise overnight in the sealed jar and react with the silanols on the surface. If the container is left slightly ajar in an oven at 70°C overnight, then any residual ammonia will also dissipate. Open the jar in a fume-hood and remove the slides. Due to a molecular (invisible) coating they will now be very hydrophobic, repel dust particles and bead water.

Products like Rainex® and Aquapels® also work but cannot be applied in the vapour state and a thicker, perhaps streaky film results. Please note that HexamethylsilOXane is NOT the same material. HMDS is simple, easy to apply, and safely handled.

Use gloves, a hood, and respirator when handling these materials. Let the dropper and the opened jar with HMDS evaporate overnight. Do not inhale any HMDS vapours! Read the MSDS information on handling. Despite these warnings I consider HMDS is a safer product than chlorosilane - which I have experienced to spontaneously explode.

From a Microscopy Listserver posting, with permission
from Paul Beauregard
Beauregard beaurega@westol.com