Chapter 11 - Introducing ruber into the Langmuir-Blodgett technique

Abstract

The Langmuir–Blodgett (LB) technique offers the opportunity to generate suspended membranes by assembling a monolayer at the air–water interface and transferring it to cover a hole in a solid substrate. However, the preparation of suspended membranes via LB-transfer is generally more difficult than LB-transfer of thin organic coatings onto continuous smooth surfaces. Because it is not supported by an underlying substrate, the suspended membrane itself must be tough enough to withstand mechanical stress during fabrication and final use. Monolayers that are made from low-molecular-weight compounds or from liquid polymers easily rupture during transfer across a hole. Suspended membranes have been fabricated using glassy polymers, often stabilized by cross-linking. These membranes are usually rigid. For certain applications, like membranes in micro-mechanical valves and pumps, it might be advantageous to have elastomeric thin membranes available and to take advantage of the comparatively large reversible deformation of these materials. Tough and mechanically stable freely suspended membranes—spanning millimeter-sized holes in solid substrates—can be obtained from cross-linked monolayers of low Tg polymers with ionic head groups.