Microcomputer-Controlled Langmuir-Blodgett Dipping Trough.
Abstract
The lack of an inexpensive, commercial Langmuir-Blodgett film-deposition trough prompted us to build our own for the deposition of fatty-acid salts and tailor-made photochemically active agents upon a number of substrates. The films are characterized by their pressure-area isotherms, which are recorded by monitoring the film's surface pressure while compressing the surface area. Dipping requires slow immersion and removal of a substrate while continuously maintaining a preset surface pressure. Both of these tasks can be accomplished under microcomputer control. The software, run on an Apple II, is written in FORTH, allowing full, interactive control of dipping. The Apple controls a dc stepping motor, which compresses the film surface, while simultaneously monitoring a Cahn microbalance which reports surface pressure on a Wilhelmy plate. Pressure-area isotherms, standardized in molecular units of square angstroms, are displayed on the Apple screen and can also be stored or plotted. The deposition substrate is mounted on a dipping arm driven by an ac motor. When dipping a sample, the Apple maintains the optimal surface pressure(as read from the isotherm), 0-100(+ or - 0.1) dyne 1/cm, throughout the deposition process, allowing multilayer structures to be built automatically. The dipping rate is variable, allowing for slow deposition of initial layers and proceeding to faster deposition for subsequent layers. Finally, the Apple monitors the change in film area during dipping, to ensure full film uptake.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1985
- Accession Number
- ADA173772
Entities
People
- Arthur B. Ellis
- Hal Van Ryswyk
- Joann M. Eisenhart
- Nils Blom