A pure solid PTFE (polytetrafluoroethylene) has been selected as a trough material for all KSV series of Langmuir-Blodgett instruments because it is inert, highly hydrophobic and easy to clean. All troughs are form sintered solid PTFE. The dipping wells are integrated with no glue nor silicon O-rings.

KSV troughs are thermostated by circulating water or refrigerant through channels inside the aluminium base plate onto which the trough is mounted. The thickness of the PTFE trough bottom is 1.5 mm providing minimum temperature exchange resistance. Aluminium base plate, being a good conductor, distributes energy evenly throughout the whole bottom area of the trough and responds rapidly and accurately to the temperature changes. 

All troughs are independent units from the main construction of the instrument and can be easily removed by simply lifting. No tools or disassembling is needed. All sharp angles are rounded for easy access for cleaning

The troughs can be equipped with inert gas chambers making possible depositions of materials in controlled environments e.g. oxygen free atmosphere.

Stirrers can be attached to the troughs as well as temperature, pH and surface potential measuring devices.

Special troughs to fit to customers specific applications are made without additional cost. The maximum surface area without additional modification and cost is limited to 1500 cm square. For more on special troughs click here.

 Surface barriers

Hydrophilic Delrin (polyacetal) has been selected for a surface barrier material for all KSV troughs (although teflon barriers are available). Especially when one is experimenting high surface pressures the advantages of using a hydrophilic surface barrier can clearly be seen.

In order to avoid the film leakage over the edges of the trough the surface level of the subphase should be kept as low as possible. With low surface pressures this causes no problems either with hydrophilic or hydrophobic surface barriers (see figure 1.).

                                          hydrophilic barrier                      hydrophobic barrier

                                           Figure 1. Film behavior with low pressures

With high surface pressures, however, the high pressure forces the polar, hydrophilic ends of the molecules against the hydrophobic barrier and the film starts to slide under the barrier. With hydrophilic barrier the polar ends of the molecules stick to the barrier surface and no sliding will occur.

                                             hydrophilic barrier            hydrophobic barrier

                                              Figure 2. Film behavior with high pressures

Symmetric compression

The film compression in all KSV LB-Systems is symmetric by two inwardly moving barriers and the dipping is done in the center of the trough. This feature offers several advantages over the traditional single-barrier film compression systems.

Symmetric compression causes minimal film flow, increasing the accuracy of the film pressure measurement. The Wilhelmy plate is evenly compressed from both sides and no shifting along with the film flow will occur even with most condensed films.

Since the dipping of the substrate is performed at the center of the film compression where the monolayer reaches its highest uniformity the orientation of the film is maintained unchanged during the transfer from air/water interface onto the substrate. Both sides of the substrates are evenly coated and no back drag encountered with single barrier systems will occur. In addition, possible parabolic film flow pattern (center moving faster than sides) often causing major distortion with single barrier systems is minimized due to the symmetric compression.

Film compression with two barriers also results in the relative barrier speeds to drop to half of that of one barrier systems. Reduced barrier speed reduces shear resistance, an important factor when experimenting with fragile and condensed films. 

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