||1 – Frame
2 – Barriers
3 – Trough top
4 – Surface pressure sensor
5 – Dipping mechanism (LB option)
6 – Interface Unit
All troughs are precision machined from virgin PTFE (poly-tetra-fluoro-ethylene - or 'Teflon' ® DuPont). PTFE is the most inert material available and is universally accepted as being ideal for Langmuir-Blodgett troughs. It is resistant to all strong acids and is extremely hydrophobic. It does not contaminate the subphase - neither with surfactants (surface active agents) nor mineral ions. Other polymers can contaminate the subphase with surfactants, while glass will leach out mineral ions. Keeping PTFE clean is also very simple - a good wipe with a surfactant-free tissue soaked in chloroform will suffice for most applications. Other materials used in trough construction (but not in contact with the subphase) are 316 stainless steel, 6063 and 6082 aluminum (anodised for protection from oxidation) and 'Delrin'®, a DuPont polymer, which is both mechanically strong and resistant to chemical attack.
Trough Construction - Top and Frame
The complete assembly consists of a trough top resting on a frame. The top is simply lifted off the frame and then taken to a fume hood for cleaning. Different trough tops can be fitted to the same frame for different applications. The trough top consists of a precision machined PTFE block bonded to an aluminum support plate. This design lends considerable mechanical rigidity to the PTFE and prevents it from warping when exposed to temperature gradients. The trough is designed to give the perfect compromise between minimising the subphase volume (which improves temperature control and reduces consumption of ultra-pure water) and keeping a sufficient volume to prevent the need for constant re-filling. So, the trough can be filled exactly level to the rim which prevents any errors in area calculation arising from meniscus curvature. In practice, it is usually overfilled initially and then the surface is cleaned by removal of the top layer. The barriers and surface pressure sensor can be simply lifted off the trough - so that access to the trough is completed unrestricted for cleaning purposes. An overflow channel is also machined into the trough periphery to prevent minor spillages from dribbling down the side of the trough. This also allows controlled overfilling of the trough with a solvent for cleaning purposes - again without the risk of spillages.
Removable/exchangeable trough tops,even with different frames
All KSV NIMA troughs have a removable PTFE trough top as standard. This design allows users to remove the trough top from the trough base and clean it in a separate environment of their choosing. Different trough tops can also be used interchangeably on the same frame. For example one top can be made for monolayer compression only and another one specifically for deposition of Langmuir-Blodgett films. One good feature of the KSV NIMA trough/frame design is you can always use the smaller troughs on the larger frame size making the system highly configurable.
KSV NIMA use hydrophilic Delrin barriers that prevent leakage under the barrier during compression. The Delrin barriers are held in position which ensures a good seal between the trough and barriers and prevents leakages of monolayer. The barriers are easy to remove and can be cleaned thoroughly - away from the trough under a fume hood. The Delrin barriers are used for enhanced monolayer stability. We can provide barriers made from PTFE should your require them.
In order to achieve good dynamic properties, the barrier and its drive mechanism have been designed to have a minimum of inertia and friction. The barriers run on a precision linear rail and are driven by a toothed belt. This ensures low friction and slip-free positioning. The belt is driven by a low inertia motor through a high torque reduction gearbox, which ensures good low speed running. This combination of high torque and low friction ensures excellent pressure control. In fact, this design is so good, that it is easy to hold surface pressure constant to better than 0.1mN/m even in the steepest (liquid condensed phase).
Surface pressure sensor
The surface pressure is monitored by a highly sensitive balance measuring the force exerted on a Wilhelmy plate which is suspended across either the air-liquid or liquid-liquid interface. The surface pressure sensor has a measuring range up to 150mN/m with a resolution of 4µN/m. The surface pressure sensor can easily support either paper or Platinum Wilhelmy plates.
All KSV NIMA troughs have an open design that makes it easily accessible for other instruments. They can be used in almost any desired location and with many different kinds of other sensors and instrumentation. For example, they can be used for Brewster Angle Microscopy or grazing angle incidence of neutron beam or x-rays. Another popular option is a surface potential sensor and simultaneous isotherms of pressure and potential can be plotted in the software. KSV NIMA ISR and KSV NIMA PM-IRRAS can also be used together with a KSV NIMA trough.
All sensors, barriers and dippers are easily lifted off the trough top for easy access during cleaning. All inside edges and corners of the troughs have radii so that no dirt traps exist. The trough has an overflow channel machined completely around the main area of subphase, which prevent minor spillages and allows 'overfilling' for cleaning purposes. Barriers can be closed down to very low minimum areas to facilitate the removal of monolayer from the subphase surface.
The trough has channels within the aluminum support plate, through which allows the circulation of temperature controlled water from an external water bath (available separately). It should be noted though that to prevent temperature gradients across the air-water interface, a proper temperature controlled cabinet is required (also available separately).
The KSV NIMA Interface Unit is used for all KSV NIMA LB devices and Dip Coaters. The Interface Unit features an easy to read digital display and spill-proof and intuitive touch pad, USB data connection to allow simple connection to all modern computers, pH-probe attachment, temperature control (including probe) and stirrer control. It is also possible to attach an additional analogue voltage device, +/-10V, for special applications.
Specifications and appearance are subject to change without prior notice. Biolin Scientific shall not be liable for any errors in this document.