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August 2006

Drop Shape Analysis System
This article focuses on the hardware and software components used in the system to collect data for the Absorption and Surface Elastic Properties of Corresponding Fluorinated and Nonflourinated Cationic Polymer Films Measured by Drop Shape Analysis, a paper submitted to Langmuir (2001, 17, 5256-5264) by Drs. Tomas Fromyr and Finn Knut Hansen of the University of Oslo (Norway) and A. Kotzev and Andre Laschewsky of the Université Catholique de Louvain (Belgium). This paper (LA001407K) is available from the American Chemical Society.

The abstract reads as follows:

Two different types of cationic polysoaps together with their monomers were synthesized with divalent quaternary ammonium repeat units carrying a hydrocarbon side chain, respectively. Dynamic surface tensions and surface dialational rheology were measured by means of drop shape analysis of a sessile bubble, using specially developed hardware and software (outlined below). Surface dilatational rheology was measured by the oscillating bubble method. Both the monomers and polymers show strong surface activity. The hydrocarbon monomer shows a maximum surface pressure, 28 and 47 mN m-1 and for the hydrocarbon and fluorocarbon polymers, respectively. The fluorinated polymer has peculiar absorption characteristics, especially at low concentrations. All substances have very high surface dilational elasticity, up to 180 nM m-1 for the flourinated polymer, while the hydrocarbon substances give approximately half of this value. The specific surface areas are relatively high, and absorption of all these substances is considerably slower than for ordinary surfactants, probably due to their particularly bulky headgroup and charged nature. The monomers form micelles with cmcs of 0.3 and of 3.0-1 g L for the fluorinated and hydrocarbon monomer, respectively. With increasing bulk concentration, a maximum in surface elasticity is observed for the monomers, but this decreased to almost zero at high concentrations. Both this decrease and the most of the frequency dependence of the modules are believed to be caused by molecular transport between surface and the bulk. It is more pronounced for the monomers than for the polymers. Deviations from the transport theory are observed and are believed to be caused by in-surface relaxation processes.

This article will focus on the system and components used to undertake the data collection required for the above-referenced paper and study. Particular interest will be made in outlining the current products available from ramé-hart instrument co. that could be used for such a task.

The diagram above illustrates the major components used in the study with the heart of the system consisting of the ramé-hart Model 500 Goniometer. This instrument includes a base rack with leveling control, the PC and LCD with DROPimage Advanced 2.0 software. The camera communicates with the PC via a FireWire connection (F1 Series) at speeds up to 60 fps. (Older systems relied on a proprietary Frame Grabber Card and were limited to speeds up to 30 fps.) The Model 500 also includes the Fiber Optic Illuminator and corresponding backlighting subsystem. The 3-axis stage features both fine and course vertical adjustment and a leveling stage. The DROPimage software allows the user to measure surface tension via the axisymmetric drop shape method.

Mounted on the stage is the optional Environmental Chamber (p/n 100-07) with two quartz windows. This option allows the user to control the working environment. Coupled with the optional Proportional Temperature Controller (p/n 100-50), the temperature of the chamber can be controlled between ambient room temperature and 300°C. Cooling the chamber rapidly can accomplished by passing a refrigerant through the cooling ports. Temperatures below room temperature can be achieved and monitored although only heat-induced temperatures are controlled by the temperature controller.

The Automated Dispensing System, p/n 100-22-100, is an indispensable option which can be used not only for increasing the accuracy of the drop volume, but is also capable of performing dynamic studies wherein the volume of the drop is increased and decreased while readings are being taken.

Shown in the diagram above is also an Oscillator. The DROPimage Advanced software supports an in-line oscillator and we are currently in the process or redesigning this hardware. The oscillation is required in this study to measure the surface dilatational viscoelastic properties and dynamic surface tensions using a combination of the oscillating bubble and drop shape analysis methods.

In order to perform advancing / receding studies, the optional Tilting Base (p/n 100-06, not shown in diagram above) could be added to the system. The Tilting Base provides an accurate tilt from 0° to 180° allowing the user to measure left and right contact angle as the instrument and stage rotates and to determine the roll-off angle. 

In addition to the functions outlined in the study and above, the above configuration is also very useful for surface energy studies. The DROPimage Advanced software includes the Contact Angle measurement tool included with all versions of DROPimage along with a suite of tools for measuring Surface Energy. These include: the Acid-Base Tool, the (multi-liquid) Surface Energy Tool, Work of Adhesion Tool, Zisman's Plot Tool, a Solid-Liquid-Liquid Surface Energy Tool, and the new One-Liquid Surface Energy Tool.

If you have any particular interest in either the instrument setup or the referenced paper, please contact us for amplified details.

Software Upgrades
One of the most cost-effective upgrades available for users of ramé-hart goniometers is a software upgrade.

For those that may still be using our first-generation Windows program RHI, be advised that this product has been discontinued and replaced with our current DROPimage product. We have a cost-effective upgrade path that will allow you to use your existing hardware and frame grabber.

DROPimage is available in three flavors: DROPimage CA, which ships with our Model 120; DROPimage Standard, which ships with our Models 200 and 300; and DROPimage Advanced, which ships with our Models 250 and 500. CA offers Contact Angle Measurement Tools. Standard offers CA measurement as well as Surface Energy Tools. Advanced includes - in addition to CA and SE tools - surface and interfacial tension tools. Advanced is methods-based and also has an experiment wizard, session control, reporting and graphing tools, and is backward compatible with files created in RHI and all versions of DROPimage. DROPimage Standard and DROPimage Advanced both have integrated support for the Automated Dispensing; DROPimage CA does not.

Users of DROPimage CA (120) can upgrade to DROPimage Standard or DROPimage Advanced. Users of DROPimage Standard (200 and 300) can upgrade to Advanced. Special pricing is available to those upgrading from previous versions of DROPimage and RHI.

If you are thinking of upgrading your DROPimage or legacy software, require more information, or a quotation, please contact us

Thank you for your continued confidence and business. We work hard to earn your business and will continue to lengthen our stride to maintain our position as the world leader in contact angle and surface science tools. 


Carl Clegg
Director of Sales
Phone 973-448-0305
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