Measurement Strategy

The FTÅ200 is a "what you see is what you get" instrument. The action appears live on the computer screen and the salient images are captured to the computer's memory for later image analysis. The time scale can vary from 1/60 second (60 images/second) to hours and can be varied nonlinearly to efficiently follow absorptions. The system can capture both static and dynamic behavior of liquid interactions. Analysis is based on the drop shape's size and shape, and data can be plotted with built in graphing facilities or exported to standard database and spreadsheet programs. Being a Windows program, it is easy to transfer data and images to other applications and across networks.

The system functions as a transient analyzer, meaning it continually captures images and can recall any number of past images after a trigger event. A variety of dynamic events can furnish the trigger. One such trigger is real-time software detection of the drop detaching from the dispense tip. The automatic syringe pump, a timer, and user input, can also furnish triggers.

Completely automatic image analysis is available, but manual and partially automatic modes are provided to accommodate difficult images Explicit graphics show the operator where the automatic algorithms found the drop and specimen edges. The analysis will function on true grayscale images which show sample detail, as opposed to only silhouette style images.

 

Accuracy

In most cases, the standard deviation for contact angle measurements will be less than 1 degree and standard deviation for surface tensions less than 0.5 mN/m. Actual results will vary with sample preparation, image focus, and isolation from vibration and air currents. Useful resolution is 0.1 units in both cases.

 

Analysis Functions

The software can measure or calculate many quantities of interest from the drop shape including:

• Static or equilibrium contact angle

• Capillary contact angle

• Advancing contact angle

• Receding contact angle

• Pendant drop surface tension

• Pendant drop interfacial tension

• Drop volume interfacial tension

• Sessile drop surface tension

• Sessile drop spreading

• Sessile drop adsorption

• Surface energy from contact angles

• Work of adhesion/adhesion tension

• Critical micelle concentration

• Zisman critical wetting tension

Many of these are available as functions of time, that is, they are dynamic measurements. For a complete description of the many methods possible, see the FTA technical paperFTÅ200 Measurement Capabilities.

 

Hardware

The system consists of a measurement platform and a frame grabber (video capture) card running in a personal computer. The computer may be user-furnished, requiring a PCI bus, or turnkey systems are available. The system can be configured in many ways, which is part of the power of the FTA200 solution. This is a toolkit for the surface scientist and readily adapts to new configurations. The standard FTÅ200 hardware includes:

• High resolution camera and zoom microscope

• PCI frame grabber card (computer optional)

• Computer controlled syringe pump

• Adjustable specimen stage

• Computer controlled lighting

Large specimens and nonflat specimens can be accommodated and a variety of special lens are available.

 

Software

The software will run on Windows 98SE/ME/NT/2000/XP. On-line operator's manual and Help file are included. Software updates and upgrades are furnished without charge to users. Software licenses are sitewide, meaning the software may run on any number of the owner's computers.

 

Optional Equipment

• Environmental Chamber, heated to 300C, internal stage moves along axis

• Large Chamber, circulating bath stabilized, 3 axes of stage motion

• Interfacial Tension Chamber, circulating bath stabilized, pressurizable

• Motorized Stage and Mapping Software

• Syringe Heater

• Tilt Stage

• 360 Frames Per Second Camera

• Auto Zoom/Auto Focus Microscope

• Complete PC with pre-installed software