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Fig. 5. Example of a flow cell used in a TIRE system for studies of protein adsorption. An half-cylindrical prism is shown here as an example prism magnets stirring motor

Fig. 5. Example of a flow cell used in a TIRE system for studies of protein adsorption. An half-cylindrical prism is shown here as an example supported flow control system, either separate from or built into the data-acquisition software of the ellipsometer. Additional stirring in the cell can be achieved with the aid of a magnet rotated by an external motor, as shown in Fig. 5.

The measurement in a TIRE setup is performed with an ellipsometer. In most cases it is the most advanced (and expensive) part of the setup. TIRE can be performed with virtually any type of ellipsometer, either specially designed for the specific application or with a commercially available multipurpose ellipsometer. There are several types of ellipsometers available on the market today. They vary from very simple setups including laser-based single-wavelength ellipsometers with a fixed angle of incidence, to advanced multiwavelength, multiple-angle machines. Imaging ellipsome-ters with different scanning areas are also available. The wavelength range varies form ultraviolet to far-infrared. If a sensor-type setup for protein adsorption is of interest, one may pick up a green (502 nm) or red (632 nm) laser-based single-wavelength ellipsometer. For more detailed studies of, for example, multilayered protein structures, with full utilization of the SPR effect, a variable-angle spectroscopic ellipsometer is a better choice. An example on such an ellipsometer is shown in Fig. 6.

If measurements are to be performed in situ and a good monitoring over time is of importance one user a multiwavelength ellipsometer. This type of ellipsometer is capable of taking a full ellipsometric spectrum in a single shot, which speeds up measurements and provides much more data for analysis. A schematic illustration of a complete setup for TIRE is presented in Fig. 7.

Fig. 6. Comercially available spectroscopic ellipsometer. Reprinted with permission from J.A. Woollam Co

GLASS SLIDE (METAL COATED)

Fig. 7. A schematic overview of the TIRE system. Please observe the different prism configurations and ellipsometer systems available for measurements. With a white-light source (a Xe lamp without a monochromator), the detector must be wavelength selective (i. e., a grating with a diode array)

GLASS SLIDE (METAL COATED)

Fig. 7. A schematic overview of the TIRE system. Please observe the different prism configurations and ellipsometer systems available for measurements. With a white-light source (a Xe lamp without a monochromator), the detector must be wavelength selective (i. e., a grating with a diode array)

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