Patterned and switchable surfaces for biomaterial applications

Chapter 5 – Surface plasmon resonance imaging of polymer microarraysHowever, if the shift in the resonance angle after the addition of a 5 nmbiopolymer layer is measured for each spot (shown as Figure 5.7B) an equivalentresponse of approximately 0.3° is measured up to a thickness of 20 nm. A slightdecrease in the measured value is seen for polymer spots of thicknesses above 30 nm.A response of approximately 0.1° was measured for the polymer spot of thickness200 nm. This result suggests that a larger spot thickness range can be used, whenreplacing the measurement of change in signal intensity at constant angle with theshift in the resonance angle. For the PLL array discussed, equivalent measurementscould be taken over a thickness range of 0-30 nm. This is a significant improvementover the 0-5 nm thickness range that currently limits fixed angle experiments.In order to obtain real-time measurements by SPRi reflectivity measurements at afixed angle must be taken, despite the advantages of exclusively measuring shifts inthe resonance angle. However, knowing the relationship between the reflectivityagainst angle of incidence for a particular spot at the fixed angle used for real-timebiomolecular adsorption experiments, the changes in reflectivity measured duringsuch an experiment can be converted to a shift in the resonance angle using the totalchange in resonance angle measured as a result of biomolecular adsorption, asdepicted in Figure 5.8.5-180