Chemical imaging as well as nano-IR spectroscopic results give insight on the nature of different domains found in this phase-separated system. Finally, the AFM-IR method is used to examine binding events of the analyte to the receptor layer. The sensor surface was characterized after each subsequent preparation step (figure ) which are I: aptamer immobilization, and II: PEG-blocking. Also, the sensor was characterized after step III: S protein binding. Characterization was done by IRRAS, SE, and AFM-IR.