Last updated 14-Jan-2004

System-on-chip Surface Plasmon Resonance Sensors Using
Pulse-based Interface Circuits

Lisa E. Hansen and Denise Wilson

This paper presents a means for reducing the impact of dark current, photodetector mismatch (fixed pattern noise), and the background medium on the signals generated by a surface plasmon resonance (SPR) sensing system for determining the concentration of targeted analytes in solution. Results for each circuit component (simulated and experimental) correlate well, with a maximum error of 3%, 7% and 12% in basic behavior (between simulated and actual results) for the dark current reduction, background medium compensation, and weighted sum circuits at relevant operating points, respectively. System level results on SPR signals also demonstrate the usefulness of these circuits for system-on-chip style signal processing. The chip produces a single output that indicates the refractive index (and resulting analyte concentration) of an SPR probe, independent of fluctuations in the background medium.

 
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for the baseline (no analyte present/bulk refractive index) condition and the characteristic SPR dips for the measurement (analyte present) condition. A resolution of 2 X 10-4 refractive index units is possible with this system, comparable to the 5 X 10-4 RI unit resolution of conventional signal processing (software-based) approaches to processing the same data using a similar framework. This approach demonstrates experimentally the capability of the dip-based SPR probe in a portable footprint for detecting refractive index at resolution levels suitable for practical applications of these probes to field environments.