Concept, simulation, and fabrication of inverted grating structures for surface plasmon resonance sensors

Abstract

Surface plasmon resonance (SPR) sensors offer the possibility of label-free analysis of biosamples. The long-term stability of standard approaches is limited due to degradation of the grating upon contact with the analyte, and strategies to improve the performance in this regard include the use of so-called inverted configurations. By exciting surface plasmons from the back side of the grating, this design overcomes limitations of traditional grating-based SPR sensors caused by direct contact with the analyte medium and offers new design possibilities for implementing microfluidic analytical systems. Here a simulation for optimizing design parameters and a corresponding microfabrication technology to create the inverted grating are presented. An experimental evaluation of surface plasmon excitation and sensitivity enhancement demonstrates the feasibility of the approach. While the observed coupling effect of inverted grating structures is not as strong as the conventional configuration, it offers benefits like preventing surface oxidation, enabling repeated usage and new concepts for biosample processing.