Introduction

A tunable surface-plasmon resonance sensor capable of switching between imaging and angular resolved spectroscopy without moving parts. The use of e-tunable lenses permits free movements and fast changing of the system focal point, thus switching between two complementary different configurations. The optional insertion of adaptive optics components allows a finer tuning of the focal point and the aberrations compensation.

Technical features

Our SPR sensor setup is in the Kretschmann configuration: it employs a monochromatic light source properly filtered and TM-polarized, a prism to couple the radiation with the surface plasmon at the metal/dielectric interface (the material of the prism depend upon the metal used, the working wavelength, and the final application) and a bi-dimensional detector (CCD or CMOS). The apparatus includes a source of coherent light, a collimating/focusing tunable lens, adaptive optics, a glass prism optically coupled with a glass/metal chip, a (tunable) objective lens and a two dimensional detector. Besides easily switching between different configurations, this new setup also allows changing the illumination pattern on the sensing surface, gaining more information with the same setup and during the same measurement session. Experiments and validation tests, done in our labs with a first prototype, have shown promising results.

Possible Applications

• Environment: for the detection of pesticides, pollutants, etc;
• Bio- and medical: for studying the interactions between different types of biomolecules (as nucleic acids, receptors, peptides, proteins, antibodies, lipids);
• Agro-food: for the identification of chemical contaminants, toxins and bacterial pathogens, allergens.

Advantages

• Simple construction;
• Enhanced image and SPR curve quality;
• Calibrated images (thanks to the angular resolved measurement);
• Versatile (complementary measurements – angular resolve Vs imaging – on the same setup with no moving parts).