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Spreeta is an electro-optical device utilizing surface plasmon resonance to detect small changes in refractive index of liquids. The Spreeta device was developed by Texas Instruments, Inc. in the 1990s. Device design incorporates a light-emitting diode (LED) illuminating a thin metal film (usually gold) in the Kretchmann geometry (needed to excite surface plasmons). The reflected light is detected by a photodiode linear array (which translates angle of reflection to pixel position) and the resonance (a dip in the reflectivity at a specific angle of incidence) denotes the refractive index on the outer surface of the metal film. Applications include real-time measurement of binding of antigens to antibodies attached to the sensor surface, monitoring changes in oil quality, and measuring sugar content in drinks ( Brix level).

The term "Spreeta" is an anglic derivative of SPR-ITA, which combines SPR (for Surface Plasmon Resonance) with "ita" (a Spanish suffix meaning "small").

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  The top image shows an optical diagram of the sensor (in cross-section). The lower-left image is the original integrated sensor. The lower-right image is a smaller version of the sensor with less sensitivity but more amiable to system integration.

References

• U.S. Patent Number 5912456 - Filed Mar 19, 1997 - Texas Instruments Incorporated ^{[ original research?]}
• Chinowsky, T.M.; et al. (2003). "Performance of the Spreeta 2000 integrated surface plasmon resonance affinity sensor" (PDF). Sensors and Actuators. 2003 (B91). Elsevier: 266–274. doi: 10.1016/S0925-4005(03)00113-8. Retrieved 31 May 2011.

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