Spreeta

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Spreeta is a compact sensor that uses surface plasmon resonance to detect tiny changes in the refractive index of liquids. It was developed by Texas Instruments in the 1990s. The device shines light from an LED onto a thin metal film (usually gold) in Kretschmann geometry to excite surface plasmons. The reflected light is read by a line of photodiodes; the system tracks a dip in reflectivity at a specific angle, which tells you the refractive index near the metal surface.

Spreeta can measure real-time binding events (such as antigens attaching to antibodies on the sensor), monitor oil quality, and determine sugar content in drinks (Brix). The name comes from SPR (surface plasmon resonance) plus "ita," a suffix meaning small.