The SMSI® Hardware Innovation

The essence of the original SMSI® invention was to embed the excitation source in the sensing element. Specifically, the invention places a tiny, low cost LED in a matrix containing the fluorescent indicator molecules (fluorophore) (see Figure 3).

Figure 3

For in vivo applications, a version of the platform in Figure 4 is placed inside a bean-shaped waveguide, encapsulated in the indicator matrix, and combined with telemetry capabilities. A conceptual schematic is shown in Figure 4.

Figure4

This simple concept solves numerous technical and economic problems of existing optical sensors, as summarized below.

  • Sensitivity and Response Time Independent - The SMSI design has eliminated the sensitivity vs. response time trade-off inherent in existing technology. The SMSI design delivers response times as low as 20 milliseconds for oxygen.
  • Ease of Miniaturization - Nearly all of the components of the sensor platform are solid state and may be reduced to an integrated circuit.
  • Dramatic Cost Improvements - The SMSI design permits the use of relatively inexpensive, off-the-shelf components, and can be manufactured in high volumes.
  • Energy Efficiency - The SMSI design delivers optical energy with an efficiency that is far superior to the current state of the art.
  • Neither Indicator nor Analyte is Consumed - The fluorescent indicator molecule and the analyte interact directly yet reversibly. This is in stark contrast to commercialized glucose sensors and electrochemical oxygen sensors, both of which need a continuous supply of fresh glucose and/or oxygen, as well as reagents/strips.
  • Generalizable to Other Analytes - The SMSI hardware platform can easily accommodate different targets. To sense a different target analyte, we simply use a different indicator molecule in the outer layer.

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SMSI® Technology vs.
Fiber Optic Sensors


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