Patent ID: 7577469
Filing Date: 2009-08-18
Classification: A61B,G01N

Abstract:
1. A noninvasive transdermal system for detecting an analyte in interstitial fluid extracted from or underneath the skin of a subject, said noninvasive transdermal system comprising: (a) a noninvasive transdermal patch comprising a target surface having a dry chemistry component for interacting with the analyte to generate color or shade of color at said target surface, said dry chemistry component having a sensitivity which enables it to detect the analyte extracted from interstitial fluid, and a wet chemistry component for transferring the analyte from the interstitial fluid in or underneath the skin to said dry chemistry component in an amount sufficient so that said dry chemistry component can detect the analyte; and (b) a reflectometer comprising a modulated light source for emitting light to illuminate said target surface which possesses a certain color and shade of color following interaction with the analyte; an optical detector for detecting light that is reflected from said target surface and generating a first output indicative of detected light; means for processing the first output to generate a feedback signal for application to the optical detector to compensate for any shift in the first output resulting from the detection of ambient light by the optical detector, and differentially amplify the first output to generate a second output; and a detector for synchronously demodulating the second output to generate a substantially steady DC output voltage that is indicative of the color or shade of color at said target surface.