Sensing device for detecting a target substance

The sensing device comprising:

• a cartridge including:
• a sensing surface,
• an investigation region receives a fluid containing the target substance, the sensing surface forming one side of the investigation region,
• a reference element disposed directly adjacent the sensing surface such that the fluid containing the target substance does not pass between the reference element and the sensing surface;
• a light source directs an incident light beam toward the sensing surface at an angle for reflection under total internal reflection conditions at the investigation region and at the reference region generating reflected light, the reflected light from the reference region directly adjacent the reference element being not affected by a presence or absence of the fluid;
• a detector detects the reflected light and generates a first characteristic signal depending on the reflection at the investigation region and a second characteristic signal depending on the reflected light from the reference surface abutting the reference element;
• a calibrator calibrates the first characteristic signal in view of the second characteristic signal;
• and
• wherein the sensing surface at the reference region is tilted relatively to the sensing surface of the investigation region by an angle β to allow incidence of the incident light beam at the reference region to be the angle β shallower than that of a parallel incident light beam at the investigation region and still strike the investigation surface at an angle equal to or greater than a critical angle for total internal reflectance.

An analyzer system for detecting a target substance comprising:

• a sensing device including:
• a sensing surface defining an investigation region and a reference region thereon the sensing surface, or the reference region being tilted by an angle β, relative to the sensing surface at the investigation region,
• a reference element located at the reference region shields the reference region of the sensing surface from contacting the target substance such that light reflected at the reference region remains unaffected by a presence or absence of the target substance,
• an analyzer device comprising:
• an analysis region receives the sensing device,
• a light source directs incident light to the analysis region such that the incident light is directed to the investigation region incident light is reflected under total internal reflection conditions at at an angle equal to or greater than a critical angle θcrit=sin−1(n2/n1), where n1 is the refractive index of the sensing surface and n2 is the refractive index of the target substance and directed to the reference region at an angle θcrit−β thereby generating reflected light, when the sensing device is received in the analysis region,
• a detector detects the reflected light and outputs a first characteristic signal depending on the light reflected by the investigation region and a second characteristic signal depending on the light reflected by the reference region,
• a calibrator calibrates the first characteristic signal in view of the second characteristic signal.

A method for detecting a target substance, the method comprising:

• directing an incident light beam toward a sensing surface which defines an investigation region and a reference region, the reference region including a reference element disposed to shield the reference region of the sensing surface from contacting the target substance, the sensing surface at the reference region being tilted by an angle β relative to the sensing surface at the investigation region;
• reflecting incident light from the reference region of the sensing surface under total internal reflection conditions or an angle greater than θcrit−β such that the light reflected from the sensing surface at the reference region is unaffected by a presence or absence of the target substance where θcrit is an angle above which light is reflected;
• reflecting the incident light under total internal reflection conditions at the investigation region or an angle greater than θcrit such that the reflected light from the investigation region of the sensing surface is indicative of the target substance adjacent the investigation region;
• detecting the light reflected from the investigation region and generating a first characteristic signal indicative of the characteristic of the target substance in the investigation region, with a detector;
• detecting the light reflected by the reference region and generating a second characteristic signal, with the detector;
• and
• calibrating the first characteristic signal in view of the second characteristic signal, with a calibrator.