Microfluidic absorption cell

An absorption cell device for measuring absorption of a fluid analyte at a sensing wavelength, or range of sensing wavelengths, by exposing the analyte to probe light of the sensing wavelength or sensing wavelength range, the device comprising:

• a microfiuidic input channel in fluid communication with a fluid input;
• a microfiuidic output channel in fluid communication with a fluid output;
• a microfiuidic sensing channel having first and second ends in fluid connection with the input channel and output channel respectively, so as to provide a fluid path for the analyte as well as an optical path for the probe light;
• first and second windows adjacent the first and second ends of the sensing channel which are transmissive to the probe light;
• a light source operable to generate the probe light and arranged to direct the probe light into the optical path through the first window;
• and
• a photodetector operable to sense the probe light and arranged to receive the probe light from the optical path through the second window,
• wherein
• the sensing channel is formed in a tinted material which is neither transparent nor opaque to the probe light, but rather transmissive and absorbent to the probe light, and in that the first and second windows are formed in the tinted material integrally with the sensing channel.

A method of performing an absorption measurement of a fluid analyte, the method comprising:

• providing an absorption cell with a microfluidic sensing channel having a first end and a second end;
• inputting the analyte into the sensing channel;
• illuminating the analyte by coupling probe light at a sensing wavelength or range of wavelengths into the sensing channel through a first window adjacent the first end of the sensing channel;
• and
• detecting the probe light that has passed through the analyte by coupling the probe light out of the sensing channel through a second window adjacent the second end of the sensing channel, wherein the sensing channel is formed in a tinted material which is neither transparent nor opaque to the probe light, but rather transmissive and absorbent to the probe light, and in that the first and second windows are formed in the tinted material integrally with the sensing channel.