System for identifying and sorting living cells

A cytometry system, comprising:

• a microfluidic handling system including a microfluidic channel and configured to provide a flow of label-free cells through a measurement volume in the microfluidic channel, wherein the measurement volume is 50 microns or less in thickness;
• at least one quantum cascade laser (QCL) light source configured to emit a light beam at a mid-infrared wavelength that induces resonant absorption by one or more analytes of each of the cells, wherein the QCL source is operable to illuminate each sequential cell contained in the measurement volume in turn, in order to induce resonant mid-infrared absorption by one or more analytes of each of the cells in turn;
• beam shaping optics to direct the emitted mid-infrared light beam to a spot in the measurement volume, wherein the spot has a dimension of 20 microns or less as measured in a direction that is substantially perpendicular to the direction of the light beam through the microfluidic channel;
• a mid-infrared detection facility configured to measure the magnitude of the mid-infrared wavelength light transmitted through each of the cells individually;
• and
• a processor to analyze the measured transmitted mid-infrared wavelength light to identify an analyte characteristic of each of the cells.