Focusing of microparticles in microfluidic systems

A system for focusing and detecting particles flowing in a first microchannel, the system comprising:

• a body structure comprising at least first and second microchannels disposed therein which intersect at a first fluid junction;
• at least a first source of a sample fluid fluidly coupled to the first microchannel which comprises the particles;
• at least a second source of a focusing fluid fluidly coupled to the second microchannel;
• a fluid direction system operably coupled to the first and second microchannels which is configured to direct the sample fluid from the first fluid source into the first microchannel and to further direct the focusing fluid from the second fluid source into the second microchannel and into the fluid junction such that particles flowing in the sample fluid in the first microchannel are directed towards a first side of at least opposing first and second sides of the first microchannel;
• an interrogating light beam in sensory communication with the first side of the first microchannel at a first location which is downstream of the first fluid junction;
• and
• a detector which is configured to detect the particles in the focused sample fluid using the interrogating light beam.