Particle separation systems and methods

A method of co-encapsulating a plurality of distinct populations of separated particles within individual droplets, the method comprising:

• a. providing a microfluidic device comprising at least a first particle separation microchannel, a second particle separation microchannel and at least a first encapsulant microchannel, wherein the first particle separation microchannel, the second particle separation microchannel and the encapsulant microchannel each comprises at least one inlet and at least one outlet, and at least one of said outlets of said first separation microchannel, at least one of said outlets of said second separation microchannel and at least one of said outlets of said encapsulant microchannel converge together to form a shared exit microchannel;
• b. forming a first mixture comprising a first population of particles by suspending said first population of particles in an aqueous viscoelastic liquid, and forming a second mixture comprising a second population of particles by suspending said second population of particles in an aqueous viscoelastic liquid;
• c. introducing via the inlet said first mixture into said first particle separation microchannel, and introducing via the inlet said second mixture into said second particle separation microchannel;
• d. simultaneously flowing said first mixture through said first microchannel and said second mixture through said second microchannel at a flow rate (Q) of from 0.25 μl/min to 50 μl/min;
• and
• e. whilst introducing said first mixture into said first particle separation microchannel and introducing said second mixture into said second particle separation microchannel, simultaneously introducing a water immiscible encapsulation liquid via the inlet into said encapsulant microchannel, and flowing said encapsulation liquid through said encapsulant microchannel at a flow rate (Q′) of from 0.25 μl/min to 50 μl/min,
• characterised in that:
• said first and said second particle separation microchannels each satisfies the formula L/D≥2000, and said first particle separation microchannel, said second particle separation microchannel and said encapsulant microchannel converge at a position downstream of said first inlet of each of said first and said second particle separation microchannels at a distance that satisfies the formula L/D≥2000, wherein L represents the length of said microchannel and D represents the cross-sectional diameter of said microchannel;
• and said viscoelastic liquid comprises from 0.15 to 0.55 wt. % xanthan gum or from 0.05 wt. % to 1.0 wt. % hyaluronic acid.