Bubble-tolerant micro-mixers

A device for mixing at least one first fluid and one second fluid in a micro-flow system, comprising:

• at least two flow restrictors;
• a first transfer conduit in fluid communication with said first fluid and a recipient;
• and
• at least one second transfer conduit in fluid communication with said second fluid and a recipient, the second transfer conduit having at least two fluid outlets in fluid communication with said first transfer conduit,
• where each of said outlets of said second transfer conduit is downstream and in fluid communication with the outlet of one of said flow restrictors, at least one of said restrictors comprising a body with an inlet face, an outlet face and a flow channel extending there between from an inlet to an outlet, the channel having over most of its length a substantially constant, minimum hydraulic diameter D=4 A/W wherein A is the minimum local cross-sectional area of the channel and W is the minimum local wetting perimeter of the channel, wherein the channel is smoothly widened at the inlet such that:
• at distances z from the inlet face with 0<z<z1, the channel has a hydraulic diameter Dz≧k*D wherein k≧1.3;
• at distances z from the inlet face with z1<z<z2, the channel has a hydraulic diameter Dz with k*D≧Dz≧D;
• and
• at distances z from the inlet face with z2<z, the channel has a hydraulic diameter Dz with Dz≦1.02 D, except possibly for a similar widening of the channel at the outlet.

A device for mixing fluids comprising flow restrictors having tapered inlets, wherein

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• ^
• ⋆
• >
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• with τ and τ* defined as above.