Process of making a microtube and microfluidic devices formed therewith

A process of fabricating a micromachined tube of a microfluidic device, the process comprising the steps of:

• providing a first doped material having a thickness throughout which the first doped material is substantially uniformly doped;
• anisotropically etching a channel in a first portion of the first doped material in a direction of the thickness thereof, the channel extending through more than half but not entirely through the thickness of the first doped material, the channel being between second and third portions of the first doped material;
• bonding the first doped material to a second doped material so that a first portion of the second doped material overlies the first portion of the first doped material and encloses the channel therein to define a passage, and so that second and third portions of the second doped material overlie the second and third portions of the first doped material;
• masking the first portion of the second doped material;
• etching the second and third portions of the second doped material exposed by the masking step followed by etching some but not all of the second and third portions of the first doped material, such that the first portions of the first and second doped materials define a protrusion;
• bonding the first portion of the second doped material to a substrate adjacent a recess in a surface of the substrate such that a portion of the passage projects over the recess and the second doped material makes electrical contact with an electrical conductor on the substrate;
• and then
• removing the second and third portions of the first doped material such that the first portion of the first doped material and the passage therein define a tube, a freestanding portion of the tube projecting over the recess in the substrate so as to be capable of movement relative thereto.