Design — microfluid pump

Operating principle

A peristaltic pump: three cams on a shared shaft compress a silicone tube in sequence. The compression wave pushes fluid in one direction. No valves, no seals exposed to fluid, easy to sterilize (replace the tube).

Geometry

The current design uses three 120-degree offset cams on a 6mm steel shaft. The tube is 2mm ID silicone, routed through a semicircular channel that holds it against the cams. The channel radius determines the occlusion — too loose and the pump loses prime, too tight and the tube wears.

Second revision changes

• Widened the tube channel from 2.8mm to 3.2mm to reduce tube wear
• Added alignment pins between the housing halves
• Moved the motor mount from side to bottom (shorter shaft, less wobble)
• Redesigned the barb fittings with a longer insertion depth

Open questions

• Should the cams be eccentric circles or involute profiles? Involute gives more even flow but is harder to print accurately at this scale.
• Is 2mm ID the right tube diameter? Going to 3mm would increase flow rate but also increase the motor torque required.