Why a BOM Beats a Shopping List
A scribbled shopping list — "5 Luers, some tubing, two syringes" — is how labs end up with mismatched OD/ID, missing plugs for unused ports, and three trips to the supply room. A real BOM forces you to count every part *and* its mating part: every chip-side connector has an instrument-side fitting, every tubing run has the right OD for the connector, every unused port has a plug.
The 30 minutes you spend generating a clean BOM saves a half day of "the experiment is delayed because we are waiting on a $4 ferrule." It also makes the rig reproducible — anyone can rebuild it from the BOM card, no tribal knowledge required.
Tubing OD vs ID: A Two-Sentence Explainer
OD (outer diameter) has to match your fitting. 1/16" Luer fittings only accept 1/16" OD tubing. 1/32" fittings only accept 1/32" OD tubing.
ID (inner diameter) controls flow rate, backpressure, and dead volume. For a given OD you can pick from a small range of IDs — thicker walls give smaller ID and more pressure tolerance; thinner walls give larger ID and lower backpressure. Always confirm ID is less than the bore of your OD class.
Luer vs Mini-Luer vs Threaded Ferrule vs Press-Fit
Luer (≈ 5 μL): the universal default. Cheap, fast to swap, fits everything. Use when dead volume is not the limit.
Mini-Luer (≈ 2 μL): same workflow as Luer but with smaller bore. Drops connector dead volume ~60%. Use for precious-sample work.
Threaded ferrule (≈ 0.5 μL): nut + ferrule + tubing pressed into a flat-bottom port. Smallest dead volume of the four, highest pressure tolerance, slowest to swap. Use for high-pressure (> 5 bar) or single-cell work.
Press-fit (≈ 1 μL): tubing pushes directly into a chip-port boss. No nut. Common on commercial chips with built-in interconnects. Fast and clean but only works with the matching chip format.
