Microfluidic Dead Volume & Priming Calculator

Why Dead Volume Matters

A microfluidic experiment that uses 5 μL of sample on the chip can easily waste 200 μL priming the path between the syringe and the chip inlet. For precious samples — primary cells, patient-derived material, expensive proteins — that waste is the difference between running 50 conditions and running 5.

Dead volume also drives carryover. If your system holds 100 μL of fluid and you switch from sample A to sample B without enough flush, B will be diluted by residual A. For quantitative readouts (qPCR, flow cytometry, MS) carryover destroys the data.

2× vs 3× Priming Factor

For routine reagent swaps where 1–2% carryover is acceptable, 2× system volume is the standard minimum.

For quantitative work — qPCR, single-cell, mass spec, or any assay where the next reading depends on the previous reading being fully flushed — use 3× system volume. The extra flush is cheap insurance against carryover artifacts that look like real signal.

For sticky reagents (proteins that adsorb to PEEK, surfactants, viscous samples), even 3× may not be enough. In that case, switch to a chemically-resistant tubing (FEP or PFA) and consider a wash buffer between samples.

How to Reduce Dead Volume

Three levers, in order of impact: