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Microfluidic Dead Volume & Priming Calculator.

Compute total system volume, priming volume, priming time, reagent waste, and runs per reservoir from your tubing, connectors, chip, and flow rate. Free. Client-side.

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Validated2026-04-07
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Load example microfluidic dead volume calculator data to see the full workflow

Tubing Segments

#1

Connectors

Chip & Flow

Run Sheet

Tubing volume
150.80 μL
Connectors volume
10.00 μL
Chip volume
10.00 μL
Total system volume
170.80 μL
Priming volume (2×)
341.59 μL
Priming time
6.83 min
Runs per reservoir
2 runs (waste 341.59 μL per run)

When to use

  • Sizing a new microfluidic rig before ordering tubing and connectors
  • Estimating reagent waste per run for a budget proposal
  • Choosing between 2× and 3× priming for a quantitative assay
  • Comparing dead volume across two candidate plumbing layouts
  • Documenting priming volume in an SOP or methods section

Do not use for

  • For pulsatile flow systems (peristaltic pumps with high carryover)
  • For gas-phase systems
  • For chips with internal valving or storage chambers (use vendor-supplied volumes)
  • For pressure-driven systems where priming depends on backpressure, not just volume

Tubing volume scales with ID²

Doubling the inner diameter quadruples the volume per length. The biggest single dead-volume win is dropping from 1/16" to 1/32" tubing where flow rates allow it.

Connectors are sneakier than they look

A typical 6-connector setup adds 30+ μL of dead volume — often more than the chip channel itself. Always count connectors when sizing dead volume.

Priming time goes up at low flow rates

For shear-sensitive cell work you may be stuck at 5–10 μL/min. A 200 μL prime at 5 μL/min is 40 minutes per sample swap. Plan your day around it.

Reservoir-to-chip dead volume is reset every run

You pay the priming penalty once per sample switch, not once per run. Runs of the same sample share the priming volume, so for repeated technical replicates the per-run cost amortizes down to zero.

1

Method

Tubing volume = Σ π\pi (ID/2)² ×\times length (mm3\text{mm}^{3} → μL, 1 mm3\text{mm}^{3} = 1 μL). Connector volumes from published Darwin Microfluidics / Idex defaults. Total system = tubing + connectors + chip. Priming volume = total ×\times 2 (minimum) or ×\times 3 (quantitative). Priming time = priming volume / flow rate. Runs per reservoir = floor(reservoir / priming volume).

2

Validated

Last validated 2026-04-07. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.

3

How to cite

How to Cite

ConductScience Microfluidic Dead Volume & Priming Calculator (v1.6.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/microfluidic-dead-volume-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.

The fix is to know your dead volume before you build the rig. Use the shortest tubing, the narrowest ID compatible with your flow rate, and the fewest connectors. Measure-twice, plumb-once.

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:

1. Shorter tubing. Volume scales linearly with length. Cutting a 30 cm line down to 10 cm cuts that segment's volume by 67%.
2. Narrower ID. Volume scales with ID2\text{ID}^{2}. Going from 0.8 mm ID to 0.5 mm ID cuts the volume by 61% (same length). Watch for backpressure though — narrow tubing at high flow rates can exceed your pump's pressure rating.
3. Fewer connectors. Each Luer adds ≈5 μL, each tee ≈8 μL. Direct chip-to-syringe connections (no inline filters, no Y-junctions) win the dead volume war.

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