Understanding Capillary Flow Time (Sec/4cm)
One of the most critical parameters in Lateral Flow Assay (LFA) development is the wicking speed of the nitrocellulose membrane. Often measured as the time required for liquid to travel 4cm (e.g., HF135, HF180), choosing the wrong speed can ruin assay sensitivity.
Fast vs. Slow Membranes: The Trade-off
| Membrane Type | Flow Rate | Sensitivity | Run Time | Application |
|---|---|---|---|---|
| Fast (e.g., HF90) | 90s/4cm | Lower | Rapid (<10 min) | High-concentration analytes (e.g., hCG) |
| Slow (e.g., HF180) | 180s/4cm | Higher | Slower (15-20 min) | Low-abundance markers (e.g., Troponin, CRISPR) |
Why Due Bio Uses “Balanced” Membranes
For our Universal Lateral Flow Strips, we standardize on a mid-slow wicking rate (approx. 135-150s/4cm). This “Goldilocks” zone provides sufficient interaction time for antibody-antigen binding (enhancing sensitivity for CRISPR/Cas targets) without causing excessive run times or false positives due to back-flow.
AI & Automation Compatibility
Consistent flow rate is vital for automated machine vision systems. Due Bio’s membranes are manufactured with strict environmental humidity control, ensuring that the capillary rise time varies by less than ±3% across batches. This consistency is essential for training AI interpretation models (as highlighted in recent research from Rice University).