Engineering LogQ3 2026 · 6 min read

Overcoming Fluidic Resistance in High-Density Disc Arrays

Microfluidic disc systems at the nanoliter scale face a fundamental trade-off between throughput and haematocrit-induced viscosity variation. This log documents our systematic mitigation of pressure-head losses across 72-chamber arrays.

BiQadx Core Engineering

Q3 2026

6 min read

91.3%

Variance Reduction

↑ from 18.4% → 1.6%

4.0

Rev Iterations

72 chambers per disc

<2%

Volume Variance

At 2.5G lateral load

◆ Engineering Process Flow

DESIGN

FEA MODEL

BUILD

TEST

VALIDATE

◆ Key Findings

Dual-siphon architecture reduced inter-chamber variance from 18.4% to 1.6% — a 91.3% improvement
Tapered vent channels eliminated haematocrit-dependent breakthrough events across the full clinical range
Rev 4.0 geometry operates without parameter adjustment from Hct 30% to 60%

Viscosity as a Variable Load

Whole blood viscosity ranges from 3.5 mPa·s at low haematocrit (35%) to 5.5 mPa·s at high haematocrit (55%) — a 57% swing. At rotational speeds below 2,000 rpm in our initial disc geometry, this caused sample distribution skew exceeding 18% across radial metering chambers. Conventional fixed-pressure designs cannot accommodate this dynamic range without inter-chamber cross-contamination.

Geometric Interventions Applied

Our FEA team modelled 14 channel geometry variants in COMSOL Multiphysics™ v6.1. Three key changes were implemented: (i) meniscus-retaining microstructures at junction intersections to prevent capillary breakthrough at low spin, (ii) radially tapered vent channels to equalize back-pressure across all sectors, and (iii) a dual-siphon sample metering architecture that decouples fill volume from spin sequence timing.

Field Validation & Boundary Condition Testing

Validation was conducted using 500 individual disc replicates across six clinical sites. We simulated 'extreme boundary' conditions, including 45°C ambient transport temperatures and high-vibration environments typical of mobile diagnostic units. Data showed that the Rev 4.0 geometry maintained < 2% volume variance even when subjected to 2.5G lateral acceleration during the spin cycle — a critical requirement for Dr. POCT military-grade mobility specification.

◆ Disc Pressure-Head Loss — Geometry Iterations

Geometry Rev	Hct 35%	Hct 55%	ΔP Variance	Distribution Error
Rev 1.0 (Baseline)	18 mbar	42 mbar	24 mbar	18.4%
Rev 2.3 (Tapered vent)	14 mbar	28 mbar	14 mbar	9.1%
Rev 3.1 (Dual siphon)	12 mbar	17 mbar	5 mbar	2.8%
Rev 4.0 (Final)	11 mbar	14 mbar	3 mbar	1.6%

All tests at 3,500 rpm. n=30 discs per revision. Errors are volume-weighted mean across 72 chambers.BiQadx Engineering Data

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Research Context Only: This document is published as an engineering log for transparency. All content describes R&D-phase investigations. No clinical diagnostic claims are made. This is not a regulatory filing or clinical performance specification.