Etalon@lateral flow strip for integrated separation-sensing microfluidic platforms
M. Zhang (TU Delft - Engineering Thermodynamics)
A. J. Loeve (Co van Ledden Hulsebosch Center for Forensic Science and Medicine, TU Delft - Medical Instruments & Bio-Inspired Technology)
M. J. Serpe (University of Alberta)
H. Bazyar (TU Delft - ChemE/Transport Phenomena)
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Abstract
Lateral flow assays (LFAs) are widely favored for on-site analysis due to their simplicity and cost-effectiveness. However, their limited quantitative capabilities constrain them to qualitative testing. In contrast, etalon sensors offer high sensitivity and enable quantitative detection. They operate by producing interference-based optical signals through multiple reflections of light within a cavity formed by two parallel reflective surfaces. This requires a stable optical path length, traditionally limiting their use to smooth substrates.
This study presents an integrated separation-sensing microfluidic platform (EtLFA). By fabricating etalons on commercial membranes and evaluating sensor's sensitivity and surface roughness, we determined that membrane surface roughness must meet two criteria — Sa < 0.5 μm and Smr > 90% — to support functional etalons. Capillary and permeability remain intact after etalon integration, ensuring membrane's purification performance. We further functionalized the etalon to respond specifically to glucose, to demonstrate the quantitative detection of glucose levels in a mimic blood sample. A glucose-responsive etalon@nylon served as the sensor module, while regenerated cellulose membrane enabled separation. This dual-module configuration filtered PDMS particles mimicking red blood cells and produced a 25 nm shift for 100 mg/dL glucose, enabling linear quantification via portable spectrometry. By incorporating etalon sensor onto rough membrane substrates, our platform transforms conventional LFAs into a quantitative analytical tool, offering novel avenues for enhancing analytical capabilities and broadening the applications of lateral flow assays.
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