Non-constrictive bead immobilization leading to decreased and uniform shear stress in microfluidic bead-based ELISA

TL;DR

This paper introduces a non-constrictive bead immobilization method using poly-carbonate membranes in microfluidic ELISA, significantly reducing shear stress and flow variance around sensor beads, thereby improving sensor performance.

Contribution

The study presents a novel immobilization technique that minimizes shear stress and flow variance compared to traditional constrictive methods in microfluidic biosensors.

Findings

Shear stress was reduced by three orders of magnitude.

Flow variance around beads decreased significantly.

Successful detection of EpCAM protein with multi-wavelength operation.

Abstract

Microfluidic biosensors have been utilized for sensing a wide range of antigens using numerous configurations. Bead based microfluidic sensors have been a popular modality due to the plug and play nature of analyte choice and the favorable geometry of spherical sensor scaffolds. While constriction of beads against fluid flow remains a popular method to immobilize the sensor, it results in poor fluidic regimes and shear conditions around sensor beads that can affect sensor performance. We present an alternative means of sensor bead immobilization using poly-carbonate membrane. This system results in several orders of magnitude lower variance of flow radially around the sensor bead. Shear stress experienced by our non-constrictive immobilized bead was three orders of magnitude lower. We demonstrate ability to quantitatively sense EpCAM protein, a marker for cancer stem cells and operation under both far-red and green wavelengths with no auto-fluorescence.