[2020] Electronic lateral flow immunoassay

Lateral flow immunochromatographic tests are used to detect biochemical markers in a fluid. This typically involves the movement and fixation of functionalized nanoparticles (usually gold, but other materials are also used). The flow happens within a porous membrane. Lateral flow tests are widespread – the most common one is the hCG pregnancy test. There is a lot of interest in the development of quantitative measurement techniques. Optical reflective methods are the most common, but other methods can also be applied.

Figure 1 Lateral flow architecture. (Source: NASA)

Figure 2 Concept of electronic readout for lateral flow test.

NXP Semiconductors Belgium is investigating an optical transmission method, and a capacitive method to obtain quantitative measurements. The capacitive method used small fringe capacitors embedded below the membrane to measure the particles and ions flowing through the membrane, coupled to the NHS3153 sensor IC. There are however several open questions:

1. Fundamental The capacitive measurements see changes in ion concentrations and dielectric constants. Multiple effects play at the same time, and gold nanoparticles have non-trivial properties. (Physics, multi-physics models, experiments)
2. Design Which electrode design works best, given the properties of the membranes, fluids, PCB types, and how should it be integrated (PCB design, 3D modeling, multi-physics models, mechanical manufacturing, 3D printing, experiments)
3. Interpretation The signal seen by the electrodes evolve over time and depend on the types of fluid, ion concentration, reactions, and electrode. Going from raw signals from multiple sensors along the membrane to a quantitative and repeatable measurement is a challenge (embedded programming, DSP, AI/ML, experiments)

One or more research subjects can be defined based on these questions. NXP has a working proof-of-principle implementation.
The research would be executed at NXP Belgium, located close to Leuven, in the Product Line Personal Health.

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Last modified: 2022-07-16