Biosensor Stack Designer

A whole device, not an idealisation: substrate, buried oxide, a patterned device layer, the functionalisation chemistry and the captured biomarker — the last two as conformal shells that wrap the ridge tops, sidewalls and groove floors, the way they sit on a real chip. Rigorous electromagnetics, entirely in your browser.

Metatech Sensors · rigorous coupled-wave analysis, TE and TM, cross-checked against the analytical modal solver to 3×10−8

Start from

Analyte

Biomarker layer

A captured protein monolayer is 2–10 nm at n ≈ 1.40–1.45. Leave the thickness at 0 for the bare, ready-to-use chip.

Functionalisation

Silane plus linker, typically 3–8 nm. It is always there, so it belongs in the baseline, not in the signal.

Device layer

Below

Measurement

“Flat film” is the common shortcut of stacking the biolayers on top of the grating. It is here for comparison — it throws away the sidewalls.

Numerics

The Fourier integrals are exact, so a 3 nm shell is represented exactly however thin it is and only the series truncation matters. ±11 already matches ±27 to five figures.

Cross-section

The functionalisation and biomarker layers coat the ridge tops, the sidewalls and the groove floors. At true scale that shell is a third of a pixel, so on the left it is drawn thicker by the stated factor — same geometry, same wrapping, just visible. The inset on the right is the real proportion at a ridge corner.

biomarker functionalisation device layer BOX analyte substrate

Reflectance and transmission

reflectance transmission resonance

Binding curve

Resonance shift as the biomarker layer grows on top of the functionalisation. The initial slope is the surface sensitivity.

Where the mode is

The analyte share is na·S/λ, an exact identity, not a fit: it is the fraction of the resonance that lives in the buffer. Raise it and the sensitivity rises while Q falls — the same field cannot be both well confined and well exposed.