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bioRxiv · 10.1101/2025.03.26.645463

Lambda Theta Reflectometry: a new technique to measure optical film thickness applied to planar protein arrays

Klose, A. M.·Katz, J. D.·Boni, R.·Nelson, D.·Miller, B. L.
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Abstract

Quantitative protein measurements provide valuable information about biological pathways, immune system functionality, and mechanisms of disease. The most accurate methods for detecting proteins are label-free and preserve native protein binding interactions. Label-free biomolecular interaction analysis includes reflectometry, a group of techniques that detect proteins by measuring the reflectance properties of a thin film on a substrate. Most of these techniques are limited in some way by instrument complexity, sensitivity, or consumable manufacturing requirements. To address these issues, we introduce Lambda Theta Reflectometry (LTR), a new reflectometric technique that measures changes in film thickness by determining the location of null reflectivity as a function of wavelength (lambda) and angle of incidence (theta). The substrate is simultaneously illuminated with a range of angles and wavelengths and reflected light is angularly and spectrally resolved. Our prototype LTR reflectometer can measure SiO2 layer thickness with milli-[A]ngstrom precision. LTR measurements of Si/SiO2 oxide films are in excellent agreement with spectroscopic ellipsometry for film thicknesses ranging from 1390-1465 [A]. This technique enables sensitive measurements across a range of biological analyte concentrations without requiring stringent control over probe deposition thickness or substrate manufacturing.

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Klose, A. M., Katz, J. D., Boni, R., Nelson, D., Miller, B. L.. 2025-03-29. Lambda Theta Reflectometry: a new technique to measure optical film thickness applied to planar protein arrays. https://doi.org/10.1101/2025.03.26.645463

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