Congratulations to Zachary Martin in the Sharon Weiss research group! Zach’s paper, “Multichromatic porous silicon RGB rugate filters for use in smartphone biosensing,” published in Applied Optics, has been selected as this week’s Spotlight Publication.
This work is motivated by the goal of developing smartphone-based sensing devices that can quantify biomarker concentration, but with the detection capabilities of standard laboratory tests like ELISA. Smartphones are portable, widely available, and provide a practical platform for colorimetric biosensing outside of traditional laboratory settings, and without the need of specialized equipment. In this work, a porous silicon multichromatic rugate filter was fabricated to convert broadband white light from a smartphone’s flash LED into narrow red, green, and blue illumination bands to enable multichromatic sensing, where color change indicates capture of target biomolecules. The filter was designed using transfer matrix simulations, fabricated through electrochemical etching of porous silicon, and experimentally verified to produce three distinct reflection peaks. Smartphone imaging and CIE chromaticity analysis confirmed that the filter produced the intended multichromatic light, while simulations show that this filtered illumination can generate larger color changes in response to biomolecule-induced refractive index shifts than ordinary white-light illumination. This research is a step forward in the design of a low-cost, smartphone-based point-of-care biosensing platform that can perform quantitative analysis without external light sources.
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