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2021–2025 active Lab

Photodiode-based Colorimetric Sensor for Biomarker Detection

EMC Class B-certified, sub-$500 colorimetric biomarker detection system using photodiodes in reflectance mode. 5 µM resolution with real blood/plasma samples, deployed at Valleywise and OHSU.

PhotodiodeColorimetricEMC Class BNIH-SBIREmbeddedSignal ProcessingFDA PathwayProduct Development
Photodiode-based Colorimetric Sensor for Biomarker Detection hero image
Role
Lead Hardware Engineer · PhD Candidate
Collaborators
Dr. Erica Forzani (advisor), Dr. MaryLaura Lind Thomas (co-advisor), Sequitur Health Corporation, Mayo Clinic Scottsdale, Valleywise Health (Phoenix), Oregon Health & Science University, Biodesign Institute, ASU
Funding
NIH SBIR, NSF SBIR

Overview

Designed and built a compact, low-cost colorimetric biomarker detection device using photodiodes and LEDs in reflectance mode. The system measures biomarker concentrations from chemical substrates using a modified Beer–Lambert law approach, complete with signal processing software, environmental compensation, and a user-facing UI on a microprocessor.

Problem

Clinical-grade chemistry systems like the Vitros 5600 can measure 100+ biomarkers but cost over $300,000, consume 1,500W, and occupy an entire room. This makes them completely inaccessible to low-income populations and resource-limited clinics, both in the US and globally.

Approach

Iterated through seven PCB designs, from a single low-power LED to a quadruple-LED configuration, systematically solving for light coverage, signal strength, and manufacturing feasibility. The full system covers hardware, firmware, and the algorithms that turn a raw photodiode trace into a clinically meaningful number:

  • Real-time analyte insertion detection, endpoint extraction, and polynomial calibration-curve fitting.
  • Artifact-detection algorithms that identify substrate displacement and user misuse during the 2-minute reaction window.
  • Integrated temperature, pressure, and humidity sensors to compensate for environmental variability.
  • Embedded UI on a low-power microprocessor, fully self-contained, no host computer required.

Results

  • 5 µM biomarker resolution validated with real blood and plasma samples.
  • Under $500 total device cost, a 600× reduction from the Vitros 5600 reference.
  • Under 5 W power consumption (300× reduction).
  • 15″ × 15″ × 15″ footprint (versus 40″ × 68″ × 110″, fits on a clinic counter).
  • Noise-threshold algorithm validated against 500+ real datasets, successfully flagging human-handling artifacts.
Calibration curve from real plasma samples
Calibration curve: polynomial fit across the biomarker range
Device undergoing EMC Class B testing
EMC Class B testing at Salt Lake City facility

The device cleared EMC Class B certification at a Salt Lake City test facility, confirming regulatory readiness for hospital and residential environments.

In the field

The device has been deployed in clinical settings at Valleywise Health in Phoenix, Arizona and Oregon Health & Science University (OHSU) in Portland, Oregon, moving from bench characterization into real-world validation with the clinicians who will eventually use it.

Demo video

System walk-through: sample loading, measurement, readout.

What’s next

FDA application is on track, moving the device from clinical validation toward formal regulatory clearance for commercial use.

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