Polarix: Monitoring Multi-Component Liquids via Polarized Light

Abstract

Optically active substances such as sugars and amino acids are critical quality indicators in biomanufacturing and food safety, yet they typically coexist as multi-component mixtures. Existing monitoring techniques either require expensive instruments (e.g., HPLC) with per-sample costs and turnaround times ill-suited for online control, or rely on optical methods that cannot resolve individual component concentrations from a mixture. We present Polarix, a training-free polarimetric platform built from $100 in hardware that exploits a fundamental physical property: the specific optical rotation of each optically active substance varies with temperature at a distinct, substance-dependent rate. By sweeping the sample temperature across a bounded 15°C window, Polarix transforms the underdetermined problem into a solvable system, mathematically disentangling each component's concentration. Its optical design improves robustness against real-world disturbances including turbidity, flow, and mechanical drift. We validate Polarix on three real-world tasks: amino-acid fermentation tracking, trace byproduct detection, and honey adulteration screening against rice syrup and HFCS-55. Polarix resolves individual component concentrations with a mean relative error of 12.1%.