Cell‐Like Portable Biologics‐Free Sensors for Stress Diagnostics

ABSTRACT Mental health is a pressing and widespread global concern, necessitating accessible, reliable and cost‐effective tools for its ongoing monitoring and effective management. Herein, a portable “molecule‐probe” platform is presented that integrates a specific chemical reaction within a hydrogel microreactor with n ‐type semiconductor doping for signal amplification. This biologics‐free sensing platform enables rapid, sensitive cortisol detection, a key stress biomarker, with superior response time‐selectivity compared to conventional antibody‐, aptamer‐, or chemical‐based detection systems. The specific chemical reaction ensures over 50‐fold selectivity for cortisol against other biochemicals including cholesterol and glucose. Utilizing non‐invasive saliva‐based sampling and a biodegradable hydrogel matrix, the device offers low post‐waste and high cost‐effectiveness. With a short diagnosis time (∼ 8 min) and low production cost (∼ 7 dollars per unit, projected to drop to 4 dollars at scale), the portable sensor is particularly well‐suited for frequent, point‐of‐care applications in resource‐limited or decentralized healthcare settings. By eliminating costly biological recognition elements such as antibodies or aptamers and long diagnosis time, this work introduces a new design paradigm for sustainable biochemical sensing, enhancing accessibility to chronic stress monitoring and mental health assessment across socio‐economic boundaries.