Sensitive Hormone and Neurotransmitter Detection with Carbon Flower Electrodes

Carbon‐based electrochemical sensors have attracted substantial attention for continuous health monitoring due to their high surface area, wide potential window, capability for repeated measurements, and compatibility with soft wearable electronics. However, they face challenges when detecting target biomarker concentrations in the low nanomolar range ( sensitivity ) and differentiating them in a mixture ( selectivity ), limiting their applicability in real scenarios. Herein, we present sensitive and selective “carbon flower” sensors, fabricated via a facile and patternable spray‐coating process on soft, stretchable substrates. Carbon flowers are obtained through the synthesis of polyacrylonitrile and subsequent heat treatments. They exhibit unique hierarchical morphologies, high surface area, and excellent conductivity, ideal for mass transport and electrochemical detection. We demonstrate the detection of estradiol, serotonin, melatonin, dopamine, uric acid, and ascorbic acid with detection limits as low as sub‐nanomolar. The carbon flower sensors exhibit good repeatability across 100 cycles and over several weeks, robustness to pH and salt variations, and excellent performance in artificial saliva. In mixtures containing up to four analytes, they differentiate individual molecules, demonstrating high selectivity. This combination of sensitivity, selectivity, and mechanical compatibility makes carbon flower sensors well‐suited for biomolecular sensing in soft, skin‐conformable wearable electronic patches.