BioCosMe: Lip-based Cosmetics with Colorimetric Biosensors for Salivary Analysis

This paper introduces a lipstick biosensor as a novel form factor for health monitoring that displays pH levels through color variation. Using the unique properties of lipstick—different colors, easy application and reapplication on lips, interaction with saliva and drinks—we aim to provide an always-available and non-invasive access to information typically obtained through lab analysis. Our skin-safe fabrication processes and technical evaluations include three lips products: lipstick, lip tint, and lip gloss, all using anthocyanin for sensing pH levels as the proof of concept biosensor. We created a mobile app with a Convolutional Neural Network (CNN) model to detect pH levels based on the lipstick's color changes. Our dataset involved five users under eight different lighting conditions and seven pH levels. The results showed improved detection of pH variations compared to traditional methods. A user study with 11 participants was conducted to evaluate application, comfort, and perceptions of privacy and usability. This approach offers a stylish, convenient way to monitor biochemical information, blending self-expression with health awareness.