Non-invasive biosensors enable rapid, real-time measurement and quantification of biological processes, such as metabolic state. Currently, the most accurate metabolic sensors are invasive, and significant cost is required, with few exceptions, to achieve similar accuracy using non-invasive methods. This research, conducted within the Biodesign Institute Center for Bioelectronics and Biosensors, leverages the selective reactivity of a chemical sensing solution to develop a sensor which measures acetone in the breath for ketosis and ketoacidosis diagnostics, which is relevant to body weight management and type I diabetes. The sensor displays a gradient of color changes, and the absorbance change is proportional to the acetone concentration in the part- per-million range, making applicable for detection ketosis and ketoacidosis in human breath samples. The colorimetric sensor response can be fitted to a Langmuir-like model for sensor calibration. The sensors best performance comes with turbulent, continuous exposure to the samples, rather than batch sample exposure. With that configuration, these novel sensors offer significant improvements to clinical and at- home measurement of ketosis and ketoacidosis.

Energy Expenditure (EE), a key diagnostic measurement for treatment of obesity, is measured via indirect calorimetry method through breath biomarkers of CO2 production and/or O2 consumption rates (VCO2 and/or VO2, respectively). Current technologies are limited due to prevailing designs requiring wearable facial accessories that present accuracy, precision, and usability concerns with regards to free living measurement. A novel medical device and smart home system, named Smart Pad, has been developed, with the capability of energy expenditure assessment via VCO2 measured from a room’s CO2 concentration. The system has 3 distinct capabilities: contactless EE measurement, air quality optimization via actuation of room ventilation, and efficiency optimization via ventilation actuation of only human-occupied environments. The Smart Pad shows accuracy of 90% for 14-19 minutes of resting measurement and accuracy of 90% for 4.8-7.0 minutes of exercise measurement after calibrating for air exchange rate (λ [hour-1]) using a reference method. Without reference instrument calibration, the Smart Pad system shows average accuracy of nearly 100% with correlations of Y=1.02X, R=0.761 for high resolution measurements and Y=1.06X, R=0.937 for averaged measurements over 50-60 minutes. In addition, the Smart Pad validation for contactless EE measurement has been performed in different environments, including a vehicle, medical office, a private office, and an ambulatory enclosure with rooms, ranging in volume from 3.1 m3 to 18.8m3. It was concluded that contactless EE measurements can be accurately performed in all tested scenarios with both low and high air exchange environments with λ ranging from 1.5 Hours-1 to 10.0 Hours -1. The system represents a new way to assess EE of individuals under free-living conditions in an unobstructive, passive, and accurate manner, and it is comparable or better in single breath gas measurement accuracy (with comparisons sourced from FDA data) than other medical devices (e.g. Vyntus CPXTM, MasterScreen CPXTM, Oxycon ProTM, and MedGemTM) which were 510(k) cleared by the FDA for prescription use in metabolic/cardiopulmonary diagnostics.