Soft Candy as an Electronic Material Suitable for Salivary Conductivity-Based Medical Diagnostics in Resource-Scarce...

Soft candy was discovered to be an excellent electronic material and was used to fabricate electrodes for salivary conductivity-based diagnostics. Using a simple molding process, a soft candy (Tootsie Roll) was made into 20 × 20 × 5 mm electrodes with a stable frequency response (0.1-100 kHz). The soft candy electrode-liquid interface circuit model was also developed for the first time. Using 0.01, 0.05, and 0.1 M phosphate-buffered saline and artificial saliva of varying conductivities, the performance of the soft candy (Tootsie Roll) electrode was evaluated. The electrode has a low temperature coefficient of ∼0.02 V/C, and the evaporation-induced mass change during measurement (<3 min) was negligible. Using a trenched surface, a limit of detection (LOD) of ∼1630 μS/cm was obtained and was lower than the saliva conductivity of a healthy adult at ∼3500 μS/cm. Thus, it is suitable for monitoring the ovulation cycle for natural family planning as well as chronic kidney disease diagnosis. Given the ubiquity of soft candy, the simplicity of the molding process, and the negligible medical waste stream, it is a more appropriate approach to diagnostics design for resource-scarce clinical settings, such as those in developing countries. The broader impact of this work will be the paradigm shift of soft candy from food to a new class of edible, moldable, high-resistivity, and stable electronic materials.