A surface acoustic wave biofilm sensor integrated with a treatment method based on the bioelectric effect

Bacterial biofilms have an extensive impact on quality of life, ranging from severe infections in the clinical field to water facility contamination in environmental science. Biofilms are comprised of diverse bacteria that produce an extracellular matrix which prevents drug diffusion through them. Hence traditional antibiotic therapies require 500-5000 times the concentration used to eliminate non-biofilm-associated infections. Early biofilm detection is critical for effective eradication. Moreover, developing an alternative biofilm treatment method that utilizes low doses of antibiotics is desired. In this paper, a real-time microsystem is shown to detect growth of biofilms as well as their removal through integrated treatment. Detection of biofilms is achieved using a surface acoustic wave (SAW) sensor that monitors the total biomass by measuring the resonant frequency of the system. Biofilm treatment is based on the bioelectric effect (BE), a combination of low-dose antibiotics with application of both alternating and direct current signals. The detection limit of the SAW system is approximately 166 pg, corresponding to a bacterial population on the order of hundreds of bacteria. The system is used to observe an 80% reduction of total biomass when treated by the BE as compared to traditional antibiotics. Through system integration of the BE with the SAW sensor, simultaneous biofilm detection and treatment is achieved. The system consumes 194 μW of power, with the sensor and treatment consuming 100 μW and 94 μW, respectively. The integrated sensing and treatment capabilities of this system advance the development of an innovative biofilm control method.