A saliva-powered paper biobattery for disposable biodevices

We created a paper-based microbial fuel cell (MFC) which generated power from human saliva. Upon adding one drop of saliva, the dried exoelectrogens, pre-inoculated in a conductive paper reservoir of the MFC, activated their respiration by oxidizing organic substrates (e.g. glucose) in the saliva and transferring electrons to the anode. The device generated the maximum current density of 10.5μA/cm² and power density of 1.1μW/cm² with the glucose concentration of 19.4mg/dl in the saliva, which is enough to be directly used as an energy harvester in portable point-of-care (POC) devices. The biobattery fuses the art of paper microfluidics and the technology of biofuel cells and has the potential to shift the paradigm for disposable POC diagnostic tools by providing a practical power supply readily accessible everywhere. Furthermore, its electron harvesting capability as a quantitative indicator for the presence of organic substances (e.g. glucose) in saliva can potentially be utilized as a self-powered biosensor for monitoring the matter levels.