To measure urine sugar levels in elderly or long-term care patients, sensors can be embedded directly into their diapers. By wirelessly transmitting the acquired data, diaper sensors can greatly simplify caretaking and health monitoring tasks.

The scientists developed a paper-based biofuel cell that, through a pair of reduction-oxidation reactions, outputs electrical power proportional to the amount of glucose in the urine. Important considerations in the design of such biofuel cells are the amount of urine needed to generate enough power and the overall stability and durability of the device.

The scientists developed a special anode, the negative terminal of an electrochemical cell, using a process known as graft polymerization that allowed them to firmly anchor glucose-reactive enzymes and mediator molecules to a porous carbon layer, which served as the base conductive material. They tested their self-powered biosensor in diapers using artificial urine at various glucose concentrations. They used the generated energy to power up a Bluetooth low energy transmitter and remotely monitored the measured concentration using a smartphone. They found that the biofuel cell could detect urine sugar within 1 second.

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