Bio fuel cell in PCB layers for wearable designs

July 13, 2020 //By Nick Flaherty
A Glucose Fuel Cell (GFC) developed at the University of Bath can be stacked four deep on a PCB to generate power from sweat
A Glucose Fuel Cell (GFC) developed at the University of Bath can be stacked four deep on a PCB to generate power from sweat

Researchers at the University of Bath in the UK have developed the first fuel cell that can be stacked in a printed circuit board

Glucose Fuel Cells (GFCs), also called biofuel cells, generate power from any body fluid at room temperature, including sweat for wearables and blood for embedded medical devices

The team led by Carla Gonzalez-Solino at the Centre for Biosensors, Bioelectronics and Biodevices (C3Bio) at the University of Bath developed an integrated arrays of GFCs and successfully demonstrate their operation at physiological concentrations of glucose.

Each GFC consists of a porous gold anode and a Pt/Au cathode in a single layer, and generates a maximum power of 14.3 μW/cm 2 a 297mV with a 6 mM concentration of glucose. This has a linear response to glucose within a concentration range that includes both low and high glucose levels and so could also be used with embedded medical sensors that are powered by blood.

The challenge for individual GFCs is the low voltage output, so the team also connected four GFCs in parallel in a stack on a PCB. This generated between 1.4V and 0.9V.

Each board measures 42.5 mm x 34.5 mm consisted of four rows that include a circular electrode (geometric area: 1.54 mm2) used as the anode, and a crescent electrode, used as the cathode (geometric area: 7.22 mm2).

To demonstrate meaningful energy harvesting, the four GFC stack was connected to a commercial off-the-shelf power management system using a BQ25504 PMIC from Texas Instruments that can handle the low output voltage. The BQ25504 system is designed to operate with input voltages as low as 100 mV, a range that covers most fuel cells. It has a built-in Maximum Power Point Tracking (MPPT) function that finds the open circuit potential (OCP) of the fuel cell and sets the operating point by varying the effective load impedance seen by the fuel cell to  around 80 percent of this voltage.

The OCP is sampled for 256 ms, which,

Picture: 
A Glucose Fuel Cell (GFC) developed at the University of Bath

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