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Biofuel Cells

Various biofuels pathways have been under research in the last decades, but most of them have showed limited applications because of their insufficient energy output (inferior to the minimal threshold of 5 mW/mL needed to supply biomedical devices). For instance, systems that utilize vibrations or body movements to scavenge power for an implanted device are currently limited to few μW/mL in the best cases due to low frequency of body movements or heart contractions. Seebeck thermoelectric effect cannot be used for implanted devices because there is almost no differential temperature inside the body. Betavoltaic cells could be used for isotope energy conversion but current density is still low like NanoTritium™ from Citylabs which current is 0.1 μA/cm2 for 0.7V.

 

In recent years, two types of Biofuel Cells have been making headlines for their energy output potential:

- Glucose BioFuel Cells (GBFC), which exploiting the ubiquitous presence of glucose in body fluids for energy production.

- Biomimetic Biofuel Cells (BBFC), capable of turning NaCl gradient into electrical energy.

 

Glucose Biofuel Cells (GBFC)

A GBFC consists of two bioelectrodes modified by immobilized enzymes catalyzing the oxidation of glucose at the anode, mainly by glucose oxidase (GOx) and the reduction of dioxygen at the cathode via laccase (Lc) or bilirubin oxidase. The concomitant oxidation and reduction processes at the electrodes yield electrical power.

Fig. Schema of principle of a GBFC

At the anode, glucose is oxidized to gluconolactone and electron, and the electrons are transferred from the GOX to CNT. At the cathode, electrons are transferred from CNT to Lc and dioxygen is reduced.

Unlike batteries, GBFC systems are constantly replenished with fresh reactants from the body fluids, and are therefore theoretically capable of operating indefinitely, as long as there is a constant supply of reactants.

 

Biomimetic Biofuel Cells (BBFC)

Biomimetic Biofuel cell systems present great potential in the near future. Such systems build on biomimetic lipid membranes which are a key element of several biosensors that incorporate transport proteins into the lipid membranes.