An"ON-OFF" switchable power output of enzymatic biofuel cell controlled by thermal-sensitive polymer

A novel "ON-OFF" switchable enzymatic biofuel cell (EBFC), controlled by in situ thermal-stimuli signal, has been consciously designed. Poly (N-isopropylacrylamide) (PNIPAm) chains were used to act as "ON" and "OFF" channels. Consecutively switching of temperature below and above the lower critical solution temperature (LCST), the reversible conformation changing of the PNIPAm chains between superhydrophilicity and superhydrophobicity was achieved, which constructed the "ON" and "OFF" channel for the transfer of the electrochemical probe to the underlying electrode correspondingly. Gold nanoparticles (AuNPs) protected glucose oxidase and laccase were successfully entrapped into the intelligent thermal-sensitive PNIPAm chains, and performed as the catalysts for the oxidation of glucose and the reduction of O₂, respectively. Below the LCST, the fuels and the mediator could access to the catalytic centers of enzymes (set as "ON" state); while above the LCST, the reaction was impeded because the process of reactant transmission was blocked (set as "OFF" state). By switching the "valve" of mass transfer, the fabricated EBFC displayed the obvious "ON-OFF" controllable behavior. At the "ON" state, the open circuit voltage (E_cell^ocv) and maximal power output density (P_max) could reach to 0.70V and 20.52μWcm^-2, respectively; while at the "OFF" state, the E_cell^ocv and P_max were only 0.30V and 3.28μWcm^-2 correspondingly. The switchable process was repeatable, and the response time was only several minutes.