The present invention includes methods for effecting phenotype conversion in a cell by transfecting the cell with phenotype-converting nucleic acid. The circuit is adapted to deliver power to a load by providing power generated by the energy harvesting device to the load without delivering excess power to the battery and to supplement the power generated by the energy harvesting device with power from the battery if the power generated by the energy harvesting device is insufficient to fully power the load. A torsion spring is attached to the at least one flap member to urge the same to pivot against a fluid pressure differential, from the first position to the second position when the fluid pressure differential is smaller than a predetermined level.