Functional Electrical Stimulation (FES) and Deep Brain Stimulation (DBS) are clinical therapies for injuries and disorders of the nervous system. In FES, implanted stimulating electrodes deliver small amplitude electric currents to motor nerves to restore control and movement of paralyzed extremities in spinal cord injury and stroke patients (Popovic et al. 2001). In DBS, an electrode is surgically implanted deep in the brain and programmed to deliver a stimulating pulse train to the surrounding neural tissue to treat neurological disorders such as PD, OCD, Major Depression, and HD (Lee et al. 2009). Cochlear implants incorporating stimulation electrodes that excite the auditory nerve have partially restored lost hearing, and retinal implants consisting of microelectrode arrays interfaced with retinal ganglion cells are under development to treat lost vision (Squire et al. 2003; Wang et al. 2006). The NEI between the electrode and the surrounding neural tissue must be engineered to achieve the following: 1) biocompatibility to preclude immune responses to the implanted device and to promote long-term stability of electrode performance, 2) miniaturization to a size comparable to neural cells to facilitate electrode placement close to target cells, and 3) reduced impedance to improve the stimulation effi ciency. PPy-coated VACNFs in MBA confi guration can be used as a fl exible supporting substrate for neuronal growth with minimized mechanical stress, improved biocompatibility, reduced impedance, and enhanced stimulation effi ciency compared to contemporary metal microelectrodes. The combination of these properties can make a much more reliable NEI for FES and DBS potentially.