A chronic photocapacitor implant for minimally invasive neurostimulation with deep-red light

Implantable neuroelectronic devices are limited by a lack of
reliable, safe, and minimally invasive methods to wirelessly modulate neural
tissue. Here, we report the
development of organic electrolytic photocapacitors to stimulate a peripheral
nerve via the transduction of tissue-penetrating deep-red light into electrical
signals. The photocapacitor relies on efficient charge generation by nanoscale
organic semiconductors comprising non-toxic pigments, integrated on an
ultrathin flexible cuff with ultralow volume (0.1 mm3). The device can be wirelessly operated from an
external light source (via irradiation pulses of 50-1000 microseconds, at a
wavelength of 638 or 660 nanometres), actuating the implanted device at a depth
of approximately 10 millimetres below the skin’s surface. We demonstrate the
device’s functionality in vivo on the sciatic nerve of a rat, where a
microfabricated zip-tie mechanism stabilizes it into a fixed position and
enabled its long-term implantation, allowing neurostimulation that can be
sustained for over 100 days. Devices
operated by organic electrolytic photocapacitors are a biocompatible approach
to wireless neuromodulation and could be applicable to an array of clinical
bioelectronics.