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.