Abstract
Objective. For decades electrical stimulation has been used in neuroscience to investigate brain networks and been deployed clinically as a mode of therapy. Classically, all methods of electrical stimulation require implanted electrodes to be connected in some manner to an apparatus which provides power for the stimulation itself. Approach. We show the use of novel organic electronic devices, specifically organic electrolytic photocapacitors (OEPCs), which can be activated when illuminated with deep-red wavelengths of light and correspondingly do not require connections with external wires or power supplies when implanted at various depths in vivo. Main results. We stimulated cortical brain tissue of mice with devices implanted subcutaneously, as well as beneath both the skin and skull to demonstrate a wireless stimulation of the whisker motor cortex. Devices induced both a behavior response (whisker movement) and a sensory response in the corresponding sensory cortex. Additionally, we showed that coating OEPCs with a thin layer of a conducting polymer formulation (PEDOT:PSS) significantly increases their charge storage capacity, and can be used to further optimize the applied photoelectrical stimulation. Significance. Overall, this new technology can provide an on-demand electrical stimulation by simply using an OEPC and a deep-red wavelength illumination. Wires and interconnects to provide power to implanted neurostimulation electrodes are often problematic in freely-moving animal research and with implanted electrodes for long-term therapy in patients. Our wireless brain stimulation opens new perspectives for wireless electrical stimulation for applications in fundamental neurostimulation and in chronic therapy.
Highlights
Neuromodulation using electrical stimulation is a technique to activate or inhibit excitable tissues such as the brain directly via the delivery of an electric current
With the flexible parylene-C/Au organic electrolytic photocapacitors (OEPCs) tested in our work, we found that PEDOT:PSS modification (150 nm thickness) leads to substantial improvements in performance
The devices are modeled over the barrel region of the somatosensory cortex, field vales can be seen to penetrate deeper into the cortex as expected for the devices covered in the additional PEDOT layer
Summary
Neuromodulation using electrical stimulation is a technique to activate or inhibit excitable tissues such as the brain directly via the delivery of an electric current. Electrical stimulation techniques were pioneered already in the beginning of the 20th century to reveal function and connectivity of brain regions. Penfield further developed the electrical stimulation method known as the ‘Montréal Procedure’ [2], which is still employed today during resective surgeries in epilepsy where electrical stimulation allows the delineation of healthy brain tissue versus epileptogenic areas to be resected. One feature common to all methods of electrical stimulation of brain tissue is the necessity to provide power to implanted electrodes via some manner of wire interfacing, typically via cables to power supplies or batteries. Batteries in vivo always have limited lifetimes and are restrictively bulky for convenient deployment in experimental animals [6, 7]
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