A. Charlton, N. Yousefpour, A. Parrott, X. Jia
Virginia Tech,
United States
Keywords: polymer fibers, electrophysiology, neural devices, biointerfacing, thermal drawing
Summary:
The world of neural implants has become an exciting and rapidly advancing field in neuroscience for applications ranging from studying diseases, in order to better understand their complex mechanisms, to developing biointerfacing devices for diagnostic and therapeutic use. One specific application is deep brain stimulation, which is used for neurodegenerative disease studies of conditions like Parkinson’s, Alzheimer, and epilepsy, using electrophysiology techniques and metal electrodes. Additionally, brain computer interfaces target conditions that involve damage to or loss of motor functions and aim to enhance quality of life of patients. However, conventional brain computer interfaces utilize silicon technologies, which are rigid, carrying the risk of breaking when inserted into the brain, and therefore lack chronic biocompatibility. These limitations have enabled the field of polymer neural probes to boom; the innovation of a flexible implantable device that can electrically interface with the brain, while concurrently performing multiple additional functionalities, opens many avenues for research and clinical advancement. Multifunctional, multimaterial fiber based neural probes have been used reliably for in vivo applications. Flexible, biocompatible materials such as polycarbonate have been used to fabricate the fiber itself. Additionally, materials such as tungsten, bismuth tin, and nickel chromium have been implemented as electrodes, which can be functionalized for each unique application. Through the use of each electrode working in tandem with integrated microfluidic channels, optical waveguides, and electrical transducers, these devices can be translated for use in applications ranging from neural stimulation and recording to drug delivery and biosensing. Cutting edge fabrication techniques allow us to design and manufacture intricate fiber geometries on the micron scale. As the field of neurodegenerative disease research expands, these methods will aid in the scalability, cost effectiveness, and customizability of our devices. Here we present an innovative probe design, fabricated with a high electrode count fiber in a compact, flexible package. This fiber device is comprised of sixteen metal electrodes housed in a biocompatible polymer cladding. This fiber device is then functionalized post fabrication to allow for an improved signal to noise ratio and targeted signal acquisition. Additionally, the electrode functionalizing allows our devices to interface along the length of the device, whereas current fiber technology sense from the device tip, limiting the neurons and depth they record at. This level of sensing has already been accomplished by predicate silicon devices; however, the novel, flexible nature of our fiber device, in combination with the increased functional surface area, provides the viable opportunity for chronic neural interfacing, unlike the rigid silicon probes in the market today.