PhD Defense: "Microfabrication of Biomimetic Structures for Neural Interfaces"

Samuel Beach

September 12th (Friday), 11:00am
Elings Hall (CNSI), Room 1605

Interfacing with the brain is a challenging problem. While many innovative methods for providing input and output to neural systems have been developed and demonstrated successfully in human patients, these invasive systems use less biologically compatible means than are realizable. Materials and mechanisms which are closer mimics to biological systems in their behaviors can lead to more stable and effective medical prosthetic and research devices.

Retinal prosthetics as well as Cochlear implants, are neural implants which provide stimulation via electrical impulses. Currents passing across neurons trigger neurons to begin firing or generating an action potential down their axons, stimulating neurons with dendrites connected to those axons terminals. This scheme transduces the desired simulation into neural firing spikes, but the majority of applied current is shunted around neurons rather than contributing to stimulation. Excess current contributes to the power and thermal budgets of neural simulation devices, which are implanted in tissue, limiting their functionality. Additionally, the electrical contacts which provide a source and return for the stimulation currents are subject to degradation over time, as currents are repeatedly applied during stimulation events. Stimulation of neurons via local delivery of potassium in excess of available intercellular potassium can be used in place of direct electrical stimulation and promises to be a more biologically compatible method.

An orthogonal issue is neural recording. Several devices have been developed and the widest know and highest density is the Utah array, a 3D array of silicon spires, which can record from their tips when inserted into neural tissue. While this 3D array topology can access a field of neural activity, the stiffness of these silicon spires is very different than that of neural tissue, which can lead to an unwanted inflammatory response. Conductive polymer pillars made of softer materials that are a closer match to neural tissues, while mirroring the Utah array’s density and insertion length, may provide a better recording mechanism due to their improved mechanical compatibility with neural tissues.
This thesis investigates microfabrication schemes to produce biomimetic structures that can enable neural simulation and recording devices which feature greater biological stability and improve utility.

About Samuel Beach:

Samuel Beach graduated from the University of California Santa Barbara with a Bachelors of Science in Electrical Engineering in 2007. He earned his Masters in Electrical and Computer Engineering at UCSB in 2009 and a GPMP certificate in 2010. Samuel has a passion for microfabrication and since beginning his graduate education, has enjoyed assisting the Electrical and Computer Engineering department's microfabrication course sequences as well as NNIN Chip Camps. Samuel joined the Biomimetic Circuits and Nanosystems Group in 2008. He has worked on several research projects involving microfabrication. His primary focus has been to develop structures and fabrication techniques to facilitate the development of high-density neural implants (HDNI), flexible neural recording pillar electrodes, alumina nanoporous membranes, and electrically gated selective ion pumps. Samuel has worked for both IBM and Intel and will be joining Intel this fall.

Hosted by: Professor Luke Theogarajan