Electrical & Computer Engineering
Department of Electrical and Computer Engineering
University of California, Santa Barbara
Santa Barbara, CA 93106
Personal web site
Bio-ionic Retinal Prosthesis
The final envisioned molecular prosthesis
Neural prosthetic devices offer a means of restoring functions that have been lost due to neural damage. Since the discovery of electrically excitable cells by Galvani, most interfaces with neural tissue have relied on electrical signals. The approach can be successful, as demonstrated impressively by the cochlear implant; however electrical interfaces employed by the cochlear implant or the currently investigated microelectrode arrays for retinal prostheses are not always optimal. The key limitation of electronic prosthetic devices is fundamental: electronic interfaces and the natural neural environment are incompatible in both form and function. One approach, that we are investigating in our group, to overcome this key issue is to use potassium ions rather than electrons to communicate with neural tissue. This method has several advantages over the currently used electrical approach, namely: 1) requires lower power, 2) is non-neurotoxic in concentrations required for stimulation and 3) allows for focal stimulation. Furthermore, unlike other chemical stimulation approaches, the potassium ions can be actively sequestered from the background extracellular fluid. The elimination of large storage reservoirs by this approach renders it safer since accidental release of large quantities of a neuroactive compound can lead to catastrophic destruction of neural tissue. Though the electronic interface is sub-optimal, the strength of electronic devices is their ability to process information. Harnessing the power of this mature technology will be key to the success of any neural prosthetic device. Hence we are developing a hybrid device with the information processing performed by low power electronic circuitry and the interface being ionic. We are concurrently investigating conventional electronic brain-machine interfaces to gain deeper understanding of functional restoration using neural implants.
Our group is a diverse mix of electrical engineering, biophysics, chemistry and neuroscience. Since the bio-ionic approach is an instance of a molecular machine we are also broadly investigating the design of biomimetic molecular machines, new polymeric constructs for self-assembly and novel supramolecular assemblies.
In addition to neural prostheses which is the fundamental focus of our group, we are also investigating the development of smart biosensors that couple nanoscale sensors with conventional CMOS circuits using micro/nanofabrication techniques.
Theogarajan is currently a Assistant Professor at the University of California, Santa Barbara in Electrical and Computer Engineering. His research interests include combining the processing power of electronics with the versatility of synthetic chemistry to develop neural prosthetic devices, integrating CMOS circuits with nanoscale sensors to develop novel biosensors and developing simple synthetic mimics of biological function to gain a deeper physical understanding of biological phenomena. Before starting his Ph.D, he worked for intel for 5 years where he was part of the Pentium 4 design team. He has published both in the field of electrical engineering and polymer chemistry and holds 4 patents.
See complete list of publications
- A Low Power 15-Channel Retinal Stimulator Chip, Journal of Solid-State Circuits, In Press, 2008, L. Theogarajan
- Versatile Synthesis of Self-assembling ABA Triblock copolymers with Polymethyloxazoline A-blocks and a Polysiloxane B-block Decorated with Supramolecular Receptors, Polymer International, 57, 2008, 660-667, L. Theogarajan, S. Desai, M. A. Baldo and C. Scholz
- Minimally Invasive Retinal Prosthesis, Solid-State Circuits, 2006 IEEE International Conference Digest of Technical Papers (ISSCC), 2006, 99-100, L. Theogarajan et. al