PROJECT SUMMARY/ABSTRACT Photoelectrical stimulation of cells is an emerging technique with tremendous potential for expanding the toolset for tissue engineering as well as enabling new therapies for treating neurological diseases, but its potential applications are limited by the large size of the existing photoelectrical-stimulation devices. The objective of this proposed study is to develop a novel device for photoelectrical stimulation. The device, which is termed microdevice, is featured by a sub-10 µm size and disk-like shape, a well-defined layered structure for converting light to electrical signals via the photovoltaic mechanism, and engineerable surface properties. These features potentially allow the microdevices to bind to individual cells and modulate their behaviors through photoelectrical stimulation. The specific aims are to (1) establish a protocol for fabricating the designed microdevices, and (2) evaluate the performance of the microdevices in photoelectrical stimulation of cells. Successful completion of the proposed research will validate feasibility of the microdevice and lay a foundation for its further development into a viable tool for tissue engineering research and neuromodulation therapy.