MEMS as implantable neuroprobes

MEMS devices are particularly promising as neuronal recording tools due to their small dimensions, suitability for multielectrode recording, integration with on-chip electronics, and potential for implantability. This chapter gives a recent overview of the state of the art in neural MEMS. Starting with a brief background on neuronal communication, the chapter reviews the development and latest advances in the well-known Michigan and the UTAH probes. The neural probe design from the EU-funded project is contrasted with these established Si-based probes for extracellular recording. The chapter touches on drug delivery and optical stimulation mechanisms that have been built into MEMS-based neural probes. It addresses the need for and issues of flexible neural probes that attempt to reduce the mechanical mismatch at the probe tissue interface, leading to a lower degree of host response and inflammation. Several different fabrication approaches for neural probes from single-sided assembly to flexible probes to growth of neural probes using vapor-liquid-solid mechanism have been discussed. Neural recording with MEMS devices are largely for extracellular neuronal recording. The chapter looks at intracellular neuronal recording with MEMS and the challenges in micromachining these devices. The chapter ends by discussing the biological response of tissue to implanted probes and the integrated circuit (IC) challenges for wireless recording with implantable devices.