Novel nanowire structures and devices for nanoelectronic bioprobes

Abstract

Semiconductor nanowire materials and devices provide unique opportunities in the frontier between nanoelectronics and biology. The bottom-up paradigm enables flexible synthesis and patterning of nanoscale building blocks with novel structures and properties, and nano-to-micro fabrication methods allow the advantages of functional nanowire elements to interface with biological systems in new ways. In this thesis, I will focus on the development of bottom-up nanoscience platforms, which includes rational synthesis and assembly of semiconductor nanowires with new capabilities, as well as design and fabrication of the first free-standing three-dimensional (3D) nanoprobes, with special focus on applications in intracellular recording and stimulation. I will first introduce kinked p-n junction nanowires as a new and powerful family of high spatial resolution biological and chemical sensors with proof-of-concept applications. Next, I will discuss a variety of functional kinked nanowires with synthetically controlled properties and the potential of achieving more detailed and less invasive cellular studies. Furthermore, I will present a general shape-controlled deterministic nanowire assembly method to produce large-scale arrays of devices with well-defined geometry and position. Then, I will present the design of a general method to fabricate these nanowire structures into free-standing 3D probes. I will show that free-standing nanowire bioprobes can be manipulated to target specific cells and record stable intracellular action potentials. I will demonstrate simultaneous measurements from the same cell using both kinked nanowire and patch-clamp probes. Moreover, I will discuss two strategies of multiplexed recording using free-standing probes. Finally, I will report localized stimulation on single cells enabled by the unique properties of p-n kinked nanowires. I will show with simulation and electrical characterization that in reverse bias, localized electric field generated around the nanoscale p-n junction should exceed the threshold for opening voltage-gated sodium channels. Moreover, I will present measurements of localized cell stimulation using p-n nanowire free-standing probes. Together with the capability of stable intracellular recording, these results complete the two-way communication between semiconductor nanowire electronics and biological systems at a natural nanoscale, which can open up new directions in the fields ranging from cellular electrophysiology, brain activity mapping to brain-machine interface.