Construction of Single Molecule Electronic Devices, with Applications to Biosensing
Background: "Molecular Electronics" (ME) generally refers to a class of novel electronic devices in which the electronic response and function are entirely controlled by single molecules. In principle, a wide range of devices can result from the incorporation of different types of molecules (e.g. molecules that switch, store charge, absorb light, or otherwise participate in reactions). Covalently linking a single molecule of interest between two electrical conductors enables the electrical interrogation of that molecule as it dynamically interacts with the surrounding environment. In practice, however, working single-molecule devices remain exceedingly difficult to fabricate. Successes based on very small electrode gaps fabricated lithographically, electrically, or by scanning probe techniques generally suffer from low fabrication throughput; electrical, mechanical, and chemical instabilities; poorly defined bonding to the molecule of interest; and, sometimes, inconclusive proof that only a single molecule is addressed. Single-walled carbon nanotubes (SWNTs) have several favorable characteristics for building high-quality, single-molecule devices. Electrically, they are high-conductivity, one-dimensional (1D) conductors that can deliver signals to and from attached molecules. Chemically, SWNTs have long, inert sidewalls but reactive ends to which the tools of organic chemistry can covalently attach a wide variety of species. Geometrically, SWNTs' small profile maximizes access to the target molecule by reagents, optical probes, or electrostatic fields. Many strategies for building functioning, nanometer-scale circuits have focused on complex manipulation or high-resolution lithographies. Technology: University of California researchers have developed an alternative technique that does not require high-resolution lithography and is effective for molecules of any size. The general scheme is to fabricate circuits using individual SWNTs and then use the SWNT conductance G as a real-time indicator of SWNT chemical modification. With the use of electrochemically driven reactions, the introduction of functional groups can be electronically controlled and monitored with microsecond temporal resolution, so that point functionalization can be achieved with better than 90% yield. We used covalent attachments to single-walled carbon nanotubes (SWNTs) to fabricate single molecule electronic devices. The technique does not rely on submicrometer lithography or precision mechanical manipulation, but instead uses circuit conductance to monitor and control covalent attachment to an electrically connected SWNT. Discrete changes in the circuit conductance revealed chemical processes happening in real time and allowed the SWNT sidewalls to be deterministically broken, reformed, and conjugated to target species. By controlling the chemistry through electronically controlled electrochemical potentials, we were able to achieve single chemical attachments. We routinely functionalized pristine, defect-free SWNTs at one, two, or more sites and demonstrated three-terminal devices in which a single attachment controls the electronic response. Application: The primary invention described here is a versatile process for fabricating ME devices starting from circuits of single-walled carbon nanotubes (SWCNTs). Our fabrication incorporates single molecules into each ME circuit and is demonstrated using two different proteins. The resultant circuits can serve a wide range of commercial and scientific purposes as sensitive biosensors, chemical sensors, and tools for scientific investigation.
Type of Offer:
« More Biotech Patents« More Biomedical Patents