UCLA Researchers Usher in Molecular Electronics Age - Demonstrate Molecular Nano Valve –
Molecular Filter Based on Bistable Molecular Switch
Under funding from the National Science Foundation, researchers at the University of California
at Los Angeles have developed a nano valve that is capable of controlling the passage of molecules. A discussion of
the work is to be published in the July 19th issue of the Proceedings of the National Academy of Sciences. . According to
Jeffrey I. Zink, one of the researchers at the California NanoSystems Institute at UCLA, "This paper demonstrates unequivocally
that the machine works. With the nano valve, we can trap and release molecules on demand. We are able to control molecules
at the nano scale." Professor Zink also indicated that the new device has the potential be used as a drug delivery system.
The device can be used to both trap and release molecules.
The lead author on the paper, Thoi Nguyen, described the nano valve’s
operation, "The valve is like a mechanical system that we can control like a water faucet. Trapping the molecule inside and
shutting the valve tightly was a challenge. The first valves we produced leaked slightly."
The nano valve uses switchable rotaxane molecules (redox-activated
bistable), which are described as moving parts that are similar in appearance to linear motors. The nano valve demonstrated
was attached to glass or porous silica, which measured 500 nanometers, and is punctuated with pores that are only a few nanometers.
Commenting on the pores, Zink said, "It's big enough to let molecules in and out, but small enough so that the switchable
rotaxane molecules can block the hole."
The nano valve is opened and shut with a power supply that is molecular
in nature itself. A single electron serves as the basis chemical energy that opens and closes the valve. A luminescent molecule
is used to indicate if a molecule has been captured.
California NanoSystems Institute director Fraser Stoddart characterized
the behavior of the nano valve in relation to silicon, "The fact that we can take a bistable molecule that behaves as a switch
in a silicon-based electronic device at the nanoscale level and fabricate it differently to work as part of a nano valve on
porous silica is something I find really satisfying about this piece of research. It shows that these little pieces of molecular
machinery are highly adaptable and resourceful, and means that we can move around in the nanoworld with the same molecular
tool kit and adapt it to different needs on demand."
Switchable rotaxanes, according to UCLA, have already been used
in molecular electronics, which the UCLA team under the direction of Stoddart, are being adapted for artificial molecular
machinery applications.
The integrated circuit age was also ushered in with a switch device,
the diode and transistor, which has formed the basis for the integrated circuit, a device which now days can easily contain
over a billion transistors connected together to form an advanced system. The same basic hierarchical technology used to design
integrated circuits, known as Electronic Design Automation (EDA), may also be fundamental to the design of molecular systems
that may one day also contain billions if not trillions of nano valves.
