Molecular devices and molecular motors: Applications in nanotechnology.

摘要

Computer chip technology has been fast growing for several decades. But including more circuitry onto silicon chips now faces fundamental limits. The devices are made so small that they no longer function. In recent years, scientists have been trying to find a new path to overcome these limits: using single molecules and small chemical groups to make transistors and other standard components of computer chips. That is how “molecular electronics” gets its name. Molecular electronics, which deals with materials mostly in nanometer scale, gives scientists much more opportunities in developing nano- and molecular-scale electronics.; However, the realization of molecular-scale devices is much more difficult than theory. Although lots of work has been done in basic research, a real working device has not come out until recent years. Yet, there are many questions and suspicions in this area waiting for answers and solutions. That is the situation where this thesis comes out. Starting with basic research methods, this thesis presents several novel processes in developing molecular-scale devices, some are successful, some are not. These work include the physical characterization of self-assembled monolayers (SAMs), such as ellipsometry and contact angle measurements; and also provide insight into the electrical characterization of SAMs, including molecular probe station and membrane-template synthesized in-wire molecular junctions. But because none good molecule candidate exists, the development of molecular electronics are limited.; So, this thesis starts to take a different approach to investigate materials with even simpler structures. A large area testing device is investigated which is built from charge-transfer molecules (TCNQ) and solid polymer electrolytes. A known redox effect is observed for this system and it is believed to have memory potentials. Although it is not a real molecular device, it provides information on how to direct our research to find the good candidate molecules for future molecular memories.; A second approach is the application of molecular motor system. It is a new area coming out in recent years which uses the power of biological machines. This system uses kinesin and microtubules. Kinesins are biological motor proteins that transport intracellular cargo in vivo along microtubules. These motors move at roughly 1 μm/sec and are capable of generating cumulative forces in the order of nN per μm2. The size, efficiency, and potential power density suggest that it is possible to build sophisticated micro- and nano-devices powered by these motors. This thesis work employs microlithography as a tool to pattern channels on glass in order to extract useful work from these motors and orient microtubules traveling over kinesin-coated surfaces. In order to build simple devices, such as “lab-on-a-chip”, which uses the power of kinesin/microtubule system to sort out specific bio-molecules, arrowheads and bifurcations are made in order to obtain unidirectional movement of microtubules and DC and AC electric fields are used to guide microtubules to defined locations. Nanowire movement by this motor system is also observed, which indicates that the force generated by this system is sufficient for more general applications.; The author hopes that the demonstrations of building molecular devices, screening molecules with memory effects, and the manipulation of kinesin motor/microtubule system can give readers some information on new applications of nanotechnology and provide useful thoughts on the development of micro- and nano-electronics.