Electrically controllable microfluidic devices based on bistable rotaxanes

ORGN 183

Lei Fang, lfang@chem.ucla.edu1, Ying-Wei Yang, yyang@chem.ucla.edu1, and J. Fraser Stoddart, stoddart@chem.ucla.edu2. (1) The California Nanosystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Dr. East, Los Angeles, CA 90095-1569, (2) California Nanosystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Dr. East, Los Angeles, CA 90095-1569
Microfluidics is the science and technology of systems that process or manipulate small (10-8 to 10-9 liters) amounts of fluids, using channels with dimensions of tens to hundreds of micrometres. As a technology, microfluidics offers many advantages for biological and chemical analysis. Molecular switches can modulate surface wetability. Macroscopic transport of liquid on surface by synthetic stimuli-responsive molecular shuttles has been achieved based on such surface wetability switch. This concept can also be utilized in fluid-pumping in microfluidics. The figure shows the proposed fluid-pumping mechanism using bistable [2]rotaxanes which can be switched by electricity or light. In (A), a layer of bistable rotaxane is on the surface of the electrode. The liquid segment is initially hydrophobic (nonwetting) with the entire surface. On applying a voltage between liquid and electrode, the molecules will experience internal mechanical motion and become hydrophilic, changing the contact angle of the meniscus at the bottom right corner. Consequently, the liquid segment will move to the right because the left hand side of the segment remains nonwetting while the right hand side is partially wetting. Alternatively, this molecular machine-based fluid pumping system can also be triggered by light. In (B), liquid droplets are sandwiched between two photoactive bistable rotaxanes-coated glass substrates. Applying light on one side of the droplet will result in an asymmetrical surface tension pattern on the droplet and drive fluid from left to right. We developed novel electrochemical-driven bistable rotaxanes 1 and 2, whose controllable mechanical motion can induce switchable hydrophobicity/hydrophilicity. The study of their applications in operations of microfluid is under exploring.

 

Total Synthesis, Materials, Devices and Switches, Molecular Recognition and Self-Assembly, Biologically-Related Molecules and Processes
8:00 PM-10:00 PM, Sunday, August 19, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Organic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007