Catalytically-Driven Nanomotors
Nanoscale moving systems are currently the subject of intense interest due in part to their potential applications in nanomachinery, nanoscale assembly, robotics, tribology, fluidics, and chemical/biochemical sensing. We have demonstrated that one can build nanomotors “from scratch” that mimic biological motors by using catalytic reactions to create forces based on chemical gradients. These motors are autonomous in that they do not require external electric, magnetic, or optical fields as energy sources. Instead, the input energy is supplied locally and chemically. Depending on the shape of the object and the placement of the catalyst, different kinds of motion can be achieved. The resulting nanomotors can, in principle, be tethered or coupled to other objects to act as the “engines” of nanoscale assemblies. Additionally, an object that moves by generating a continuous surface force in a fluid can, in principle, be used to pump the fluid by the same catalytic mechanism. Thus, by immobilizing these nanomotors, we have developed micro/nanofluidic pumps that transduce energy catalytically. Read more...Read about our work in Scientific American from May 6, 2009... | [mirror]
Read about our work in NSF Discoveries from November 20, 2008... | [mirror]
Read our Nature Highlight from November 1, 2007... | [mirror]
Read about our work in PhysicsWorld from November 6, 2007... | [mirror]
Read about our work in NanoTechWeb from Novermber 8, 2007... | [mirror]
Read our Science News Highlight from January 22, 2005... | [mirror]
Read the C&E News Highlight on nanomotors from February 21, 2005... | [mirror]
Polymer synthesis
One major goal of our ongoing research is the design of metal-catalyzed systems for the homo and copolymerization of functional polar vinyl monomers. Currently, both electron-rich (e. g., vinyl esters and ethers) and electron-deficient (e. g., acrylates, acrylonitrile, vinyl and vinylidene chlorides, and perfluoroalkenes) polar vinyl monomers are commercially produced by free-radical polymerization. As such, there is very little control over tacticity and molecular weight. Clearly, the discovery of general metal-catalyzed pathways for the homo and copolymerization of polar vinyl monomers would constitute a major breakthrough in polymer synthesis.We have been the first to describe the controlled radical copolymerization of polar vinyl monomers with simple alkenes, fluoroalkenes, and norbornene derivatives. This has led to the synthesis of unique random and block copolymers. Additionally, some of the copolymers of fluoroalkenes with polar vinyl monomers form strong adherent, yet hydrophobic, coatings on a variety of surfaces. Read more...
Materials
Bottom-up Assembly of Ordered Metamaterials: In conventional solids nature does not typically allow for much tuning of the bonding and electronic structure. Considerable interest has arisen in ordered arrays of quantum structures, such as quantum dots, that are linked together by molecules that facilitate electronic, magnetic and thermal communication. With such a metamaterial approach there is much more flexibility in designing the electronic structure by varying the linker molecules, the terminating end groups and the semiconductor quantum structures than there is for conventional solids. Our focus is on synthesis of well-ordered and structurally well-characterized 2 and 3-dimensional nanocomposite metamaterials. We have begun with an investigation of the synthesis of smaller, soluble clusters of ordered metamaterials, followed by extension of these studies to extended crystalline arrays. Read more...Read about our work in C&EN from January 10, 2008... | [mirror]
Read about our Editor's Choice feature in Science Magazine from January 11, 2008... | [mirror]
Novel Antimicrobial Polymers and Composites: Our research involves the design of polymers and polymer/inorganic nanoparticle composites with antimicrobial properties. In our work, we have sought to (a) develop new antimicrobial polymers and composites, (b) understand the structure-property relationships underlying their efficacy, and (c) bind the antimicrobials to surfaces to confer antiseptic properties to latter. Our synthesized materials have potent antibacterial activity towards both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Furthermore, the coated surfaces resist biofilm formation. These materials are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications. Read more...