Keith Bonin's research

Optical Physics - Nanoscopic Physics and Molecular Motors

Professor Bonin's research interests include studying fundamental optical properties of nanoparticles and in using nanoparticles to study important physical systems - specifically nanomotors and biomolecular motors. Light forces and light torques have been applied in unique ways to nanoscopic systems. Most recently, we have been working at producing a nanomotor using optical tweezers. Such a nanomotor would have broad applicability to many areas of science, including laser trapping, rotational biomotors, nanomanipulation and nanotechnology, nanorheology and cellular structure studies, and single-particle optical spectroscopy. We are also developing techniques for optical manipulation of single-particle nanostructures to produce novel nanoelectronics or chemical sensors. Nanomotors will be a critical component of nano electromechanical systems (NEMS). These investigations involve cw lasers and a research-class microscope in conjunction with interesting nanostructures. Our optical tweezers nanomotor setup currently consists of an one of either an infrared or green DPSS Nd:YAG laser coupled into an Olympus microscope. The sample is imaged onto a Point-Grey (square pixel) CCD camera controlled by Streampix software. We record at frame rates in excess of 150 Hz.

We are interested in applying novel optical techniques, such as single-molecule detection, optical tweezers, and total-internal reflection to investigate and understand the operation of biological motors. In collaboration with biophysicists in the department, we are using a novel combination of Atomic Force Microscopy and Fluorescence Microscopy to select useful aptamers for drug delivery. This research involves the use of an inverted Zeiss microscope, a VEECO AFM, and an emccd camera for ultrasensitive light detection. Total Internal Fluorescence (TIRF) Micrsocopy is also being used to improve the signal-to-noise ratio of the system. This effort is being spearheaded by Prof. Martin Guthold in the Physics Dept, and includes Prof. Jed Macosko (Physics), Prof. Jim Vaughn (WFUSM), and other outside collaborators.

We have also used light forces to measure the optical properties of atoms and nanoparticles, e.g. C60. By scattering cluster beams through a laser light grating, the electric-dipole polarizability of clusters can be measured. Interesting studies include the electrical response and structure of fullerenes, endohedral fullerenes, and charged cluster beams. These techniques are important in providing experimental benchmarks for theoretical calculations of linear and nonlinear optical properties of clusters, nanostructures, and thin films.