Location: Bldg. 216, Rm. D106
Nanoparticles come in a huge variety of materials, shapes and surface properties. The ability to configure their properties precisely makes them useful as fundamental building blocks for new materials and devices. Traditional, top-down methods of fabrication and assembly are not suitable for handling large numbers of small particles. Instead, the processes of self-assembly and directed self-assembly must be used. Understanding the forces acting between nanoparticles and between nanoparticles and surfaces is the first step in developing methods to control their interactions and assembly. We have developed particle tracking techniques using optical microscopy that use sophisticated image and statistical analysis methods to follow the motion of nanoparticles in three dimensions and in real time. Even though the image size of a single particle under an optical microscope is limited by diffraction, our methods can determine the particle position with a precision of a few nanometers. By collecting information on the relative amount of time a particle spends in a given location, the forces experienced by the particle can be mapped out. This information can then be used to determine all the forces acting between particles or between particles and nanostructured surfaces. Our highly precise particle tracking techniques can also be used to monitor particle position during closed-loop feedback control of particle position, and we have developed a microfluidic system using electro-osmotic flow that enables such control.