Methods and apparatus for use of optical forces for identification, characterization and/or sorting of particles

Abstract

Apparatus and methods are provided for interacting light with particles, including but not limited to biological matter such as cells, in unique and highly useful ways. Optophoresis consists of subjecting particles to various optical forces, especially optical gradient forces, and more particularly moving optical gradient forces, so as to obtain useful results. In biology, this technology represents a practical approach to probing the inner workings of a living cell, preferably without any dyes, labels or other markers. In one aspect, a particle may be characterized by determining its optophoretic constant or signature. For example, a diseased cell has a different optophoretic constant from a healthy cell, thereby providing information, or the basis for sorting. In the event of physical sorting, various forces may be used for separation, including fluidic forces, such as through the use of laminar flow, or optical forces, or mechanical forces, such as through adhesion. Various techniques for measuring the dielectric constant of particles are provided.

1 . A method for separating particles comprising the steps of:
 subjecting particles to optical gradient force,   analyzing, based at least in part on the relative motion of the particles, and   separating using at least in part an optical gradient force the desired particle from other particles.   
     
     
         2 . A method for separating particles comprising the steps of:
 providing a plurality of particles supported on a first surface, the first surface interfacing with a volume, and   providing an optical gradient force to cause selected ones of the particles to be moved from the support of the first surface to the volume.   
     
     
         3 . The method for separating particles of  claim 2  wherein the optical gradient results from interference. 
     
     
         4 . The method for separating particles of  claim 3  wherein the interference is generated by shining an optical beam onto a mirror. 
     
     
         5 . The method for separating particles of  claim 4  wherein the mirror comprises the surface. 
     
     
         6 . The method for separating particles of  claim 2  further including the step of disposing an adhesive structure adjacent the volume to adhere at least certain of the particles moved from the support.