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. The invention includes methods for separating
particles in a medium where the particles having differing dielectric
constants by providing a medium having a dielectric constant between the
dielectric constants of the particles, subjecting the particles in the
media to an optical gradient field, and separating the particles.
