Photoelectrochemical molecular comb

An apparatus for separating molecules, said apparatus comprising:

• a substrate having a surface;
• a film in contact with said surface, and defining a substrate/film interface;
• an electrode electrically connected to said film which applies a potential between said electrode and said substrate to form a depletion region in said substrate at said substrate/film interface;
• and
• a photon energy source generating photon energy having an energy level greater than said potential, and directed at said depletion region to form electron-hole pairs in said depletion region, at least one of said electron-hole pairs being separated by said potential into an independent electron and an independent hole having opposite charges and move in opposing directions to create a photopotential in said film causing charged molecules in said film to move in response to the localized photovoltage, wherein one of said photon energy from said photon energy source and said substrate/film interface is movable relative to the other of said photon energy and substrate/film interface to scan said photon energy across said substrate/film interface at least once.