Charging of Heated Colloidal Particles Using the Electrolyte Seebeck Effect

We propose a novel actuation mechanism for colloids, which is based on the Seebeck effect of the electrolyte solution: Laser heating of a nonionic particle accumulates in its vicinity a net charge Q, which is proportional to the excess temperature at the particle surface. The corresponding long-range thermoelectric field E proportional to 1/r(2) provides a tool for controlled interactions with nearby beads or with additional molecular solutes. An external field E-ext drags the thermocharged particle at a velocity that depends on its size and absorption properties; the latter point could be particularly relevant for separating carbon nanotubes according to their electronic band structure.