On-chip manipulation of levitated femtodroplets

We report diamagnetic levitation of droplets and/or particles of pico-femtoliter volume and demonstrate their on-chip storage and high precision manipulation (translation, merging, assembling and rotation). We also demonstrate a levitation based microfluidic processor to process droplets/particles with up to a billion times smaller volume than in typical microfluidic devices. The levitated particles can be positioned with up to 300 nm accuracy and precisely rotated and assembled, providing a different physical approach for micro-electro-mechanical systems. Force can be applied to the droplets/particles via magnetic, electric, and gravitational fields with up to femto-Newton accuracy, and potential energy can be controlled with up to 0.2 zepto J(0.05k(B)T) precision, thus providing experimental tools for fundamental studies. (C) 2004 American Institute of Physics.