Prof Ramin Golestanian

Abstract:

A design is proposed for a mechanical device made of a nanoscale pinion sandwiched without contact between two racks that exert opposing forces rooted in the quantum fluctuations of the electromagnetic field via the lateral Casimir force. The built-in frustration in the design of the system helps it to react dramatically to minute changes in the geometrical features, which suggests that it could act as a good sensor. The noncontact nature of this device could help solve the infamous wear problem in nanoscale mechanical devices. © 2009 IOP Publishing Ltd.

Abstract:

To achieve permanent propulsion of micro-objects in confined fluids is an elusive but challenging goal that will foster future development of microfluidics and biotechnology. Recent attempts based on a wide variety of strategies are still far from being able to design simple, versatile, and fully controllable swimming engines on the microscale. Here we show that DNA-linked anisotropic colloidal rotors, composed of paramagnetic colloidal particles with different or similar size, achieve controlled propulsion when subjected to a magnetic field precessing around an axis parallel to the plane of motion. During cycling motion, stronger viscous friction at the bounding plate, as compared to fluid resistance in the bulk, creates an asymmetry in dissipation that rectifies rotation into a net translation of the suspended objects. The potentiality of the method, applicable to any externally rotated micro/nano-object, is finally demonstrated in a microfluidic platform by guiding the colloidal rotors through microscopic-size channels connected in a simple geometry.