We demonstrated that a combination of thermophoresis and fluid flow can be used to trap molecules and particles. We showed that heating by scanning motion of an elongated laser spot creates a strong thermal trap. Additionally, it induces a global fluid flow that feeds the trap. Such “thermal sieve” can accumulate molecules from a large surrounding region within seconds into a 10 μm spot.
COBISS.SI-ID: 28423207
We report the transport of microparticles by rapid movement of a laser spot in a thin layer of a nematic liquid crystal. The transport is achieved by fluid flow, caused by two different mechanisms. The thermoviscous expansion effect induces colloidal transport in the direction opposite to the laser movement, whereas thermally induced local melting of the liquid crystal pulls the particles in the direction of the laser movement. We demonstrate control of colloidal transport by changing the speed of the laser spot movement and the laser power.
COBISS.SI-ID: 30397479
We have systematically investigated, experimentally and by modeling, the flow in a long microcavity and found that the flow properties depend decisively on the depth/width ratio of the cavity. If this cavity aspect ratio is higher than approximately 0.51, counter-flow vortices emerge in the cavity even at vanishing Reynolds number. In the vortex-free regime below the threshold aspect ratio, the flow velocity decays exponentially away from the cavity entrance, with a decay length that scales with the width of the cavity and depends also on the aspect ratio of its cross section. The results of our numerical simulations are supported by a theoretical analysis and are in good agreement with experimental data, acquired by optical velocimetry with optical tweezers.
COBISS.SI-ID: 2917732
We report on a maskless lithography rapid prototyping system for the fabrication of multimaterial hybrid structures in standard i-line negative photoresists enriched by the addition of functionalization particles. The system uses a combination of image recognition methods to detect particle positions in the photoresist and laser direct imaging to illuminate it with a focused ultraviolet laser. As a result, hybrid micron-sized structures composed of a base particle embedded in a photoresist frame can be manufactured using a one-pass process.
COBISS.SI-ID: 29246247