Abstract
We demonstrate manipulation of microbeads with diameters from 1.5 to 10 µm and Jurkat cells within a thin fluidic device using the combined effect of thermophoresis and thermal convection. The heat flow is induced by localized absorption of laser light by a cluster of single walled carbon nanotubes, with no requirement for a treated substrate. Characterization of the system shows the speed of particle motion increases with optical power absorption and is also affected by particle size and corresponding particle suspension height within the fluid. Further analysis shows that the thermophoretic mobility (DT) is thermophobic in sign and increases linearly with particle diameter, reaching a value of 8 µm2 s−1 K−1 for a 10 µm polystyrene bead.
Highlights
We demonstrate manipulation of microbeads with diameters from 1.5 to 10 μm and Jurkat cells within a thin fluidic device using the combined effect of thermophoresis and thermal convection
By varying the focal plane of the microscope it was observed that a small number of particles at different heights in the fluid exhibited different behaviour: some particles close to the substrate moved towards the single walled carbon nanotubes (SWNTs) cluster, were redirected upwards as they approached the cluster, and moved away from the cluster
We have developed an alternative way to move microparticles with optical-thermophoretic tweezers using a combination of thermal convention and thermophobic thermophoresis
Summary
We demonstrate manipulation of microbeads with diameters from 1.5 to 10 μm and Jurkat cells within a thin fluidic device using the combined effect of thermophoresis and thermal convection. In electrical approaches, electrokinetics[16] and dielectrophoresis (DEP)[17] require an electric field to be established in the fluid to move particles, both techniques place restrictions on the electrical conductivity of the buffer 16–18. Other approaches, such as hydrodynamic flow[18,19], magnetic t weezers[20,21] and acoustic tweezers[22,23,24], are not capable of producing arbitrary patterns of microparticles.
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