“School of Nano-Sciences”
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| Paper IPM / Nano-Sciences / 16918 |
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| Abstract: | |||||||||||
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Several fundamental research and applications in biomedicine and microfluidics often require controlled manipulation of suspended micro- and nanoscale particles. Speckle tweezers (ST) by incorporating randomly distributed light fields have been used to control microparticles with refractive indices higher than their medium and to perform manipulation tasks such as guiding and sorting. Indeed, compared to periodic potentials, ST represents a wider possibility to be operated for such tasks. Here, we extend the usefulness of ST into micro-particles of low index with respect to the surrounding. Repelling of such particles by high intensity regions into lower intensity regions makes them to be locally confined, and the confinement can be tuned by changing the average grain intensity and size of the speckle patterns. Experiments on polystyrenes and liposomes validate the procedure. Moreover, we show that ST can also manipulate the nanoparticle (NP)-loaded liposomes. Interestingly, the different interactions of NP-loaded and empty liposomes with ST enable collective manipulation of their mixture using the
same speckle pattern, which may be explained by inclusion
of the photophoretic forces on NPs. Our results on the
different behaviors between empty and non-empty vesicles
may open a new window on controlling collective
transportation of drugmicro-containers alongwith itswide
applications in soft matter.
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