Manas Khan | Indian Institute of Technology, Kanpur (original) (raw)

Books by Manas Khan

Research paper thumbnail of Optical Tweezers: Methods and Applications in Contemporary Research

Research paper thumbnail of Optical Tweezers to Probe and Manipulate Soft, Nano and Bio Systems

Papers by Manas Khan

Research paper thumbnail of Local collective motion analysis for multi-probe dynamic imaging and microrheology

Journal of physics. Condensed matter : an Institute of Physics journal, Aug 7, 2016

Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely af... more Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely affect multi-probe dynamic imaging and passive particle-tracking microrheology experiments. Alternatively, active driving by molecular motors can cause interesting non-Brownian motion of probes in local regions. Existing drift-correction techniques, which require large ensembles of probes or fast temporal sampling, are inadequate for handling complex spatio-temporal drifts and non-Brownian motion of localized domains containing relatively few probes. Here, we report an analytical method based on local collective motion (LCM) analysis of as few as two probes for detecting the presence of non-Brownian motion and for accurately eliminating it to reveal the underlying Brownian motion. By calculating an ensemble-average, time-dependent, LCM mean square displacement (MSD) of two or more localized probes and comparing this MSD to constituent single-probe MSDs, we can identify temporal regimes dur...

Research paper thumbnail of Optical Tweezers: Methods and Applications in Contemporary Research

Research paper thumbnail of Trajectories of probe spheres in generalized linear viscoelastic complex fluids

Soft matter, Jan 7, 2014

We have developed a fast simulation that generates a random walk of an isolated probe sphere in a... more We have developed a fast simulation that generates a random walk of an isolated probe sphere in a generalized linear viscoelastic complex fluid over a highly extended dynamic range. We introduce a coupled harmonically bound Brownian particle (c-HBBP) model, in which the relaxation modes of the viscoelastic medium are treated as harmonic wells. These wells are coupled to the probe sphere and perform Brownian motion in bound harmonic potentials corresponding to the next-longer relaxation mode, according to the relaxation spectrum of the viscoelastic material. We implement this c-HBBP model by generating variable temporal step sizes that have a uniform distribution in logarithmic time. We create and analyze trajectories for several different viscoelastic complex fluids: a polymer system at its gel point, a dense emulsion system, a blend of two monodisperse polystyrene polymers for which the relaxation spectrum has been measured, and a model anisotropic soft system that shows dense emul...

Research paper thumbnail of Tunable Brownian vortex at the interface

Research paper thumbnail of Optical trapping and transportation of carbon nanotubes made easy by decorating with palladium

Research paper thumbnail of Nanorotors using asymmetric inorganic nanorods in an optical trap

Research paper thumbnail of Optically Driven Nanorotors: Experiments and Model Calculations

Journal of Nanoscience and Nanotechnology, 2007

Research paper thumbnail of Irreversibility-to-reversibility crossover in transient response of an optically trapped particle

EPL (Europhysics Letters), 2011

Research paper thumbnail of Out-of-equilibrium microrheology using optical tweezers to probe directional viscoelastic properties under shear

EPL (Europhysics Letters), 2010

Research paper thumbnail of Optical tweezer for probing erythrocyte membrane deformability

Applied Physics Letters, 2009

Research paper thumbnail of Digital Imaging of Colloidal Systems

Research paper thumbnail of Tunable Brownian Vortex at the Interface

A general kind of Brownian vortexes are demonstrated by applying an external nonconservative forc... more A general kind of Brownian vortexes are demonstrated by applying an external nonconservative force field to a colloidal particle bound by a conservative optical trapping force at a liquid-air interface. As the liquid medium is translated at a constant velocity with the bead trapped at the interface, the drag force near the surface provide enough rotational component to bias the particle's thermal fluctuations in a circulatory motion. The interplay between the thermal fluctuations and the advection of the bead in constituting the vortex motions is studied, inferring that the angular velocity of the circulatory motion offers a comparative measure of the interface fluctuations.

Research paper thumbnail of epl draft Irreversibility to Reversibility Crossover in Transient Response of an Optically Trapped Particle

Research paper thumbnail of Random-Walk Trajectories of Probe Particles in Viscoelastic Complex Fluids

Bulletin of the American Physical Society, 2014

Research paper thumbnail of Optical Tweezers To Probe And Manipulate Soft, Nano And Bio Systems

Research paper thumbnail of Random walks of colloidal probes in viscoelastic materials

Physical Review E, Apr 1, 2014

Research paper thumbnail of Optical Tweezers Microrheology Maps the Dynamics of Strain-Induced Local Inhomogeneities in Entangled Polymers

Research paper thumbnail of Optically-driven red blood cell rotor in linearly polarized laser tweezers

Research paper thumbnail of Local collective motion analysis for multi-probe dynamic imaging and microrheology

Journal of physics. Condensed matter : an Institute of Physics journal, Aug 7, 2016

Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely af... more Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely affect multi-probe dynamic imaging and passive particle-tracking microrheology experiments. Alternatively, active driving by molecular motors can cause interesting non-Brownian motion of probes in local regions. Existing drift-correction techniques, which require large ensembles of probes or fast temporal sampling, are inadequate for handling complex spatio-temporal drifts and non-Brownian motion of localized domains containing relatively few probes. Here, we report an analytical method based on local collective motion (LCM) analysis of as few as two probes for detecting the presence of non-Brownian motion and for accurately eliminating it to reveal the underlying Brownian motion. By calculating an ensemble-average, time-dependent, LCM mean square displacement (MSD) of two or more localized probes and comparing this MSD to constituent single-probe MSDs, we can identify temporal regimes dur...

Research paper thumbnail of Optical Tweezers: Methods and Applications in Contemporary Research

Research paper thumbnail of Trajectories of probe spheres in generalized linear viscoelastic complex fluids

Soft matter, Jan 7, 2014

We have developed a fast simulation that generates a random walk of an isolated probe sphere in a... more We have developed a fast simulation that generates a random walk of an isolated probe sphere in a generalized linear viscoelastic complex fluid over a highly extended dynamic range. We introduce a coupled harmonically bound Brownian particle (c-HBBP) model, in which the relaxation modes of the viscoelastic medium are treated as harmonic wells. These wells are coupled to the probe sphere and perform Brownian motion in bound harmonic potentials corresponding to the next-longer relaxation mode, according to the relaxation spectrum of the viscoelastic material. We implement this c-HBBP model by generating variable temporal step sizes that have a uniform distribution in logarithmic time. We create and analyze trajectories for several different viscoelastic complex fluids: a polymer system at its gel point, a dense emulsion system, a blend of two monodisperse polystyrene polymers for which the relaxation spectrum has been measured, and a model anisotropic soft system that shows dense emul...

Research paper thumbnail of Tunable Brownian vortex at the interface

Research paper thumbnail of Optical trapping and transportation of carbon nanotubes made easy by decorating with palladium

Research paper thumbnail of Nanorotors using asymmetric inorganic nanorods in an optical trap

Research paper thumbnail of Optically Driven Nanorotors: Experiments and Model Calculations

Journal of Nanoscience and Nanotechnology, 2007

Research paper thumbnail of Irreversibility-to-reversibility crossover in transient response of an optically trapped particle

EPL (Europhysics Letters), 2011

Research paper thumbnail of Out-of-equilibrium microrheology using optical tweezers to probe directional viscoelastic properties under shear

EPL (Europhysics Letters), 2010

Research paper thumbnail of Optical tweezer for probing erythrocyte membrane deformability

Applied Physics Letters, 2009

Research paper thumbnail of Digital Imaging of Colloidal Systems

Research paper thumbnail of Tunable Brownian Vortex at the Interface

A general kind of Brownian vortexes are demonstrated by applying an external nonconservative forc... more A general kind of Brownian vortexes are demonstrated by applying an external nonconservative force field to a colloidal particle bound by a conservative optical trapping force at a liquid-air interface. As the liquid medium is translated at a constant velocity with the bead trapped at the interface, the drag force near the surface provide enough rotational component to bias the particle's thermal fluctuations in a circulatory motion. The interplay between the thermal fluctuations and the advection of the bead in constituting the vortex motions is studied, inferring that the angular velocity of the circulatory motion offers a comparative measure of the interface fluctuations.

Research paper thumbnail of epl draft Irreversibility to Reversibility Crossover in Transient Response of an Optically Trapped Particle

Research paper thumbnail of Random-Walk Trajectories of Probe Particles in Viscoelastic Complex Fluids

Bulletin of the American Physical Society, 2014

Research paper thumbnail of Optical Tweezers To Probe And Manipulate Soft, Nano And Bio Systems

Research paper thumbnail of Random walks of colloidal probes in viscoelastic materials

Physical Review E, Apr 1, 2014

Research paper thumbnail of Optical Tweezers Microrheology Maps the Dynamics of Strain-Induced Local Inhomogeneities in Entangled Polymers

Research paper thumbnail of Optically-driven red blood cell rotor in linearly polarized laser tweezers

Research paper thumbnail of Local collective motion analysis for multi-probe dynamic imaging and microrheology

Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely af... more Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely affect multi-probe dynamic imaging and passive particle-tracking microrheology experiments. Alternatively, active driving by molecular motors can cause interesting non-Brownian motion of probes in local regions. Existing drift-correction techniques, which require large ensembles of probes or fast temporal sampling, are inadequate for handling complex spatio-temporal drifts and non-Brownian motion of localized domains containing relatively few probes. Here, we report an analytical method based on local collective motion (LCM) analysis of as few as two probes for detecting the presence of non-Brownian motion and for accurately eliminating it to reveal the underlying Brownian motion. By calculating an ensemble-average, time-dependent, LCM mean square displacement (MSD) of two or more localized probes and comparing this MSD to constituent single-probe MSDs, we can identify temporal regimes during which either thermal or athermal motion dominates. Single-probe motion, when referenced relative to the moving frame attached to the multi-probe LCM trajectory, provides a true Brownian MSD after scaling by an appropriate correction factor that depends on the number of probes used in LCM analysis. We show that LCM analysis can be used to correct many different dynamical artifacts, including spatially varying drifts, gradient flows, cell motion, time-dependent drift, and temporally varying oscillatory advection, thereby offering a significant improvement over existing approaches.

Research paper thumbnail of Trajectories of probe spheres in generalized linear viscoelastic complex fluids

We have developed a fast simulation that generates a random walk of an isolated probe sphere in a... more We have developed a fast simulation that generates a random walk of an isolated probe sphere in a generalized linear viscoelastic complex fluid over a highly extended dynamic range. We introduce a coupled harmonically bound Brownian particle (c-HBBP) model, in which the relaxation modes of the
viscoelastic medium are treated as harmonic wells. These wells are coupled to the probe sphere and perform Brownian motion in bound harmonic potentials corresponding to the next-longer relaxation mode, according to the relaxation spectrum of the viscoelastic material. We implement this c-HBBP model by generating variable temporal step sizes that have a uniform distribution in logarithmic time. We create and analyze trajectories for several different viscoelastic complex fluids: a polymer system at its gel point, a dense emulsion system, a blend of two monodisperse polystyrene polymers for which the
relaxation spectrum has been measured, and a model anisotropic soft system that shows dense emulsion-like and gel-point behaviors along two orthogonal directions. Except for unusual viscoelastic materials, such as the polymer system at its gel point, the generated trajectories are neither self-similar
nor self-affine. The resulting mean square displacements predicted by the c-HBBP model are consistent with the single-particle generalized Stokes–Einstein relation of linear passive microrheology.