Nucleation and growth of thermoreversible polymer gels

Gomez-Solano, Juan Ruben; Blickle, Valentin; Bechinger, Clemens

doi:10.1103/physreve.87.012308

Cited by 12 publications

(11 citation statements)

References 23 publications

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“…Although this phenomenological description includes neither the detailed flow field around the microswimmer [35,36], nor a possible modification of the noise and friction due to the non-equilibrium particle motion [37,38], it reproduces the main non-trivial features observed in the experiments. Therefore, our findings are expected to be robust to such details and to happen for active colloids in other kinds of viscoelastic media [39,40], as well as for deformable microswimmers [41][42][43]. Moreover, it will be important to explore memoryinduced effects for microswimmers in viscoelastic media under other experimental conditions, e.g.…”

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confidence: 94%

Memory-Induced Transition from a Persistent Random Walk to Circular Motion for Achiral Microswimmers

2018

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We experimentally study the motion of light-activated colloidal microswimmers in a viscoelastic fluid. We find that, in such a non-Newtonian environment, the active colloids undergo an unexpected transition from enhanced angular diffusion to persistent rotational motion above a critical propulsion speed, despite their spherical shape and stiffness. We observe that, in contrast to chiral asymmetric microswimmers, the resulting circular orbits can spontaneously reverse their sense of rotation and exhibit an angular velocity and a radius of curvature that nonlinearly depend on the propulsion speed. By means of a minimal non-Markovian Langevin model for active Brownian motion, we show that these nonequilibrium effects emerge from the delayed response of the fluid with respect to the self-propulsion of the particle without counterpart in Newtonian fluids.

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confidence: 94%

Memory-Induced Transition from a Persistent Random Walk to Circular Motion for Achiral Microswimmers

2018

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“…In particular, it provides alternative methods to bulk rheology to investigate flow and deformation properties of microlitre samples of viscoelastic materials. For example, linear shear moduli can be inferred in passive microrheology from the thermal fluctuations of suspended colloidal particles via a generalized Stokes-Einstein relation [11][12][13][14]. On the other hand, in active microrheology, small-amplitude oscillatory forces can be applied to the particle, which enables the dynamical measurement of the linear viscoelastic response of the surrounding fluid [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Transient dynamics of a colloidal particle driven through a viscoelastic fluid

Gomez-Solano

Bechinger

2015

New J. Phys.

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We study the transient motion of a colloidal particle actively dragged by an optical trap through different viscoelastic fluids (wormlike micelles, polymer solutions, and entangled λ-phage DNA). We observe that, after sudden removal of the moving trap, the particle recoils due to the recovery of the deformed fluid microstructure. We find that the transient dynamics of the particle proceeds via a double-exponential relaxation, whose relaxation times remain independent of the initial particle velocity whereas their amplitudes strongly depend on it. While the fastest relaxation mirrors the viscous damping of the particle by the solvent, the slow relaxation results from the recovery of the strained viscoelastic matrix. We show that this transient information, which has no counterpart in Newtonian fluids, can be exploited to investigate linear and nonlinear rheological properties of the embedding fluid, thus providing a novel method to perform transient rheology at the micron-scale.

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“…It is indeed impossible to verify that the position where the particle is when the sample gelled is exactly the position of the laser, and a drift of only a few nm can be visible. This kind of drift can be avoided by having a more powerful heating laser to completely melt the gelatin on a larger area, as in [18]. Figure 13: 20 first trajectories for a quench at T fb = 28 • C, sampled at 400 Hz.…”

Section: Time N Trajectories δTmentioning

confidence: 99%

Fluctuations in an aging system: the absence of an effective temperature in the sol–gel transition of a quenched gelatin sample

et al. 2015

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We study the fluctuations of a Brownian micro particle trapped with optical tweezers in a gelatin solution undergoing a fast local temperature quench below the sol-gel transition. Contrary to what was previously reported, we observe no anomalous fluctuations in the particle's position that could be interpreted in terms of an effective temperature. A careful analysis with ensemble averages shows only equilibrium-like properties for the fluctuations, even though the system is clearly aging. We also provide a detailed discussion on possible artifacts that could have been interpreted as an effective temperature, such as the presence of a drift or a mixing in time and ensemble averages in data analysis. These considerations are of general interest when dealing with non-ergodic or non-stationary systems.

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Nucleation and growth of thermoreversible polymer gels

Cited by 12 publications

References 23 publications

Memory-Induced Transition from a Persistent Random Walk to Circular Motion for Achiral Microswimmers

Memory-Induced Transition from a Persistent Random Walk to Circular Motion for Achiral Microswimmers

Transient dynamics of a colloidal particle driven through a viscoelastic fluid

Fluctuations in an aging system: the absence of an effective temperature in the sol–gel transition of a quenched gelatin sample

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