Direct observation of athermal photofluidisation in azo-polymer films

Hurduc, Nicolae; Donose, Bogdan C.; Macovei, Alina; Păiuş, Cristina; Ibănescu, Constanţa; Scutaru, Dan; Hamel, Matthieu; Branza‐Nichita, Norica; Rocha, Licinio

doi:10.1039/c4sm00397g

Cited by 72 publications

(69 citation statements)

References 49 publications

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“…We interpret these voids as the effect of the successive isomerizations of the chromophores on the surrounding material, in agreement with the fluidization process recently reported around the chromophores [14][15][16] and with the increase of the diffusion predicted by simulations. By decreasing the temperature, we slow down the formation and organization of patterns, using the large increase of the viscosity and relaxation time of the azopolymer.…”

Section: Discussionsupporting

confidence: 91%

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Light mediated emergence of surface patterns in azopolymers at low temperatures

et al. 2015

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Polymer thin films doped with azobenzene molecules do have the ability to organize themselves in spontaneous surface relief gratings (SRG) under irradiation using a single polarized beam. To shed some light on this still unexplained phenomenon, we use a new method that permits us to access experimentally the very first steps of the pattern formation process. By decreasing the temperature, we slow down the formation and organization of patterns, due to the large increase in the viscosity and relaxation time of the azopolymer. As a result, decreasing the temperature allows us to access and study much shorter time scales, in the physical mechanisms underlying the pattern formation, than those previously reported. We find that the patterns organize themselves in sub-structures which size increases with the temperature, following the diffusion coefficient evolution of the material. This result suggests that the pattern formation and organization are mainly governed by diffusive processes, in agreement with some theories of SRG formation. Upon decreasing the temperature further, we observe the emergence of small voids located at the junction of the sub-structures.

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Section: Discussionsupporting

confidence: 91%

“…Various mechanisms have been proposed 1 to explain this transport. [14][15][16] Another important result is that the pressure needed to stop the isomerization of the chromophores is very high (P 4 1 GPa). 11 Interestingly, a few important results recently shed some light in that still unexplained huge isomerization induced transport.…”

Section: Introductionmentioning

confidence: 99%

Light mediated emergence of surface patterns in azopolymers at low temperatures

et al. 2015

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“…Indeed, characteristics of the glass-transition physics like cooperative motions called dynamic heterogeneities were reported to be generated during the motion of various motors [38][39][40][41][42]. The photo-fluidization and softening of the host material, or transient liquid-like behaviors, were also reported by different groups experimentally and by simulations [38,[43][44][45][46] with particular motors. These behaviors and possible cage-breaking processes induced by the motor [47,48] suggest that molecular motors small stimuli can be used to probe the physics of the glasstransition.…”

Section: Introductionmentioning

confidence: 89%

Folding time dependence of the motions of a molecular motor in an amorphous medium

et al. 2017

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We investigate the dependence of the displacements of a molecular motor embedded inside a glassy material on its folding characteristic time τ f . We observe two different time regimes. For slow foldings (regime I) the diffusion evolves very slowly with τ f , while for rapid foldings (regime II) the diffusion increases strongly with τ f ( D ≈ τ −2 f ) suggesting two different physical mechanisms. We find that in regime I the motor's displacement during the folding process is counteracted by a reverse displacement during the unfolding, while in regime II this counteraction is much weaker. We notice that regime I behavior is reminiscent of the scallop theorem that holds for larger motors in a continuous medium. We find that the difference in the efficiency of the motor's motion explains most of the observed difference between the two regimes. For fast foldings the motor trajectories differ significantly from the opposite trajectories induced by the following unfolding process, resulting in a more efficient global motion than for slow foldings. This result agrees with the fluctuation theorems expectation for time reversal mechanisms. In agreement with the fluctuation theorems we find that the motors are unexpectedly more efficient when they are generating more entropy, a result that can be used to increase dramatically the motor's motion.

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“…[17] Light responsivity is typically obtained by dispersing or chemically binding photoactive units within the polymer network. [19,20] Such a photoisomerization is crucial in triggering the so-called directional photofluidization [21,22] and induce deformation effects in azopolymers, [23,24] which have been extensively exploited as a fabrication mean to reversibly inscribe/erase surface relieves (SR) on continuous, homogenous planar films. [19,20] Such a photoisomerization is crucial in triggering the so-called directional photofluidization [21,22] and induce deformation effects in azopolymers, [23,24] which have been extensively exploited as a fabrication mean to reversibly inscribe/erase surface relieves (SR) on continuous, homogenous planar films.…”

Section: Doi: 101002/advs201801826mentioning

confidence: 99%

Driving Cells with Light‐Controlled Topographies

et al. 2019

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Cell–substrate interactions can modulate cellular behaviors in a variety of biological contexts, including development and disease. Light‐responsive materials have been recently proposed to engineer active substrates with programmable topographies directing cell adhesion, migration, and differentiation. However, current approaches are affected by either fabrication complexity, limitations in the extent of mechanical stimuli, lack of full spatio‐temporal control, or ease of use. Here, a platform exploiting light to plastically deform micropatterned polymeric substrates is presented. Topographic changes with remarkable relief depths in the micron range are induced in parallel, by illuminating the sample at once, without using raster scanners. In few tens of seconds, complex topographies are instructed on demand, with arbitrary spatial distributions over a wide range of spatial and temporal scales. Proof‐of‐concept data on breast cancer cells and normal kidney epithelial cells are presented. Both cell types adhere and proliferate on substrates without appreciable cell damage upon light‐induced substrate deformations. User‐provided mechanical stimulation aligns and guides cancer cells along the local deformation direction and constrains epithelial colony growth by biasing cell division orientation. This approach is easy to implement on general‐purpose optical microscopy systems and suitable for use in cell biology in a wide variety of applications.

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Direct observation of athermal photofluidisation in azo-polymer films

Cited by 72 publications

References 49 publications

Light mediated emergence of surface patterns in azopolymers at low temperatures

Light mediated emergence of surface patterns in azopolymers at low temperatures

Folding time dependence of the motions of a molecular motor in an amorphous medium

Driving Cells with Light‐Controlled Topographies

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