Precision Marangoni-driven patterning

Arshad, Talha; Kim, Chae Bin; Prisco, Nathan A.; Katzenstein, Joshua M.; Janes, Dustin W.; Bonnecaze, Roger T.; Ellison, Christopher J.

doi:10.1039/c4sm01284d

Cited by 30 publications

(61 citation statements)

References 34 publications

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“…Perturbations can be created atop a polymer film, on a mesoscopic length-scale in a variety of ways. Unfavourable wetting properties [33][34][35][36][37], electrohydrodynamic instability [38][39][40], Marangoni flow [41][42][43][44], and thermocapillary forces [45][46][47][48][49] can all drive a flat film away from a uniform film thickness. The film viscosity η, surface tension γ, and unperturbed film thickness h 0 , are three parameters that influence the effective mobility of a film, which affects the relaxation of an applied surface perturbation.…”

Section: Introductionmentioning

confidence: 99%

Symmetry plays a key role in the erasing of patterned surface features

Benzaquen

Ilton

Massa

et al. 2015

Applied Physics Letters

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We report on how the relaxation of patterns prepared on a thin film can be controlled by manipulating the symmetry of the initial shape. The validity of a lubrication theory for the capillary-driven relaxation of surface profiles is verified by atomic force microscopy measurements, performed on films that were patterned using focused laser spike annealing. In particular, we observe that the shape of the surface profile at late times is entirely determined by the initial symmetry of the perturbation, in agreement with the theory. Moreover, in this regime the perturbation amplitude relaxes as a power-law in time, with an exponent that is also related to the initial symmetry. The results have relevance in the dynamical control of topographic perturbations for nanolithography and high density memory storage. arXiv:1503.08728v1 [cond-mat.soft]

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Section: Introductionmentioning

confidence: 99%

Symmetry plays a key role in the erasing of patterned surface features

Benzaquen

Ilton

Massa

et al. 2015

Applied Physics Letters

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“…The bidirectional flow of the polymer film materials here is driven by melt-state surface tension gradients caused by photochemically imposed chemical patterns. The magnitude of variations in surface tension needed to cause Marangoni flow is extremely small 24 and is potentially below the uncertainty associated with conventional surface energy analysis from water contact angle or pendant drop measurements. To verify the surface tension changes beyond uncertainty, host polymer films subjected to both chemical transformations were dewetted from the top of a hydrophobic surface, and the contact angles of the vitrified droplets were measured using AFM.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…Dehydrogenation of 6% of the repeat units in PS homopolymer results in a surface energy increase of 0.2 dyn/cm at 150°C. 24 This value enabled prediction of the surface energy change for the dehydrogenated styrene−acrylic acid copolymer used in this work.…”

Section: ■ Introductionmentioning

confidence: 99%

Bidirectional Control of Flow in Thin Polymer Films by Photochemically Manipulating Surface Tension

et al. 2015

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The Marangoni effect causes liquids to flow toward localized regions of higher surface tension. In a thin film, such flow results in smooth thickness variations and may represent a practically useful route to manufacture topographically patterned surfaces. An especially versatile material for this application should be able to be spatially programmed to possess regions of higher or lower relative surface tension so that the direction of flow into or out of those areas could be directed with precision. To this end, we describe here a photopolymer whose melt-state surface tension can be selectively raised or lowered in the light exposed regions depending on the wavelength and dose of applied light. The direction of Marangoni flow into or out of the irradiated areas agreed with expected surface tension changes for photochemical transformations characterized by a variety of spectroscopic techniques and chromatographic experiments. The maximum film thickness variations achieved in this work are over 200 nm, which developed after only 5 min of thermal annealing. Both types of flow patterns can even be programmed sequentially into the same film and developed in a single thermal annealing step, which to our knowledge represents the first example of harnessing photochemical stimuli to bidirectionally control flow. ■ INTRODUCTIONLiving organisms have evolved in remarkable ways to exploit surface tension and interfacial phenomena. 1−4 For example, water striders of the genus Microvelia possess an emergency ability to propel themselves forward by directing surface tension gradients on the water surface. By excreting organic, surfactant-like molecules to their rear, they create localized regions where the surface tension is 23 dyn/cm lower than its surroundings. 5 Microvelia are pulled, in the direction of higher surface tension via the Marangoni effect, which describes fluid transport due to surface tension gradients. 6,7 The Marangonidriven propulsion yields speeds of 17 cm/s, twice Microvelia's normal water walking rate. 5 Inspired by Microvelia, we seek to direct chemical changes in materials that rapidly alter the liquid surface tension in desired regions. To build upon observations of nature, we describe here a solid film that can be patterned with light to increase or decrease its melt-state surface tension in the light exposed regions. Light is an ideal stimulus to direct these changes because a wide array of chemical transformations can be applied with spatial precision 8,9 using photomasks. Control of the directionality of melt-state surface tension changes is obtained by selecting irradiating wavelengths and doses that activate different photochemistries in the solid state. To confirm directionality, the solid is heated to a liquid state, at which point Marangoni-flow occurs spontaneously from low-to-high surface tension regions. As a consequence, film thickness variations develop, which can be monitored in situ by optical microscopy or on cooled, vitrified films by atomic force microscopy (AFM) and profilometry. P...

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“…It is confirmed that the surface tension gradient should be the primary factor, and the other physical changes inside the film are negligible in our system. A small change in the surface tension can cause large mass convection in polymer films 39 . Hence, the surface tension gradient should be taken into more consideration in SRG studies.…”

Section: Srg Film Essentially Without Colourmentioning

confidence: 99%

Photo-triggered large mass transport driven only by a photoresponsive surface skin layer

Kitamura

Kato

Berk

et al. 2020

Sci Rep

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Since the discovery 25 years ago, many investigations have reported light-induced macroscopic mass migration of azobenzene-containing polymer films. Various mechanisms have been proposed to account for these motions. This study explores light-inert side chain liquid crystalline polymer (SCLCP) films with a photoresponsive polymer only at the free surface and reports the key effects of the topmost surface to generate surface relief gratings (SRGs) for SCLCP films. The top-coating with an azobenzene-containing SCLCP is achieved by the Langmuir-Schaefer (LS) method or surface segregation. A negligible amount of the photoresponsive skin layer can induce large SRGs upon patterned UV light irradiation. Conversely, the motion of the SRG-forming azobenzene SCLCP is impeded by the existence of a LS monolayer of the octadecyl side chain polymer on the top. These results are well understood by considering the Marangoni flow driven by the surface tension instability. This approach should pave the way toward in-situ inscription of the surface topography for light-inert materials and eliminate the strong light absorption of azobenzene, which is a drawback in optical device applications. Surface morphology generations on azobenzene(Az)-containing polymer films induced by patterned irradiation have been the active area in photofunctional material research. In 1995, Natansohn's 1 and Tripathy's 2 groups independently reported the induction of surface relief gratings (SRGs) on Az amorphous films using interference irradiation of two laser beams. Since then, photoinduced SRG processes have been reported using various photofunctional materials such as amorphous polymers 1-20 , side chain liquid crystalline polymers (SCLCPs) 21-27 , supramolecular systems 24,27-29 , amorphous molecular materials 30. Additionally, SRG formation can be realised using other photoresponsive units 31-35. Various mechanistic models for mass transfer have been proposed: isomerisation pressure due to volume change 7,8 , gradient force 9-11 , mean-field model 12 , directed softening or fluidisation 13-15 , molecular diffusion 16-18,34 , molecular orientation force 19,20 , etc. With regard to Az-containing SCLCPs 21-27 , UV light irradiation leads to a photochemical phase transition between the liquid crystal (LC) and isotropic phases. This phase change plays an important role in highly efficient SRG formation 23,25,26 , which requires an overall dose of much less than 1 J cm-2. Typically mass transport depends on the light irradiation conditions and physicochemical properties. Consequently, a universal explanation about the mechanism has yet to be provided. Recent studies have noted the importance of the surface effect on the mass transfer process. Ambrosio et al. 17,18 proposed an anisotropic light-driven molecular diffusion model for spiral morphology induction under vortexbeam illumination. Their model stressed enhanced molecular diffusion in proximity of the free surface. Ellison et al. 36-39 have proposed microfabrications via the Marangoni flow by photo...

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Precision Marangoni-driven patterning

Cited by 30 publications

References 34 publications

Symmetry plays a key role in the erasing of patterned surface features

Symmetry plays a key role in the erasing of patterned surface features

Bidirectional Control of Flow in Thin Polymer Films by Photochemically Manipulating Surface Tension

Photo-triggered large mass transport driven only by a photoresponsive surface skin layer

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