1
|
Choudhury MD, Das S, Banpurkar AG, Kulkarni A. Regression analysis of wetting characteristics for different random surface roughness of polydimethylsiloxane using sandpapers. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
2
|
Roumpos K, Fontaine S, Pfohl T, Prucker O, Rühe J, Reiter G. Measurements of periodically perturbed dewetting force fields and their consequences on the symmetry of the resulting patterns. Sci Rep 2021; 11:13149. [PMID: 34162940 PMCID: PMC8222397 DOI: 10.1038/s41598-021-92544-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 06/11/2021] [Indexed: 12/02/2022] Open
Abstract
We studied the origin of breaking the symmetry for moving circular contact lines of dewetting polymer films suspended on a periodic array of pillars. There, dewetting force fields driving polymer flow were perturbed by elastic micro-pillars arranged in a regular square pattern. Elastic restoring forces of deformed pillars locally balance driving capillary forces and broke the circular symmetry of expanding dewetting holes. The observed envelope of the dewetting holes reflected the symmetry of the underlying pattern, even at sizes much larger than the characteristic period of the pillar array, demonstrating that periodic perturbations in a driving force field can establish a well-defined pattern of lower symmetry. For the presented system, we succeeded in squaring the circle.
Collapse
Affiliation(s)
- Konstantinos Roumpos
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3a, 79104, Freiburg, Germany
- Freiburg Materials Research Center, Stefan-Meier-Straße 21, 79104, Freiburg, Germany
- Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany
| | - Sarah Fontaine
- Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, 79110, Freiburg, Germany
| | - Thomas Pfohl
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3a, 79104, Freiburg, Germany
| | - Oswald Prucker
- Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, 79110, Freiburg, Germany
| | - Jürgen Rühe
- Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, 79110, Freiburg, Germany
| | - Günter Reiter
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3a, 79104, Freiburg, Germany.
- Freiburg Materials Research Center, Stefan-Meier-Straße 21, 79104, Freiburg, Germany.
- Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany.
| |
Collapse
|
3
|
|
4
|
Basu S, Sarkar J. Selective adsorption of oil on self-organized surface patterns formed over soft thin PDMS films. Chem Eng Sci 2019. [DOI: 10.1016/j.ces.2019.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
5
|
|
6
|
Bhandaru N, Sharma A, Mukherjee R. Programmable Nanopatterns by Controlled Debonding of Soft Elastic Films. ACS APPLIED MATERIALS & INTERFACES 2017; 9:19409-19416. [PMID: 28610425 DOI: 10.1021/acsami.6b09127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report a facile patterning technique capable of creating nanostructures with different feature heights (hS), periodicities (λS), aspect ratios (AR), and duty ratios (DR), using a single grating stamp with fixed feature height hP and periodicity λP. The proposed method relies on controlling the extent of debonding and morphology of the contact instability features, when a rigid patterned stamp is gradually debonded from a soft elastic film to which it was in initial conformal contact. Depending on whether the instability wavelength (λF scales with the film thickness hF as λF ≈ 3hF) and the periodicity of the stamp feature (λP) are commensurate or not, it is possible to obtain features along each stamp protrusion when λF ≈ λP or patterns that span several stripes of the stamp when λF > λP. In both cases, the patterns fabricated during debonding are taller than the original stamp features (hS > hP). We show that hS can be modulated by controlling the extent of debonding as well as the shear modulus of the film (μ). Additionally, when λF > λP, progressive debonding leads to the gradual peeling of replicated features, which, in turn, allows possible tuning of the duty ratio (DR) of the patterns. Finally we show that by the simultaneous modulation of AR, DR, and hS, it becomes possible to create surfaces with controlled wettability.
Collapse
Affiliation(s)
- Nandini Bhandaru
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur , Kharagpur 721302, West Bengal, India
| | - Ashutosh Sharma
- Department of Chemical Engineering and Nanoscience Center, Indian Institute of Technology Kanpur , Kanpur 208016, Uttar Pradesh, India
| | - Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur , Kharagpur 721302, West Bengal, India
| |
Collapse
|
7
|
Chaudhari N, Deshpande T, Singh YRG, Patil S, Kulkarni M, Raut J, Sharma A. Cavity shape transformation during peeling on elastic microchannel-patterned substrates filled with a viscous liquid. SOFT MATTER 2017; 13:2394-2401. [PMID: 28282091 DOI: 10.1039/c7sm00016b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Inspired by the detachment mechanics of natural adhesive pads, we studied the change in cavity shape during peel tests on a 10% cross-linked polydimethylsiloxane (PDMS) elastic microchannel filled with 1% cross-linked viscous PDMS liquid (patterned bilayer). During peeling, we explored cavity shape as a function of microchannel dimensions and correlated the dimensionless cavity shape factor (CSF) and characteristic stress decay length, K-1. The peel test on the liquid-filled elastic microchannel shows three distinct cavity-shape regimes, elliptical, circular, and binary, based on the values of CSF and K-1. Such cavity formation and shape regimes could be important for improving the design of pressure-sensitive adhesives.
Collapse
Affiliation(s)
- Nayantika Chaudhari
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| | - Tushar Deshpande
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| | - Yogesh R G Singh
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| | - Sandip Patil
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| | - Manish Kulkarni
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| | - Janhavi Raut
- Unilever R&D, 64 Main Road, Whitefield, Bangalore 560066, India
| | - Ashutosh Sharma
- Department of Chemical Engineering and Center for Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India.
| |
Collapse
|
8
|
Patil S, Ranjan A, Maitra T, Sharma A. One-Step Fabrication of Microchannels Lined with a Metal Oxide Coating. ACS APPLIED MATERIALS & INTERFACES 2016; 8:10494-10498. [PMID: 27035524 DOI: 10.1021/acsami.6b00413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate a simple, single-step method for metal/metal oxide coating on interior walls of microchannels in an elastomeric material like PDMS, which is the mainstay of microfluidic devices. The fabrication process involves electrodeposition of cuprous oxide on a metallic wire or a sheet, embedding it inside a PDMS matrix along with the cross-linker, curing and then swelling the PDMS elastomer, and finally pulling out the template metal wire or the metal sheet from the PDMS matrix. Stronger attachment of the metal oxide layer to PDMS allows the transfer of the metal oxide coating originally present on the template surface (wire or sheet) to the channel wall resulting in a microchannel/microslit lined with the metal/metal oxide layer. In view of the catalytic activity associated with transition metal oxides, this simple method offers a cost-effective and versatile technique to fabricate microfluidic and lab-on-a-chip devices which can be utilized as microcatalytic reactors or chemical filters. As a proof of concept, we have successfully tested the metal oxide coated microchannels and microslits as active sites for adsorption of iodide ions.
Collapse
Affiliation(s)
- Sandip Patil
- Department of Chemical Engineering and Center for Nanosciences Indian Institute of Technology Kanpur Kanpur-208016 Uttar Pradesh, India
| | - Amit Ranjan
- Department of Chemical Engineering Rajiv Gandhi Institute of Petroleum Technology Raebareli Ratapur Chowk, Raebareli-229010 Uttar Pradesh, India
| | - Tanmoy Maitra
- Department of Chemical Engineering and Center for Nanosciences Indian Institute of Technology Kanpur Kanpur-208016 Uttar Pradesh, India
| | - Ashutosh Sharma
- Department of Chemical Engineering and Center for Nanosciences Indian Institute of Technology Kanpur Kanpur-208016 Uttar Pradesh, India
| |
Collapse
|
9
|
Mukherjee R, Sharma A. Instability, self-organization and pattern formation in thin soft films. SOFT MATTER 2015; 11:8717-8740. [PMID: 26412507 DOI: 10.1039/c5sm01724f] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The free surface of a thin soft polymer film is often found to become unstable and self-organizes into various meso-scale structures. In this article we classify the instability of a thin polymer film into three broad categories, which are: category 1: instability of an ultra-thin (<100 nm) viscous film engendered by amplification of thermally excited surface capillary waves due to interfacial dispersive van der Waals forces; category 2: instability arising from the attractive inter-surface interactions between the free surface of a soft film exhibiting room temperature elasticity and another rigid surface in its contact proximity; and category 3: instability caused by an externally applied field such as an electric field or a thermal gradient, observed in both viscous and elastic films. We review the salient features of each instability class and highlight how characteristic length scales, feature morphologies, evolution pathways, etc. depend on initial properties such as film thickness, visco-elasticity (rheology), residual stress, and film preparation conditions. We emphasize various possible strategies for aligning and ordering of the otherwise isotropic structures by combining the essential concepts of bottom-up and top-down approaches. A perspective, including a possible future direction of research, novelty and limitations of the methods, particularly in comparison to the existing patterning techniques, is also presented for each setting.
Collapse
Affiliation(s)
- Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721 302, India.
| | - Ashutosh Sharma
- Department of Chemical Engineering and Nano-science Center, Indian Institute of Technology, Kanpur, 208016, India.
| |
Collapse
|
10
|
Annepu H, Sarkar J. Miniaturized pattern formation in elastic films cast on sinusoidally patterned substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12278-12286. [PMID: 25238212 DOI: 10.1021/la502933c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The various morphologies that are formed when van der Waals forces or electric field is induced between film cast on a sinusoidal substrate and in contact proximity with a contactor or electrode are studied. Remarkably smaller length scales are achieved (λc < 2.96h) than those obtained with films cast on flat substrates. With van der Waals interactions, the patterns are uniformly formed throughout the film but are not regularly ordered. When electric field is used at critical voltage, more ordered, localized patterns are formed at the zones of large local interaction strengths. When these patterns are evolved by increasing the applied voltage, coexistence of all three phases-cavities, stripes, and columns-is observed throughout the film. The localized patterns that are initially formed vary with the voltage applied and strongly dictate the phases of evolution. A patterned substrate/patterned contactor assembly can be made to operate like its unpatterned counterpart by making the interaction strength same everywhere and yet yield uniform, regularly ordered, highly miniaturized patterns. Such patterns are very useful in various applications like microfluidics; they are formed with great ease and can be morphologically tuned by tuning the externally applied electric field.
Collapse
Affiliation(s)
- Hemalatha Annepu
- Chemical Engineering Department, Indian Institute of Technology Delhi , New Delhi 110 016, India
| | | |
Collapse
|
11
|
Dey M, Bandyopadhyay D, Sharma A, Qian S, Joo SW. Charge Leakage Mediated Pattern Miniaturization in the Electric Field Induced Instabilities of an Elastic Membrane. Ind Eng Chem Res 2014. [DOI: 10.1021/ie500378k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mohar Dey
- School
of Mechanical Engineering, Yeungnam University, Gyeongsan 712749, South Korea
| | - Dipankar Bandyopadhyay
- Department
of Chemical Engineering, Indian Institute of Technology Guwahati, 781039, Assam, India
- Centre
for Nanotechnology, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Ashutosh Sharma
- Department
of Chemical Engineering, Indian Institute of Technology Kanpur, UP 208016, India
| | - Shizhi Qian
- Department
of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Sang Woo Joo
- School
of Mechanical Engineering, Yeungnam University, Gyeongsan 712749, South Korea
| |
Collapse
|
12
|
Shahsavan H, Zhao B. Bioinspired Functionally Graded Adhesive Materials: Synergetic Interplay of Top Viscous–Elastic Layers with Base Micropillars. Macromolecules 2013. [DOI: 10.1021/ma4018718] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hamed Shahsavan
- Department
of Chemical Engineering
and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1
| | - Boxin Zhao
- Department
of Chemical Engineering
and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1
| |
Collapse
|
13
|
Zhang Z, Wang L, Ding Y. Influence of substrate confinement on the phase-correlation in the capillary breakup of arrays of patterned polymer stripes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:3073-3079. [PMID: 23394439 DOI: 10.1021/la304528t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigated the influence of substrate confinement on the capillary breakup of parallel nonaxisymmetric polymer stripes suspended on top of, or confined between, another immiscible polymer pattern. When the residual layer thickness of the pattern was reasonably large, the PS (or PMMA) stripes confined within PMMA (or PS) trenches broke up, either nucleated, out-of-phase, or without clear phase correlation depending on the geometry and viscosity ratio between the two polymers. In stark contrast, for the two extreme cases of viscosity ratios we studied, in-phase breakup of confined polymer stripes was always observed when the alternating PS/PMMA stripes were formed, that is, without residual layer, regardless of the specific geometry.
Collapse
Affiliation(s)
- Zheng Zhang
- Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309-0427, USA
| | | | | |
Collapse
|
14
|
Lin CC, Yang F, Chin JW, Sung L, Lee S. Stress-assisted formation of surface gratings on polymer films. POLYM ENG SCI 2012. [DOI: 10.1002/pen.23395] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
15
|
Roy S, Mukherjee R. Ordered to isotropic morphology transition in pattern-directed dewetting of polymer thin films on substrates with different feature heights. ACS APPLIED MATERIALS & INTERFACES 2012; 4:5375-85. [PMID: 22999159 DOI: 10.1021/am301311d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Controlled dewetting of a thin polymer film on a topographically patterned substrate is an interesting approach for aligning isotropic dewetted structures. In this article, we investigate the influence of substrate feature height (H(S)) on the dewetting pathway and final pattern morphology by studying the dewetting of polystyrene (PS) thin films on grating substrates with identical periodicity (λ(P) = 1.5 μm), but H(S) varying between 10 nm and 120 nm. We identify four distinct categories of final dewetted morphology, with different extent of ordering: (1) array of aligned droplets (H(S) ≈ 120 nm); (2) aligned undulating ribbons (H(S) ≈ 70-100 nm); (3) multilength scale structures with coexisting large droplets uncorrelated to the substrate and smaller droplets/ribbons aligned along the stripes (H(S) ≈ 40-60 nm); and (4) large droplets completely uncorrelated to the substrate (H(S) < 25 nm). The distinct morphologies across the categories are attributed to two major factors: (a) whether the as-cast film is continuous (H(S)≤ 80 nm) or discontinuous (H(S)≥ 100 nm) and (b) in case of a continuous film, whether the film ruptures along each substrate stripe (H(S)≥ 70 nm) or with nucleation of random holes that are not correlated to the substrate features (H(S)≤ 60 nm). While the ranges of H(S) values indicated in the parentheses are valid for PS films with an equivalent thickness (h(E)) ≈ 50.3 nm on a flat substrate, a change in h(E) merely alters the cut-off values of H(S), as the final dewetted morphologies and transition across categories remain generically unaltered. We finally show that the structures obtained by dewetting on different H(S) substrates exhibits different levels of hydrophobicity because of combined spatial variation of chemical and topographic contrast along the surface. Thus, the work reported in this article can find potential application in fabricating surfaces with controlled wettability.
Collapse
Affiliation(s)
- Sudeshna Roy
- Department of Chemical Engineering, Indian Institute of Technology-Kharagpur, West Bengal, 721 302, India
| | | |
Collapse
|
16
|
Patil S, Mangal R, Malasi A, Sharma A. Biomimetic wet adhesion of viscoelastic liquid films anchored on micropatterned elastic substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:14784-14791. [PMID: 23035779 DOI: 10.1021/la302460y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Inspired by the natural adhesives in the toe pads of arthropods and some other animals, we explore the effectiveness and peel failure of a thin viscoelastic liquid film anchored on a micropatterned elastic surface. In particular, we focus on the role of the substrate pattern in adhesion energy of the liquid layer and in allowing its clean separation without cohesive failure. Peel tests on the microfabricated wet adhesives showed two distinct modes of adhesive (interfacial) and cohesive (liquid bulk) failures depending on the pattern dimensions. The adhesion energy of a viscoelastic liquid layer on an optimized micropatterned elastic substrate is ~3.5 times higher than that of a control flat bilayer and ~26 times higher than that of a viscoelastic film on a rigid substrate. Adhesive liquid layers anchored by narrow microchannels undergo clean, reversible adhesive failure rather than the cohesive failure seen on flat substrates. An increase in the channel width engenders cohesive failure in which droplets of the wet adhesive remain on the peeled surface.
Collapse
Affiliation(s)
- Sandip Patil
- Department of Chemical Engineering, Indian Institute of Technology, Kanpur-208016, U.P., India
| | | | | | | |
Collapse
|
17
|
Dey M, Bandyopadhyay D, Sharma A, Qian S, Joo SW. Electric-field-induced interfacial instabilities of a soft elastic membrane confined between viscous layers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:041602. [PMID: 23214594 DOI: 10.1103/physreve.86.041602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Indexed: 06/01/2023]
Abstract
We explore the electric-field-induced interfacial instabilities of a trilayer composed of a thin elastic film confined between two viscous layers. A linear stability analysis (LSA) is performed to uncover the growth rate and length scale of the different unstable modes. Application of a normal external electric field on such a configuration can deform the two coupled elastic-viscous interfaces either by an in-phase bending or an antiphase squeezing mode. The bending mode has a long-wave nature, and is present even at a vanishingly small destabilizing field. In contrast, the squeezing mode has finite wave-number characteristics and originates only beyond a threshold strength of the electric field. This is in contrast to the instabilities of the viscous films with multiple interfaces where both modes are found to possess long-wave characteristics. The elastic film is unstable by bending mode when the stabilizing forces due to the in-plane curvature and the elastic stiffness are strong and the destabilizing electric field is relatively weak. In comparison, as the electric field increases, a subdominant squeezing mode can also appear beyond a threshold destabilizing field. A dominant squeezing mode is observed when the destabilizing field is significantly strong and the elastic films are relatively softer with lower elastic modulus. In the absence of liquid layers, a free elastic film is also found to be unstable by long-wave bending and finite wave-number squeezing modes. The LSA asymptotically recovers the results obtained by the previous formulations where the membrane bending elasticity is approximately incorporated as a correction term in the normal stress boundary condition. Interestingly, the presence of a very weak stabilizing influence due to a smaller interfacial tension at the elastic-viscous interfaces opens up the possibility of fabricating submicron patterns exploiting the instabilities of a trilayer.
Collapse
Affiliation(s)
- Mohar Dey
- School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, South Korea
| | | | | | | | | |
Collapse
|
18
|
Deb Roy R, Sil D, Jana S, Bhandaru N, Bhadra SK, Biswas PK, Mukherjee R. Creation of Self-Organized Complex Meso Patterns in Sol–Gel Thin Films by Confined Capillary Dynamics. Ind Eng Chem Res 2012. [DOI: 10.1021/ie300012m] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | - Nandini Bhandaru
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, West Bengal 721 302, India
| | | | | | - Rabibrata Mukherjee
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, West Bengal 721 302, India
| |
Collapse
|
19
|
Roy S, Ansari KJ, Jampa SSK, Vutukuri P, Mukherjee R. Influence of substrate wettability on the morphology of thin polymer films spin-coated on topographically patterned substrates. ACS APPLIED MATERIALS & INTERFACES 2012; 4:1887-1896. [PMID: 22468781 DOI: 10.1021/am300201a] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We show that the morphology of a thin polymer film spin coated directly on to a topographically patterned substrate is strongly influenced by the wettability of the substrate, in addition to other well-known parameters such as concentration of the polymer solution (c(n)), spin speed (RPM), and spin duration. Similar to spin coating on a flat surface, (1, 2) on a topographically patterned substrate as well, a continuous film forms only above a critical polymer solution concentration (c(t)*), for a specific RPM and dispensed drop volume. It is believed that for c(n) > c(t)*, the resulting continuous film on a topographically patterned substrate has an undulating top surface, where the surface undulations are in phase with the underlying substrate patterns. (3) On the basis of experiments involving spin coating of polymer thin films on topographically patterned grating substrates, we show that the surface undulations on the film are in phase with the substrate patterns only when the substrate is completely wetted (CW) by the solvent. In contrast, when the substrate is partially wetted (PW) by the solvent, then the undulations are 180° out of phase with respect to the substrate patterns. We further show that for c(n) < c(t)*, a variety of ordered and disordered structures, like array of aligned droplets, isolated strips of polymers, etc., result on both CW and PW substrates, depending on c(n).
Collapse
Affiliation(s)
- Sudeshna Roy
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, West Bengal, India
| | | | | | | | | |
Collapse
|
20
|
Patil S, Ranjan A, Sharma A. Prefracture Instabilities Govern Generation of Self-Affine Surfaces in Tearing of Soft Viscoelastic Elastomeric Sheets. Macromolecules 2012. [DOI: 10.1021/ma202339y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Sandip Patil
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology, Kanpur, India
| | - Amit Ranjan
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology, Kanpur, India
| | - Ashutosh Sharma
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology, Kanpur, India
| |
Collapse
|
21
|
Patil S, Malasi A, Majumder A, Ghatak A, Sharma A. Reusable antifouling viscoelastic adhesive with an elastic skin. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:42-46. [PMID: 22201420 DOI: 10.1021/la203871c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Although the viscoelasticity or tackiness of a pressure-sensitive adhesive gives it strength owing to energy dissipation during peeling, it also renders it nonreusable because of structural changes such as the formation of fibrils, cohesive failure, and fouling. However, an elastic layer has good structural integrity and cohesive strength but low adhesive energy. We demonstrate an effective composite adhesive in which a soft viscoelastic bulk layer is imbedded in a largely elastic thin skin layer. The composite layer is able to meet the conflicting demands of the high peel strength comparable to the viscoelastic core and the structural integrity, reusability, and antifouling properties of the elastic skin. Our model adhesive is made of poly(dimethylsiloxane), where its core and skin are created by varying the cross-linking percentage from 2 to 10%.
Collapse
Affiliation(s)
- Sandip Patil
- Department of Chemical Engineering and DST Unit on Nanosciences, Indian Institute of Technology, Kanpur-208016, UP, India
| | | | | | | | | |
Collapse
|
22
|
Mukherjee R, Sharma A. Creating self-organized submicrometer contact instability patterns in soft elastic bilayers with a topographically patterned stamp. ACS APPLIED MATERIALS & INTERFACES 2012; 4:355-62. [PMID: 22148714 DOI: 10.1021/am201422h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The surface of a thin elastic bilayer becomes spontaneously unstable when it is brought in proximity to another rigid contactor. The instability patterns, which are random and isotropic, exhibit a dominant lateral length scale of instability λ, which linearly scales with the bilayer thickness (h) as: λ = R(F)h. It is known that for an elastic bilayer, R(F) exhibits a nonlinear dependence on the ratios of individual film thicknesses (H) and shear moduli (M) of the two constituent layers, and can have values as low as 0.5 under specific conditions. This is in contrast to a near constant value of R(F) ≈ 3 for a single layer elastic film. (1) These isotropic contact instability patterns in a bilayer can be ordered, aligned and modulated using a topographically patterned stamp. The precise morphology of the aligned structures depends on commensuration between λ and the stamp periodicity (λ(P)), and on the intersurface separation distance. A variety of patterns, like an array of circular holes, double periodic channels, etc., in addition to a positive and a negative replica of the stamp pattern, can be engineered with a simple stamp having 1D grating structure. A lower value of R(F) in a bilayer allows generating patterns with sub 500 nm lateral resolution, which is impossible to create by elastic contact lithography (ECL) of a single layer film due to strong surface tension effects in ultrathin films. Thus, control of elastic instability in a bilayer with a patterned stamp represents a flexible soft lithography tool allowing modulation of length scales, morphology, and order.
Collapse
Affiliation(s)
- Rabibrata Mukherjee
- Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721 302, India.
| | | |
Collapse
|
23
|
Atta A, Crawford DG, Koch CR, Bhattacharjee S. Influence of electrostatic and chemical heterogeneity on the electric-field-induced destabilization of thin liquid films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:12472-12485. [PMID: 21888320 DOI: 10.1021/la202759j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A numerical model for thin liquid film (<100 nm) drainage in the presence of an external electric field is developed. Long-wave theory is applied to approximate and simplify the governing equations. A spatiotemporal film morphology evolution equation thus obtained is then solved using a combination of finite difference to resolve the spatial dimensions and an adaptive time step ODE solver for the temporal propagation. The effect of fluid properties, namely, viscosity and surface tension, on the film drainage time is observed for a homogeneous electric field, which leads to random dewetting spots. Electrically heterogeneous fields, achieved by modeling electrodes with various periodic patterns, are explored to identify their effect on the drainage time and behavior. Finally, the chemical heterogeneity of the substrate is coupled with the periodic electric heterogeneity to understand the implications of combined heterogeneity. It is observed that the introduction of any heterogeneity results in faster drainage of the film when compared to that of the homogeneous field. In all cases, the thin film is drained, leaving submicrometer-scale structures at the interface. Well-controlled surface patterns are found on the application of periodic heterogeneity. This study effectively demonstrates the immense potential of electrically induced thin film drainage as a means for faster de-emulsification and for the creation of ordered submicrometer-scale surface patterns on soft materials.
Collapse
Affiliation(s)
- Arnab Atta
- Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | | | | | | |
Collapse
|
24
|
|
25
|
Moosavi A, Rauscher M, Dietrich S. Dynamics of nanodroplets on topographically structured substrates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:464120. [PMID: 21715884 DOI: 10.1088/0953-8984/21/46/464120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Mesoscopic hydrodynamic equations are solved to investigate the dynamics of nanodroplets positioned near a topographic step of the supporting substrate. Our results show that the dynamics depends on the characteristic length scales of the system given by the height of the step and the size of the nanodroplets as well as on the constituting substances of both the nanodroplets and the substrate. The lateral motion of nanodroplets far from the step can be described well in terms of a power law of the distance from the step. In general the direction of motion depends on the details of the effective laterally varying intermolecular forces. But for nanodroplets positioned far from the step it is solely given by the sign of the Hamaker constant of the system. Moreover, our study reveals that the steps always act as a barrier for transporting liquid droplets from one side of the step to the other.
Collapse
Affiliation(s)
- A Moosavi
- Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, PO Box 11365-9567 Tehran, Iran
| | | | | |
Collapse
|
26
|
Bandyopadhyay D, Sharma A, Rastogi C. Dewetting of the thin liquid bilayers on topographically patterned substrates: formation of microchannel and microdot arrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:14048-14058. [PMID: 19360942 DOI: 10.1021/la802404s] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A long-wave nonlinear analysis of the defect induced instabilities engendered by van der Waals forces in thin (<100 nm) viscous bilayers is presented. The major focus of this study is on generation of periodic patterns and its miniaturization by exploiting the self-organized instabilities of thin bilayers on topographically patterned substrates. A large variety of self-organized interfacial patterns such as periodic arrays of open and closed micro/nanochannels, isolated and encapsulated micro/nanodroplets, and membranes with ordered pores are obtained on different types of prepatterned substrates. In addition, we show that a bilayer can also be a suitable tool for (i) pattern transfer involving replication of the morphology of the lower layer interface to the free surface of the upper layer and (ii) generation of a mold by the upper layer material filling the periodic interstitial spaces formed by dewetting of the lower layer. Simulations suggest a profound influence of the substrate pattern directed lateral confinement, which governs the length scale of the dewetted structure when the substrate pattern periodicity is well below the spinodal length scale of the unstable bilayer. The influence of the initial configuration of the interfaces on the dewetting pathway and the dewetted structures are also shown.
Collapse
Affiliation(s)
- Dipankar Bandyopadhyay
- Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016, India
| | | | | |
Collapse
|
27
|
Pangule RC, Banerjee I, Sharma A. Adhesion induced mesoscale instability patterns in thin PDMS-metal bilayers. J Chem Phys 2008; 128:234708. [DOI: 10.1063/1.2940330] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|