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Lilin P, Bischofberger I. Criteria for Crack Formation and Air Invasion in Drying Colloidal Suspensions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7442-7447. [PMID: 35605177 DOI: 10.1021/acs.langmuir.2c00397] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The drying of sessile drops of aqueous colloidal suspensions leads to the formation of a close-packed particle deposit. As water evaporates, a solidification front propagates from the edge of the drop toward the center, leaving behind a thin disk-shaped deposit. For drops with sufficiently large particle volume fractions, the deposit eventually covers the entire wetted area. In this regime, the dynamics of the deposit growth is governed by volume conservation across a large range of particle volume fractions and drying times. During drying, water flows radially through the deposit to compensate for evaporation over the solid's surface, creating a negative pore pressure in the deposit which we rationalize with a hydrodynamic model. We show that the pressure inside the deposit controls both the onset of crack formation and the onset of air invasion. Two distinct regimes of air invasion occur, which we can account for using the same model that further provides a quantitative criterion for the crossover between the two regimes.
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Affiliation(s)
- Paul Lilin
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Irmgard Bischofberger
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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2
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Kumar S, Kumar H, Basavaraj MG, Satapathy DK. Formation and suppression of secondary cracks in deposits of colloidal ellipsoids. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.128579] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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3
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Lee Y, Kim J, Lee S, Wooh S, Yoon H, Char K. Cracking of Colloidal Films to Generate Rectangular Fragments. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4935-4941. [PMID: 35404063 DOI: 10.1021/acs.langmuir.2c00328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Cracks are common in nature. Cracking is known as an irreversible and uncontrollable process. To control the cracking patterns, many researchers have proposed methods to prepare notches for stress localization on films. In this work, we investigate a method of controlling cracks by making microscale pyramid patterns that have notches between the pyramids. After preparing pyramid patterns consisting of colloidal particles with organic residue, we annealed them to induce volume shrinkage and cracking between the pyramids. We studied the effect of film thickness on cracking and the generation of rectangular fragments consisting of multiple pyramids. The area of rectangular fragments was in good agreement with the results of scaling analysis. The concept of controlling cracks by imprinting notches on a film and the relationship with the film thickness can guide the study of cracking phenomena.
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Affiliation(s)
- Yunchan Lee
- The National Creative Research Initiative Center for Intelligent Hybrids, The World Class University Program for Chemical Convergence for Energy and Environment, School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Jaekyoung Kim
- Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea
| | - Soojin Lee
- The National Creative Research Initiative Center for Intelligent Hybrids, The World Class University Program for Chemical Convergence for Energy and Environment, School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Sanghyuk Wooh
- School of Chemical Engineering & Materials Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hyunsik Yoon
- Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea
| | - Kookheon Char
- The National Creative Research Initiative Center for Intelligent Hybrids, The World Class University Program for Chemical Convergence for Energy and Environment, School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Parsimehr H, Pazokifard S. Ambient temperature cross-linkable acrylic latexes: effect of cross-link density, glass transition temperature and application temperature difference on mechanical properties. Polym Bull (Berl) 2021. [DOI: 10.1007/s00289-020-03515-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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6
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Meng W, Liu M, Gan Y, Pauchard L, Chen CQ. Cracking to curling transition in drying colloidal films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2020; 43:64. [PMID: 33009958 DOI: 10.1140/epje/i2020-11985-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 08/31/2020] [Indexed: 06/11/2023]
Abstract
Drying-induced cracking is widely encountered in nature and is of fundamental interest in industrial applications. During desiccation, the evolution of water content is nonlinear. Considering the inhomogeneous procedure of desiccation, it is worth considering whether water content will affect the crack pattern formation. To address this concern, in this paper, we report an experimental investigation on the effect of water content on the failure mode in drying colloidal films. A distinct failure transition from random cracking to curling is found when the initial water content increases gradually. When the water content is below a critical value for given film thickness, random desiccation cracking driven by shrinkage is observed. Beyond this critical water content, the film curls with the advent of several main cracks. It is also found that the critical water content corresponding to the transition point depends on the film thickness. In order to qualitatively interpret the experimental observation, a theoretical model is established by adopting the fracture mechanics based on the energy method. The model is found to agree well with the experimental results, elucidating the effects of initial water content on the crack patterns and the transition of failure modes.
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Affiliation(s)
- Weipeng Meng
- Department of Engineering Mechanics, CNMM & AML, Tsinghua University, 100084, Beijing, China
| | - Mingchao Liu
- Department of Engineering Mechanics, CNMM & AML, Tsinghua University, 100084, Beijing, China
- Mathematical Institute, University of Oxford, OX2 6GG, Oxford, UK
| | - Yixiang Gan
- School of Civil Engineering, The University of Sydney, NSW 2006, Sydney, Australia
| | | | - C Q Chen
- Department of Engineering Mechanics, CNMM & AML, Tsinghua University, 100084, Beijing, China.
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7
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Suh Y, Gowda H, Won Y. In situ investigation of particle clustering dynamics in colloidal assemblies using fluorescence microscopy. J Colloid Interface Sci 2020; 576:195-202. [PMID: 32422448 DOI: 10.1016/j.jcis.2020.04.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/04/2020] [Accepted: 04/11/2020] [Indexed: 12/13/2022]
Abstract
Colloidal self-assembly is a process in which dispersed matter spontaneously form higher-order structures without external intervention. During self-assembly, packed particles are subject to solvent-evaporation induced dynamic structuring phases, which leads to microscale defects called the grain boundaries. While it is imperative to precisely control detailed grain boundaries to fabricate well-defined self-assembled crystals, the understanding of the colloidal physics that govern grain boundaries remains a challenge due to limited resolutions of current visualization approaches. In this work, we experimentally report in situ particle clustering dynamics during evaporative colloidal assembly by studying a novel microscale laser induced fluorescence technique. The fluorescence microscopy measures the saturation levels with high fidelity to identify distinct colloidal structuring regimes during self-assembly as well as cracking mechanics. The techniques discussed in this work not only enables unprecedented levels of colloidal self-assembly analysis but also have potential to be used for various sensing applications with microscopic resolutions.
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Affiliation(s)
- Youngjoon Suh
- Department of Mechanical and Aerospace Engineering, University of California, Irvine 5200 Engineering Hall, CA 92617-2700, USA
| | - Hamsa Gowda
- Department of Biomedical Engineering, University of California, Irvine 3120 Natural Sciences II, CA 92697-2715, USA
| | - Yoonjin Won
- Department of Mechanical and Aerospace Engineering, University of California, Irvine 5200 Engineering Hall, CA 92617-2700, USA.
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8
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Tomar BS, Shahin A, Tirumkudulu MS. Cracking in drying films of polymer solutions. SOFT MATTER 2020; 16:3476-3484. [PMID: 32211630 DOI: 10.1039/c9sm02294e] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Thin films of polymer coatings have important industrial applications ranging from paints and coatings to pharmaceuticals. In many applications, the coatings are obtained by applying thin films of dilute polymer solutions, wherein the solvent evaporates to leave behind a thin polymer film. In some cases, the thin films may crack due to shrinkage stresses developed during drying. While a number of studies have focused on the stress development, the phenomenon of cracking in polymer films is not fully investigated. In the present work, thin films of a silicone polymer solution were cast on substrates of varying Young's moduli and investigated for cracking as a function of film thickness and substrate modulus. Micro-Raman spectroscopy measurements show that thin films dry uniformly while thick films form a skin at the top surface leading to slow drying rates. Transverse stresses were measured using the cantilever technique and related to the extent of cracking in the film. We investigated the influence of substrate rigidity on the cracking behavior and found that decreasing the stiffness of the substrate increases the extent of cracking.
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Affiliation(s)
- Bhawana Singh Tomar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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Bouchaudy A, Salmon JB. Drying-induced stresses before solidification in colloidal dispersions: in situ measurements. SOFT MATTER 2019; 15:2768-2781. [PMID: 30734814 DOI: 10.1039/c8sm02558d] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We first report an original setup that enables continuous measurements of stresses induced by the drying of confined drops of complex fluids. This setup is mainly based on a precision scale working with an electromagnetic force compensation technique that provides accurate measurements of forces, while allowing simultaneously controlled evaporation rates, in situ microscopic observations, and thus quantitative estimates of normal stresses. We then performed an extensive study of the drying of a charged colloidal dispersion using this setup. Stress measurements clearly show the emergence of large tensile stresses during drying, well-before the solidification stage evidenced by the invasion of the porous colloidal material by air. Combined measurements of solid deformation and concentration profiles (particle tracking, Raman micro-spectroscopy) help us to demonstrate that these stresses are due to the formation of a solid at a low volume fraction, which further undergoes drying-induced shear deformations up to the colloid close-packing, as also supported by large deformation poroelastic modeling. Above all, our results highlight the importance of repulsive colloidal interactions in the build-up of mechanical stresses during drying.
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Affiliation(s)
- Anne Bouchaudy
- CNRS, Solvay, LOF, UMR 5258, Univ. Bordeaux, F-33600 Pessac, France.
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10
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Osman A, Goehring L, Patti A, Stitt H, Shokri N. Fundamental Investigation of the Drying of Solid Suspensions. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.7b02334] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Abdulkadir Osman
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Lucas Goehring
- School
of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, U.K
| | - Alessandro Patti
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Hugh Stitt
- Johnson Matthey
Technology Centre, Billingham TS23 1LB, U.K
| | - Nima Shokri
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M13 9PL, United Kingdom
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11
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Weldon AL, Joshi K, Routh AF, Gilchrist JF. Uniformly spaced nanoscale cracks in nanoparticle films deposited by convective assembly. J Colloid Interface Sci 2017; 487:80-87. [PMID: 27750069 DOI: 10.1016/j.jcis.2016.09.078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 09/29/2016] [Indexed: 10/20/2022]
Abstract
Rapid convective deposition is used to assemble nanoparticle coatings from suspension, with controllable thickness. Varying film thickness generates stress-induced linear cracks with highly monodisperse spacing. Film thickness is controlled through mechanical means, suspension volume fraction, and the use of applied thermal gradients. These cracks extend in the deposition direction, and a uniform crack spacing from 2 to 160μm is observed. The nanoparticle film thickness is the relevant length scale for hydrodynamic flow, and films will crack with this spacing, in a characteristic manner to minimize the system energy and capillary stresses. As expected from this energy minimization problem and relevant theory, the correlation between coating thickness and crack spacing is highly linear. Because this process is continuous, continuous cracks have potential as a high-throughput method of fabricating nanoscale channels for microfluidics and MEMS.
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Affiliation(s)
- Alexander L Weldon
- Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Kedar Joshi
- Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Alexander F Routh
- BP Institute and Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK
| | - James F Gilchrist
- Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015, USA.
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12
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Bahmani L, Neysari M, Maleki M. The study of drying and pattern formation of whole human blood drops and the effect of thalassaemia and neonatal jaundice on the patterns. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2016.10.065] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Boulogne F, Kong YL, Nunes JK, Stone HA. Effect of the Polydispersity of a Colloidal Drop on Drying Induced Stress as Measured by the Buckling of a Floating Sheet. PHYSICAL REVIEW LETTERS 2016; 116:238001. [PMID: 27341259 DOI: 10.1103/physrevlett.116.238001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 06/06/2023]
Abstract
We study the stress developed during the drying of a colloidal drop of silica nanoparticles. In particular, we use the wrinkling instability of a thin floating sheet to measure the net stress applied by the deposit on the substrate and we focus on the effect of the particle polydispersity. In the case of a bidisperse suspension, we show that a small number of large particles substantially decreases the expected stress, which we interpret as the formation of lower hydrodynamic resistance paths in the porous material. As colloidal suspensions are usually polydisperse, we show for different average particle sizes that the stress is effectively dominated by the larger particles of the distribution and not by the average particle size.
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Affiliation(s)
- François Boulogne
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Yong Lin Kong
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Janine K Nunes
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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14
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Kiatkirakajorn PC, Goehring L. Formation of Shear Bands in Drying Colloidal Dispersions. PHYSICAL REVIEW LETTERS 2015; 115:088302. [PMID: 26340215 DOI: 10.1103/physrevlett.115.088302] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Indexed: 05/15/2023]
Abstract
In directionally dried colloidal dispersions regular bands can appear behind the drying front, inclined at ±45° to the drying line. Although these features have been noted to share visual similarities with shear bands in metal, no physical mechanism for their formation has ever been suggested, until very recently. Here, through microscopy of silica and polystyrene dispersions, dried in Hele-Shaw cells, we demonstrate that the bands are indeed associated with local shear strains. We further show how the bands form, that they scale with the thickness of the drying layer, and that they are eliminated by the addition of salt to the drying dispersions. Finally, we reveal the origins of these bands in the compressive forces associated with drying, and show how they affect the optical properties (birefringence) of colloidal films and coatings.
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Affiliation(s)
| | - Lucas Goehring
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany
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15
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Khatun T, Dutta T, Tarafdar S. Topology of desiccation crack patterns in clay and invariance of crack interface area with thickness. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:83. [PMID: 26248703 DOI: 10.1140/epje/i2015-15083-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 05/16/2015] [Accepted: 06/25/2015] [Indexed: 06/04/2023]
Abstract
We study the crack patterns developed on desiccating films of suspensions of three different clays-bentonite, halloysite nanoclay and laponite on a glass substrate. Varying the thickness of the layer, h gives the following new and interesting results: i) We can identify a critical thickness h c for bentonite and halloysite, above which isolated cracks join each other to form a fully connected network. ii) A topological analysis involving the Euler number is shown to be useful for characterising the patterns. iii) We find, further, that the total vertical surface area of the clay A v, which has opened up due to cracking, and the total area of the glass substrate A s, exposed by the hierarchical sequence of cracks are constant, independent of the layer thickness for a certain range of h. These results are shown to be consistent with a simple energy conservation argument, neglecting dissipative losses. Finally we show that if the crack pattern is viewed at successively finer resolution, the total cumulative area of cracks visible at a certain resolution scales with the layer thickness.
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Affiliation(s)
- Tajkera Khatun
- Condensed Matter Physics Research Centre, Physics Department, Jadavpur University, 700032, Kolkata, India,
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Mechanical Stresses Induced by Evaporation in Consolidated Colloidal Suspensions of Hard Particles. Poroelasticity Theory Versus Experiments. Transp Porous Media 2013. [DOI: 10.1007/s11242-013-0209-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Routh AF. Drying of thin colloidal films. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:046603. [PMID: 23502077 DOI: 10.1088/0034-4885/76/4/046603] [Citation(s) in RCA: 225] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
When thin films of colloidal fluids are dried, a range of transitions are observed and the final film profile is found to depend on the processes that occur during the drying step. This article describes the drying process, initially concentrating on the various transitions. Particles are seen to initially consolidate at the edge of a drying droplet, the so-called coffee-ring effect. Flow is seen to be from the centre of the drop towards the edge and a front of close-packed particles passes horizontally across the film. Just behind the particle front the now solid film often displays cracks and finally the film is observed to de-wet. These various transitions are explained, with particular reference to the capillary pressure which forms in the solidified region of the film. The reasons for cracking in thin films is explored as well as various methods to minimize its effect. Methods to obtain stratified coatings through a single application are considered for a one-dimensional drying problem and this is then extended to two-dimensional films. Different evaporative models are described, including the physical reason for enhanced evaporation at the edge of droplets. The various scenarios when evaporation is found to be uniform across a drying film are then explained. Finally different experimental techniques for examining the drying step are mentioned and the article ends with suggested areas that warrant further study.
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Affiliation(s)
- Alexander F Routh
- BP Institute and Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
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Goehring L, Clegg WJ, Routh AF. Plasticity and fracture in drying colloidal films. PHYSICAL REVIEW LETTERS 2013; 110:024301. [PMID: 23383905 DOI: 10.1103/physrevlett.110.024301] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Indexed: 05/15/2023]
Abstract
Cracks in drying colloidal dispersions are typically modeled by elastic fracture mechanics, which assumes that all strains are linear, elastic, and reversible. We tested this assumption in films of a hard latex, by intermittently blocking evaporation over a drying film, thereby relieving the film stress. Here we show that although the deformation around a crack tip has some features of brittle fracture, only 20%-30% of the crack opening is relieved when it is unloaded. Atomic force micrographs of crack tips also show evidence of plastic deformation, such as microcracks and particle rearrangement. Finally, we present a simple scaling argument showing that the yield stress of a drying colloidal film is generally comparable to its maximum capillary pressure, and thus that the plastic strain around a crack will normally be significant. This also suggests that a film's fracture toughness may be increased by decreasing the interparticle adhesion.
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Affiliation(s)
- Lucas Goehring
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany.
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Smith MI, Sharp JS. Effects of substrate constraint on crack pattern formation in thin films of colloidal polystyrene particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:8009-8017. [PMID: 21650173 DOI: 10.1021/la2000624] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Crack formation and the evolution of stress in drying films of colloidal particles were studied using optical microscopy and a modified cantilever deflection technique, respectively. Drying experiments were performed using polystyrene particles with diameters of 47 ± 10 nm, 100 ± 16 nm, and 274 ± 44 nm that were suspended in water. As the films dried, cracks with a well-defined spacing were observed to form. The crack spacing was found to be independent of the particle size used, but to increase with the film thickness. The characteristic crack spacing was found to vary between 20 and 300 μm for films with thickness values in the range 3-70 μm. Cantilever deflection measurements revealed that the stresses that develop in the film increase with decreasing film thickness (increasing surface-to-volume ratio). The latter observation was interpreted in terms of the effects of a substrate constraint which causes the build up of stresses in the films. This interpretation was confirmed by crack formation experiments that were performed on liquid mercury surfaces in which removal of the substrate constraint prevented crack formation. Experiments were also performed on compliant elastomer surfaces in which the level of constraint was varied by changing the substrate modulus. The cracking length scale was found to increase with decreasing substrate modulus. A simple theory was also developed to describe the substrate modulus dependence of the cracking length scale. These combined experiments and theory provide convincing evidence that substrate constraints are an important factor in driving crack formation in thin colloidal films.
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Affiliation(s)
- M I Smith
- School of Physics and Astronomy and Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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