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Binysh J, Wilks TR, Souslov A. Active elastocapillarity in soft solids with negative surface tension. SCIENCE ADVANCES 2022; 8:eabk3079. [PMID: 35275714 PMCID: PMC8916726 DOI: 10.1126/sciadv.abk3079] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 01/20/2022] [Indexed: 06/14/2023]
Abstract
Active solids consume energy to allow for actuation, shape change, and wave propagation not possible in equilibrium. Whereas active interfaces have been realized across many experimental systems, control of three-dimensional (3D) bulk materials remains a challenge. Here, we develop continuum theory and microscopic simulations that describe a 3D soft solid whose boundary experiences active surface stresses. The competition between active boundary and elastic bulk yields a broad range of previously unexplored phenomena, which are demonstrations of so-called active elastocapillarity. In contrast to thin shells and vesicles, we discover that bulk 3D elasticity controls snap-through transitions between different anisotropic shapes. These transitions meet at a critical point, allowing a universal classification via Landau theory. In addition, the active surface modifies elastic wave propagation to allow zero, or even negative, group velocities. These phenomena offer robust principles for programming shape change and functionality into active solids, from robotic metamaterials down to shape-shifting nanoparticles.
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Affiliation(s)
- Jack Binysh
- Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Thomas R. Wilks
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
- Exact Sciences Innovation, Sherard Building, Edmund Halley Road, Oxford OX4 4DQ, UK
| | - Anton Souslov
- Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK
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Deriy I, Toftul I, Petrov M, Bogdanov A. Bound States in the Continuum in Compact Acoustic Resonators. PHYSICAL REVIEW LETTERS 2022; 128:084301. [PMID: 35275659 DOI: 10.1103/physrevlett.128.084301] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
We reveal that finite-size solid acoustic resonators can support genuine bound states in the continuum (BICs) completely localized inside the resonator. The developed theory provides the multipole classification of such BICs in the resonators of various shapes. It is shown how breaking of the resonator's symmetry turns BICs into quasi-BICs manifesting themselves in the scattering spectra as high-Q Fano resonances. We believe that the revealed novel states will push the performance limits of acoustic devices and will serve as high-Q building blocks for acoustic sensors, antennas, and topological acoustic structures.
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Affiliation(s)
- Ilya Deriy
- School of Physics and Engineering, ITMO University, 191002 St. Petersburg, Russia
| | - Ivan Toftul
- School of Physics and Engineering, ITMO University, 191002 St. Petersburg, Russia
| | - Mihail Petrov
- School of Physics and Engineering, ITMO University, 191002 St. Petersburg, Russia
| | - Andrey Bogdanov
- School of Physics and Engineering, ITMO University, 191002 St. Petersburg, Russia
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McCraney J, Weislogel M, Steen P. The draining of capillary liquids from containers with interior corners aboard the ISS. NPJ Microgravity 2021; 7:45. [PMID: 34764319 PMCID: PMC8585966 DOI: 10.1038/s41526-021-00173-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/08/2021] [Indexed: 11/09/2022] Open
Abstract
In this work, we analyze liquid drains from containers in effective zero-g conditions aboard the International Space Station (ISS). The efficient draining of capillary fluids from conduits, containers, and media is critical in particular to high-value liquid samples such as minuscule biofluidics processing on earth and enormous cryogenic fuels management aboard spacecraft. The amount and rate of liquid drained can be of key concern. In the absence of strong gravitational effects, system geometry, and liquid wetting dominate capillary fluidic behavior. During the years 2010-2015, NASA conducted a series of handheld experiments aboard the ISS to observe "large" length scale capillary fluidic phenomena in a variety of irregular containers with interior corners. In this work, we focus on particular single exit port draining flows from such containers and digitize hours of archived NASA video records to quantify transient interface profiles and volumetric flow rates. These data are immediately useful for theoretical and numerical model benchmarks. We demonstrate this by making comparisons to lubrication models for slender flows in simplified geometries which show variable agreement with the data, in part validating certain geometry-dependent dynamical interface curvature boundary conditions while invalidating others. We further compare the data for the draining of complex vane networks and identify the limits of the current theory. All analyzed data is made available to the public as MATLAB files, as detailed within.
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Affiliation(s)
- Joshua McCraney
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, 14850, United States.
| | - Mark Weislogel
- Department of Mechanical and Materials Engineering, Portland State University, Portland, OR, 97201, United States
| | - Paul Steen
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14850, United States
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Tamim SI, Bostwick JB. Oscillations of a soft viscoelastic drop. NPJ Microgravity 2021; 7:42. [PMID: 34728641 PMCID: PMC8563899 DOI: 10.1038/s41526-021-00169-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 10/01/2021] [Indexed: 12/31/2022] Open
Abstract
A soft viscoelastic drop has dynamics governed by the balance between surface tension, viscosity, and elasticity, with the material rheology often being frequency dependent, which are utilized in bioprinting technologies for tissue engineering and drop-deposition processes for splash suppression. We study the free and forced oscillations of a soft viscoelastic drop deriving (1) the dispersion relationship for free oscillations, and (2) the frequency response for forced oscillations, of a soft material with arbitrary rheology. We then restrict our analysis to the classical cases of a Kelvin-Voigt and Maxwell model, which are relevant to soft gels and polymer fluids, respectively. We compute the complex frequencies, which are characterized by an oscillation frequency and decay rate, as they depend upon the dimensionless elastocapillary and Deborah numbers and map the boundary between regions of underdamped and overdamped motions. We conclude by illustrating how our theoretical predictions for the frequency-response diagram could be used in conjunction with drop-oscillation experiments as a "drop vibration rheometer", suggesting future experiments using either ultrasonic levitation or a microgravity environment.
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Affiliation(s)
- Saiful I Tamim
- Department of Mechanical Engineering, Clemson University, Clemson, SC, 29634, USA
| | - Joshua B Bostwick
- Department of Mechanical Engineering, Clemson University, Clemson, SC, 29634, USA.
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Tamim SI, Bostwick JB. Model of spontaneous droplet transport on a soft viscoelastic substrate with nonuniform thickness. Phys Rev E 2021; 104:034611. [PMID: 34654114 DOI: 10.1103/physreve.104.034611] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 09/13/2021] [Indexed: 11/07/2022]
Abstract
Dynamic wetting of droplets on soft solids has many industrial and biological applications which require an understanding of the underlying fluid transport mechanism. Here we study the case of a droplet on a viscoelastic substrate of variable thickness which is known to give rise to a spontaneous droplet transport. This phenomenon is known as droplet durotaxis and has been observed experimentally. Here we develop a model assuming a small linear gradient in substrate thickness to reveal the physical mechanism behind this transport phenomena. We show the variable thickness causes an asymmetric deformation along the drop contact line, which causes a variation in the contact angle. This generates a net driving force on the drop, causing it to move in the direction of higher thickness. The resulting drop velocity is determined by balancing the work done by the moving drop with the viscoelastic dissipation of the substrate (viscoelastic braking) and computed from a self-consistent model. We find our results to be in qualitative agreement to previously reported experimental findings.
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Affiliation(s)
- S I Tamim
- Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634, USA
| | - J B Bostwick
- Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634, USA
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Tamim SI, Bostwick JB. Plateau-Rayleigh instability in a soft viscoelastic material. SOFT MATTER 2021; 17:4170-4179. [PMID: 33881117 DOI: 10.1039/d1sm00019e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A soft cylindrical interface endowed with surface tension can be unstable to wavy undulations. This is known as the Plateau-Rayleigh instability (PRI) and for solids the instability is governed by the competition between elasticity and capillarity. A dynamic stability analysis is performed for the cases of a soft (i) cylinder and (ii) cylindrical cavity assuming the material is viscoelastic with power-law rheology. The governing equations are made time-independent through the Laplace transform from which a solution is constructed using displacement potentials. The dispersion relationships are then derived, which depend upon the dimensionless elastocapillary number, solid Deborah number, and compressibility number, and the static stability limit, critical disturbance, and maximum growth rate are computed. This dynamic analysis recovers previous literature results in the appropriate limits. Elasticity stabilizes and compressibility destabilizes the PRI. For an incompressible material, viscoelasticity does not affect stability but does decrease the growth rate and shift the critical wavenumber to lower values. The critical wavenumber shows a more complex dependence upon compressibility for the cylinder but exhibits a predictable trend for the cylindrical cavity.
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Affiliation(s)
- S I Tamim
- Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA.
| | - J B Bostwick
- Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA.
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Shao X, Bevilacqua G, Ciarletta P, Saylor JR, Bostwick JB. Experimental observation of Faraday waves in soft gels. Phys Rev E 2020; 102:060602. [PMID: 33466108 DOI: 10.1103/physreve.102.060602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 12/04/2020] [Indexed: 11/07/2022]
Abstract
We report the experimental observation of Faraday waves on soft gels. These were obtained using agarose in a mechanically vibrated cylindrical container. Low driving frequencies induce subharmonic standing waves with spatial structure that conforms to the geometry of the container. We report the experimental observation of the first 15 resonant Faraday wave modes that can be defined by the mode number (n,ℓ) pair. We also characterize the shape of the instability tongue and show the complex dependence upon material properties can be understood as an elastocapillary effect.
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Affiliation(s)
- X Shao
- Department of Mechanical Engineering, Clemson University, Clemson, 29634 South Carolina, USA
| | - G Bevilacqua
- MOX, Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy
| | - P Ciarletta
- MOX, Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy
| | - J R Saylor
- Department of Mechanical Engineering, Clemson University, Clemson, 29634 South Carolina, USA
| | - J B Bostwick
- Department of Mechanical Engineering, Clemson University, Clemson, 29634 South Carolina, USA
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