Journal of Engineering Science & Mechanics
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 The Journal of Engineering Science & Mechanics (JESM) is a scientific
journal dedicated to highlighting mechanics research performed by
undergraduate students. Virginia Tech's Department of Engineering Science & Mechanics has
created JESM to provide students an avenue for showcasing their research
and communicating their ideas to the broader scientific community. The journal highlights research papers written by undergraduates
about research performed by undergraduates. The manuscripts are
peer-reviewed by professors, graduate students, and industrial
scientists. JESM's Website...
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Elastic Instabilities for Form and Function |
| D.P. Holmes, iMechanica - Journal Club, February 2012. [Link] |
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Welcome to February 2012's Journal club, which will include a discussion on elastic instabilities for form and function. Not long ago, the loss of structural stability through buckling generally referred to failure and disaster. It was a phenomenon to be designed around, and rarely did it provide functionality*. The increasing focus on soft materials, from rubbers and gels to biological tissues, encouraged scientists to revisit the role of elastic instabilities in the world around us and inspired their utilization in advanced materials. Now the field of elastic instabilities, or extreme mechanics, brings together the disciplines of physics, mechanics, mathematics, biology, and materials science to extend our understanding of structural instabilities for both form and function. In this journal club, we're going to look at research on the wrinkling, crumpling, and snapping of soft or slender structures. Read More... |
Mechanics of Surface Area Regulation of Cell Membranes |
| M. Staykova, D.P. Holmes, C. Read, and H.A. Stone, Proc. Natl. Acad. Sci, 108(22), 9084-9088, 2011. [PDF] |
| Selected Press: Nature Materials |
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 We approach the complex problem of cell area regulation by using a model membrane system and a novel experimental setup, which couples a lipid bilayer to the controlled straining of an elastic sheet to study the response of pure lipid membranes to lateral stretch and compression. We demonstrate that even a single component fluid lipid bilayer can controllably regulate its surface area upon straining by either the absorption of vesicles upon membrane dilation or through nanotube expulsion upon compression. The processes of lipid membrane remodeling in our experiments closely resemble steps in the membrane traffic via exo- and endo-cytosis observed in biological cells. Our results offer a simple insight into these complex cell processes as well as into the role of the lipid bilayer in their regulation and coordination.
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Bending and Twisting of Soft Materials by Non-Homogenous Swelling |
D.P. Holmes, M. Roché, T. Sinha, and H.A. Stone, Soft Matter, 7, 5188, 2011 [PDF] |
 Soft materials, e.g. biological tissues and gels, undergo morphological changes, motion, and instabilities when subjected to external stimuli. Tissues can exhibit residual internal stresses induced by growth, and generate elastic deformations to move in response to light or touch, curl articular cartilage, aid in seed dispersal, and actuate hygromorphs, such as pine cones. Understanding the dynamics of such osmotically driven movements, in the influence of geometry and boundary conditions, is crucial to the controlled deformation of soft materials. We examine how thin elastic plates undergo rapid bending and buckling instabilities after anisotropic exposure to a favorable solvent that swells the network. An unconstrained beam bends along its length, while a circular disc bends and buckles with multiple curvatures. In the case of a disc, a large-amplitude transverse travelling wave rotates azimuthally around the disc.
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Draping Films: A Wrinkle to Fold Transition |
| D.P. Holmes and A.J. Crosby, Physical Review Letters, 105, 038303, 2010. [PDF] [Supplemental Material] |
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Selected Press: Science News, Discovery News, Physics
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A polymer film draping over a point of contact will wrinkle due to the strain imposed by the underlying substrate. The wrinkle wavelength is dictated by a balance of material properties and geometry; most directly the thickness of the draping film. At a critical strain, the stress in the film will localize, causing hundreds of wrinkles to collapse into several discrete folds. In this paper, we examine the deformation of an axisymmetric sheet and quantify the force required to generate a fold. The onset of folding, in terms of a critical force or displacement, scales as the thickness to the four-ninth power, which we predict from the energy balance of the system. The folds increase the tension in the remainder of the film causing the radial stress to increase, thereby decreasing the wavelength of the remaining wrinkles. |
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Crumpled Surface Structures |
D.P. Holmes, M. Ursiny, and A.J. Crosby. Soft Matter, 4, 82, 2008. [PDF] |
 The topographic control of pattern features is of great interest for a range of applications including the generation of ultrahydrophobic surfaces, microfluidic devices, and the control and tuning of adhesion. In these areas, surface patterning is achieved by a variety of techniques including: photolithography, imprint lithography, and surfaces wrinkling. In this paper, we present a scalable patterning method based on surface plate buckling, or crumpling, to generate a variety of topographies that can dynamically change shape and aspect ratio in response to stimuli.
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Snapping Surfaces |
| D.P. Holmes and A.J. Crosby. Advanced Materials, 19, 3589, 2007 [PDF] |
| Selected Press: Discovery News, Wired |
 The responsive mechanism of the Venus flytrap has captured the interest of scientists for centuries. Although a complete understanding of the mechanism controlling the Venus flytrap movement has yet to be determined, a recent publication highlights the importance of geometry and material properties for this fast, stimuli-responsive movement. Specifically, the movement is attributed to a snap-through elastic instability whose sensitivity is dictated by the length scale, geometry, and materials properties of the features. Here, we use lessons from the Venus flytrap to design surfaces that dynamically modify their topography. We present a simple, biomimetic responsive surface based on an array of microlens shells that snap from one curvature to another when a critical stress develops in the shell structure.
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email: dpholmes at vt.edu [CV] |
The mechanics of soft structures and how they accommodate large stresses and dramatic elastic instabilities provides a great framework to study problems ranging from biological interfaces to the design of responsive materials.
I am interested in using elasticity, soft materials, and instabilities such as snap-buckling, crumpling, wrinkling, and folding to generate responsiveness and impact properties such as adhesion, optics, and flow at surfaces or within devices.
My research on synthetic and biological membranes and how they deform and interact with fluids allows me to address important fundamental questions that lie at the interface between fluids and soft materials.
| Virginia Tech |
Assistant Professor |
2011-2012 |
| Engineering Science & Mechanics |
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| School of Biomedical Engineering & Sciences |
Core Faculty Member |
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| Materials Science & Engineering |
Affiliate Faculty |
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| Princeton University |
Postdoctorate |
2009-2011 |
| Mechanical & Aerospace Engineering |
| Advisor: Howard A. Stone |
| University of Massachusetts, Amherst |
Ph.D. |
2009 |
| Polymer Science & Engineering |
| Advisor: Alfred J. Crosby |
| University of Massachusetts, Amherst |
M.S. |
2005 |
| Polymer Science & Engineering |
| University of New Hampshire |
B.S. |
2004 |
| Chemistry |
| Advisor: Donald C. Sundberg |
| Mechanics of Deformable Bodies |
ESM 2204 |
Fall 2012 |
| Mechanical Behavior of Materials |
ESM 3054 |
Spring 2012 |
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