patterns around us sat stem program, umass amherst
DESCRIPTION
March 9 2013 . Patterns around us Sat STEM program, Umass Amherst. What is a “pattern”? . Basic structure repeated many times One characteristic length (or a few, or many ..) . Spontaneous. Engineered . Hybrid . Types of patterns . Spontaneous. - PowerPoint PPT PresentationTRANSCRIPT
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Patterns around usSat STEM program, Umass Amherst
March 9 2013
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What is a “pattern”?
• Basic structure repeated many times • One characteristic length (or a few, or many ..)
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Types of patterns
Spontaneous Engineered Hybrid
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Spontaneous Reflect competition of 2-3 elementary forces
Described by simple models
An indirect probe of various system parameters
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Outline
• Why do we study patterns
• Pattern formation theory in a nutshell
• A glimpse at some work at UMass Amherst
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Outline
• Why do we study patterns
• Pattern formation theory in a nutshell
• A glimpse at some work at UMass Amherst
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The taxpayer perspective
NSF-MRSEC
Surface instabilitiesIn polymers
W.M. Keck Foundation
Unfurling of ultrathin sheets
NSF-DMR
Origami-inspired material design
NSF-DMR
Morphologies of tensed sheets
Goal I: Creating ``good” patterns e.g. cheap patterning of surfaces at nano-scale
Goal II: Eliminating ``bad” patterns e.g. wrinkles and scars on skin, cracks in materials
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The physicist’s perspective
Exploring universal mechanisms in nature: across different scales across distinct physical systems
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The student perspective
Eye opening experience
Bridging bio-physics-chemistry Zest for Math
thickness
wrin
kle
leng
th
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Spontaneous patterns
basic physics
interdisciplinary
applications
stimulus and practice ofmathematical thinking
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Outline
• Why do we study patterns
• Pattern formation theory in a nutshell
• A glimpse at some work at UMass Amherst
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Buckling
Instability governed by weak bending resistance of thin objects
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Wrinkling on a liquid bath
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Wrinkling on a liquid bath
Wavelength governed by competition of forces: bending resistance (sheet) versus gravity (liquid)
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Wrinkling on a liquid bath
film’s thicknessw
rinkl
e le
ngth
Usage: Indirect measurement of thickness of ultrathin films
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Wrinkling on flesh
Wavelength governed by competition of forces:
bending resistance of sheet (=skin) versus Stiffness of substrate (=flesh)
Usage: Indirect measurement of elasticity of flesh Probing the stress in a skin (e.g. for surgery)
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Viscous Fingering
Wavelength governed by competition of rates:
Injection rateversus Viscous diffusion of liquid pressure
Usage/relevance: Oil recovery from porous rocks
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Chemical reactions
(??)
Wavelength governed by competition of rates:
reaction rate versus diffusion rate
Alain Turing 1950’s Zhabotinsky-Belosov 1960’s-1970’s
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Faraday waves
Wavelength and pattern governed by competition of forces:
Shaking rate (inertia) versus Gravity
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Summary (I)
• Interdisciplinary experience: an overarching principle for pattern formation in distinct systems
• Applicability e.g. metrology of ultrathin films
• Math skills: plot data --> fit to elementary functions --> discover new physical laws
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Outline
• Why do we study patterns
• Pattern formation theory in a nutshell
• A glimpse at some work at UMass Amherst
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What do you see ?
Chocolate ??
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What do you see ?
spontaneous pattern formation:
Wrinkles,Crumples, Folds, Blisters,Creases, …
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Glue a flat sheet on sphere
Frustration !!
Sheet on a curved surface
To delaminate (blister) ?orTo stay attached (wrinkle) ?
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A sheet on a drop
drop
sheet
Decreasing drop’s radius R …
top view(experiment)
R
side view(schematic)
sheet
drop
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A sheet on a drop
drop
sheet
Decreasing drop’s radius Rfurther …
R
side view(schematic)
sheet
drop
top view(experiment)
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A sheet on a drop
drop
sheet
Decreasing drop’s radius Reven further …
R
side view(schematic)
sheet
drop
top view(experiment)
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A sheet on a drop
drop
sheet
Finally …
R
side view(schematic)
sheet
drop
top view(experiment)
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A sheet on a drop
drop
sheetR
sheet
drop
From wrinkling to crumpling
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A sheet on curved surface: wrinkles, crumples, blisters
blisters wrinkles crumples
Questions:
1) How can we suppress/enhance blistering?2) How fast does a sheet spread on liquid bath?
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Summary
• Spontaneous pattern formation is cool !
• Thanks you for listening !