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Patterns around us Sat STEM program, Umass Amherst

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Patterns around us Sat STEM program, Umass Amherst March 9 2013 Patterns around us 1. Introduction I: spontaneous patterns show many examples: spontaneous, engineered ... – PowerPoint PPT presentation

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Title: Patterns around us Sat STEM program, Umass Amherst


1
Patterns around us Sat STEM program, Umass Amherst
March 9 2013
2
What is a pattern?
  • Basic structure repeated many times
  • One characteristic length (or a few, or many ..)

3
Types of patterns
Spontaneous
Engineered
Hybrid
4
Spontaneous
Reflect competition of 2-3 elementary forces
Described by simple models
An indirect probe of various system parameters
5
Outline
  • Why do we study patterns
  • Pattern formation theory in a nutshell
  • A glimpse at some work at UMass Amherst

6
Outline
  • Why do we study patterns
  • Pattern formation theory in a nutshell
  • A glimpse at some work at UMass Amherst

7
The taxpayer perspective
NSF-MRSEC Surface instabilities In 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
8
The physicists perspective
  • Exploring universal mechanisms in nature
  • across different scales
  • across distinct physical systems

9
The student perspective
  • Eye opening experience
  • Bridging bio-physics-chemistry
  • Zest for Math

wrinkle length
thickness
10
interdisciplinary
basic physics
applications
Spontaneous patterns
stimulus and practice of mathematical thinking

11
Outline
  • Why do we study patterns
  • Pattern formation theory in a nutshell
  • A glimpse at some work at UMass Amherst

12
Buckling
Instability governed by weak bending resistance
of thin objects
13
Wrinkling on a liquid bath
14
Wrinkling on a liquid bath
Wavelength governed by competition of forces
bending resistance (sheet) versus gravity
(liquid)
15
Wrinkling on a liquid bath
wrinkle length
films thickness
Usage Indirect measurement of thickness of
ultrathin films
16
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)

17
Viscous Fingering
Wavelength governed by competition of rates
Injection rate versus Viscous diffusion of
liquid pressure
Usage/relevance Oil recovery from porous rocks
18
Chemical reactions
Alain Turing 1950s
Zhabotinsky-Belosov 1960s-1970s
Wavelength governed by competition of rates
reaction rate versus diffusion rate
(??)
19
Faraday waves
Wavelength and pattern governed by competition
of forces Shaking rate (inertia) versus
Gravity
20
Summary (I)
  • Interdisciplinary experience
  • an overarching principle for pattern
    formation in distinct systems
  • Applicability
  • e.g. metrology of ultrathin films
  • Math skills
  • plot data --gt fit to elementary functions
    --gt discover new physical laws

21
Outline
  • Why do we study patterns
  • Pattern formation theory in a nutshell
  • A glimpse at some work at UMass Amherst

22
What do you see ?
Chocolate ??
23
What do you see ?
spontaneous pattern formation Wrinkles, Crumples
, Folds, Blisters, Creases,
24
Sheet on a curved surface
Glue a flat sheet on sphere
Frustration !!
To delaminate (blister) ? or To stay attached
(wrinkle) ?
25
A sheet on a drop
top view (experiment)
26
A sheet on a drop
sheet
drop
top view (experiment)
27
A sheet on a drop
sheet
drop
top view (experiment)
28
A sheet on a drop
sheet
drop
top view (experiment)
29
A sheet on a drop
sheet
drop
From wrinkling to crumpling
30
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?
31
(No Transcript)
32
Summary
  • Spontaneous pattern formation is cool !
  • Thanks you for listening !

33
Doing it with surface tension
low tension
high tension
34
Patterns around us
1. Introduction I spontaneous patterns
  • show many examples spontaneous, engineered,
    intermediate
  • what is a pattern?
  • some recognized structure (simply periodic,
    partly periodic e.g. spirals, ordered chaos)
  • repeated appearance / dominance of a few
    length scales
  • Classification into
  • engineered patterns metro lines, manhattan
  • spontaneous - sand dunes, ocean waves,
    dendritic growth, ion sputtering, plant leaves,
    zebra stripes
  • intermediate venation networks, pinecorns,
    bacterial colonies, spider web

2. Introduction II Why to study patterns?
  • Funding Origami grant, Career grant, Keck
    grant , MRSEC IREG II
  • Tax-payer perspective (show me the money)
  • Useful applications material science - cheap
    nano-patterning,
  • Bio-applications treating wrinkles and
    scars.
  • Physical insight Recognizing universality in
    phenomena -
  • across different length scales, across distinct
    physical systems
  • Education (why should kids be interested in this)
  • Eye opening experience.
  • Bridging bio-physics-chemistry
  • Zest for Math
  • A graph with circles Spontaneous patterns gt
    usefulness, physics, stimulate math skills

35
3. Principles of pattern formation
  • Euler buckling instability
  • Wrinkling on water (Huang) and on flesh (Cerda
    03) force balance (competing forces),
  • show data from PRL 2010, demo skin
  • Viscous fingering (later here). competition of
    rates driving versus viscous diffusion of
    pressure.
  • Faraday wave
  • Zebra stripes / ZB (competing rate of diffusion
    and reaction)
  • Learning Universal principle (see pattern -
    look for competing mechanisms)
  • Usefulness (one application metrology)
  • Math skills (plot data - gt fit to functions -gt
    discover simple physical laws

4. What do we do here
  • Wrinkling and crumpling (start by chocolate
    picture, go to blisters and to drop on sheet
    from Oxford)
  • Keck paragraph and picture shrink-wrap,
    nanometric wall paper, ..
  • Suppressing delamination (contrast wrinkles and
    blisters picture)
  • New metrology (measure wrinkle pattern to
    determine properties of ultrathin films)
  • patterning surfaces (Crosby)
  • Medical applications (find tension direction)
  • Sharp folds (Menon and Dominic), and creases
    (Hayward, Evan) from here to brain (show
    picture)
  • Origami-inspired design
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