Mesoscale SelfAssembly

1
Mesoscale Self-Assembly

• Organizing the barely visible.

2
An Overview

• Defining Mesoscale Self-Assembly (MeSA) and its
  characteristics
• Why MeSA?
• The Force Regimes
• Mixing the forces
• Where MeSA is going
• Solving MeSAs problems

3
What is MeSA?

• Minimization of system energy
• Size scale µm mm
• Aggregation occurs over a length scale a few
  times the objects dimension
• Different system parameters

4
How is MeSA different?

• Number of components
• Component preparation
• Function
• Relevant forces
• System energies
• Reaction hierarchies
• Stability

5
System Parameters

• Activation energy
• Stagnant, Assembly, and Random regimes
• Reaction reversibility
• Irreversible vs Reversible
• Energy dynamics
• Static vs Dynamic (energy-dissipating)

gt All Application Dependent!
6
Why MeSA?

• Widely applicable size regime (circuit-level)
• Bridges from molecular/nano SA
• Picks up where machining leaves off
• High-yield
• Fab decoupling
• Quasi-equilibrium
• Secondary SA
• Easily deployable analogue to smaller systems

7
Being forceful
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Hydrophobic Capillary Assembly

• High interfacial energies promote agglomeration
  of hexagonal discs

N. Bowden, I.S. Choi, B.A. Grzybowski, G.M.
Whitesides, J. Am. Chem. Soc., 121, No. 23, 1999
9
Solder-based capillary

• Hydrophobicity of solder propels bonding
• Heated system melts solder

Boncheva et al. PNAS, 99, 8, 49374940, 2002
10
MacroTemplated Self-Assembly

• Mechanical-templating force
• Framework reinforced by polymer mould replaced
  by arbitrary material

H. Wu, V.R. Thalladi, S. Whitesides, G.M.
Whitesides, J. AM. CHEM. SOC., 124, 48, 2002
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• MeSA Periodic arrays of arbitrary shape

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-gt Colloidal assemblies in in photolithographed
cavities
J. Li et al. / Colloids and Surfaces A
Physicochem. Eng. Aspects 269 (2005) 2227
13
Magnetic Field Driven Self-Assembly

• Programmable magentization
• 8-10 µm wells
• High-spatial control of placement
• Control of collection
• System energy important!

Yellen and Friedman, Langmuir 2004, 20, 2553-2559
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All lights in line
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Magnetic Nanowire-Assisted Cell Trapping

• Magnetic cell separation
• Ni nanowires from Anodisc template
• µMagnetic point matrix on glass
• NIH-3T3 mouse fibroblasts cells
• Cells integrated with wires

M. Tanase, E.J. Felton, D.S. Gray, A. Hultgren,
C.S. Chenc, D.H. Reich, Lab Chip, 2005, 5, 598605
16

• Wires are arranged by µMagnets
• Flow-assisted trapping
• Cells form regular, controllable array

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3D MeSA in ferrofluid under gradient

• Magnetic field is applied with a gradient
• Ferrofluid exerts P based on this field
• Assembles µm scale parts into mm forms
• Agitation by flow

E. Feinstein, M. Prentiss, J. Appl. Phys. 99,
064901 2006
18
Magnetic Dipole MeSA 3D Formation
Boncheva et al., PNAS, 102, 11, 3925, 2005
19
B.T. Burnley, J.P.L. Cox, Materials Science and
Engineering C, 25, 529540, 2005
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Magnetically-Tunable Band Gap
Periodic Structures

• Self-assembled sphere act as stop-band
• Moving toward photonic crystal

M. Golosovsky et al., Synthetic Metals, 139,
705709, 2003
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Resulting Band-Pass Behaviour
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3D Periodicity
Y Saado et al., Optical Materials, 17, 1-6, 2001
24
Magnetic Orientation and Induction Welding

• Magnetic field applies torque, moves part to
  equilibrium position ?D TfieldWhLMSHextcos(?)
• Time-varying field then melt solder through
  hysterisis-loss and eddy-current loss
• Is this true SA despite directed localization and
  irreversibility?

Yang, Lin, Fang, J. Micromech. Microeng. 16
(2006) 2732
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Circuit-level magnetic assembly
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Dynamic Self-Assembly

• Magnetic mm-scale PDMS discs suspended over water
• Chiral forms
• Aggregate with agitation depending on form

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Dynamics of Shear-Assembly
B.A. Grzybowski, G.M. Whitesides, Science, 296,
5568
28
Casimir Forces What can the exclusion
of EM modes do for you?

• QM result that allows for geometry induced forces
• Measurement with torsion pendulum
• Results within 5 of theory

S. K. Lamoreaux, Physical Review Letters, 78, 1,
1997
29
MEMS Design Now with more Psis!

• Interaction force modulated by charge density
• Measured force between gold sphere and high/low
  resistivity Si
• Applications to MEMS design

F. Chen, G. L. Klimchitskaya, V. M. Mostepanenko,
U. Mohideen, Phys Rev Let, 97, 170402 (2006)
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Autonomous Self-Assembly

• Random self-propelled movement
• Effective simulation of life?

R.F. Ismagilov, A. Schwartz, N. Bowden, G.M.
Whitesides, Angew. Chem., 114, 4, 2002
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The Hierarchical Dream A Mesoscopic
Caste System

• Complex design integrating the aciton of multiple
  forces
• Force regimes controlled by external stimulation
  and system energy
• Length domains
• Time domains (simultaneous v sequential)

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The building blocks
S. Maksimuk, X. Teng, H. Yang, Phys. Chem. Chem.
Phys., 2006, 8, 46604663
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The Unknown

• Defect tolerance, yield after many stages of MeSA
• How to design beyond the simplest shapes

34
Special thanks

• Prof. George Whitesides
• Prof. Sue Whitesides
• Prof. George Whitesides
• The NPR
• Fiery Furnaces, The Black Keys, The Islands, We
  Are From Barcelona