Selfsys

Fluidic mediated self‐assembly for complex,
hybrid micro/nanosystems
J. Brugger, A. Martinoli, N. Spencer, B. Nelson,
H. Wolf, H. Knapp, L. Sciboz

SELFSYS - Fluidic-mediated self-assembly for hybrid functional micro/nanosystems

Assembly challenge of N/MEMS
Today The challenge of tomorrow
• Many different kinds of • Finding a way to assemble the
micro/nano devices, MEMS, bricks into functional
S&A, CMOS, OLED, etc micro/nano-systems

SELFSYS - Fluidic-mediated self-assembly for hybrid functional micro/nanosystems 2

SoA for integrating multifunctional N/MEMS
• Co-integration (if possible)
• Separate fabrication followed by joining
• Wafer Bonding; Tape automatic bonding
• Pick & Place; Robotic assembly

• Challenge for highly miniaturized systems
• Challenge for very large numbers of components

• SELFSYS:  Contribute with enabling manufacturing for
future micro-assembly applications


Fluidic mediated self-assembly
• Known concept in R&D
• Using capillary forces to align components
• At the interface of liquids
• First industrial examples emerging

Hydrophobic area Lubricant

Srinivasan, Boehringer, Mastrangeli, van Hof, Lambert
U Washington, Seattle IMEC, Belgium



10 mm



MEMS

Modelling

Surfaces

RFID chip

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Applications
10 mm Microfluidic


SELFYS synapsis


Loic Jacot‐Descombes

Cathrein Hückstädt

Jonas Wienen
Maurizio Gullo

(ETHZ)
(EPFL)

(CSEM)
(EPFL)

Didi Xu
(ETHZ)

Deepak Kumar
M. Mastrangeli

(ETHZ)
(EPFL)

V. Nagaiyanallur
GMermoud
(EPFL)

(ETHZ)
M/NEMS: J. Brugger (EPFL), Distributed systems: A. Martinoli (EPFL), Surface
chemistry: N. Spencer (ETHZ), Nano-Robotics: B. Nelson (ETHZ), Microfluidics: H.
Knapp (CSEM), Self assembly: H. Wolf (IBM), RFID: L. Sciboz (icare Sion);
 add-on SELFSYS+: Ch: Hierold, D. Poulikakos (ETHZ)

Progress within SELFYS

• MEMS part fabrication
• Surface functionalization
• In-liquid self-assembly experiments
• Field induced assembly
• Template induced assembly
• Modeling RFID chip

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Progress within SELFYS


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Investigated shapes
Main Expected Expected
Shape: Scheme: Picture:
material: advantages: disadvantages :

Disc not restricted
1 SU‐8 low SA yield
slices to pairs

easy assembly
Flat
2 SU‐8 fabrication possible on
cylinders
and handling opposite side

Rounded higher
3 SU‐8
cylinders pairing yield

Half‐ SU‐8 or even higher smaller volume
4
spheres Ormocomp yield in SA (cavity)


Self-assembly of SU-8 cylinders
At water – Si oil interface: At water surface:

At the bottom: After water evaporated:


Fabrication of SU-8 microcapsules


Fabrication of Bi-color SU-8 cylinders

SEM images of the cylinders before release Optical image of un‐specific assembled parts in DI
(diameter ~ 100 um and height ~100 um) water after stirring.


Surface functionality for specific assembly

Yield(assembled/total): ~ 65 %


Surface Modification of SU8
Plasma treatment:

CA 70‐80 deg

CA < 10 deg


Photo-cleavable polymer layer
Covalent grafting of any desired polymer
onto SU‐8 can be achieved by this
methodology.


Half-sphere shape by inkjetting

D
Angle max at the edge: ν = CA + 180° ‐ ф

100 um


Adhesion force modulation
Calculated surface correlation:
1.60E+06

1.40E+06

Ring
Goal
E2
1.20E+06

Multi ring
1.00E+06

Force
8.00E+05

6.00E+05
dE
4.00E+05

2.00E+05
E1 40um
0.00E+00

‐60 ‐40 ‐20 0 20 40 60 Microfabricated
Srinivasan et al. 2001, J.
Alignment [um] capsules
Microelectromech. Syst. 10
17–24

Materials investigated:
Carbon coated tip/sample
Teflon (C4F8) coated tip/sample SphereTip©
Au coated + dodeca thiols (DDT)
monolayer tip/sample R=2µm


Force Curves / Teflon Coated Tip and Sample
movement parameter value
tip # curves 500 None or only very small and unstable
# positions 100 attracting force could be observed
teflon
speed 0.5 Hz for the Teflon coated tip and sample
DI water
rest time on sample 0.5 s measurements
sample
temperature 22°C
humidity 33%
Force Curve Adhesion Force

DI water

Sample

retractive
snap out


Forces between surfaces / summary

Material Attraction Force Adhesion force Material E2 E1 dE
DDT 6e-6 nN/nm^2 3.8e-4 nN/nm^2 DDT 1.16 mN 0.29 mN 0.87 mN
Carbon 3e-5 nN/nm^2 4e-4 nN/nm^2 Carbon 1.23 mN 0.31 mN 0.92 mN
Teflon 0 nN/nm^2 1e-4 nN/nm^2 Teflon 0.31 mN 0.08 mN 0.23 mN

•Hydrophobic interaction forces could be
1.60E+06

Ring
quantitatively assessed by AFM.
1.40E+06

1.20E+06
Goal
Multi ring E2
1.00E+06

•Carbon and DDT show similar adhesion
Force

8.00E+05

force.
6.00E+05

dE
4.00E+05

•Carbon better suited for micro fabrication.
2.00E+05
E1
0.00E+00

‐60 ‐40 ‐20 0 20 40 60
Alignment [um]


Progress within SELFSYS


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3 stage fluidic assembly system
1. Preparation - Transfer of parts into
functional fluid
2. Assembly - Agitation of particles to drive
self-assembly
3. Sorting - Sorting out and transferring back Supply fluid cycle
not correctly assembled parts Sedimentation filter

Reaction
Container for chamber
assembled parts

Functional fluid cycle

Sorter


Reaction chamber
Chamber size: 1 cm diameter Glass unit
Outlet (filtered)

Inlet and filtered outlet (laser cut) Filter
within
Piezo-actuation sealing
RC‐Core
Change in amplitude/frequency Outlet
Inlet
Shear forces at bubbles
Bubbles moving around PDMS ‐
Sealing

US‐transducers




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Field assisted assembly
Dielectrophoretic assisted Octomag motion of
assembly magnetic SU-8 flaps
• RFID chips (mCHIP/Hitachi) • Magnetic nanoparticle in
in liquid. photo-patternable SU-8
• Micro-chips with unique
codes

RFID chip

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Multi-scale modeling
Can we devise a unique methodological framework for modeling and controlling
these self‐assembling systems, across length‐scales?
2D 2D 3D

Robotic building block MEMS building block
5cm ALICE robot Typical size 50 to 500 um
Typical size: 2 centimeters
Swarm Typical swarm size: 10^2 to
Typical swarm size: a few dozen
Power to move 10^3 units
units
Simple on board Passive units: only local
Active units: sensing and actuation
intelligence interactions»»
Capillary and magnetic forces»»
Collective behavior Hydrophobic forces»»
Stochastic, fluidic control (pump)
Stochastic, fluidic control
(piezo)


Modeling Distributed Systems
Macroscopic 1: rate equations, mean field
approach, whole population

Abstraction
Common metrics
Macroscopic 2: Chemical Reaction Network,
stochastic simulations

Microscopic 1: Monte Carlo model, 1 robot = 1
agent, non-spatial

Microscopic 2: Agent-Based model, 1 robot = 1
agent, spatial

Experimental time
Define physical parameters suitable for
simulation of distributed, self-organizing
(micro) systems


Modeling / simulation
• 2-body motion / • 100-bodies
encounter

Material Attraction Force Adhesion force
DDT 6e-6 nN/nm^2 3.8e-4 nN/nm^2
Carbon 3e-5 nN/nm^2 4e-4 nN/nm^2
Teflon 0 nN/nm^2 1e-4 nN/nm^2


Add-on tasks SELFSYS+
• Magnetic particles embedded in SU-8*
• DNA coating on microcapsules
• Thermal modeling**
•  enhance control of assembly/separation

a) directionality b) selectivity c) reversibility

Para‐
magnetic
capsule

T>Tm B=on Mix=on T<Tm B=on Mix=off T>Tm B=off Mix=on

* add‐on partner Ch. Hierold
** add‐on partner D. Poulikakos/J. Thome


Summary & Outlook
MEMS Modeling Fluidic assembly system

100 um

Controlled liquid‐release
Hollow capsules Capsule disassembly
opening

T>Tm B=off Mix=on


Loic Jacot‐Descombes

Cathrein Hückstädt

Jonas Wienen
Maurizio Gullo

(ETHZ)
(EPFL)

(CSEM)
(EPFL)

Didi Xu
(ETHZ)

Deepak Kumar
M. Mastrangeli

(ETHZ)
(EPFL)

V. Nagaiyanallur
GMermoud
(EPFL)

(ETHZ)
M/NEMS: J. Brugger (EPFL), Distributed systems: A. Martinoli (EPFL), Surface
chemistry: N. Spencer (ETHZ), Nano-Robotics: B. Nelson (ETHZ), Microfluidics: H.
Knapp (CSEM), Self assembly: H. Wolf (IBM), RFID: L. Sciboz (icare Sion);
 add-on SELFSYS+: Ch: Hierold, D. Poulikakos (ETHZ)

Liquid release from micro-capsule

Self‐assembled Blue ink encapsulated Ink released


Hollow SU-8 microcapsules

Side view

Top view

13 drops… overflow


Functionalization of SU-8 surface

PDDA

PSS

The charge characteristics are tested by dispersing SiO2 particles
Poly(diallyldimethylammonium chloride)(PDDA) – positively charged surface
Poly styrene sulfonate (PSS) – negatively charged surface

Microdrop printing of functional material

Polymer Microlenses
Fakfouri MNS 2009 Luminescent NCs
Kim Small 2009

Printing on Hot‐Surface Bio‐Printing
Lee APL 2007 Pataky in prep


Inkjet set-up


Force Curves / Carbon Coated Tip and Sample
Attraction Force
movement
parameter value
tip # curves 500

carbon # positions 100

DI water speed 0.5 Hz

sample rest time on sample 0.5 s
temperature 22°C
Force Curve
humidity 33%

DI water
attractive
snap in Adhesion Force

Sample

retractive
snap out


Force Curves / DDT Coated Tip and Sample

Adhesion Force C A

A DDT
DI water

Fresh tip / sample

B

B C

DI water DDT DDT
DI water

Displacement of DDT Rearrangement of DDT

Sung et al, Appl. Phys.
A 81, 109–114 (2005)


Modeling SA across scales

~ m ~ cm

SelfSys Lily


Summary

• Hollow MEMS fabrication
• Surfaces: O2 plasma, polymer

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Selfsys

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Selfsys