2011-pnna-seminar dip-pen-nanolithography on...

Nanolithography on Responsive MaterialsProton-fountain Electric-field-assisted

Nanolithography (PEN)

PNNA Seminar Nanomaterials Fabrication - Spring-2011 PSU

Andres La Rosa,1 Mindi Yan,2Damian Hegsted,1 and Hui Wang2

Physics1 and Chemistry2 Department, Portland State University, Portland OR

NanoFab 2011

AcknowledgmentXiaohua Wang, Xin Wang, Carsten Maedler, Leo Ocola,

Rodolfo Fernandez, Sailaja Chada,* and Xiquan Cui


In memoriamSailaja Chada




I. Motivation: Underlying emerging biomimetic engineeringPEN as a method for creating erasable nanostructures usingresponsive materials

II. Comparison between “PEN” and “Dip pen nanolithgraphy”

III. Fabrication procedure III.A Preparation of P4VP responsive materialIII.B Preparation of acidic fountain tip

IV. Underlying working mechanisms of swelling in hydrogelsThe osmotic pressure. Lattice model for calculating the entropy: Ideal liquid vs Polymer solutions.



P4VP

Si

P4VP

Swollen feature

Water meniscus

+V

H3O+

[ H3O+ ]

‘Pen’ preparation

Polymer film preparation

F

Patterns formationon soft materials

Si

+V

F


Silicon wafer(“Piranha”

cleaned)

Spin coatedP4VP film)

(uv-cross-linked)

AFM probe k = 40 N/m

acidic phosphate buffer

Pattern formation in responsive polymer films

triggered by local protonation

P4VP


Responsive materialsRespond to a stimulus (mechanical, chemical, optical,changes in environmental conditions, etc.)Ref: B. Bhushan, “Biomimetics: lessons from nature-an overview,” Phil. Trans. R. Soc. A 367, 1445 (2009).

One current focus in biomimetic materialsDevelopment of versatile synthetic responsive thin films

Underlying emerging biomimetic technologies

In one approach, the complex synthetic hierarchy (needed to mimic natural bio-systems)is conceived as a combination of domains separated by stimuli-responsive thin films that regulate the interactions between the domain compartments.Ref: Tokarev, M. Motornov, and S. Minko; “Molecular-engineered stimuli-responsive thin polymer film: a platform for the development of integrated multifunctional intelligent materials,” J. Mater. Chem. 19, 6932 (2009).


Underlying emerging biomimetic technologies

In another approach, a cell is conceived not just as a chemical but also as a mechanical device,It is found that the cell membrane is very sensitive to the mechanical properties of its surrounding matrix (affecting their growth, differentiation, migration, and, eventually, apoptosis,) Ref: C. Cofield, “Cell is mechanical device,” The American Physical Society, APS news, Series II, 19, 4 (June 2010).

Both approaches emphasize the need for harnessing thefabrication of synthetic thin film responsive materials


Underlying emerging biomimetic technologiesTop-Down and Bottom-up approaches

Research on biomimetic materials have resulted in the design of a variety of responsive building blocks hydrogels, brushes, hybrid systems with inorganicparticles

that respond selectively to pH, temperature, optical, and magnetic external stimuli.

Following the “bottom-up” route: self-assembly of polymeric supramolecules.

Progress using “top-down” approach: responsive polymer brushes,growth of polymers from DPN-patterned templates,chain polymerization triggered by local stimulation using a STM stylus.



PEN falls in the top-down category approach.Atomic force Dip pen PENmicroscopy nanolithography

Our description concentrates on hydrogels,since the latter describes closer the experimental results obtained in current applications of PEN.



Hydrogels,A flexible (typically) hydrophilic cross-linked polymer network and a fluid filling the interstitial spaces.The entire network holds the liquid in place thus giving the system a solid aspect. Contrary to other solid materials, these wet and soft systems are capable of undergoing very large deformation (greater than 100%).

Polymer solution Lattice model

Polymer segmentSolvent

Atomic force Dip pen PENmicroscopy nanolithography


Probe(’pen’)

Substrate

Water meniscus

Polymer film

Deposition of molecules

Molecules deposited on the

substrate constitute the patterns

The locally triggered swellings of the

substrate constitute the pattern

Allows controlling the probe-sample

distance

Deposition of

molecules(“ink”)


Probe (’pen’)

http://mcf.tamu.edu/instruments/dip-pen-nanolithographer

Substrate (’paper’)

Dip pen nanolithography

Deposition of

molecules(“ink”)


Probe‘Ink’

http://mcf.tamu.edu/instruments/dip-pen-nanolithographer

Dip pen nanolithography

“ink’ molecules deposited on the substrate constitute the pattern

+H

++

++

HH

HH

P4VPPolymer

P4VPPolymer

Coulomb repulsion between thepyridinium ions leads to an increaseof the film thickness.


Pattern formation in responsive polymer films triggered by local protonation

Swelling mechanism

P4VP

Si

P4VP

Swollen feature

Water meniscus

+V

H3O+

[ H3O+ ]

‘Pen’ preparation

Polymer film preparation (soft material)

F

Patterns formation

Si

+V

F

PNNA Seminar Nanomaterials Fabrication - Sprng-2011 PSU

Silicon wafer(“Piranha”

cleaned)

Spin coatedP4VP film)

(uv-cross-linked)

AFM probe k = 40 N/m


Pattern formation in responsive polymer films

triggered by local protonation

P4VP

The locally triggered swellings of the film constitute the pattern

Robust attachment• Scotch tape test• Boiling solvent

Ease of preparation Substrate-independent

1) Coat polymer2) UV irradiate3) Solvent extract

0

5

10

15

20

25

30

35

40

45

50

Bef

ore

UV

Afte

r 5 m

inU

V

Afte

rex

tract

ion

Thic

knes

s (n

m)

Preparation of polymer thin films Immobilization by direct UV Irradiation

Yan, M.; Harnish, B. Adv. Mater., 2003, 15, 224.

CHH2C < 280 nm

CH2C

CHCH

HC

•

•

•

CH2 • +

+ H •

+ H •

CHH2C < 280 nm

CH2C

CHCH

HC

•

•

•

CH2 • +

+ H •

+ H •

R. Rånby, J. F. Rabek, Photodegradation, Photo-oxidation and Photostabilization of Polymers, 1975, p167-172.

CH2C•

•CH2C

+ CH2CCH2C

crosslinking

HC•

+ H •

H2C

chain scission

CH2C•

•

+ O2

CH2COO

CH2CO

CH2

OH

UV

CH

CH2CO

CH2 CH

•

CH2CO

CH2 CH•

+

Oxidative Degradation

Polystyrene

OH

CH CH2

UV irradiation< 290 nm

O

CH CH2

H

OH

C CH2

H

Poly(4-vinyl phenol)

OH

CH2C

O2

OH

CH2COO

RH-R

OH

CH2COOH

CH2 CH

OH

- OH

OH

CH2CO

CH2 CH

OHOH

CH2C CH2 CH

OH

O

OH

C CH2

OH

C CH2

OH

C CH2

OH

C CH2

HC O

HC O

HC O

HC O

HC O

HC O

Uppalapati, S.; Chada, S.; Engelhard, M. H.; Yan, M. Macromol. Chem. Phys. 2010, 211, 461.

HC

O

HC

O

CH2 CH

O

CH

O

CH2

CH2

0 1 2 3 4 5 6 7 8

0

1000

2000

3000

P4VPPNVPPSGold

pH

0 500 1000 1500 2000 2500-3000

-2000

-1000

0

1.0 2.0 3.0 3.5 4.0 4.5 5.0 6.0 7.0

pH

time (s)

n

N

n

P4VP PS

NnO

PNVP

• large response • fast • reversible

Harnish, B.; Robinson, J.; Pei, Z.; Ramstrom, O.; Yan, M. Chem. Mater. 2005, 17, 4092.

Thin films stimuli-responsiveCharacteristics: Evaluation

Protontransfer

Swelling


molecules

C. Maedler, S. Chada, X. Cui, M. Taylor, M. Yan, and A. La Rosa, J. Appl. Phys. 104, 014311 (2008).

Probe


P4VPPolymer

Electrostaticrepulsion

Dwelling time: 6 s, 4 s, 2 s

Pattern formation

Pattern formation in responsive polymer films triggered by local protonation

Swollenstructure

Protontransfer

Swelling


molecules

Probe


P4VPPolymer

Electrostaticrepulsion

Writing: rate=0.04 line/s; i.e. 100 nm/s or 1 pixel / 250ms)

Imaging: rate=2 line/s; i.e. 5 µm/s or 1pixel / 5ms)

Sequential fabrication and imaging

A. La Rosa and, M. Yan, in “Tip Base Nanolithography” (to be published in June-2011)

Pattern formation in responsive polymer films via local protonation

Role of humidity


AFM Chamber

Water

Nitrogen

C. Maedler, H. Graaf, S. Chada, M. Yan, and A. La Rosa, "Nano-structure Formation Driven by Local Protonation of Polymer Thin Films", Proc. SPIE 7364, 736409-1 – 736409-8 (2009).

Effect of Electric Field and Contact Force

P4VPSi

Water meniscus

+V

Applied bias voltage (V)

Applied contact force (N)

Force

Xiaohua Wang, Xin Wang, R. Fernandez, L. Ocola, M. Yan, and A. La Rosa; “Electric Field-Assisted Dip-Pen Nanolithography on Poly(4-vinyl Pyridine) Films,” ACS Appl. Mater. Interface 2, 2904–2909 (2010).

PENFinest line structures

P4VPSi

Water meniscus

+V

Force


PENReversibility


Underlying working mechanisms of swelling in hydrogels

A. La Rosa and, M. Yan, in “Tip Base Nanolithography” (to be published in June-2011)

A B Semi-permeable membrane Polymer solution

Solvent + solute Pure solvent

SoluteSolvent

Polymer segmentSolvent

h

Lattice model Lattice model Vapor of pure solvent

P2 P1

Chemical potential of water in phase-A (pure solvent water)is greater thanthe chemical potential of water in phase-B (solven + solute)

AP,waterB

P,water <


Gibbs free energy G = G (T, P, N).

Being the temperature T and pressure P intensive quantities, G has to have the form

G = N f(T, P),

where N is the number of particles of the analyzed system.

Since dG = -S dT + V dP + dN and = (dG/dN)T,P, the extensive property G = N f(T, P) implies that is only a function of T and P; that is,

= G/N = f(T, P).


Accordingly, is the Gibbs free energy per molecule, andit is a quantity independent of N. Thus,

d(G/N) = d = - (S/N) dT + (V/N) dP,

which implies,

V/NPd

d

.


This expression is pertinent to the quantification of the osmotic pressure. In effect, it reflects the change in chemical potential due to an increase in pressure, =( V/N) P (where it has been assumed that the volume does not change with pressure.) Using v ≡ ( V/N), one obtains

.

BP2,water A

P1,water- = v (P2 – P1),

BP2,water A

P1,water- = v osmotic

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