ROTATING THIN FILM DISK

SLIDER / HEAD

X - (CF2O)y (CF2CF2O)z CF2 - X

X CH2OH (functional group) y perfluoromethylene oxide groups (C1)z perfluoroethylene oxide groups (C2)

polargroup

polargroupbackbone

• Confined film undergo “glass transitions” at a temperatures well above the bulk Tg (56 vs. -115 °C).

• Kinetics is dependent on the relative flexibility of the PFPE backbone.

• Changes occur in time dependence as well as bonding rate constant.

Monolayer Lubrication of Hard Drives

NanoScience & LubricationNanoScience & Lubrication

1 10

40

Si

Cr

CHxZdol

[nm]

250 350 360 370 380 400

0

Tg

xL

85

90

95

100

105

0 50 100 150 200 250 300FILM THICKNESS, ( nm )

Tg (

oC

)

12.0 kDa PS

FOX-FLORY (BULK)

7

27

87

67

47

127

107

MOLECULAR WEIGHT [Mn]103 104 105 106 107

Tg

( O

C )

C. Buenviaje, et al., ACS symposium series; 781 (2001): 76-92

SHEARDISPLACEMENT,

XMOD

SHEAR RESPONSE

XL

SAMPLE

CANTILEVER

TIP

NO-SLIPCONTACT

HEATING / COOLING STAGE

SHEARDISPLACEMENT,

XMOD

SHEARDISPLACEMENT,

XMOD

SHEAR RESPONSE

XL

SHEAR RESPONSE

XL

SAMPLE

CANTILEVER

TIP

CANTILEVER

TIP

NO-SLIPCONTACT

HEATING / COOLING STAGE

GlassTransition

SFM ModesSFM Modes

Contact Thermal Modulation Analysis

T [K]

Kinetic Experiments 10.5 ± 0.5Å Zdol, 2500 CHx

0 20 40 60 80 100 120 140 1600.00

0.05

0.10

0.15

0.20

T = 54°C

T = 86°C

t-1. 0

= 0.8

t-

t -0. 5

k b

TEMPERATURE (°C)0 20 40 60 80 100 120 140 160

0.010

0.015

0.020

0.025

0.030

0.035

T = 85°C

T = 56°C

SH

EA

R R

ES

PO

NS

E (

a.u

.)

TEMPERATURE (°C)

LOW TEMPERATURE5.0)( tktk b

• “GLASS LIKE”• SHORTER RANGE INTERACTIONS• DIFFUSION LIMITED

HIGH TEMPERATURE0.1)( tktk b

• “LIQUID LIKE”• DISPERSIVE INTERACTIONS• ACTIVATION BARRIER LIMITED

Shear Modulated SFM

Fractal Bonding in Hard-Drive LubricationNanoScience & LubricationNanoScience & Lubrication

HOLES / BITS

SUBSTRATEPOLYMER

Thermomechanical storage in thin polymer films demands unique flow and retaining properties of polymers.

NanoScience & Information StorageNanoScience & Information Storage

Quest for Higher Density Storage Media

Widely expected for Magnetic Storage Devices: Superparamagnetic Limit of 100 Gb/in.2

SUBSTRATEPOLYMER

SUBSTRATEPOLYMER

Q

CANTILEVER TYPE READ / WRITE

PROBE

Q

Heat Cantilever Resistively

Q

A possible alternative to magnetic recording: Thermomechanical Ultrahigh Density Storage in PolymersExpected recording density: 1 Tb/cm2 (1000 Gb/cm2)

NanoScience & Information StorageNanoScience & Information Storage

Millipede Storage Concept

2 mm 200 m 20 m 2 m

A 2D ARRAY OF LOCAL PROBES IS OPERATED IN A PARALLEL / MULTIPLEX FASHION.

Cantilever Array: (7 14 mm2)

32 32 (1024) Cantilevers

Vettiger, et al., IEEE Transactions on Nanotechnology, 1 (2002)

NanoScience & Information StorageNanoScience & Information Storage

Millipede – A Heat Transfer Challenge

Holes show undesired

- Rim Formations

For instance:

Concerns are

- local thermal transport,

- dewetting instabilities and hole retention,

- and timed backflow (bit erasing).

Fundamental Challenge:The scaling behavior of thermoplastic and thermoset polymers is simply not well-established, neither in fundamental understanding nor in performance.

Vettiger, et al., IEEE Transactions on Nanotechnology, 1 (2002)

Nano-Remediation and Energy Conservation

Significance: Environment and Energy Conservation

• Sieves/Membranes: Novel approaches for single pore separation systems.• Proton Exchange Membrane (PEM): Shift from

Combustion to Chemical Reaction for Energy Generation.

Nano-Remediation and Energy Conservation

Proton Exchange Membrane (PEM) Fuel Cell

PEM

50-175m5-50m

ACTIVE LAYER

ANODE CATHODE

4H++4e-+O22H2OH+H22H+ + 2e-

NafionNafion consists of a hydrophobic tetrafluoroethylene (TFE) backbone with pendant side chains of perfluorinated vinylethers terminated by ion-exchange groups.

Nano-Remediation and Energy Conservation

60 70 80 90 100 110 120 130 1400.048

0.050

0.052

0.054

0.056

0.058

0.060

0.062

0.064

0.066T

c=79 oC T

g=116 oC

Am

plitu

de R

espo

nse

(A. U

.)

Temperature (oC)

Control of Transport Properties from a Nanoscopic Interfacial Perspective

Topography Elastic Response Map

Working principle illustrated on N2 diffusive flux through a Ceramic Zeolite Membrane, measured in-situwith surface morphology.

50 nm

PEM Efficiency a Function of Structural and Relaxation properties of NAFION©

Structural and Relaxation StudyLocal Flux Measurements

Ionic Clusters (T = 300 K)

1 m

Arrows indicate location at which fluxes were determined.

A

Tc= 79 oC Tg= 116 oC

CB

High PEM efficiency above ~80 oC

A: poor water transportA/B: polymer re- organization promotes water transportB: evaporationB/C: Tg=116 oC

Nano-Remediation and Energy Conservation

Zeolite FP gradient

(nN/kPa) permeability

(mol/sm2KPa)

1 0.0542 9.90E-05 2 0.132 3.70E-04 3 0.1654 4.70E-04

Motivation for Nanoscale PEM Research

< 1 mm ~ 10-100 mm

PDMS

PDMS

MEA

Cross-section (schematic)

Lithographical Mask of the Flow Field Plate

with ~100 m wide Flow Channels

Skin-thick Fuel Cell Coatings

Ultrathin Flow-field Plates

Nano-Remediation and Energy Conservation

MEA: Membrane Electrode Assembly

Porous ElectrodeThin Pt FilmNafion

Nanocontrolled Semiconducting Polymeric MaterialsNanocontrolled Semiconducting Polymeric Materials

Nanocontrol of Material Properties in Optoelectronics and Photonics

Potential Applications for:Potential Applications for: • Light emitting Diodes

• Lasing

• Solar Cells

• Ultrafast Optical Switches

One of the major challenges One of the major challenges to date:to date:

- Spectral Stability

Demands improved control over the Molecular Mobility.

Example: Blend Stabilization with high TExample: Blend Stabilization with high Tgg material material (e.g., PVQ, PS, …)(e.g., PVQ, PS, …)

0

0.2

0.4

0.6

0.8

1

1.2

400 450 500 550 600 650

9.2 V

11.5 V

10.2 V

No

rmal

ize

d E

L In

ten

sity

Wavelength [nm]

(a) PFO

0

0.2

0.4

0.6

0.8

1

1.2

400 450 500 550 600 650

7.0 V

10.0 V

14.0 V

No

rmal

ize

d E

L in

ten

sit

y

Wavelength [nm]

(b) 5 % PVQ blend

PFO:PVQ Blend

PFO: Conjugated poly(9,9 dioctylfluorene)

Pure PFO: poor spectral stability

PFO:PVQ Blend: good spectral stability

A.P. Kulkarni, S.A. Jenekhe, Macromolecules, 36, 5285 (2003).

Nanocontrol of Material Properties in Optoelectronics and Photonics

The glass transition The glass transition temperaturetemperature ■

The photo-luminescence (PL) The photo-luminescence (PL) efficiencyefficiency ▲

140 160 180 200 220 240 260 28055

60

65

70

75

80

85

90

Conversion Temperature (oC)

Tra

nsitio

n T

em

pera

ture

(o C

)

0.100

0.120

0.140

0.160

0.180

PL Q

uantu

m E

fficie

ncy

Predicting Optical Performance via Molecular Mobility Predicting Optical Performance via Molecular Mobility on ultrathin Spin Coated Filmson ultrathin Spin Coated Films

nn

S+

n

Cl-

S+

n

Cl-

h

T. Gray et al., 2003, Appl. Phys. Lett, 83, 2563

Material: conjugated polymer poly(p-phenylenevinylene) (PPV)

Film preparation involved spin coating of precursor with subsequent conversion

60 80 100 120

Tg2 = 99 oC

Tg1 = 75 oC

Re

spo

nse

Am

plit

ud

e (

a.u

.)

Temperature oC

Flow of photons

Chromophore containingdendronized side chains

V

Electrode

Electrode

Electro-Optical SwitchElectro-Optical Switch(electric/photonic signal conversion)

Dendronized chromophore grafted polymer:

PS Backbone

Chromophore

Dendromers

Collaboration between the groups of Jen and Overney (UW)

Two mobilities have to be considered:

- Relaxation in Chromophore containing dendronized side chains (Tg1)

- Matrix relaxation (glass transition) (Tg2)

Nanocontrol of Material Properties in Optoelectronics and Photonics