innovative perfluorinated materials

Innovative perfluorinated materials

V. Arima1, I. Viola1, G. Maruccio1, P. Metrangolo2, R. Liantonio2, T. Pilati3, R. Resnati2,3, G. Gigli1,

R. Cingolani1, R. Rinaldi1

1 National Nanotechnology Laboratory of CNR-INFM, via per Arnesano, 73100 Lecce, Italy2 Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering “G. Natta”, Politecnico di Milano, Via L. Mancinelli 7, 20131 Milan, Italy.3 C.N.R.-Institute of Molecular Sciences and Technologies, University of Milan, Via C. Golgi 19, 20133 Milan, Italy

Outline

• Perfluorinated materials and their properties• Innovative perfluorinated materials assembled

by halogen-bond• Scanning Probes studies on them• Microfluidic studies within PDMS

microchannels

Perfluorinated materials

• chemical inertness, resistance to heat, ability to repel water and oil

• low surface tensions, very low friction coefficients, low dielectric constants,

• Low refractive indexes, high densities, viscosities, and gas solubilities

Innovative perfluorinated materialsassembled by halogen-bond

• Halogen-bond definition• Halogen-bond driven self assembling processes

of crystals • Halogen-bond driven self assembling processes

of amorphous films

Halogen-bond definition

A halogen bond is the nonconvalent attractiveinteraction between an electron poor halogenatom (usually iodine or bromine) and an electronrich site such as that presented by a Lewis base.Halogen bonding refers only to the case in whichhalogen works as an electrophilic species

Halogen-bond driven self assembling processes of crystals

R. Liantonio, P. Metrangolo, T. Pilati, G. Resnati, G., Cryst. Growth Des., 2003, 3, 355.

G. Maruccio, V. Arima, R. Cingolani, R. Liantonio, P. Metrangolo, T. Pilati, G. Resnati and R. Rinaldi, to be submitted to J. Mater.Chem.

Halogen-bond driven self assembling processes of amorphous films

R. B. Walsh, C. W. Padgett, P. Metrangolo, G. Resnati, T. W. Hanks, W. T. Pennington, Cryst. Growth Des., 2001, 1, 165

Scanning Probes studies

• Brief overview of Scanning Probe Microscopy (SPM)

• SPM on perfluorinated crystals• SPM on amorphous films• Probing the halogen-bond strength by SPM

Brief overview of Scanning Probe Microscopy (SPM)

Atomic Force Microscopy (AFM): Contact and Tapping modes

Surface potential (SP) imaging

Lateral Force Microscopy (LFM)

Topographic (left) and LFM(right) images of the surfaceof a polished polycrystallinesilicon carbide film.

From Veeco appl. Notes

Force-Distance Curves

AFM force measurements: A) the approach (“non-contact” region, B) jump to contact, C) contact, D) adhesion, E) pulloff.



Schematic of “sensor force microscopy”. A sensor molecule is attached to an AFM tip with a molecular tether. The sensor molecule is scanned across the surface while force measurements detect whether a binding event occurs when a target molecule is encountered.

Cantilever deflection curves of an avidin tip on a biotinylated agarose bead A) before and B) after blockage with an excess of free avidin. C) magnification of B.

EL Florin, VT Moy, and HE Gaub Science, 1994, 264, 415-17.

SPM on perfluorinated crystals

(001) Crystallinesurface

a) Constant amplitude topographic image

b) SP image. Well-defined crystalline terraces having alternated SP values are visible.

c) LFM image. The terraces show alternatively low and high friction region.

d) Proposed interpretation of the exposed molecular functionalities.


Force-Distance spectroscopy

• High adhesion and low adhesion region

• Strong and low interaction of the tip with the surface


A regions• High adhesion between tip and sample

• SP behaviour analogous to PFC sample alone

• Low SP

• High friction between tip and sample

B regions• Low adhesion between tip and sample

•SP behaviour analogous to the sample after PFC removing

• High SP

• Low friction between tip and sample

SPM on amorphous films

SP preliminary results• Before irradiations: circular clusters with a diameter ranging from 350 to 400nm and a height of 20nm. rms 9.61nm. • Before irradiations: NO apparent contrast in SP • Irradiation: mask with 15-μm-width stripes (ν=300 nm, time = 1 hour).

• After irradiation: amorphous aggregates alternated to flat region. rms 5.16nm.• After irradiation: SP showed contrasts of 150mVbetween the stripes

2μm

2μm

Probing the halogen-bond (XB) strength by SPM

• Gold substrate functionalization with 5-[1,2]dithiolan-3yl-pentanoic acid 8-(2,3,5,6-tetrafluoro-4-phenoxy)-octyl ester

• Tip covered by a thin gold layer

• Tip functionalization with 5-[1,2]dithiolan-3yl-pentanoic acid 8-(pyridin-4-yloxy)-octyl ester

• Tip characterization after gold and molecules deposition

• Force-distance measurements with a tip without and with molecules on the functionalized substrate

XB electron acceptor

XB electron donor

Tip characterization

• SEM image

• Resonance frequency shifts of the tip

• Changes in the elasticity of the lever from 0.086N/m to 0.142N/m

Force-distance plotsPreliminary results

Before tip functionalization

Adhesion force: 20nN

After tip functionalization

Adhesion force: 50nN

Microfluidic behaviour of perfluoro-polyether fluids

Why Microfluidics ?

Prevalent tool for the local control of liquid flows

Manipulation of gas and liquid fluids within micro-networks

Fabrication of miniaturized devices and micro-array

Integration of functional components ( Mixers, Valves, Filters and Pumps) for Electronics, Chemistry and Biology

The direction of flow results from the pressure differential between two hydraulically connected regions and is such as to decrease the pressure difference.

Surface properties have significant effects on the liquid behavior at sub-millimeter scale, also by modifying the meniscus shape.

h

LV

Rcos2P ϑγ

=Δ Laplace pressure Rh ~ V/S

Capillary dynamics

B. Zhao et al., Science 291, 2001I. Viola et al., Anal.Chem., 77, 591, 2005

Flow dynamics control

zcosG2

zPG

dtdz LV

ηθγ

=ηΔ

=

ΔP Laplace pressure

G Geometrical factor

η Viscosity

θ Contact angle

γ Surface energy

θ

Ease of realization

Flexibility

Low cost

Wide area transfer

Good reproducibility

Wide range of materials

(polymers, organic molecules…)

Advantages

Soft-Lithography

G. Whitesides et al., J. Mat.Chem 7, 1997G. Gigli et al., Adv. Mater., 14, 2002

Disadvantages

Slowness of the filling process

Soft materials swelling phenomena

Micro-sized system geometrical confinement

Visco-elastic liquid (polymeric or biological solutions)

non-linear mechanical properties

Local flow control internal pressure, elastic instability

A. Groisman et al., Nature 405, 2000

Soft-Lithography

Our microfluidic system

Si substrate

PDMS mold

( ) 21

0

21

LVH0 tt

2cosR)t(z)t(z −⎟⎟

⎠

⎞⎜⎜⎝

⎛η

θγ=−

I. Viola et al., Anal.Chem.,77, 591, 2005

Fluid

Washburn law

Perfluoro-polyether FOMBLIN® γ=24 dyne/cm

Polyurethane NOA72®γ=40 dyne/cm

GALDEN : CF3-[(OCFCF3CF2)m-(OCF2)n-OCF3FOMBLIN : HOCH2CF2O-(CF2CF2O)p-(CF2O)q-CF2CH2OHNOA72: -R-NH-CO-NH-R

Surface Tension γLV

Filling velocity

212

1

LVH t2

cosR)t(z ⎟⎟⎠

⎞⎜⎜⎝

⎛η

θγ=

Effects at liquid interface

I. Viola et al., J. Fluor. Chem, 128, 1335, 2007

• Visco-elastic fluid non-linear mechanical properties• Poor shear thinning behaviour

Rheometric analysis

Temperature dependence of viscosity η

⎟⎟⎠

⎞⎜⎜⎝

⎛−

η=η0

00 TT

DTexp)T(

Vogel-Fulcher-Tamman lawD fragilityT0 freezing temperature

21

zi2

1

0i

02

1

0i t)F,T(At

TTDT

21expPG2)T,t(z ⋅=⋅⎟⎟

⎠

⎞⎜⎜⎝

⎛−

−⎟⎟⎠

⎞⎜⎜⎝

⎛ηΔ

=

FOMBLIN NOA72

T-dependence in non-Newtonian behaviour

Fragility coefficient (D) Freezing temperature (T0)

FOMBLIN ZDOL2000 0.34 262.2

NOA72 1.9 242.6

Effects at solid interface

0 20 40 600

2

4

6

8

10

z[m

m]

t[sec]

I.Vio

la, 2

006

PDMS A

PDMS B

untreated

Hydrophobic liquid: polyurethane

Hydrophobic functionalities:

UR31: Fomblin –Si(OEt)3 terminated

Surface Energy γSV

Filling velocity

Hydrophilic liquid: water Hydrophobic functionalities:PDMS A: C.A. 112°PDMS B: C.A. 117°

I

OH

OH

OH

PD

MS (1)

O

O

O

PDM

S

Si (CH2)3 NCO(2) O

O

O

PDM

S

Si (CH2)3 NH

O

O (CH2)8 O

F F

FF

PDM

S UV

PDMS A

Surface Energy γSV

Filling velocity

Conclusions

• Microfluidic approach for the direct investigation of a liquid at real operation conditions (internal pressure, wetting properties…), during the driving process and in confined geometrical system

• The role of fluorine-containing liquid sample in microfluidic set-up enhance the in-situ control of manifold operations inside integrated circuits (lab-on-chip; MEMS, micro-reactors etc…)

• Relaxation time of the polymer chain is strongly affected by the increase of the working pressure typical of integrated microfluidic systems

• Fragile behaviour of perfluoro-polymers during molecular diffusion can be strategic for enhancing of mixing inside microfluidic integrated networks.

innovative perfluorinated materials

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