photopatterning of cellulose films for the creation of 2 ... · 1 w i s s e n t e c h n i k l e i d...

1W I S S E N T E C H N I K L E I D E N S C H A F T

Photopatterning of Cellulose Films for the Creation of 2- and 3-D Nanostructures

u www.ictm.tugraz.at

Stefan Spirk

Institute for the Chemistry and Technology of Materials, TU Graz, Austria

Institute for the Engineering of Materials and Design, University of Maribor, Slovenia

22 Outline

• Introduction• Structured Cellulose Thin Films

Macrostructured Microstructured

13.11.2014Stefan Spirk, Institute for the Chemistry and Technology of Materials, TU Graz, Austria

Sub Micron-Structured Thin Films Photoregeneration and Patterning Organic Thin Film Transistors 3-D Microfabrication

33 Introduction - Why Patterned Surfaces?• Superhydrophobic surfaces (lotus-effect)• Microreactors, Microfluidics• (Bio)Sensors


Many products on market, partly realized with cellulose substrates

44 Introduction - Why Patterned Surfaces?• Microelectronics, organic electronics

Paper based transistors: paper as substrate

+ Price (very low), easy to print on paper- Roughness, Thickness, not suitable for organic thin

film transistors (OTFT)

Cellulose: good dielectric properties• Cellulose thin films based dielectric in OTFTs?


55 Cellulose Thin FilmsSpin coating of trimethylsilyl cellulose (TMSC) with high DSSi


TMS TMS TMS TMS

Substrate

OH OH OH OH

SubstrateHCl (g)

Regeneration

TMSC film Cellulose filmSpin-coating

Klemm et al. Adv. Mat., 1993, 5, 919.Kontturi et al. Langmuir, 2003, 19, 5735.

Kontturi et al. JACS, 2010, 132, 3678.

→Films shrink upon regeneration

66 Macro-structured cellulose filmsGlass slide, water

contact angle ca. 10°hydrophobization

contact angle ca. 90°

grid,TMSC

grid UV/ozone

silane-coating(d~0.8 nm)


Cellulose-pad, Hydrophilic, CA: 35°

Hydrophobic, CA: 90°

Hydrophilic, CA: 10°



HCl, 10%

ACS Appl. Mat. Interfaces, 2010, 2, 2956.

77 Protein detection systems…


12 pM

12 pM

Chem. Comm., 2013, 49, 11530.

88 Cationic Cellulose on Cellulose Thin Films forEnhanced Protein Adsorption

• Cellulose: very low unspecific protein adsorption good for antifouling surfaces bad for sensors and arrays

Cationic charge leads to increase


• Cationic charge leads to increasein protein affinity

• Model protein BSA, often used for unspecific proteinadsorption• Available also fluorescent-labeled (F-BSA)

99 QCM-D and SPR-two powerful surfacesensitive techniques


Wet mass, viscoelastic properties,Based on Eigenfrequency of AT cut quartz

Dry mass, refractive index,Optical technique based on surface plasmon resonance

1010 Cationized Cellulose for Enhanced Protein Adsorption (F-BSA) by QCM-D and SPR


QCM-D mass includes water, SPR measures dry mass Difference: coupled water inside the layer (92 % at pH 5) Highest adsorption at pH 5 Static water contact angles unusually high after (F-)BSA

adsorption (up to 102 deg!!!)

1111 ssDNA detection systems

10

DNA/CMC/EDC DNA/CMC (No EDC) CMC: carboxymethyl celluloseEDC: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide


0.08Before hybridization

Afterhybridization

Complementary DNA with a concentration of 80 nM could easily be detected

Adv. Funct. Mat., 2013, 23, 308.

1212 Cellulose Thin Films –Structuring using Soft Lithography and Enzymes


AFM image of a singlecellulose stripe

Fluorescence micrograph image of a structured cellulose film

Adv. Funct. Mat., 2013, 23, 308.

1313 From Micro to Sub-Micron Scale – Photolithography

Lack of easy patterning technique for cellulose

Photolithography and photo acid generators (PAG)

• PAG creates an acid upon UV irradiation• Can we use PAGs to convert TMSC to cellulose?• How small can we make the patterns?• Can these structures be used in OTFTs as dielectrics?


PAG/UV

1414 PAGs - examples


1515 Photolithography of TMSC using PAG - Concept

TMSC/PAGMask

Negative developmentRinsing

Positive dev.Enzymes

UV

Addition of photoacid generators to TMSC solution prior tospin-coating

Irradiation with a mask (polychromatic UV, filter for l<300 nm) Development by rinsing or enzymatic digestion


development

Cellulose

1616 Photolithography of TMSC using PAG –negative development

Mask


After Illumination

(E = 5.4 J cm-2)

After negative Develop-

ment

Rq~ 0.6 nm

EP13002405

1717 Photolithography of TMSC using PAG –positive development using enzymes

CelluloseTMSC/PAG TMSC/PAG

cellulase

Cellulose


Molecules 2014, 19, 16266-16273

1818 Photoregeneration, optimization for OTFT


Incompletely regenerated cellulose performs best regardinge (TMSC with DSSi = 0.5) = 4.8, compare Al2O3: 4.5, SiO2: 3.9

1919 Cellulose Thin Films – As Gate Dielectrics in Organic Thin Film Transistors

negative type developed film, d: 32 nm, pentacene

Gate leakcurrents:


Von: -0.8 VVthres: -1.25 V

currents:80 pA

Interface trap states:

1010 cm-2 eV-1

(comp. Amorph. Si:1012 cm-2 eV-1)

Good Performance

2020 Towards use of Eco-Solvents in thePhotoregeneration… DSSi > 2.5 : Toluene, chloroform DSSi ~ 1.5: THF, ethylacetate (ecosolvent)


After illumination(5.2 J cm-2)

After Development

Ethyl acetate

2121 From 2-D Patterns to 3-D Microfabrication… 2-Photon Absorption Lithography

Our Motivation:3-D microstructures made from cellulose tissue engineering, biosensors


http://www.tuwien.ac.at/en/news/news_detail/article/7444/

2222 2-Photon-Absorption (TPA) - Principle

Excitation of a molecule/atom by 2 photonsinto excited state Energy of a single photon too low bridgeenergy gap between ground and excited state Two photons must be absorbed at same time Two photons must be absorbed at same time (femtoseconds) for excitation unlikely, high energy density required (~I2, non-linear) only in focus of Laser beams Lateral resolution limit below 100 nm, sharp edges, patters also inside the material


2323 2-Photon-Absorption (TPA) - Principle

TPA active compound required Addition to polymer solution Material preparation (e.g. dropcasting, spincoating) Use of CAD program to define structures Laser beam realizes CAD structure Development

Can we do this with TMSC?


2424 3-D cellulose structures from TMSC via TPA lithography - sub-micron Patterning

PAG used for 2-D patterning also TPA active Submicron structures in 200 nm cellulose thinfilm


FWHM: 554 nmCellulose, 2014, DOI 10.1007/s10570-014-0471-4

2525 Summary


FWHM: 554 nm

2626 Thanks to

Uni MariborK. Stana-KleinschekR. Kargl, T. Mohan

Photolithography and Transistor

Enzymatic digestion/Soft Lithography

Uni LeobenT. GriesserA. Wolfberger

LandesmuseumDr. Bernd Moser


TU GrazH. EhmannK. NiegelhellD. ReishoferS. Winter

Joanneum ResearchB. Stadlober, A. Fian, A. Peritz

FWF, Project TRP 181-N19Marie Curie Career Integration Grant

“PhotoPattToCell”

photopatterning of cellulose films for the creation of 2 ... · 1 w i s s e n t e c h n i k l e i d...

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