Nanolithography on Responsive Materials Proton-fountain Electric-field-assisted Nanolithography (PEN) PNNA Seminar Nanomaterials Fabrication - Spring-2011 PSU Andres La Rosa, 1 Mindi Yan, 2 Damian Hegsted, 1 and Hui Wang 2 Physics 1 and Chemistry 2 Department, Portland State University, Portland OR NanoFab 2011 Acknowledgment Xiaohua Wang, Xin Wang, Carsten Maedler, Leo Ocola, Rodolfo Fernandez, Sailaja Chada,* and Xiquan Cui
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Nanolithography on Responsive MaterialsProton-fountain Electric-field-assisted
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.
Nanolithography on Responsive MaterialsProton-fountain Electric-field-assisted
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).
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.
Underlying emerging biomimetic technologiesTop-Down and Bottom-up approaches
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
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
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).
PENReversibility
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).
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 <
Underlying working mechanisms of swelling in hydrogels
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).
Underlying working mechanisms of swelling in hydrogels
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
.
Underlying working mechanisms of swelling in hydrogels
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