Gordon Research Conference

G.W. Scherer
Princeton University, Princeton, NJ

Synopsis of the presentation:

A major cause of damage to stone, as well as concrete, is the stress generated by crystallization of salts within the pores of the body. The first requirement for large stresses is a high supersaturation of salt, but that is not sufficient; if the crystal makes contact with the pore wall and stops growing, then the stress stops increasing. Thus, the maximum stress that can arise depends on the repulsive forces that discourage the crystal from growing into contact with the wall. For ice, even the van der Waals forces between the ice crystal and the mineral surface are repulsive (so that a pressure of tens of MPa is required to bring the surfaces into contact), but that is not true for salt crystals. In the latter case, it appears to be the hydration forces at the interface that cause the repulsion, and sustain a nanometer-scale film of liquid between the salt and mineral surfaces. To understand this more clearly, we intend to perform molecular dynamics studies of the interfacial region (but we will have no results by the time of this meeting).

Given the magnitude of the stress exerted by the crystal on the pore wall, we would like to predict the probability of crack growth. For the stress to act on the larger flaws, the region subjected to stress must be of a size comparable to the flaw size. If the flaws are micron-scale and the pores are nanometer-scale, then the crystals must propagate through a substantial region of the pore space before they can drive crack growth. In fact, the crystals probably have to percolate through the pore network, which means that the driving force must be sufficient to let the crystals pass through the characteristic pore size (or, breakthrough radius). That size can be estimated from mercury intrusion, nitrogen desorption, or permeability measurements.

If the crystals are assumed to be in thermodynamic equilibrium, then the stresses are predicted to be large only if the crystals reside in small pores. However, under nonequilibrium conditions, large stresses can develop in large pores.

This talk will explain these points in more detail, and describe the research we are doing to measure and to modify the forces between crystals and minerals.

Key outstanding areas relevant to this presentation:

• Molecular dynamics simulation of the mineral/solution/crystal interface to assess the magnitude and origin of the repulsion
• Direct measurement of the crystallization pressure exerted by crystals on minerals
• Pattern of growth of salt crystals in porous media
• Modifying the interfacial forces by chemical treatment of mineral surfaces

Selected publications for background information:

1. G.W. Scherer, "Crystallization in Pores", Cement and Concrete Research, 29 1347-1358 (1999).
   
   
2. G.W. Scherer, "Stress from Crystallization of Salt in Pores", Proc. of the 9th. International Congress on Deterioration and Conservation of Stone, Vol 1., Ed. By V. Fassina, pg 187, 2000
   
   
3. G.W. Scherer, R. Flatt and G. Wheeler, "Materilas Science Research for the Conservation of Sculpture and Monuments", MRS Bulletin, 44-50 (January 2001)

Contact information of the speaker:

George W. Scherer
Professor
Princeton University
Eng. Quad. E-319
Dept. Civil & Environmental Eng.
Princeton Materials Institute
Princeton, NJ 08544 USA

Phone 1-609-258-5680
FAX 1-609-258-1563

Email scherer@princeton.edu
URL: http://www.cee.princeton.edu/faculty_CV.html/scherer.html

Vinayak P. Dravid
Northwestern University, Evanston, IL

Synopsis of the presentation:

While some "hype" is invariably associated with "nano-somethings", there remain genuinely exciting prospects for scientific exploration with technological implications for "nano-things". Of particular interest is the merger and synergy of bioactive, organic and physical structures, which indeed promise to open new vistas for advanced materials and functional architectures of true benefit to the society at-large.

Our work at Northwestern University is geared towards designing intricate architecture of functional oxide nanostructures as well as using them as building blocks for device systems for sensing, diagnostics and therapeutics. Embedded in this scheme are several nanopatterning approaches, which are based on the original invention of Dip-Pen Nanolithography (DPN) developed at Northwestern. The nominal DPN approach is extended in our group to pattern, at nanoscale, templates for inorganic and organic-inorganic complexes of arbitrary shape/size on arbitrary substrates, thus extending the efficacy and elegance of DPN. Subsequently, several direct methods (e.g. nano-fountain-pen and nano-ballpoint pen) have been developed for site- and shape-specific patterning of ceramics at nanoscale, thus circumventing the two-step template-based approach.

The talk will outline modified DPN as an enabling approach to pattern and characterize magnetically, electronically, chemically- and optically-active nanostructures at the nanoscale. Success is already evident for magnetic oxides, inorganic mesoporous structures, ferroelectrics and optically-active structures. The real need for characterizing structure, 3-D morphology, local chemistry and conformation of such nanopatterns will be emphasized. The prospects for patterning at single-molecule resolution, especially for bioactive molecules, both by themselves and as templates for inorganics, will also be outlined.

It will be argued that functional nanostructures go beyond the "hype", and present challenging yet exciting avenues for synthesis-structure-architecture-form-function-performance relationships, especially in hybrid organic-inorganic systems.

The ceramics community should capitalize on its broad basic science background and the know-how in various sub-plots (e.g. colloidal processing, microstructure development etc..) in this emerging field to enhance both the "old" and "new" forms of ceramics and associated phenomena, albeit at a much smaller scale.

Thus, teaching "new" tricks to "old" ceramics should help the broader ceramic community to be a viable and effective partner in advancing the field of functional nanostructures in concert with other disciplines, yet maintain and retain its unique niche' while expanding its horizons!

Key outstanding areas relevant to this presentation:

Site- and Shape-Specific Nanopatterning of Inorganics

Preamble:

There appears (or certainly will be, in a few years) to be a paradigm shift in "synthesis and construction" of functional devices and systems. The "conventional" top-down approach, as championed in microelectronics revolution, will likely come to a grinding halt later this decade. The bottom-up approach of self- or directed-assembly is gaining momentum.

It is thus likely that future initiatives will likely combine strengths of both top-down and bottom-up approaches for creating synthetic, complex and hierarchical architectures- combining various biological and physical materials, and make use of diverse phenomena and properties of the ensemble.

My Gordon talk will highlight a unique and emerging approach to creating functional (inorganic) nanostructures, based on AFM-type techniques. Though serial and thus slow, this approach is being rapidly progressed (e.g. IBM millipede) and will provide an interesting alterative or complement for all- "niche" device construction, basic fundamental measurements of site- and shape-specific nanostructures, and intermediary approach to top-down methods for creating hierarchical architecture crossing physical and biological discipline barriers.

Specific Future/Emerging Research Areas in this Topic/Subject:

- Fundamental and basic measurements of "size, shape, conformation and proximity" effects in functional nanostructures:-
Facilitated by the new and emerging techniques and approaches to site- and shape-specific "patterning" of nanostructures, one could:

" Explore and understand of limits of "critical phenomena" such as: ferro-piezo-pyro-dielectrics, ferro-/ferri-superpara-magnetism, electron confinement- transport phenomena, including superconductivity, optical emissive and absorption properties, mechanical properties..etc..

- Ability to "position and pattern" nanostructures with precision and accuracy:

Measurement of proximity effects: i.e. coupling or decoupling of critical phenomena: as in superconductivity, magnetism, optical etc..

- Synergy, symbiosis and convergence of biological and physical sciences with systems engineering:

Integration of emerging bottom-up methods of assembly with top-down conventional lithographic approaches.

Use of biologically active elements as templates for inorganics: i.e. using DNA, Proteins.. as "intelligent" templates for assembling inorganic building blocks, such as ferroelectrics, catalysts, sensors, magnetics…

Integrating biological recognition elements with physical and engineering detection or transduction phenomena: e.g. enhancement or alteration of optical properties, magnetic or electronic signatures etc..

Integrating biological processes with physical and engineering systems, e.g. gene therapy, gene expression, protein synthesis etc.. combined with physical and engineering instrumentation and techniques.

- Device and component engineering:

Using patterned nanostructures as "device elements" to enhance device properties or functionality owing to combination of size/shape/distribution, as well as miniaturization aspect.. e.g. ultra-high sensitivity patterned catalytic elements, localized single-molecule gas/fluid sensors, in-vivo diagnostics and/or therapeutics via implanted devices based on patterned functional nanostructures, etc..

Selected publications for background information:

1. Whitesides GM, Ostuni E, Takayama S, Jiang XY, Ingber DE, Soft lithography in biology and biochemistry, ANNUAL REVIEW OF BIOMEDICAL ENGINEERING, 3: 335-373 2001
   
   
2. Xia YN, Whitesides GM, Soft lithography, ANNUAL REVIEW OF MATERIALS SCIENCE, 28: 153-184 1998
   
   
3. Brittain S, Paul K, Zhao XM, Whitesides G , Soft lithography and microfabrication, PHYSICS WORLD, 11 (5): 31-36 MAY 1998
   
   
4. Piner RD, Zhu J, Xu F, Hong SH, Mirkin CA , "Dip-pen" nanolithography SCIENCE, 283 (5402): 661-663 JAN 29 1999
   
   
5. Werts MHV, Lambert M, Bourgoin JP, Brust M, Nanometer scale patterning of Langmuir-Blodgett films of gold nanoparticles by electron beam lithography, NANO LETTERS, 2 (1): 43-47 JAN 2000.
   
   
6. Weimann T, Geyer W, Hinze P, Stadler V, Eck W, Golzhauser A, Nanoscale patterning of self-assembled monolayers by e-beam lithography, MICROELECTRONIC ENGINEERING 57-8: 903-907 SEP 2001.
   
   
7. Lopes WA, Jaeger HM, Hierarchical self-assembly of metal nanostructures on diblock copolymer scaffolds, NATURE, 414 (6865): 735-738 DEC 13 2001
   
   
8. Huang Y, Duan XF, Wei QQ, Lieber CM, Directed assembly of one-dimensional nanostructures into functional networks, SCIENCE, 291 (5504): 630-633 JAN 26 2001.
   
   
9. L. Fu, Vinayak P. Dravid et al. , Self-assembled bilayer molecular coating on magnetic nanoparticles, Applied surface science, 181, 173-178, 2001
   
   
10. M. Su and Vinayak P. Dravid et al., "Moving beyond molecules: Patterning solid-state features via dip-pen nanolithography with sol-based inks", JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 124 (8): 1560-1561 FEB 27 2002
    
    
11. Lei Fu, Vinayak P. Dravid et al., "Arrays of magnetic nanoparticles patterned via "dip-pen" nanolithography", ADVANCED MATERIALS, 14 (3): 231-+ FEB 5 2002
    
    
12. Ming Su and Vinayak P. Dravid, "Colored-Ink Dip-Pen Nanolithography", Appl. Phys. Lett., June 3, 2002
    
    

Contact information of the speaker:

Vinayak P. Dravid
Professor, Materials Science & Engineering
Director, Electron Probe Instrumentation Center (EPIC)
Northwestern University, Evanston, IL 60208, USA

Phone: 847-467-1363
Fax: 847-491-7820

URL: http://vpd.ms.northwestern.edu
http://epic.ms.northwestern.edu

Session Chair Contact Info

Martin P. Harmer
Alcoa Foundation Professor
Director of Materials Research Center
Department of Materials Science and Engineering
Lehigh University
5 E. Parker Ave.
Bethlehem, PA 18015

Phone: 610-758-4227
Fax: 610-758-4244

Email: mph2@lehigh.edu
URL: http://www.lehigh.edu/~Einmatsci/faculty/Harmer.html