Transcript Slide 1
Microcontact Printing (Stamping) Andrew van Bommel February 7th, 2006 Formation of Master Stamp • Photolithography or micromachining of silicon wafers- desired pattern is etched on substrate hn Polydimethylsiloxane Stamp • Elastomeric PDMS stamp fabricated • PDMS poured and cured (polymerization) Inking • Molecules (proteins, thiols, lipids) in solvent (toluene, ethanol) placed on stamp PDMS Stamping • Stamp metal (Au, Ag, Cu, Al) PDMS metal Si Large Area Stamping • Large area printing with roller stamp Si Etching • Etching Resists • Used as: – Arrays of microelectrodes – Diffractive optical components – Secondary masks (for etching of underlying substrate) Si Dipping • A dipping in a second thiol may lead to contrasts in: – Hydrophobicity – Protein binding Si Next slides will show… • …a more in-depth review of the mCP process and its components! Master Stamp (Printhead) • Usually silicon grid • Fabricated from photolithography or micromachining • Use of diffraction gratings or TEM grids • Surface first silanized with (tridecanfluoro1,1,2,2-tetrahydro-octyl)-1-tricholorosilane prior to molding (to ease lift-off) Si PDMS (Polydimethylsiloxane) Stamp •☺ – – – – – – Elastomer Confoms to substrate over large area Chemically inert Homogeneous, isotropic, optically transparent Durable (multiple stamping) Able to modify surface properties PDMS PDMS Stamp •☺ – PDMS stamp may be prone to: • Pairing • Sagging • Shrinking PDMS Ink • Thiols, lipids, or proteins in dilute solvent (toluene, ethanol) • Species that form SAMs on metal surfaces are chosen (see next slides…) PDMS Metal Substrate • Au: widely used, electrode material • Ag: more chemically reactive (easier to etch) and excellent electrical and thermal conductor • Transfer of ink results in formation of selfassembled monolayers… Si SAMs • Form spontaneously by chemisorption (in less than 1 sec.) • In thiols: S atoms bonded to the gold surface bring the alkyl chains into close contact Si Nanofeatures • Through chemical control of length of alkyl chain, the thickness of SAMs can be controlled to a precision of 0.1 nm • Smallest lateral features obtained from the combination of mCP and selective etching: – Etched 35 nm wide trenches – Microcontact printing with hexadecanethiol – Dr. Hans Biebuyck (IBM) Comparison • Photolithography: – – – – Limited by optical diffraction Expensive Cannot be easily applied to non-planar surfaces Provides little control over the chemistry of the patterned surfaces Comparison • Soft lithographic techniques: – Not limited by optical diffraction – Provide alternate route to formation of structures less than 100 nm – New: • • • • Types of surfaces Optical Structures Sensors Systems previously difficult to fabricate Literature Soft Lithography Xia, Y., Whitesides, G. M. Annu. Rev. Mater. Sci. 1998. 28: 153-84. Soft Lithography Xia, Y., Whitesides, G. M. Angew. Chem. Int. Ed. 1998. 37: 550-575. New Approches to Nanofabrication: Molding, Printing, and Other Techniques Gates, B. D., Zu, Q., Stewart, M., Ryan, D., Willson, C. G., Whitesides, G. M. Chem. Rev. 2005. 105: 1171-1196. Unconventional Methods for Fabricating and Patterning Nanostructures Xia, Y., Rogers, J. A., Paul, K. E., Whitesides, G. M. Chem. Rev. 1999. 99: 1823-1848 Microcontact Printing Hull, R., Chraska, T., Liu, R., Longo, D. Mater. Sci. Eng. 2002. 19: 383-392. .