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Yat Li Department of Chemistry & Biochemistry University of California, Santa Cruz
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Yat Li Department of Chemistry & Biochemistry University of California, Santa Cruz

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  1. CHEM 146C_Experiment #7 Soft Lithography: Patterning Yat Li Department of Chemistry & Biochemistry University of California, Santa Cruz

  2. Objective In this laboratory experiment, we will learn: The principle of soft lithography and the fabrication of poly(dimethylsiloxane) (PDMS) stamp Microcontact printing technique to create patterned metal electrodes (or interesting features) on a substrate

  3. Micro- and nanofabrication Microfabrication, through its role in microelectronics and optoelectronics, is an indispensable contributor to information technology. Photolithoghaphy: ~ 1 micrometer (resolution limited by diffraction of light) E-beam lithography: < 50 nm lithography Photo or E-beam resists Develop Metal evaporation Lift-off Drawback: expensive, time consuming (e-beam), poorly suited for patterning nonplanar surface

  4. Soft lithography Soft lithography represents a non-photolithographic strategy based on self assembly and replica molding for carrying out micro- and nanofabrication Generate patterns and structures with feature sizes ranging from 30 nm to 100 mm Convenient, effective, and low-cost Xia, Y. N. and Whitesides, G. M. “Soft Lithography”. Annu. Rev. Mater. Sci.28, 153-184 (1998)

  5. Poly(dimethylsiloxane) (PDMS) Poly(dimethylsiloxanes): A unique combination of properties resulting from the presence of an inorganic siloxane backbone and organic methyl groups attached to silicon. Very low glass transition temperatures and hence are fluids at room temperature. Can be readily converted into solid elastomers by cross-linking. SYLGARD® 184 SILICONE ELASTOMER KIT base cure PDMS:

  6. Mechanism of cross-linking Dean J. Campbell, Katie J. Beckman

  7. Preparation of PDMS elastomeric block Xia, Y. N. and Whitesides, G. M. “Soft Lithography”. Annu. Rev. Mater. Sci.28, 153-184 (1998) Dean J. Campbell, Katie J. Beckman

  8. Microcontact printing The concept of microcontact printing is use the relief pattern on the surface of a PDMS stamp to form patterns of SAMs on the surfaces of substrates by contact. For example, alkylthiol on Au and Ag surfaces. Simple and suitable for non-planar substrates! Xia, Y. N. and Whitesides, G. M. “Soft Lithography”. Annu. Rev. Mater. Sci.28, 153-184 (1998)

  9. Making metal thin films Typical methods to make high quality metal films: Sputtering Evaporation Tollens process: [Ag(NH3)2]+ + reducing agent Ag film Solution A: a mixture of AgNO3 and NH4NO3 Solution B: NaOH Solution C: Glucose (C6H12O6)

  10. Making metal electrodes by microcontact printing Gerber, R. W. and Oliver-Hoyo, M. T. “Selective Etching via Soft Lithography of Conductive Multilayered Gold Films with Analysis of Electrolyte Solutions”. Journal of Chemical Education85, 1108-1111 (2008)