Abstract：We have studied the so-called roof collapse in microcontact printing.  Roof collapse is due to the adhesion between the PDMS stamp and substrate, and it may affect the quality of microcontact printing.  Our analysis accounts for the interactions of multiple punches and the effect of elastic mismatch between the PDMS stamp and substrate.  A scaling law is established among the stamp modulus, punch height and spacing, and work of adhesion between the stamp and substrate.  Such a scaling law leads to a simple criterion against the unwanted roof collapse.  The present study agrees well with the experimental data.

Biography: Yonggang Huang received Ph.D. from Harvard (advisor: John Hutchinson), and was a postdoc at Harvard (advisor: James Rice). He is now the Visiting Clark Millikan Professor of California Institute of Technology, and also the Shao Lee Soo Professor of UIUC.  His recent awards include the Society of Engineering Science Young Investigator Medal (2006), ASME Melville Medal (2004), and ASME Larson Award (2003). He has published more than 180 journal papers in Science, Nature Materials, PRL, JMPS, Acta Materialia, ...  Four of his papers published in 1999, 2000, 2002 and 2004 are the most cited paper among all (>9700) papers published in all 110 mechanics journals listed in SCI in the corresponding years.