Diffusion of oligomers from polydimethylsiloxane stamps in microcontact printing: Surface analysis and possible application

The present study investigates polydimethylsiloxane (PDMS) oligomer diffusion occurring when contacting PDMS rubber against another material. Several surface analysis techniques (ToF-SIMS, XPS, contact angle measurement, AFM, SEM, interferential polarized microscopy: Sarfus) are used to characterize surfaces that have been in contact with noninked PDMS rubber stamps. While the effect of several parameters such as time of contact and ageing of prepatterned surfaces seem to give comprehensible effects on the oligomer deposition, other parameters such as the stamp's shape give paradoxical but reproducible results on the deposited quantity. The results provide us with a better understanding of the transfer and diffusion of PDMS oligomers on certain types of substrates (Al, SiO2). In addition to establishing a better control of the side effects in microcontact printing, this study suggests applications that take advantage of oligomer diffusion. In particular, the capability of using PDMS transfer on a metallic surface to protect selected areas from chemical etching is assessed. In this context, oligomers are no longer harmful contaminants but the actual ink needed for a soft-lithographic process. Copyright (c) 2007 John Wiley & Sons, Ltd.