Mechanical Behavior Of Elastomeric Stamps During Microcontact Printing Patterns: Direct Observation Of Stamps And Inks

Microcontact printing is a straightforward and effective method for generating surface patterns of micron or submicron lateral dimensions. The fidelity of the ultimate pattern is a complex interplay of mechanical behavior of the elastomeric stamp, fluid transfer between surfaces and the ability of the ink to self-assemble on the new surface. We present here experimental observations and modeling of stamp deformation during precise external loads and visualization of inked surfaces by high contrast analytical methods. Stamp behavior was observed visually in an inverted microscope and load-displacement relationships used to determine onset of failure modes such as roof collapse and buckling of slender relief features as a function of stamp geometry. The load was applied with a glass sphere so as to obviate problems with alignment and to precisely determine contact areas. A “robotic stamper” fabricated from an AFM instrument can deliver ink under conditions of precise load. Surfaces inked with varying densities or combinations of SAMs can be imaged with excellent contrast by scanning surface potential microscopy (SSPM). The same area of the sample can then be examined using time-of-flight SIMS or other surface analytical technique with no additional etching or sample preparation. In this way the fidelity and density of the patterned monolayers can be evaluated. The effect of load on ink pattern quality can also be established.