Microcontact printing trapping air: A versatile tool for protein microarray fabrication

The present work introduces a new method for the fabrication of protein micro-patterns, microcontact printing trapping air. The method is based on microcontact printing, a well-established soft-lithographic technique for printing bioactive protein patterns. Usually, the stamp used is made of poly(dimethylsiloxane) obtained by replicating a lithographically microfabricated silicon master. In microcontact printing, the dimensions of the features in the stamp are critical, since the high compressibility of poly(dimethylsiloxane) causes high aspect ratio features to collapse, leading to the printing of undesired areas. In most cases, this is an unwanted effect, which interferes with the printing quality. In this work we used a poly(dimethylsiloxane) stamp bearing an array of micro-posts which, when placed over a flat surface, collapses with consequent formation of an air gap around the entire array. This effect is linked to the distance between the posts that form the array and can be exploited for the fabrication of protein microarrays having a remarkably low background noise for fluorescence detection.