Micropatterned structures for studying the mechanics of biological polymers

Studying the mechanics of nanometer-scale biomolecules presents many challenges; these include maintaining light microscopy image quality and avoiding interference with the laser used for mechanical manipulation, that is, optical tweezers. Studying the pushing forces of a polymerizing filament requires barriers that meet these requirements and that can impede and restrain nanoscale structures subject to rapid thermal movements. We present a flexible technique that meets these criteria, allowing complex barrier geometries with undercut sidewall profiles to be produced on #1 cover glass for the purpose of obstructing and constraining polymerizing filaments, particularly microtubules. Using a two-layer lithographic process we are able to separate the construction of the primary features from the construction of a depth and shape-controlled undercut. The process can also be extended to create a large uniform gap between an SU-8 photoresist layer and the glass substrate. This technique can be easily scaled to produce large quantities of shelf-stable, reusable microstructures that are generally applicable to microscale studies of the interaction of cellular structures with defined microscale features.