Force-controlled microcontact printing using microassembled particle templates

In this paper, force-controlled microcontact printing using microassembly-based particle templates is investigated. Polystyrene microparticles are assembled semi-automatically into a desired pattern on a glass substrate using an atomic force microscope nanoprobe installed on a nanopositioning stage. The micropattern on glass is sputtered with aluminum and removed of microparticles by ultrasonic vibration, resulting in a template with microfeatures corresponding to the microparticles. A soft lithography method is used to mold elastomeric polymers on the template, resulting in a stamp. The stamp is inked and printed using a force-controlled system onto a polystyrene substrate. Depending on the particle size and contact force, a smaller micro to nanometer sized pattern can be formed. As the spherical patterns on the stamp collapse due to interfacial contact forces, force-controlled microcontact printing is crucial for controlling the size of stamped features. Green fluorescent protein is used as the ink, enabling the use of fluorescent imaging to observe the stamped imprints. Preliminary experiments using 4.5 and 10 mum diameter polystyrene particles shows the feasibility of our technique. Thus it is possible to realize micro/nanopatterns using assembled microparticle-based stamps in high volumes