Ink-jet printing of proteins and functional nanoparticles for automated functionalization of surfaces

Ink-jet printing is a relatively straightforward fabrication process. The targeted material deposition avoids material spill-over and is therefore very much applicable for processing of high-cost materials such as biological substances. Our objective is to identify biocompatible fluids that meet the needs for a stable piezo ink-jet printing process. We will present results concerning substrateactivation, ink-preparation, and the maintenance of biological functions during the ink-jet process. Recently, ink-jet printing technology has been used to fabricate electronic, medical, optical and polymeric devices [1, 2, 3, 4]. In contrast to classical coating techniques as spin-coating, dip-coating or spray-coating printing allows for patterned material deposition. Many formats of 2-D drawings can be rasterized into X- and Y-coordinates and directly be converted into multi-material patterns via the printing process. The physico-chemical properties of inks determine their jettability: surface tension and viscosity are two primary chemical properties that determine printing success. The optimum viscosities for jettable fluids in piezo drop-on-demand printheads are 5 mPa s to 12 mPa s, surface tension has to be in the range of 24 mN/m to 33 mN/m. However, most biological materials are water-based and exhibit very low viscosities (0.1 mPa s to 1 mPa s) and very high surface tension values (58 mN/m to 60 mN/m). In order to enable economical biofunctional substrate-coating and to integrate substrate-functionalization in a process capable of being fully automated we develop ink formulations containing biomolecules or (bio-)functional components.