The optimization of quill-pin printed protein and DNA microarrays

Microarray density has been optimized as a function of substrate wettability and composition of the printing buffer. Features were printed across contact angle gradients to determine the effect of surface wettability on feature spreading. Feature size increased by nearly 50% and feature geometry transitioned from square to round as the array progressed from hydrophobic to hydrophilic for a wide range of pin sizes. The viscosity of water-glycerol and water-sucrose buffers were varied from 1-160 cP resulting in increases of up to 160% in printed feature size. Viscosity values were chosen to represent the potential working range for protein and DNA solutions. The amount of observed spread was determined to be independent of the size of the printing pin. Spreading diagrams that predict the spread in feature size beyond the size of the printing pin as a function of the water contact angle of the substrate and the viscosity of the printing buffer have been generated. Solutions containing proteins and DNA of various sizes have also been characterized, printed and demonstrated to fall within the trends observed in the buffer. Finally, initial work has been conducted using a planar waveguide system to study the kinetics of microarray performance.