Mass fabrication of size-controllable hydrogel microarrays by dip-pen nanolithography with viscosity-tunable ink

• Mass fabrication of size-controllable hydrogel microarrays is demonstrated.
• Proof of concept of viscosity-tunable ink for dip-pen nanolithography.
• Hydrogel microarray can be used as a small molecule-embedded template.

A method of mass fabricating poly(ethylene glycol) (PEG) hydrogel microarrays is demonstrated. Microarrays of poly(ethylene glycol) dimethacrylate (PEG-DMA) with photoinitiator were patterned by one-dimensional (1-D) parallel dip-pen nanolithography (DPN), and the microarrays were cross-linked to form PEG hydrogels by UV irradiation in N2 air. As an ink material for DPN printing, solid and liquid phase of PEG-DMA were mixed and prepared to tune viscosity of the ink material by temperature. Thus, the diameter of the microarrays was able to be averagely controlled from 1.7 to 6.2 μm as temperature during printing was increased from 25 °C to 37 °C, respectively. The overall microarrays showed less than 16% coefficient of variation (C.V.). Moreover, small molecules, such as fluorescence dyes, were able to be embedded in the PEG hydrogel microarrays.