Light-addressable electrochemical micropatterning of cell-encapsulated alginate hydrogels for cell-based microarray

We proposed a light-addressable electrolytic system to perform a micropatterning of calcium alginate hydrogels using a digital micromirror device (DMD). In this system, a patterned light illumination projected to a photoconductive substrate served as a photo-anode to electrolytically produce protons ions, which can lead to a decreased pH gradient. The low pH generated at the anode can locally release calcium ions from insoluble calcium carbonate (CaCO₃) to produce gelation of the calcium alginate. By controlling illumination patterns on the DMD, the micropatterning of calcium alginate hydrogels with different shapes and sizes as well as multiplexed micropatterning were performed. The concentration effects of the alginate and CaCO₃ solution on the dimensional resolution of alginate hydrogel formation were experimentally examined. An array of 3×3 cell-encapsulated alginate hydrogels was successfully demonstrated through light-addressable electrochemical micropatterning. Our proposed method provides a programmable method for the spatiotemporally controllable assembly of cell populations for cell-based microarray.