In this study, we introduce an optofluidic method for the rapid construction of large-area cell-sized droplet assemblies
with user-defined re-writable two-dimensional patterns of functional droplets. Light responsive water-in-oil droplets
capable of releasing fluorescent dye molecules upon exposure were generated and self-assembled into arrays in a
microfluidic device. This biological architecture was exploited by the scanning laser of a confocal microscope to ‘write’ user
defined patterns of differentiated (fluorescent) droplets in a network of originally undifferentiated (non-fluorescent)
droplets. As a result, long lasting images were produced on a droplet fabric with droplets acting as pixels of a biological
monitor, which can be erased and re-written on-demand. Regio-specific light-induced droplet differentiation within a large
population of droplets provides a new paradigm for the rapid construction of bio-synthetic systems with potential as tissue
mimics and biological display materials.