Abstract: A method and apparatus for 4-dimensional printing are disclosed. The apparatus includes a polymer pen array translatable in three axes, a light source for illuminating the polymer pen array, a reactive surface disposed opposite the polymer pen array, and a flow-through microfluidic cell having a reactive chamber in fluid communication with influx and outflux conduits. Solutions containing reagents are introduced into the reactive chamber, the polymer pen array is inserted into the reactive chamber, and is then illuminated with the light source so as to initiate polymerization between the reagents and the reactive surface.