Researchers have determined how to control the shape of a polymer system at the microscale with a technique akin to half-tone printing.
The polymer they use swells like a microscopic sponge when exposed to water, however, printing resist dots in the polymer substrate creates points that will not swell (see 1). When all resist dots in one area are the same size, the area undergoes uniform expansion and the structure remains flat (see 2). When the dot size changes, however, buckling occurs from the mismatch in growth from one area to another (see 3). With a proper half-tone pattern of resist dots, almost any 3-D shape can be achieved. This illustration shows a square piece of polymer. Each side of the square is roughly the width of a mechanical pencil lead. If it were possible to draw a world map on this square, we could watch the map warp and wrap itself into almost a perfect sphere, a micro-globe.
Credit: Zina Deretsky, National Science Foundation