How to copy biological growth, and transform 2D gels into 3D shapes

Biological organisms have a nifty trick, where they can grow uniform materials into three dimensional shapes by limiting growth in certain areas. As some cells expand, others don't, causing the object to warp in three dimensions. Now researchers have applied that same theory to gel sheets, and developed a way of transforming them between flat planes and 3D shapes.

The technique has been dubbed halftone gel lithography — the scientists used an ultraviolet sensitive thin polymer sheet, and exposed it to differing levels of light. The areas exposed would become crosslinked, and not able to expand when placed in water. Thus, areas that were illuminated would stay stationary, and the ones less so would shift and expand when soaked.

By mimicking printmaking, the researchers used halftone patterns, exposing the gel to dots of light of varying size and shapes. By strictly controlling these, a number of shapes were able to be developed, including spheres, saddles and cones. Simply soak it, and it achieves the shape, and then dry it and it'll return to flat. The researchers hope this technique could help with creating a new type of tissue engineering, or an alternative form of 3D printing.

Image: A halftone printing method is used to program the growth of a flat sheet into a sphere through a pattern based on the Peirce quincuncial map projection (shown in the background). Gel images: J. Kim, J.A. Hanna, M. Byun, C.D. Santangelo, R.C. Heyward; Background Map: NOAA's Office of Coast Survey Historical Map & Chart Collection.