Photo-Printing Technology Developed for 3-D Polymer Shapes

Polymer shapes (NIST.gov)

Researchers at University of Massachusetts in Amherst have developed a simple technology for producing three-dimensional shapes from thin polymer films. The findings of the work by Ryan Hayward, Christian Santangelo, and their UMass colleagues appear in the current issue of the journal Science (paid subscription required).

The new method, funded by National Science Foundation, involves exposing ultraviolet-sensitive sheets of a thin polymer gel to patterns of light created by a photomask. The polymer sheets are about 10 micrometers thick, about five times thinner than a human hair, and spread on a substrate before exposure.

The amount of UV light absorbed at each position on the sheet programs the amount that this region will expand when placed in contact with water. The process thus resembles nature’s ability to direct certain cells to grow while suppressing the growth of others.

Areas of the gel film exposed to light become crosslinked, restricting their ability to expand, while nearby unexposed areas will swell like a sponge as they absorb water. As in nature, this growth directed by patterns of light causes the gel to buckle into the desired shape. Unlike in nature, however, these materials can be repeatedly flattened and re-shaped by drying out and rehydrating the sheet.

Hayward and Santangelo adopted the concept of halftones from printing for this technology. In printing, presses can create a range of shades from four basic colors — cyan, yellow, magenta, and black — by using dots of varying sizes. Smaller dots take up less space and allow more white light to reflect from the paper, so they appear as a lighter color shade than larger dots.

The same concept applies to patterning the growth of the gel sheets. Rather than making smooth patterns with many different levels of growth, the researchers were able to print dots of highly restricted growth and vary the dot size to program a patterned shape.

Hayward and Santangelo believe the technology can benefit the fields of optics and robotics, and even bioengineering. “For biomedicine or bioengineering, one of the questions has been how to create tissues that could help to grow you a new blood vessel or a new organ,” says Santangelo. “We now know a little more about how to go from a flat sheet of cells to a complex organism.”

Read more: One-Step Process Developed to Produce Multi-Color Polymer

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