Plastic Sheet Curvature Can Now Be Controlled With Light

A team of researchers recently came up with a technique that makes use of light to curve 2-D plastic sheets into 3-D structures such as bowls, tubes, or spheres. The new development takes place over some previous accomplishments that focused on automatic folding of three-dimensional structures. The primary advancement here is that in place of having the plastic sheets being folded along sharp lines for formation of a polygon, the plastics now bend directly into curves. So no sharp edges now.

The research was led by a professor of biomolecular and chemical engineering, Michael Dickey, at the North Carolina State University. He worked in association with Jan Genzer who is also a professor from the same department. It was in 2011 that they wrote a paper together in which they described a technique under which regular inkjet printer can be used for printing bold black lines over a pre-strained plastic sheet. This plastic sheet was then cut into the required pattern and kept under the infrared light emitting heat lamp.

These printed lines then absorbed more and more energy from that infrared light as compared with rest of the material causing the plastic to heat up and contract to formulate a hinge that folded the sheets into 3-D shapes. When they varied the width of printed lines or the hinges, they were able to alter the pace and extent to which the hinges folded. The technique is now compatible with latest commercial printing techniques that include screen printing, inkjet printing, or roll-to-roll printing. All of these are known for being highly inexpensive and capable of giving better outputs then 2D printing machines. Now, they took a similar approach for a completely different result.

Dickey explains, “By controlling the number of lines and the distribution of ink on the surface of the material, we can produce any number of curved shapes. All of the shapes use the same amount of ink; it’s simply a matter of where the ink is applied to the plastic.” Another Ph.D. student at the North Carolina state and also a co-lead author of this paper, further adds, “Our work was inspired by nature, because natural shapes rarely incorporate crisp folds, instead opting for curvature. And we found that, in order to make functional objects, we often needed to use a combination of curved and folded shapes. Other researchers have developed techniques for creating self-curving materials, but they did this using soft material, such as hydrogels. Our work is the first attempt to accomplish the same using thermoplastics—which are stronger and stiffer than the soft materials. That makes them more attractive for use in performing some practical actions, such as gripping an object.”