Make It Fast And Make It Tiny – Two Photon Lithography

Scientists at the Vienna University of Technology (TU Vienna) have built a 3D printer capable of making exquisitely intricate objects as tiny as a grain of sand, but it’s not the size of the objects that’s novel, it’s the speed at which they’re made which is unique.

Via a process known as “two-photon lithography,” the printer uses liquid resin which contain molecules that cause the liquid around them to harden into a polymer as they’re exposed to laser light.

So, you ask, how is that different from traditional stereolithography?

In order for this special polymer to be activated, the molecules require the absorption of two photons of light at once.

Since there’s only one location where the laser’s beam is intense enough to make that happen – right at its very center – the process allows for extreme precision during printing.

Two-photon lithography also allows for solid material to be created anywhere within the depth of the liquid resin rather than the layer-by-layer process used in traditional methods to obtain hardened material.

And aside from the proprietary resin involved, the TU Vienna printer takes advantage of a high-speed motorized mirror system to directs the beam of the laser within that resin, and the constant motion of the mirrors throughout the printing process cuts the acceleration and deceleration of the beam to the minimum, thus more time is spent actually creating the target object.

“The printing speed of two-photon lithography used to be measured in millimeters per second,” said Professor Jürgen Stampfl of TU Vienna. “Our device can do five meters in one second.”

Once the team works out the kinks in using a bio-compatible resin which is now under development, the team envisions it being used to create micro-scaffolding for use as a support structure capable of hosting a patient’s living cells.

In the video below, a replica of a race car 330 x 130 x 100µm3 in size is fabricated, and the finished product is made up of 100 layers, each made of an average of 200 polymer lines.

The entire piece is completed in just 4 minutes. The finished product matches the source CAD file to a precision of ±1µm.