Research

3D prints get another layer of security from Nanoscribe two-photon lithography

The security of 3D printed parts is a chief concern for high-value manufacturers in industry. Quantum dots, that glow when hit with a UV light, are one possibility for  protecting 3D prints from counterfeiting. Chemical “ghost signatures” are another, and can be found embedded in the layers of 3D printed parts.

Working with two-photon lithography, i.e. 3D microprinting, Nanoscribe has developed a new method for creating microscopic security features.

A microscope on two-photon lithorgaphy

In two-photon lithography a pulsed laser is used to solidify a photoreactive material in a series of layers. The size of the laser’s focal spot is so fine that it is capable of 3D printing objects that could fit onto the tip of a pencil, or be injected into the body.

For security tags, Nanoscribe scientists make what is called multi-level diffractive optical elements (DOEs) – a name derived from how features in the 3D printed object split and direct light to make an image.

Nanosribe logo projected through a DOE with a laser. Photo via Nanoscribe GmbH
Nanosribe logo projected through a DOE with a laser. Photo via Nanoscribe GmbH

DOEs are usually made using a photomask, which contains the “to-be-printed” pattern. The process of making this mask is lengthy and expensive. By cutting out the middle man, two-photon lithography is a maskless method of 3D microprinting which is quick and cost-effective.

From serial numbers to peacock spiders

In the process a design, such as a company logo or serial number, is loaded into the computer as a bitmap image. Containing pixel-like data of the image to-be-printed, the bitmap is fed directly to a Photonic Professional GT lithography system.

The finished product is a microscopic cluster of dots or lines that create a 2.5D projection when hit with a laser.

"Multifocal diffraction pattern generated by a red laser pointer passing though a diffractive optical element (DOE)." Photo and caption via Nanoscribe GmbH
“Multifocal diffraction pattern generated by a red laser pointer passing though a diffractive optical element (DOE).” Photo and caption via Nanoscribe GmbH

As a relatively low-cost solution, two-photon lithography can be used to test new security prototypes, or create a master mold for mass-manufacturing multiple products.

This technique was recently used to discover how peacock spiders change color, and is also integral to efforts improving fiber-optic communications.

Nanoscribe will be demonstrating this latest two-photon application at Photonics West annual conference run by SPIE (the international society for optics and photonics) from 30th January – 1st February 2018.

Does Nanoscribe deserve an award for its outstanding research efforts? Nominate now in the 2018 3D Printing Industry Awards.

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Featured image shows “Photonic colors generated by Bragg reflection of gratings. The inset shows sub-micrometer resolution and features of the periodic lines.” Photo and caption via Nanoscribe GmbH

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