Micro-Optics and the World of Nano 3D Printing
Michael Molitch-Hou posted on February 24, 2017 | 9005 views

When zoomed into the nanoscale, it’s possible to see that tiny universe as just as immense and complex as the universe of planets, galaxies and other macro phenomena. And, while many in the 3D printing industry may be focused in our day-to-day lives on the macro, there are those like Nanoscribe who work to advance 3D printing at the nanoscale.

Microscopic lenses 3D printed using Nanoscribe’s technology. (Image courtesy of Nanoscribe.)
Microscopic lenses 3D printed using Nanoscribe’s technology. (Image courtesy of Nanoscribe.)

Nanoscribe has developed a unique method for 3D printing photopolymers that can be leveraged to create the tiniest objects for some of the most breakthrough applications, including optics, electronics and medical device manufacturing. Piqued by a recent breakthrough in the use of Nanoscribe’s technology to create nano-optics, ENGINEERING.com spoke with the company’s CEO, Martin Hermatschweiler, and head of Sales & Marketing, Andreas Frölich, to learn more. 

Two-Photon Polymerization

After about six years of research, Nanoscribe was spun out of the Karlsruhe Institute of Technology (KIT) in Germany in 2007. It was at KIT that foundations for a process called two-photon polymerization was developed.

Two-photon polymerization is similar to more familiar types of photopolymerization like stereolithography and digital light processing, in that a light-sensitive photopolymer is selectively cured using a light source. The difference with Nanoscribe’s technology, however, is that it is capable of very fine details. 

This is possible through the use of a high-powered laser, which directs two photons of near-infrared light in ultrashort pulses at a photocurable resin. Piezo-driven actuators and focusing optics, combined with this laser technology, enable the process to print details finer than 200 nm (7.9 µin).

Two-photon polymerization was commercialized through the Photonic Professional GT 3D printing systems. Hermatschweiler pointed out that, though the company’s machines are capable of printing tiny objects, they are not limited to such small details.

“Today, Nanoscribe offers 3D printers for the nano-, micro- and mesoscale as well as photoresists and process solutions tailored to specific application areas,” Hermatschweiler said. “[Our] high-tech company has established itself in this field as the technological and global market leader with its laser lithographic processes underlying the technique of two-photon polymerization.”

Applications of Nanoscale 3D Printing

As one might guess, the applications for such a technology are highly specialized, leaving its primary use for those in the research field. “Our primary customers are universities and research facilities in science and industry investigating a vast variety of applications often in multiuser environments. Worldwide, more than 560 users work with our systems,” Hermatschweiler explained.

Increasingly, researchers are using the ability to 3D print at the nanoscale to create tiny medical devices for targeted drug delivery. Scientists at the University of California, San Diego, for instance, were able to 3D print nanoscopic fish-shaped objects with platinum loaded onto their tails for propulsion. Coated with iron oxide on their tips, these swimmers could be magnetically directed to a specific spot to perform toxic cleanup. 

Nanoscribe’s facilities. (Image courtesy of Nanoscribe.)
Nanoscribe’s facilities. (Image courtesy of Nanoscribe.)

Hermatschweiler mentioned some of the other work that is being achieved in the biomedical field. “[R]esearchers of the Italian Institute of Technology (IIT) described how the reproduction of the natural biological microenvironment in vitro should improve the understanding of cell behavior for exploiting cell functions in various health-care applications. They 3D printed bone trabeculae obtained by μ-CT scans of a biopsy from the human femoral neck,” Hermatschweiler said.

Less tangible applications include the creation of nearly invisible sculptures, something that artist Jonty Hurwitz did with Nanoscribe’s platform. Unfortunately for Hurwitz, however, these sculptures are only visible under a microscope, and a breath of air caused them to be blown away, where they became lost among the dust particles of the surrounding room. 

Hermatschweiler spoke further on the exact use cases for the technology. “The multitude of applications is ranging from optics and photonics, to complex structures for the microfluidics, 3D templates for cell migration and stem cell differentiation studies up to the fabrication of micro machines for life sciences. As disruptive technology, 3D laser lithography is an enabler for novel applications and will provide solutions for a broad range of industrial applications, e.g., in fields of optical interconnections, micro-sized parts or in the fabrication of micro-optical elements.”

3D Printing Micro-Optical Elements

The creation of micro-optical elements is one of the latest breakthroughs achieved with Nanoscribe’s technology. Due to the ability to 3D print free-form objects at such a small scale, the Photonic Professional GT has proven ideal for 3D printing microscopic optical lenses for a new generation of microchips.

Researchers from the University of Stuttgart 3D printed doublet lenses directly onto CMOS image sensors to create a high-performance and compact imaging system. Printed as an array 1 square centimeter in total and semispheres with a height of 150 µm, the lenses have a shape accuracy that is better than 1 µm and a surface roughness that is better than 10 nm Ra.

Microscopic lenses of different sizes are grouped together in bundles of four to replicate the mechanics of the fovea. (Image courtesy of Science Advances.)

Microscopic lenses of different sizes are grouped together in bundles of four to replicate the mechanics of the fovea. (Image courtesy of Science Advances.)

Frölich explained the implications of the research, “Micro-optical components are pretty much commonplace in a lot of devices ranging from optical instrumentation to consumer electronics. However, it is not an easy task to get master-shapes for their cheap and reliable production, for example, by injection molding. Our high-precision 3D printing solutions enable the micro-optics industry to innovate by additive manufacturing. Masters can be fabricated as well as a broad range of almost arbitrary micro-optical shapes, including standard refractive micro-optics, freeform optics, diffractive optical elements or even multiplet lens systems, can now be printed in a one-step process.”

The images above demonstrate the type of image that the foveated lenses can capture. (Image courtesy of Science Advances.)

The images above demonstrate the type of image that the foveated lenses can capture. (Image courtesy of Science Advances.)

The lenses mimic foveated vision, a type of vision that enables predators to focus on a single object within a wide field of view made possible by a small area of color-sensing cones, called the fovea, located at the back of the eye. The fovea is the only part of the eye where light hits the cones directly, making that area of vision clearer than the lower resolution areas surrounding it. 

To replicate this ability, the researchers used a set of four different sized lenses, some that see from a wide angle and others that have a more focused view. The various images are then combined digitally. In addition to foveated vision, the camera developed by the Stuttgart team is extremely small, which is necessary for the increasingly small world of electronics, as well as the world of medical devices.

“[R]esearchers at the University of Stuttgart demonstrated that Nanoscribe´s 3D printers have the potential to pave the way for the construction of novel and extremely small endoscopes which are suited for the smallest body openings or machine parts that can be inspected,” Frölich said.

As researchers like those at the University of Stuttgart forge ahead with their research, so too will Nanoscribe according to Frölich. “We continuously work on expanding our capabilities in micro-optics. The next step will be to make our in-house developed know-how about microlens mastering using the two-photon polymerization technology available in the form of a solution that can be used with our Photonic Professional GT printers.”

To learn more about Nanoscribe’s work and technology, head to the company’s website

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