Nanoscribe introduced the new IP-n162 photoactive resin, a printing material with special properties for micro-optical elements such as microlenses, prisms, or complex freeform optics. The new photopolymer resin features a high refractive index in combination with a high dispersion, which corresponds to a low Abbe number. These properties are particularly beneficial for the 3D Microfabrication of innovative micro-optical designs, even without rotational symmetries, and for compound refractive optical systems with three-dimensional shapes and more than one refractive surface. With a low absorption in the infrared region, the photo resin is the best choice for the fabrication of infrared micro-optics, but also for applications where low absorption losses are critical such as optical communication, quantum technology and photonic packaging.
The novel printing material is specifically designed for additive manufacturing based on Two-Photon Polymerization (2PP) in a straightforward 3D printing workflow. The high refractive index material enables innovative micro-optical designs with high shape accuracy and takes high-precision microlenses and freeform 3D micro-optics to the next level.
Thanks to their optical properties, high refractive index polymers facilitate a variety of applications related to disruptive technologies. For example, in optoelectronic applications, they enhance the visual properties of display devices or camera and projector lenses. Moreover, the availability of these materials for 3D Microfabrication can establish a new class of complex 3D micro-optical elements in much smaller sizes than possible with today’s classical technologies. Examples are microlenses in miniaturized imaging systems, endomicroscopy and 3D sensing for AR/VR applications.
IP-n162: high refractive index and high dispersion
The main advantage of IP-n162 is its high refractive index of 1.62 at a wavelength of 589 nm. Compared to Nanoscribe’s other 2PP resins, the new printing material offers the highest refractive index. In addition, the printing material exhibits a low Abbe number of 25, making it the Nanoscribe resin with the highest dispersion.
The optical properties of structures printed with IP-n162 are close to optical polymers typically used in injection molding and can be compared to polycarbonate or polyesters. IP-n162 can be easily used for 3D printing on the microscale, enabling almost any thinkable micro-optical design. Thus, the direct prototyping of 3D or 2.5D micro-optics is achieved in an easy and quick process. And for subsequent replication processes, the time-consuming and expensive iterative fabrication of injection molds by diamond milling within the development phase is no longer necessary.
One possible application of high dispersion materials is the fabrication of achromatic optical systems. By printing compound optics, consisting of elements made of a lower refractive index next to a higher refractive index material such as IP-n162, achromatic optical systems can be additively manufactured on the microscale. “The currently commercially available resins are too similar in their refractive indices, which limits innovations in micro-optical systems. IP-n162 has promising optical properties to develop a useful achromatic system required, for example for display devices, ultra-sensitive detectors and medical applications,” comments Matthias Kraus, scientific researcher at the University of Applied Sciences in Jena, who has pilot-tested IP-n162 in novel optical applications.
A new era of freeform micro-optics
“A high refractive index photoresin like IP-n162 gives the designer additional freedom to create lenses that are more powerful, thinner, less curved, more compact and that can be also 3D printed faster and cheaper” said Simon Thiele, project participant of the BMBF funded project PRINTOPTICS and CTO of the spin-off company of the same name. In this project, Nanoscribe is partnering with the University of Stuttgart and the medical technology company Karl Storz in the printing of miniature optics on fibers for endoscopy applications.
“The most powerful design I realized with IP-n162 was a complex optical system consisting of two lenses with complete freeform surfaces to achieve a distortion-free image. A special feature is the integrated diffractive lens containing fine stair-structures on the top of the lens to correct the color error,” says Thiele about his experiences with the new photoactive resin. “The high refractive index of IP-n162 helps to make these steps smaller and to reduce stray light”, Thiele concluded.