Recently, researchers from the Singapore University of Technology and Design and Southern University of Science and Technology in Shenzhen, China, announced a breakthrough in the digital fabrication of microlens arrays using oscillation-assisted Digital Light Processing (DLP) 3D printing method.

To date, producing microlens arrays has proven to be difficult, according to the researchers. The current manufacturing technologies are time- consuming, have high process complexity, have a lack of fabrication flexibility, and face difficulty in consistency control.

Now, using a novel process of projection lens oscillation, the research teams have been successfully testing an approach for producing microlens arrays with proper surface smoothness using DLP 3D printing. 

Micro Lens Arrays – A gentle Introduction

A microlens array (brief: MLA) consists of multiple micron-sized lenses with optical surface smoothness. An MLA has a supporting substrate with often individual lenses of about 10 micrometers on it. It is formed in a one-dimensional or two-dimensional direction. Today, MLA’s have become an important micro-optics device used in various compact imaging, sensing, and optical communication applications.

With the exception of Netherlands based Luximprint, a global leader in Additive Optics Fabrication, most traditional 3D printing methodologies have been unsuccessful in fabricating any optical component thus far, due to the presence of coarse surface roughness in 3D printed objects.

Projection Lens Oscillation

In this new approach, the computationally designed grayscale patterns are employed to realize microlens profiles upon one single UV exposure which removes the staircase effect existing in the traditional layer-by-layer 3D printing method, and the projection lens oscillation is applied to further eliminate the jagged surface formed due to the gaps between discrete pixels.

Digital Light Processing for Details

DLP 3D printing is a process that uses a digital projector to cure photopolymer resin and produce 3D printed parts. It is often used for highly detailed 3D printing, and is considered a faster method than Stereolithography, a similar 3D printing process. Although DLP 3D printing offers great flexibility in the fabrication of microlens arrays with different sizes, geometries, and profiles, it has been unable to produce parts with optically smooth surfaces. 

Oscillation DLP Printing: Ultrafast & Flexible Fabrication Method

To overcome this, the SUTD and SUSTech researchers suggested integrating DLP 3D printing with mechanical oscillation and grayscale UV exposure. Oscillation helps to remove the jagged surface formed by discrete pixels in a 3D printed part, whereas the grayscale UV exposure removes the staircase effect common to 3D printing, where layer marks are visible. The result is an ultrafast and flexible fabrication method for microlens arrays with optical surface smoothness. 

3D Printing Smooth Microlenses

Although the research team has specifically adapted DLP for producing microlens arrays, various other 3D printing technologies are already suited towards its production. 

For example, Germany-based Nanoscribe manufactures two-photon additive manufacturing systems that are capable of producing microlens arrays.

Also, for larger types of lens arrays, Dutch service provider for printed optics Luximprint offers optical quality lenses straight from the printer with zero need for post-processing.

Economic Viability & Effectiveness

To prove the viability and effectiveness of the approach, the research team has conducted detailed morphology characterizations, including scanning electron microscopy and atomic force microscopy. Results suggested that the integration of projection lens oscillation with DLP 3D printing reduces surface roughness from 200 nm to about 1 nm.

Wrapping it all up, we may fairly conclude that, although the new DLP 3D process is still under investigation and not commercially available yet, the initial results are promising, and we can’t wait to see the first 3D printing devices entering the market.

NOTE: The SUTD + SUSTech Study, “Ultrafast Three-Dimensional Printing of Optically Smooth Microlens Arrays by Oscillation-Assisted Digital Light Processing, was initially published in ACS Applied Materials & Interfaces“.