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Oscillation-aided 3D printing drives rapid fabrication of microlenses

23 Oct 2019

Co-development by SUTD, Singapore, and Southern University of Science & Technology, Shenzhen, China.

With increasing demand for miniaturization of optoelectronics, the microlens array has attracted significant attention and become an important micro-optics device widely used in compact imaging, sensing, optical communication and others. Typically, microlens array consists of multiple micron-sized lenses with optical surface smoothness and superior uniformity, which increases the requirement for machining precision.

Now researchers from the Singapore University of Technology and Design (SUTD) and Southern University of Science and Technology (SUSTech) in Shenzhen, China, have proposed an approach that integrates oscillation-assisted digital light processing (DLP) 3D printing with grayscale UV exposure. The combination is said by the partners to create "ultrafast and flexible fabrication of microlens arrays with optical surface smoothness."

The work has been published in Applied Materials & Interfaces in paper entitled Ultrafast three-dimensional printing of optically smooth microlens arrays by oscillation assisted digital light processing.

Associate Prof Qi Ge from SUSTech commented, "3D printing of small geometries with optical surface smoothness is a big challenge. In our approach, the computationally-designed grayscale patterns are used to realize microlens profiles on a single UV exposure, which removes the staircase effect existing in the traditional layer-by-layer 3D printing method. The projection lens oscillation is applied to further eliminate the jagged surface formed due to the gaps between discrete pixels."

Smooth operator

The developers added that "detailed morphology characterizations, including scanning electron microscopy and atomic force microscopy, show that the integration of projection lens oscillation considerably smoothens the lens surface and reduces the surface roughness from 200 nm to about 1 nm."

Chao Yuan, co-first author of the paper and a postdoctoral research fellow from SUTD, said, "In addition to surface roughness, lens profile also plays a key role in optical performance. In order to better assist the grayscale design for microlens array fabrication, we developed a theoretical model to describe the photopolymerization process and predict the lens profile."

Kavin Kowsari, the other co-first author of the paper and another postdoctoral research fellow from SUTD, said, "The DLP-based 3D printing affords remarkable flexibility to the fabrication of microlens arrays. Microlenses with different sizes, geometries and profiles are printable upon one single UV exposure with different grayscale patterns.

"Relative to the other fabrication method, our oscillation assisted DLP based printing method is energy- and time-efficient without degradation of optical performance, which is convenient for commercialization and deployment into mass production. Also, this approach provides instructive inspirations for other manufacturing fields with high demands for ultra-smooth surfaces."

The work was funded by SUTD's Digital Manufacturing and Design Center, which is supported by the Singapore National Research Foundation. The research 'was published in ACS Applied Materials & Interfaces.

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