title: Fine-tuned grayscale optofluidic maskless lithography for three-dimensional freeform shape microstructure fabrication.
abstract: This article presents free-floating three-dimensional (3D) microstructure fabrication in a microfluidic channel using direct fine-tuned grayscale image lithography. The image is designed as a freeform shape and is composed of gray shades as light-absorbing features. Gray shade levels are modulated through multiple reflections of light in a digital micromirror device (DMD) to produce different height formations. Whereas conventional photolithography has several limitations in producing grayscale colors on photomask features, our method focuses on a maskless, single-shot process for fabrication of freeform 3D micro-scale shapes. The fine-tuned gray image is designed using an 8-bit grayscale color; thus, each pixel is capable of displaying 256 gray shades. The pattern of the UV light reflecting on the DMD is transferred to a photocurable resin flowing through a microfluidic channel. Here, we demonstrate diverse free-floating 3D microstructure fabrication using fine-tuned grayscale image lithography. Additionally, we produce polymeric microstructures with locally embedded gray encoding patterns, such as grayscale-encoded microtags. This functional microstructure can be applied to a biophysical detection system combined with 3D microstructures. This method would be suitable for fabricating 3D microstructures that have a specific morphology to be used for particular biological or medical applications.
authors.forename: Suk-Heung
authors.initials: SH
authors.lastname: Song
authors.forename: Kibeom
authors.initials: K
authors.lastname: Kim
authors.forename: Sung-Eun
authors.initials: SE
authors.lastname: Choi
authors.forename: Sangkwon
authors.initials: S
authors.lastname: Han
authors.forename: Ho-Suk
authors.initials: HS
authors.lastname: Lee
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Kwon
authors.forename: Wook
authors.initials: W
authors.lastname: Park