Dimensionally controlled complex 3D sub-micron pattern fabrication by single step dual diffuser lithography (DDL)

Hafeez, Hassan; Ryu, Hoon; An, Ilsin; Oh, Hye−Keun; Ahn, Jinho; Park, Jin-Goo

doi:10.1016/j.mee.2015.02.053

Cited by 6 publications

(5 citation statements)

References 24 publications

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“…As a 10 by 10 UV-LED array consists of 100 discrete LEDs, the light intensity adjacent to the top of LED bulbs and the space between LED bulbs shows high contrast and may result in non-uniform micropatterning over the substrate. A diffuser could be utilized to make the light intensity uniform [11], but the system may lose light collimation, limiting its ability to fabricate tall and high-aspect-ratio microstructures. In this proposed UV-LED system, the light source is rotated to minimize the non-uniformity of the light intensity without losing light collimation.…”

Section: Uv-led Characterizationmentioning

confidence: 99%

“…However, traditionally, it has been utilized to produce twodimensional (2D) or relatively simple high aspect ratio structures (often it is called 2.5D structures). Several alternative UV lithography schemes to expand the design capability have been introduced including multidirectional UV lithography [9,10], diffuser lithography [11], and lithography combined with a timed-development-and-thermal-reflow process [12]. Although those fabrication processes have proven to be useful in 3D microfabrication, they commonly have used a conventional mercury-vapor bulb based UV light source, which poses several disadvantages.…”

Section: Introductionmentioning

confidence: 99%

“…have been introduced including multidirectional UV lithography [9,10], diffuser lithography [11], and lithography combined with a timed-development-and-thermal-reflow process [12]. Although those fabrication processes have proven to be useful in 3D microfabrication, they commonly have used a conventional mercury-vapor bulb based UV light source, which poses several disadvantages.…”

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confidence: 99%

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Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

Kim

Yoon

Allen

2016

J. Micromech. Microeng.

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This paper presents a computer-numerical-controlled ultraviolet light-emitting diode (CNC UV-LED) lithography scheme for three-dimensional (3D) microfabrication. The CNC lithography scheme utilizes sequential multi-angled UV light exposures along with a synchronized switchable UV light source to create arbitrary 3D light traces, which are transferred into the photosensitive resist. The system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computercontrol unit. System operation is such that the tilt-rotational sample holder moves in a pre-programmed routine, and the UV-LED is illuminated only at desired positions of the sample holder during the desired time period, enabling the formation of complex 3D microstructures. This facilitates easy fabrication of complex 3D structures, which otherwise would have required multiple manual exposure steps as in the previous multidirectional 3D UV lithography approach. Since it is batch processed, processing time is far less than that of the 3D printing approach at the expense of some reduction in the degree of achievable 3D structure complexity. In order to produce uniform light intensity from the arrayed LED light source, the UV-LED array stage has been kept rotating during exposure. UV-LED 3D fabrication capability was demonstrated through a plurality of complex structures such as V-shaped micropillars, micropanels, a micro-'hi' structure, a micro-'cat's claw,' a micro-'horn,' a micro-'calla lily,' a micro-'cowboy's hat,' and a micro-'table napkin' array.

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Section: Uv-led Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

Kim

Yoon

Allen

2016

J. Micromech. Microeng.

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“…Alternative methods, tweaking the conventional lithography, have been explored [ 32 , 33 , 34 ] to target the complex 3D-shapes and aspect ratios of MSAs primarily. Although these methods have demonstrated the advantage of thick photoresists’ (e.g., SU-8) 3D-sculptability, they suffer from a series of limitations.…”

Section: Introductionmentioning

confidence: 99%

“…Although these methods have demonstrated the advantage of thick photoresists’ (e.g., SU-8) 3D-sculptability, they suffer from a series of limitations. For instance, dual diffusers were used to fabricate cone-shaped microstructures but needed an additional setup to control the diffusion angle, MSAs’ dimension, and aspect ratio [ 4 , 34 ]. Backside exposure was employed to achieve various aspect ratios of MSA but was incompatible with commonly used silicon and opaque materials [ 18 , 35 ].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Tapered 3D Microstructure Arrays Using Dual-Exposure Lithography (DEL)

2020

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Three-dimensional (3D) microstructure arrays (MSAs) have been widely used in material science and biomedical applications by providing superhydrophobic surfaces, cell-interactive topography, and optical diffraction. These properties are tunable through the engineering of microstructure shapes, dimensions, tapering, and aspect ratios. However, the current fabrication methods are often too complex, expensive, or low-throughput. Here, we present a cost-effective approach to fabricating tapered 3D MSAs using dual-exposure lithography (DEL) and soft lithography. DEL used a strip-patterned film mask to expose the SU-8 photoresist twice. The mask was re-oriented between exposures (90° or 45°), forming an array of dual-exposed areas. The intensity distribution from both exposures overlapped and created an array of 3D overcut micro-pockets in the unexposed regions. These micro-pockets were replicated to DEL-MSAs in polydimethylsiloxane (PDMS). The shape and dimension of DEL-MSAs were tuned by varying the DEL parameters (e.g., exposure energy, inter-exposure wait time, and the photomask re-orientation angle). Further, we characterized various properties of our DEL-MSAs and studied the impact of their shape and dimension. All DEL-MSAs showed optical diffraction capability and increased hydrophobicity compared to plain PDMS surface. The hydrophobicity and diffraction angles were tunable based on the MSA shape and aspect ratio. Among the five MSAs fabricated, the two tallest DEL-MSAs demonstrated superhydrophobicity (contact angles >150°). Further, these tallest structures also demonstrated patterning proteins (with ~6–7 μm resolution), and mammalian cells, through microcontact printing and direct culturing, respectively. Our DEL method is simple, scalable, and cost-effective to fabricate structure-tunable microstructures for anti-wetting, optical-, and bio-applications.

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Control Systems for Precision Machines

Li¹

2019

Methods in Molecular Biology

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Dimensionally controlled complex 3D sub-micron pattern fabrication by single step dual diffuser lithography (DDL)

Cited by 6 publications

References 24 publications

Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

Fabrication of Tapered 3D Microstructure Arrays Using Dual-Exposure Lithography (DEL)

Control Systems for Precision Machines

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