A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes.

Area of Science:

• Microfluidics
• Optics
• Materials Science

Background:

• Microfluidic device fabrication relies on collimated ultraviolet (UV) light sources.
• Conventional mercury lamps are maintenance-intensive and offer unstable, broad-band illumination.

Purpose of the Study:

• To develop a stable, narrow-band UV light source for microfluidic lithography.
• To demonstrate its efficacy in fabricating micro-reliefs using SU8 and other photoresists.

Main Methods:

• Constructed a UV light source using an array of nine 365 nm light-emitting diodes (LEDs).
• Integrated converging lenses to reduce light divergence to 5.4°.
• Evaluated illumination uniformity and intensity over a 90 × 90 mm area.

Main Results:

• Achieved a mean UV intensity of ~1.7 mW cm⁻² with <3% variation over the target area.
• Successfully fabricated micro-reliefs (25–311 μm) with SU8 photoresist.
• Created polydimethylsiloxane (PDMS) replicas with consistent, nearly rectangular microchannels.

Conclusions:

• The LED-based UV light source provides stable, uniform illumination for high-quality microfluidic fabrication.
• It is a cost-effective (<$1000), low-power, and maintenance-free alternative to conventional UV sources.
• The system is suitable for research and development in microfluidics and photolithography.