This paper reports a novel technique for fabricating polymeric microlens arrays based on micro-transfer molding with soft mold. The soft mold with a micro-holes array is made by casting a pre-polymer of PDMS against a silicon master. The silicon master of the micro-cylinders array is prepared using photolithography and deep reactive ion etching. During the micro-transfer molding operation, the surface of the soft mold of the micro-holes array is filled with liquid UV curable photopolymer, and the soft mold is then pressed against the flat substrate with a slight pressure for a period of time. After the soft mold is removed from the substrate, surface tension causes the liquid photopolymer cylinders to assume a spherical shape. Finally, the liquid photopolymer is cured by UV irradiation at room temperature. A substrate with a microlens array pattern can be successfully fabricated. In this study, a micro-transfer molding facility with UV exposure capacity has been designed, constructed and tested. The 100 × 100 arrays of a polymeric microlens have been successfully produced. Under the condition of 50 kPa stamping pressure, 6 s duration and 500 mJ cm−2 UV curing dose, the microlenses were successfully formed on the plastic substrate. Their optical properties were verified with a beam profiler. In addition, microlenses of different curvatures and focal lengths can be obtained by using substrates with different surface wettabilities. This study shows that micro-transfer molding can be used for the fabrication of polymeric microlens arrays with high productivity and low cost.
[1]
M. Hutley,et al.
The manufacture of microlenses by melting photoresist
,
1990
.
[2]
G. Whitesides,et al.
Fabrication of arrays of Schottky diodes using microtransfer molding
,
1999
.
[3]
Yongkang Guo,et al.
Real-time gray-scale photolithography for fabrication of continuous microstructure.
,
2002,
Optics letters.
[4]
D. MacFarlane,et al.
Microjet fabrication of microlens arrays
,
1994,
IEEE Photonics Technology Letters.
[5]
George M. Whitesides,et al.
Demonstration of waveguide couplers fabricated using microtransfer molding
,
1997
.
[6]
R. Baets,et al.
Flexible fabrication of microlenses in polymer layers with excimer laser ablation
,
2003
.
[7]
N Q Ngo,et al.
Simple reflow technique for fabrication of a microlens array in solgel glass.
,
2003,
Optics letters.
[8]
Sung-Keun Lee,et al.
A simple method for microlens fabrication by the modified LIGA process
,
2002
.
[9]
Che-Ping Lin,et al.
Hexagonal microlens array modeling and fabrication using a thermal reflow process
,
2003
.