1. Projection micro-stereolithography using digital micro-mirror dynamic mask
by C. Sun, N. Fang, D.M. Wu, X. Zhang∗
*Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Henrique Serro /05/ /13

2. Oultine Introduction Projection micro-stereolithography system
Three-dimensional micro fabrication
Process characterization
Experimental analysis
Conclusion
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3. Introduction // Old Methods
Microelectromechanical systems (MEMS)
Micro-fabrication technology capable of fabricating complex microstructures from diverse materials (ceramic, metal alloy, polymer, and semiconductor materials)
// Old Methods
Silicon micromachining - Limited in its ability to fabricate complex microstructures, producing only simple geometric shapes from isotropic and anisotropic etching w/ limited material applications.
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4. Introduction (cont.)
LIGA – (german acronym) stands for Lithography, Electroplating, and Molding - Limited to 2,5 HAR microstructures 3D-LCVD – 3D laser chemical vapor deposition – Limited materials applications EFAB - Electrochemical fabrication - extension to the LIGA process in order to fabricate complex 3D metal microstructures – uses electrode masks - Limited materials applications
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5. Introduction (cont.) // New Methods
Micro-Stereolithography (μSL) - high precision, 3D MEMS devices - utilizes focused light spot scanning over a photo curable resin surface - a light-induced photo-polymerization occurs constructing solid microstructures.
PROS- Polyvalent fabrication regarding dimension, shape and material.
CONS – Needs plenty of masks.
First projection experiments used LCD - too rough and slow transitions. Very time-consuming.
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6. Projection micro-stereolithography system
Principle . DMD (Digital Micromirror Device) chip serves as dynamic masks generator . 3D Model built in a layer-by-layer fashion . Resin is cured through UV light exposure
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7. Projection micro-stereolithography system
DMD Microscopic view 3D illustration (2 mirrors)
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8. Projection micro-stereolithography system
Mechanical Translation Stage – Activated by stepper motor controls layer thickness (precision to 0.1 μm) UV Curable Resin – the mixture of the monomer and photo-initiator. This uses a 1,6- hexanedioldiacrylate as low viscosity monomer and Benzoin ethyl ether as the photo-initiator. Color Wavelenght: 364nm.
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9. Three-dimensional micro fabrication
Fig. 2b - The rods shown in present uniform dimensions with 30 μm in diameter, and 1 mm in height. Fig. 2c - The diameter of the coil is 150 μm and the wire diameter is 15 μm. Fig. 2d - The ultimate feature size control is demonstrated through the fabrication of suspended beams with a diameter of 0.6 μm (600nm).
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10. Process characterization
// Process Model Due to the diffractive nature of light, instead of focusing on a single point, a light spot emitted from an object will rather smear out into a blurred spot at the image plane. The spread of radiation flux is described by the point-spread function (PSF). In this work, Gaussian distribution is used as the first order approximation of PSF to describe the flux-density contribution of light spot from the image Plane.
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11. Process characterization (cont.)
// Experimental analysis
A test pattern consisting of fine
thread with different widths
is projected onto a special
designed test cell (side
figure).
Measurements of working
curves of UV curable
resins are obtained by
measuring the curing
depth under various UV
exposures.
As expected, the results
indicate that the curing depth is
linearly proportional to the
natural logarithm of UV
exposure.
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12. Conclusion
The PμSL system has been successfully developed to fabricate truly 3D microstructures.
The results indicate that the numerical model is in good agreement with the experimental results.
The UV curable resin is characterized by the developmental process model with the associated experimental measurements.
By introducing 0.3% UV doping, the curing depth of the resin is decreased from 163 to 45 μm.
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13. PμSL Videos
Printing Process
Printed Object
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14. ANY PROBLEMS?
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