Polymer object optical fabrication process
High-volume mass-production and customization of complex three-dimensional polymer and polymer-derived-ceramic microstructures are manufactured in a single step directly from three-dimensional computer models. A projection based non-degenerate two-photon induced photopolymerization method overcomes the drawbacks of conventional one and two-photon fabrication methods. The structure includes dual, synchronized, high-peak power, pulsed femtosecond and picosecond lasers combined with spatial light modulation. Applications include high-resolution rapid prototyping and rapid manufacturing with an emphasis on fabrication of various Micro-Electro-Mechanical Systems (MEMS) devices, especially in the area of MEMS packaging.
1. A method of fabricating three-dimensional micro-structures directly from computer models, comprising:
providing a container at least a part of which is optically transparent;
placing a photoreactive material into the container so that the photoreactive material is accessible by a laser light;
modifying the photoreactive material by a non-degenerate two-photon absorption;
providing an array of controllable pixel elements;
providing a femtosecond laser pulses having a wavelength selected to induce a non-degenerate two-photon polymerization;
directing the femtosecond laser pulses onto the array of controllable pixel elements so that the femtosecond laser pulses are processed by the array of controllable pixel elements into a pulsed patterned source light;
inducing the non-degenerate two-photon polymerization by the pulsed patterned source light;
providing a first optical projection system for projecting the pulsed patterned source light;
providing a picosecond pulsed laser light having a wavelength selected to induce the non-degenerate two-photon polymerization;
providing a second optical projection system for projecting the picosecond pulsed laser light;
synchronizing the pulsed patterned source light and the picosecond pulsed laser light;
aiming the pulsed patterned source light so that the pulsed patterned source light travels through the optically transparent part of the container into the photoreactive material and focuses inside the photoreactive material;
providing the second optical projection system for projecting the picosecond pulsed laser light to form a thin flat sheet;
providing the first optical projection system for projecting the pulsed patterned source light to intersect the thin flat sheet;
directing and focusing the thin flat sheet to intersect the pulsed patterned source light, wherein the intersection creates a fabrication region with the intersecting focal planes of the thin flat sheet and the pulsed patterned source light, such that the pulsed patterned source light is projected perpendicular to the thin flat sheet so that a preselected regions of the photoreactive material are cured at the fabrication region; and
directing the container having the photoreactive material therein through the intersecting focal planes at an angle less than a critical angle of a material of which the container is made and of the photoreactive material, whereby the synchronized overlapping of the pulsed patterned source light and the thin flat sheet operating at two different wavelengths of preselected energies meet the combined energy requirements necessary to achieve the non-degenerate two-photon polymerization in the fabrication region within the photoreactive material.
2. The method of claim 1 , wherein the modifying step includes patterned modification to produce solidification of the photoreactive material in accordance with the pattern.
3. The method of claim 1 , wherein the modifying step includes patterned modification to produce desolidification of the photoreactive material in accordance with the pattern.
4. The method of claim 1 , wherein the modifying step includes patterned modification to produce modification of the index of refraction of the photoreactive material in accordance with the pattern.
5. The method of claim 1 , further comprising: monitoring a real-time velocity of the container through the fabrication region with a feedback velocity monitoring sensor.
6. The method of claim 5 further comprising:
sending electronic data for each image pattern projected from the array of controllable pixel elements; and
providing a computer control system to throttle a refresh rate of the array of controllable pixel elements according to the real-time velocity feedback data obtained from the feedback velocity monitoring sensor.
7. The method of claim 5 further comprising: providing a computer control system for altering a conveyor speed in accordance with the real-time velocity feedback data obtained from the feedback velocity monitoring sensor.
8. The method of claim 5 further comprising: controlling using a computer control system to control at least one of a laser repetition rate, a light path length and the array of controllable pixel elements in accordance with the real-time velocity feedback data obtained from the feedback velocity monitoring sensor.
9. The method of claim 5 further comprising: providing a computer-executable program for extracting a series of slices of three-dimensional computer model data into a series of two-dimensional image files that are compatible with the array of controllable pixel elements.
10. The method of claim 9 further comprising:
sequentially sending the series of two-dimensional images extracted from the three-dimensional computer model data to the array of controllable pixel elements; and
allowing projection of a slice of the three dimensional computer model data into the photoreactive material as the photoreactive material translates through the fabrication region at a velocity determined by a photoreactive cure time of the photoreactive material and the real-time velocity feedback data.