A method for multi-material high resolution projection micro stereolithography for 3-D printing of a sample, at faster speeds than presently available, and wherein printing materials can be changed without interrupting the printing process, the method comprising:
- A) generating a 3D digital model of the sample to be printed in a computer, wherein the model can be an assembly of bodies of different printing materials, and then slicing the digital model into a sequence of images, wherein each of the images of the sequence represents a layer of the 3D digital model of one printing material, and wherein additional images of different bodies in the digital model form are supplied for when multiple printing materials are used to form the complete layer of the model,
- B) arranging a lens having an optical axis, a charge coupled device (CCD), and a printing head relative to a surface of a substrate, or a sample held by the substrate, so that the lens is situated between the surface of the substrate or the sample and the CCD, the lens being gravitationally above the substrate or sample, wherein the optical axis of the lens intersects the surface of the substrate or sample, and the CCD is focusable through the lens along the optical axis,
- wherein printing head has a flat tip at a side of the printing head that is closest to the substrate or sample during printing, has a flat tip, wherein the flat tip is positioned at a distance from the substrate or sample, has a hard edge that functions as a coating material scraper, and each coating thickness is equal to the distance between the flat tip and the substrate or sample,
- and wherein the printing head has inner walls, the inner walls and flat tip define an inner cone, the printing head is sealed by a non-stick, gas permeable, transparent membrane or hard window at the tip, and wherein the inner-cone has outer surfaces attached to flat printing material delivery channels, wherein each of the channels deliver a different printing material from the others,
- C) positioning the printing head so that the side carrying the printing material delivery channel that conveys the printing material for the present layer is first along a line traversing the substrate or sample, which line designates a direction that brings the printing head to a printing area,
- D) moving the printing head relative to the substrate by moving the substrate, the printing head, or both the substrate and the printing head, so that the printing head covers the printing area, wherein as the printing head moves to cover the printing area the printing material is squeezed out of an outlet of the flat delivery channel carrying the printing material for the present layer, which printing material is immediately scraped by the hard edge of the flat tip onto the surface of the substrate or sample, and then stopping the movement of the printing head relative to the substrate, and the squeezing of the printing material once the printing head covers the printing area,
- E) sending an image from the control computer to an LCD micro display chip or DLP micro display chip, projecting the image from the LCD or DLP chip through the lens onto a surface of the flat tip of the printing head and irradiating the projected image with light,
- F) and changing the printing material to be used for printing a following layer or layer section by moving the printing head off the printing area, positioning the printing head so that the side carrying the delivery channel with the printing material for the following layer or layer section is first along a line traversing the following printing area designating a direction that brings the printing head to the following printing area, then printing and scraping as in steps C, D and E, wherein the following printing area is in a new layer atop the layer just printed, a layer section adjacent to a layer section already printed.