# US 2021/0276249 A1 · Immersion multi-material projection micro stereolithography > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0276249 A1 - Document ID: US20210276249A1 - Status: Published application - Kind: A1 - Application number: 17/183,425 - Filed: 2021-02-24 - Published: 2021-09-09 - Earliest claimed: 2020-03-03 - Assignees: Bmf Material Technology Inc. - Applicants: Bmf Material Technology Inc. - Inventors: Chunguang XIA - Web page: https://patentgrep.com/patent/US20210276249A1 ## CPC - B29C 64/129: characterised by the energy source therefor, e.g. by global irradiation combined with a mask - B29C 64/393: for controlling or regulating additive manufacturing processes - B33Y 10/00: Processes of additive manufacturing - B33Y 50/02: for controlling or regulating additive manufacturing processes - B29C 64/209: Heads; Nozzles - B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) - B33Y: ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING ## Abstract A method for multi-material high resolution projection micro stereolithography for 3-D printing of a sample, comprising: A) generating a 3D digital model of the sample to be printed in a computer, B) arranging a lens having an optical axis, a charge coupled device (CCD), and a printing head relative to a surface of a substrate, C) positioning the printing head, D) moving the printing head relative to the substrate by moving the substrate, the printing head, or both the substrate and the printing head, E) sending an image from the control computer to an LCD 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 F) and changing the printing material to be used for printing a following layer or layer section. ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The method according to claim 1 wherein after a whole layer is printed, the printing head will move outside a periphery of the sample, after which the sample stage moves down a distance equal to the thickness of next layer of printing material before the next layer is printed. ### Claim 3 (depends on 1) The method according to claim 1 wherein the printing materials consist of light curable resins. ### Claim 4 (depends on 1) The method according to claim 1 wherein the membrane or hard window comprises oxygen permeable materials. ### Claim 5 (depends on 4) The method according to claim 4 wherein the membrane or hard window comprises polydimethylsiloxane or Teflon AF. ### Claim 6 (depends on 5) The method according to claim 5 wherein pressure in the printing head is controlled to compensate for deformation of the membrane or hard window due to contact with the printing material. ### Claim 7 (depends on 6) The method according to claim 6 where in the pressure within the printing head is controlled by controlling the flow rate of a gas introduced into the printing head. ### Claim 8 (depends on 7) The method according to claim 7 wherein the gas introduced into the printing head comprises oxygen. ### Claim 9 (depends on 7) The method according to claim 7 wherein the pressure P in the printing head is controlled by a combination of a mass flow controller (MFC), a downstream flow restrictor and a pressure transducer on the printing head control. ### Claim 10 (depends on 3) The method according to claim 3 wherein the outer surfaces of the inner-cone of the printing head are attached to at least 4 delivery channels, each delivery channel attached to a different surface on a different side of the inner-cone. ### Claim 11 (depends on 6) The method according to claim 6 wherein the delivery channels are connected to a liquid flow controller and shut-off valve wherein each liquid flow controller controls the flow rate of one light curable resin. ### Claim 12 (depends on 3) The method according to claim 3 wherein an image for projecting to the printing head is larger than the single exposure size and the method comprises dividing the image into multiple layer sections, printing the layer sections stepwise and stitching hem into a whole layer, wherein the printing of each section overlaps the boundaries adjacent sections by 5 um to 20 um on the shared edges. ### Claim 13 (depends on 1) The method according to claim 1 wherein the motion of the printing head is controlled by three precision stages in X, Y, and Z directions. ### Claim 14 (depends on 1) The method according to claim 1 wherein the motion of the substrate is controlled by three precision stages in X, Y, and Z directions. ### Claim 15 (depends on 1) The method according to claim 1 wherein precision stages control the motion of the printing head and/or the substrate at least X and Y directions. ### Claim 16 (depends on 8) The method according to claim 8 wherein interpolated offset error curves based on measured data from samples are fed into the translation of the XY stages to compensate mechanical tolerances to ensure that accuracy of a stitching-printed sample is within the specifications. ### Claim 17 (depends on 4) The method according to claim 4 wherein an ultrasound source with frequency larger than 10 kHz is attached to the printing head to increase the resin flow speed.