# US 11,027,479 B2 · Thermal control mold for making three-dimensional microstructures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,027,479 B2 - Document ID: US11027479B2 - Status: Granted - Kind: B2 - Application number: 15/711,254 - Filed: 2017-09-21 - Published: 2018-03-22 - Granted: 2021-06-08 - Earliest claimed: 2016-09-21 - Assignees: The Regents of the University of Michigan - Applicants: The Regents of the University of Michigan - Inventors: Khalil Najafi; Jae Yoong Cho - Web page: https://patentgrep.com/patent/US11027479B2 ## CPC - B29C 51/36: specially adapted for vacuum forming {, Manufacture thereof} - B29C 51/421: {of preforms, specially adapted for thermoforming (preheating sheets in general B29B13/023; B29C51/427 takes precedence)} - B29C 51/428: {of moulds or mould parts} - B81C 99/0085: {using moulds and master templates, e.g. for hot-embossing} - B81C 99/009: {Manufacturing the stamps or the moulds} - B29C 51/10: Forming by pressure difference, e.g. vacuum - B29L 2031/34: Electrical apparatus, e.g. sparking plugs or parts thereof - B29L 2031/752: {Measuring equipment} - B81C 1/00634: {Processes for shaping materials not provided for in groups B81C1/00444 - B81C1/00626} - G01C 19/5691: of essentially three-dimensional [3D] vibrators, e.g. wine glass-type vibrators - 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) - B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01) - B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract Methods for fabricating three-dimensional microstructures are provided. The method includes disposing a reflow material on a mold, heating the reflow material, and creating a pressure gradient across the reflow material to reflow the material towards a bottom surface of the mold. The mold includes a molding region, a boundary region, and a thermal-isolating region disposed therebetween. The molding region includes a cavity and a projection projecting upwards from a bottom surface of the cavity. The thermal-isolating region includes at least one pocket formed adjacent to and along a perimeter of the cavity of the molding region. During heating, the temperature of the molding region is higher than that of the boundary region and the thermal-isolating region controls the thermal conductivity and mass therebetween. The material reflows towards the bottom surface of the cavity and the protrusion helps shapes the reflow material to form a substantially symmetrical three-dimensional microstructure. ## Claims ### Claim 1 A method for fabricating three-dimensional microstructures, the method comprising: disposing a substantially planar reflow material on a mold having a molding region, a boundary region, and a thermal-isolating region disposed therebetween, wherein the molding region includes a cavity formed therein and a protrusion projecting upwards from a bottom surface of the cavity and the thermal-isolating region includes at least one pocket formed adjacent to and along a perimeter of the cavity of the molding region, wherein a thermal resistance of the thermal-isolating region is proportional to R 3 - R 2 T - D recess ⁢ ⁢ 2 , where R3 is an outer radius of the thermal-isolating region, R2 is an inner radius of thermal-isolating region, T is a thickness of the mold, and Drecess2 is a depth of the at least one pocket of the thermal-isolating region, and the mold has a geometrical relationship defined by two or more of [(R3−R2)/(T−Drecess2)], [(R2−R1)/Drecess1], and [(R2−R1)/Drecess2], where R1 is an outer radius of the cavity of the molding region and Drecess1 is a depth of the cavity of the molding region, wherein T and Drecess1 are different; heating the reflow material while the reflow material is disposed on the mold, wherein a thermal resistance within the at least one pocket of the thermal-isolating region is greater than a thermal resistance of the molding region, and wherein the molding region has a first temperature higher than a second temperature of the boundary region and the thermal-isolating region divides thermal masses of the molding region and the boundary region; and reflowing the reflow material towards the bottom surface of the cavity by creating a pressure gradient across the reflow material, whereby the protrusion extending from the bottom surface of the cavity helps to shape the reflow material and thereby form a three-dimensional microstructure. ### Claim 2 (depends on 1) The method of claim 1, wherein the three-dimensional microstructure has a diameter equal to or less than about 120 cm. ### Claim 3 (depends on 1) The method of claim 1, wherein the thermal mass of the molding region is proportional to [(R2−R1)×Drecess1] and [(R2−R1)×Drecess2]. ### Claim 4 (depends on 3) The method of claim 3, wherein the thermal mass of the molding region is proportional to a thermal response time of the molding region. ### Claim 5 (depends on 1) The method of claim 1, wherein the at least one pocket of the thermal-isolating region is a ring shaped recess that surrounds the cavity of the molding region, wherein the ring shaped recess has a first depth that is substantially equal to a second depth of the cavity. ### Claim 6 (depends on 1) The method of claim 1, wherein the at least one pocket of the thermal-isolating region has a first base surface at a first depth that is substantially equal to a second depth of the cavity and at least one through-hole extending through the first base surface and a second base surface of the mold. ### Claim 7 (depends on 1) The method of claim 1, wherein the at least one pocket of the thermal-isolating region includes an array of pockets that are distributed in a substantially uniformed manner around the cavity of the molding region. ### Claim 8 (depends on 1) The method of claim 1, wherein the at least one pocket of the thermal-isolating region includes an array of interdigitated pockets that are distributed in a substantially uniformed manner around the cavity of the molding region. ### Claim 9 (depends on 1) The method of claim 1, wherein the at least one pocket of the thermal-isolating region extends through a base surface of the mold. ### Claim 10 (depends on 1) The method of claim 1, further comprising controlling the pressure gradient across the reflow material independently from the heating of the reflow material, wherein at least one through-hole extends from the bottom surface of the cavity through a base surface of the mold and the method further includes fluidly coupling the at least one through-hole to a pressure source. ### Claim 11 A method for fabricating three-dimensional microstructures, the method comprising: disposing a substantially planar reflow material on a mold having a molding region, a boundary region, and a thermal-isolating region disposed therebetween, wherein the molding region includes a cavity formed therein and a protrusion projecting upwards from a bottom surface of the cavity and the thermal-isolating region includes at least one pocket formed adjacent to and along a perimeter of the cavity of the molding region, wherein a thermal resistance of the thermal-isolating region is proportional to R 3 - R 2 T - D recess ⁢ ⁢ 2 , where R3 is an outer radius of the thermal-isolating region, R2 is an inner radius of thermal-isolating region, T is a thickness of the mold, and Drecess2 is a depth of the at least one pocket of the thermal-isolating region, and the mold has a geometrical relationship defined by one or more of [(R3−R2)/(T−Drecess2)], [(R2−R1)/Drecess1], and [(R2−R1)/Drecess2], where R1 is an outer radius of the cavity of the molding region and Drecessl is a depth of the cavity of the molding region; heating the reflow material while the reflow material is disposed on the mold, wherein the molding region has a first temperature at or greater than the softening temperature of the reflow material and the boundary region has a second temperature less than the softening temperature of the reflow material and the thermal-isolating region divides thermal masses of the molding region and the boundary region; and reflowing the reflow material towards the bottom surface of the cavity by creating a pressure gradient across the reflow material, whereby the protrusion extending from the bottom surface of the cavity helps to shape the reflow material and thereby form a three-dimensional microstructure and the reflow material does not flow into the at least one pocket of the thermal-isolating region. ### Claim 12 (depends on 11) The method of claim 11, wherein the at least one pocket of the thermal-isolating region is a ring shaped recess that surrounds the cavity of the molding region, wherein the ring shaped recess has a first depth that is substantially equal to a second depth of the cavity. ### Claim 13 (depends on 11) The method of claim 11, wherein the at least one pocket of the thermal-isolating region has a first base surface at a first depth that is substantially equal to a second depth of the cavity and at least one through-hole extending through the first base surface and a second base surface of the mold. ### Claim 14 (depends on 11) The method of claim 11, wherein the at least one pocket of the thermal-isolating region includes an array of pockets that are distributed in a substantially uniformed manner around the cavity of the molding region. ### Claim 15 (depends on 11) The method of claim 11, wherein the at least one pocket of the thermal-isolating region extends through a base surface of the mold. ### Claim 16 (depends on 11) The method of claim 11, further comprising controlling the pressure gradient across the reflow material independently from the heating of the reflow material, wherein at least one through-hole extends from the bottom surface of the cavity through a base surface of the mold and the method further includes fluidly coupling the at least one through-hole to a pressure source. ### Claim 17 A method for fabricating three-dimensional microstructures, the method comprising: disposing a substantially planar reflow material on a mold having a molding region, a boundary region, and a thermal-isolating region disposed therebetween, wherein the molding region includes a cavity formed therein and a protrusion projecting upwards from a bottom surface of the cavity and the thermal-isolating region includes at least one pocket formed adjacent to and along a perimeter of the cavity of the molding region, wherein the at least one pocket of the thermal-isolating region is free from a through-hole extending therefrom, wherein a thermal resistance of the thermal-isolating region is proportional to R ⁢ ⁢ 3 - R ⁢ ⁢ 2 T - Drecess ⁢ ⁢ 2 , where R3 is an outer radius of the thermal-isolating region, R2 is an inner radius of thermal-isolating region, T is a thickness of the mold, and Drecess2 is a depth of the at least one pocket of the thermal-isolating region, and the mold has a geometrical relationship defined by one or more of [(R3−R2)/(T−Drecess2)], [(R2−R1)/Drecess1], and [(R2−R1)/Drecess2], where R1 is an outer radius of the cavity of the molding region and Drecess1 is a depth of the cavity of the molding region, wherein T and Drecess1 are different and wherein T and Drecess2 are different; heating the reflow material while the reflow material is disposed on the mold, wherein the molding region has a first temperature higher than a second temperature of the boundary region and the thermal-isolating region divides thermal masses of the molding region and the boundary region; and reflowing the reflow material towards the bottom surface of the cavity by creating a pressure gradient across the reflow material, whereby the protrusion extending from the bottom surface of the cavity helps to shape the reflow material and thereby form a three-dimensional microstructure. ### Claim 18 (depends on 17) The method of claim 17, further comprising controlling the pressure gradient across the reflow material independently from the heating of the reflow material, wherein at least one through-hole extends from the bottom surface of the cavity through a base surface of the mold and the method further includes fluidly coupling the at least one through-hole to a pressure source. ### Claim 19 (depends on 17) The method of claim 17, wherein the at least one pocket of the thermal-isolating region is a ring shaped recess that surrounds the cavity of the molding region, wherein the ring shaped recess has a first depth that is substantially equal to a second depth of the cavity. ### Claim 20 (depends on 17) The method of claim 17, wherein the at least one pocket of the thermal-isolating region includes an array of pockets that are distributed in a substantially uniformed manner around the cavity of the molding region.