US-12623398-B2 - Freeform fabrication of three-dimensional structures using a droplet-on-demand process with continuous and frequency modulated material deposition

US12623398B2US 12623398 B2US12623398 B2US 12623398B2US-12623398-B2

Abstract

A method of forming a three-dimensional structure using droplet-based freeform printing is provided. The method includes depositing a structural material through one or more nozzles onto a surface of a substrate by droplet-based freeform printing, such as inkjet printing, to form one or more three-dimensional structures including a smooth surface and one or more cross-sectional dimensions. The structural material undergoes a liquid-to-solid transition after deposition of the structural material, and the one or more cross-sectional dimensions are controlled by a droplet ejection frequency. A method of fabricating a matrix including a three-dimensional structure including forming a negative three-dimensional template using droplet-based freeform printing, depositing, such as casting, a matrix material over the negative three-dimensional template and at least a portion of the surface of the substrate and solidifying the matrix material to form a matrix including the one or more three-dimensional structures of the negative template is also provided.

Inventors

Akash Garg
O. Burak Ozdoganlar
Philip R. LeDuc
Saigopalakrishna Saileelaprasad Yerneni

Assignees

CARNEGIE MELLON UNIVERSITY

Dates

Publication Date: 20260512
Application Date: 20220825

Claims (20)

1 . A method of forming a three-dimensional structure using droplet-based freeform printing comprising: depositing a structural material while in a liquid phase through one or more nozzles onto a surface of a substrate by droplet-based freeform printing to form one or more three-dimensional structures comprising one or more cross-sectional dimensions, the structural material changing from liquid to solid form while printing to form the one or more three-dimensional structures; controlling a droplet ejection frequency while depositing the structural material to form a three-dimensional structure of the one or more three-dimensional structures such that the three-dimensional structure is formed from droplets ejected at different frequencies, wherein the structural material undergoes a liquid-to-solid transition after deposition of the structural material, and wherein the droplet ejection frequency is controlled such that the liquid-to-solid transition of a droplet of the structural material does not undergo a complete liquid-to-solid transition before a subsequent droplet of the structural material is deposited; and controlling an overhang angle or growth heading angle of the three-dimensional structure by controlling an X-Y speed of the one or more nozzles or the substrate while depositing the structural material to produce off-axis droplets that rotate a freeze-front of the three-dimensional structure, wherein the one or more cross-sectional dimensions are controlled by the droplet ejection frequency.
2 . The method of claim 1 , wherein the droplet ejection frequency is controlled between 1 Hertz (Hz) to 900 Hz.
3 . The method of claim 1 , wherein the one or more three-dimensional structures comprise a branched shape and/or a curvature.
4 . The method of claim 3 , wherein the one or more three-dimensional structures comprise a curvature and the curvature is controlled by moving the substrate and/or by moving the one or more nozzles while the structural material is deposited, wherein the one or more nozzles and the substrate move relative to each other.
5 . The method of claim 1 , wherein the one or more nozzles comprise a diameter of from 1 micron to 1,000 microns.
6 . The method of claim 1 , wherein the liquid-to-solid transition is a phase transition, such as freezing, or solidification.
7 . The method of claim 1 , wherein the structural material comprises water, an aqueous solution, camphene, or combinations thereof.
8 . The method of claim 1 , wherein the structural material comprises a metal alloy, such as eutectic gallium indium (EGaIn) or Galinstan.
9 . The method of claim 7 , wherein the structural material further comprises cell response factors, proteins, metabolites, salts, sugars, glycoconjugates, coloring agents, an electrically conductive material, water, an environmental linking agent, or any combination thereof.
10 . The method of claim 9 , wherein the structural material further comprises an electrically conductive material comprising carbon nanotubes, graphene oxide, MXenes, metal nanoparticles, or any combination thereof.
11 . The method of claim 1 , wherein the one or more three-dimensional structures comprise ice.
12 . The method of claim 1 , wherein the substrate is above 25° C., at least 25° C., at least 10° C., at least 0° C., at least −10° C., at least −20° C., at least −35° C., or below −35° C. while depositing the structural material.
13 . The method of claim 1 , wherein the one or more three-dimensional structures comprise a vascular geometry.
14 . The method of claim 1 , further comprising coating at least a portion of the one or more three-dimensional structures with a coating composition.
15 . The method of claim 14 , wherein the coating composition comprises an elastin-collagen hydrogel, alginate, hyaluronic acid, gelatin, agarose, chitosan, cellulose, poly(acrylic acid), poly(vinyl alcohol), poly(ethylene glycol), poly(ethylene oxide), poly(N-isopropylacrylamide), silicone, or a combination of two or more of any of the preceding.
16 . The method of claim 1 , wherein a subsequent droplet of the structural material is deposited offset from previously deposited droplets of the structural material to form a non-circular cross-sectional shape, such as an oval-shaped cross-section, a super ellipse-shaped cross section, or a circular triangle-shaped cross section.
17 . The method of claim 1 , wherein the three-dimensional structure is a negative three-dimensional template.
18 . The method of claim 1 , further comprising spot-heating, e.g., with a laser, a portion of the deposited structural material to modulate the rate of solidification, melt, or ablate at least a portion of the deposited structural material.
19 . A method of fabricating a matrix comprising a three-dimensional structure, comprising: forming a negative three-dimensional template using droplet-based freeform printing, wherein forming the negative three-dimensional template comprises: depositing a structural material through one or more nozzles onto a surface of a substrate by droplet-based freeform printing to form the negative three-dimensional template as one or more three-dimensional structures comprising one or more cross-sectional dimensions, the structural material comprising: water, an aqueous solution, camphene, or combinations thereof; and controlling a droplet ejection frequency while depositing the structural material to form a three-dimensional structure of the one or more three-dimensional structures such that the three-dimensional structure is formed from droplets ejected at different frequencies, wherein the structural material undergoes a liquid-to-solid transition after deposition of the structural material, wherein the one or more cross-sectional dimensions are controlled by the droplet ejection frequency, and wherein the droplet ejection frequency is controlled such that the liquid-to-solid transition of a droplet of the structural material does not undergo a complete liquid-to-solid transition before a subsequent droplet of the structural material is deposited; depositing a matrix material over the negative three-dimensional template and at least a portion of the surface of the substrate; and solidifying the matrix material to form a matrix comprising the one or more three-dimensional structures of the negative template.
20 . The method of claim 1 , wherein the droplet-based freeform printing comprises inkjet printing.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is the United States national phase of International Application No. PCT/US22/41539 filed Aug. 25, 2022, and claims priority to U.S. Provisional Patent Application No. 63/237,277, filed Aug. 26, 2021, the disclosures of which are hereby incorporated by reference in their entireties. GOVERNMENT LICENSE RIGHTS This invention was made with United States government support under AR081052 awarded by the National Institutes of Health, FA9550-18-1-0262 awarded by the Air Force Office of Scientific Research, and N00014-17-1-2566 awarded by the Office of Naval Research. The U.S. government has certain rights in the invention. BACKGROUND OF THE INVENTION Traditional three-dimensional printing processes involve the layer-by-layer printing of a positive geometry. In fabricating a range of complex geometries, this layer-by-layer three-dimensional (3D) printing process becomes time consuming, necessitate support structures that need to be removed after printing, and produce non-smooth, striated surfaces that require subsequent finishing processes. Furthermore, this layer-by-layer approach becomes inefficient at printing solid forms with intricate channel-like features or voids within a larger solid matrix, such as those encountered in vascularized engineered tissue, three-dimensional microfluidic devices, complex mechanical systems with embedded cooling channels, or pneumatic actuators for soft robotics, to name a few. In addition, the printing of positive geometries may be time consuming, and the surface of the final print may have an undesirable striated pattern. Negative or sacrificial structures have been used in traditional casting and molding processes and are commonly made from polymers and other materials that are hard to remove and can be environmentally or biologically (e.g., for tissue scaffolds) harmful. It would be desirable to have methods effective to create complex geometries with multiple length scales (from micro to macro) using environmentally friendly and biocompatible materials, and when the structure is used as a sacrificial structure, the materials of the sacrificial structure are easy to remove. SUMMARY OF THE INVENTION A continuous freeform droplet-on-demand 3D printing process is provided that may be utilized to create smooth surfaces without striated patterns and the need for support structures. The freeform droplet-on-demand 3D printing process may also be used to create negative or sacrificial geometries that may be removed after depositing a positive matrix over the geometries to create solid structures with channel-like features or voids. In addition to the aforementioned advantages, the formation is desirable to reduce processing times and increase the geometric resolution and smoothness of the internal geometries of the solid positive matrix. Provided herein according to one aspect or embodiment is a method of forming a three-dimensional structure using droplet-based freeform printing. The method includes depositing a structural material through one or more nozzles onto a surface of a substrate by droplet-based freeform printing, such as inkjet printing, to form one or more three-dimensional structures comprising a smooth surface and one or more cross-sectional dimensions. The structural material undergoes a liquid-to-solid transition after deposition of the structural material, and the one or more cross-sectional dimensions are controlled by a droplet ejection frequency. Also provided herein is a method of fabricating a matrix comprising a three-dimensional structure. The method includes: forming a negative three-dimensional template using droplet-based freeform printing, wherein forming the negative three-dimensional template includes: depositing a structural material through one or more nozzles onto a surface of a substrate by droplet-based freeform printing, such as inkjet printing, to form one or more three-dimensional structures comprising a smooth surface and one or more cross-sectional dimensions, wherein the structural material undergoes a liquid-to-solid transition after deposition of the structural material, and wherein the one or more cross-sectional dimensions are controlled by a droplet ejection frequency; depositing, such as casting, a matrix material over the negative three-dimensional template and at least a portion of the surface of the substrate; and solidifying the matrix material to form a matrix comprising the one or more three-dimensional structures of the negative template. Various aspects or embodiments of the invention are described in the following numbered clauses: Clause 1: A method of forming a three-dimensional structure using droplet-based freeform printing comprising: depositing a structural material through one or more nozzles onto a surface of a substrate by droplet-based freeform printing, such as inkjet printing, to form one or more three-dimensional structures comprising a smooth surface and one