U.S. patent application number 16/852974 was filed with the patent office on 2020-08-06 for 3d printing of composition-controlled copolymers.
This patent application is currently assigned to ADA Foundation. The applicant listed for this patent is ADA Foundation. Invention is credited to Young Jong Lee, Jirun Sun.
Application Number | 20200247062 16/852974 |
Document ID | / |
Family ID | 1000004765992 |
Filed Date | 2020-08-06 |
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United States Patent
Application |
20200247062 |
Kind Code |
A1 |
Sun; Jirun ; et al. |
August 6, 2020 |
3D PRINTING OF COMPOSITION-CONTROLLED COPOLYMERS
Abstract
A computer-controlled system for forming composition-controlled
objects using 3D printing includes two or more liquid reactant
reservoirs, and a mixing sub-system for mixing the two or more
liquid reactant compositions, which in turn includes a flow control
sub-system to control a mass ratio of the mixed two or more liquid
reactant compositions. The computer-controlled system further
includes a scanning sub-system that, under control of the computer,
causes relative motion of a mixed liquid reactants nozzle over a
substrate; thereby depositing the mixed liquid reactant
compositions onto the substrate. The system still further includes
an illuminations system, operated under control of the computer, to
polymerize the deposited mixed liquid reactant compositions.
Inventors: |
Sun; Jirun; (Rockville,
MD) ; Lee; Young Jong; (Gaithersburg, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ADA Foundation |
Chicago |
IL |
US |
|
|
Assignee: |
ADA Foundation
Chicago
IL
|
Family ID: |
1000004765992 |
Appl. No.: |
16/852974 |
Filed: |
April 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15702779 |
Sep 13, 2017 |
10625470 |
|
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16852974 |
|
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62400967 |
Sep 28, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 5/18 20130101; C08K
2003/2241 20130101; C08K 2003/2227 20130101; B33Y 80/00 20141201;
C08J 2329/10 20130101; C08J 9/26 20130101; C08J 2207/10 20130101;
B33Y 10/00 20141201; B29K 2105/0005 20130101; B29C 64/00 20170801;
B33Y 50/00 20141201; A61K 6/71 20200101; C08J 9/0061 20130101; C08K
3/22 20130101; A61K 6/62 20200101; B29K 2067/04 20130101; C08J
2201/026 20130101; B33Y 30/00 20141201; B29C 64/336 20170801; C08J
2201/0462 20130101; B29C 64/106 20170801; B29C 64/386 20170801;
A61K 6/76 20200101; B29K 2105/04 20130101; B29K 2105/0085 20130101;
C08K 3/36 20130101; B29K 2105/0002 20130101; B33Y 70/00 20141201;
B29C 64/393 20170801; A61K 6/15 20200101; G02B 1/041 20130101; C08K
5/08 20130101; B29K 2309/02 20130101; B29L 2011/0016 20130101; C08J
2201/0422 20130101; B29L 2031/7532 20130101; B33Y 50/02 20141201;
C08J 2425/06 20130101; G02B 1/04 20130101; C08J 2201/0446 20130101;
C08J 2335/02 20130101; A61K 6/887 20200101; B29K 2071/00
20130101 |
International
Class: |
B29C 64/393 20060101
B29C064/393; B29C 64/386 20060101 B29C064/386; C08J 9/00 20060101
C08J009/00; B29C 64/00 20060101 B29C064/00; B29C 64/336 20060101
B29C064/336; A61K 6/15 20060101 A61K006/15; A61K 6/62 20060101
A61K006/62; A61K 6/71 20060101 A61K006/71; A61K 6/76 20060101
A61K006/76; A61K 6/887 20060101 A61K006/887; B33Y 50/02 20060101
B33Y050/02; B33Y 80/00 20060101 B33Y080/00; B29C 64/106 20060101
B29C064/106; C08K 3/22 20060101 C08K003/22; C08K 5/08 20060101
C08K005/08; C08K 5/18 20060101 C08K005/18; G02B 1/04 20060101
G02B001/04 |
Claims
1. A computer-controlled system for forming a
composition-controlled object using 3D printing, comprising: two or
more reservoirs, each reservoir capable of storing a liquid
reactant composition, each liquid reactant composition differing in
chemical properties; a mixing sub-system for controlling liquid
reach composition flow from the reservoirs, homogeneously mixing
the liquid reactant compositions, and discharging
homogeneously-mixed liquid reactant compositions; a stage
configured to support a substrate that receives the discharged
homogeneously-mixed liquid reactant compositions; an illumination
sub system that polymerizes the received homogeneously-mixed liquid
reactant composition; and a computer control sub-system comprising:
a non-transitory computer-readable storage medium having stored
thereon, machine instructions that when executed, cause production
of a 3D composition-controlled object, and a processor that
executes the machine instructions to: control a mass ratio of each
liquid reactant composition in a homogeneous mixture of the liquid
reactant compositions; cause relative motion between a
homogeneously-mixed liquid reactants nozzle and the substrate;
deposit the homogeneously-mixed liquid reactant compositions onto
the substrate; and operate the illumination sub-system to
polymerize the deposited homogeneously-mixed liquid reactant
compositions, comprising, throughout an entire deposition process
for forming the 3D composition-controlled object, as the deposited
homogeneously-mixed liquid reactant compositions touch the
substrate, operating the illumination sub-system to rapidly
polymerize the compositions.
2. The system of claim 1, wherein the liquid reactant compositions
in the reservoirs comprise reactant(s), initiators, porogenic
particles, reinforcing particles, solvent(s), and combinations
thereof.
3. The system of claim 2, wherein the reactants are chosen from a
group consisting of monomers and monomer mixtures that form
composition-controlled copolymers at different degrees of monomer
to polymer conversion.
4. The system of claim 2, wherein the initiators are chosen from a
group consisting of initiators for free-radical polymerization,
cationic polymerization, and anionic polymerization.
5. The system of claim 2, wherein the porogenic particles are
chosen from a group consisting of water-soluble sugar,
water-soluble salt, and organic solvent soluble polymer
particles.
6. The system of claim 2, wherein the reinforcing particles are
chosen from a group consisting of metal oxide particles and
nanoparticles.
7. The system of claim 1, wherein the mass ratio of the liquid
reactant compositions is controlled by flow rate and mixture in a
container within the nozzle.
8. The system of claim 1, wherein the mass ratio of the liquid
reactant compositions is controlled by flow rate and mixture in a
container immediately adjacent to the nozzle.
9. The system of claim 1, wherein the degree of monomer to polymer
conversion is controlled using illumination intensity and
irradiation time.
10. The system of claim 1, further comprising a post-printing
treatment sub system for submitting printed products to post
printing treatments including one or more of soaking in water or
aqueous solutions, soaking in organic solvents, and annealing.
11. The system of claim 1, wherein the 3D composition-controlled
objects comprise dental devices for dental restorative material,
denture, orthodontic treatment, dental implant, dental tissue
regeneration, and dental tissue engineering.
12. The system of claim 1, wherein 3D composition-controlled
objects comprise optical devices with spatially controlled optical
properties, including refractive index, transmission, reflectance,
color, polarization, and glossiness.
13. The system of claim 1, wherein the nozzle is fixed and the
processor executes machine instructions to move the stage to
generate the relative motion.
14. A system for composition-controlled printing of a
three-dimensional (3D) object, comprising: a plurality of
reservoirs, each reservoir containing a liquid reactant composition
different from liquid reactant compositions in others of the
plurality of reservoirs; a liquid reactant composition flow control
sub-system comprising: a reservoir discharge valve for each of the
plurality of reservoirs, a mixing chamber having an intake
connected to a discharge of the reservoir discharge valves and a
mixing chamber discharge, and a mixing valve and a scanning nozzle
connected to the mixing chamber discharge; an illumination
sub-system; a scanning stage; a non-transitory, computer-readable
storage medium having stored therein machine instructions for
composition-controlled printing of 3D objects; and a computer,
wherein the computer executes the machine instructions to control
flows of the different liquid reactant compositions from the
reservoirs into the mixing chamber, wherein the computer executes
the machine instructions to: control a composition percentage of
each of the different liquid reactant compositions in the mixing
chamber comprising the computer executing the machine instructions
to individually adjust the discharge valve from each of respective
ones of the reservoirs, mix homogeneously, the different liquid
reactant compositions in the mixing chamber thereby producing a
homogeneously-mixed liquid reactant composition, and control
mechanical properties of the 3D printed object by a plurality of
step-wise depositions and polymerizations of the
homogeneously-mixed liquid reactant composition, wherein the
computer executes the machine instructions to: deposit variable
amounts of the homogeneously-mixed liquid reactant composition onto
a substrate by controlling the mixing valve and scanning nozzle;
and polymerize the deposited variable amounts of the
homogeneously-mixed liquid reactant composition by controlling a
light source such that, throughout deposition, as the deposited
homogeneously-mixed liquid reactant composition touches the
substrate, the computer executes machine instructions to operate
the light source to rapidly polymerize the deposited
homogeneously-mixed liquid reactant composition.
15. The system of claim 14, wherein the computer controls a
composition percentage by controlling one or more of a weight
percentage, a volume percentage, and a molar ratio percentage of
each of the different liquid reactants in the mixing chamber.
16. The system of claim 14, wherein the liquid reactant
compositions form azeotropic compositions, and wherein the computer
controls the mechanical properties of the 3D printed object by
controlling individual flows from the respective reservoirs to
achieve a desired molar ratio of the different liquid reactants in
the mixing chamber.
17. The system of claim 14, wherein the computer controls the
mechanical properties of the 3D printed object by controlling the
variable amounts during one or more of the step-wise depositions
and polymerizations.
18. The system of claim 14, wherein the computer controls the
mechanical properties of the 3D printed object by controlling the
intensity and duration of an illumination source of the
illumination sub-system during one or more of the step-wise
depositions and polymerizations.
19. The system of claim 14, wherein the mixing chamber and mixing
valve are combined.
20. A non-transitory, computer-readable storage medium having
encoded thereon, machine instructions for composition-controlled
three-dimensional (3D) printing, that, then executed by a
processor, cause the processor to: using two or more liquid
reactant compositions disposed in respective two or more
reservoirs, mix the two or more liquid reactant compositions by
controlling a mass ratio of the mixed two or more liquid reactant
compositions; scan a mixed liquid reactants nozzle over a
substrate; deposit the mixed liquid reactant compositions onto the
substrate; and operate a light source to polymerize the deposited
mixed liquid reactant compositions, by, throughout the entire
method for forming a 3D composition-controlled product, as the
deposited mixed liquid reactant compositions touch the substrate,
operating the light source to rapidly polymerize the compositions.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/702,779, filed Sep. 13, 2017, entitled "3D
Printing of Composition-Controlled Copolymers." This application
also claims priority to provisional patent application 62/400,967,
"Composition Controlled 3D Printing Using Photo-Polymerization,"
filed Sep. 28, 2016. The content of each of these applications is
incorporated by reference.
BACKGROUND
[0002] Three-dimensional printing using polymerization is known.
For example, U.S. Pat. No. 4,575,330 to Charles Hull discloses a
system for iterative polymerization of a liquid. However, the
system of the Hull patent results in a 3D object having a generally
consistent composition. Later systems also are limited in the sense
that the 3D objects they produce have a generally consistent
composition.
SUMMARY
[0003] A computer-controlled method for forming a
composition-controlled product using 3D printing includes disposing
two or more liquid reactant compositions in respective two or more
reservoirs; and mixing the two or more liquid reactant
compositions, which in turn includes controlling by the computer a
mass ratio of the mixed two or more liquid reactant compositions.
The computer-controlled method further includes scanning, under
control of the computer, a mixed liquid reactants nozzle over a
substrate; depositing the mixed liquid reactant compositions onto
the substrate; and operating, under control of the computer, a
light source to polymerize the deposited mixed liquid reactant
compositions.
[0004] In an embodiment of the method, the liquid reactant
compositions in the reservoirs comprise reactant(s), initiators,
porogenic particles, reinforcing particles, solvent(s), and
combinations thereof. In an aspect, the reactants are chosen from a
group consisting of monomers or monomer mixtures that form
composition-controlled copolymers at different degrees of monomer
to polymer conversion. In an aspect, the initiators are chosen from
a group consisting of initiators for free-radical polymerization,
cationic polymerization or anionic polymerization. In an aspect,
the porogenic particles are chosen from a group consisting of
water-soluble sugar or salt and organic solvent soluble polymer
particles. In an aspect, the reinforcing particles are chosen from
a group consisting of metal oxide particles and nanoparticles.
[0005] In an embodiment of the method, the mass fraction of liquid
reactant is controlled by flow rate and mixed in a container within
the nozzle or immediately adjacent to the nozzle. In an embodiment,
the degree of monomer to polymer conversion is controlled using
laser intensity and irradiation time. In an embodiment, the printed
products are submitted to post printing treatments. In an aspect,
the post printing treatments are chosen from a group consisting of
soaking in water or aqueous solutions, soaking in organic solvents,
and annealing.
[0006] In an embodiment, the method may be used for making dental
devices for dental restorative material, denture, orthodontic
treatment, dental implant, implant, tissue regeneration, and tissue
engineering.
[0007] In an embodiment, the method may be used for making optical
devices with spatially controlled optical properties, including
refractive index, transmission, reflectance, color, polarization,
and glossiness.
[0008] A computer-controlled system for forming
composition-controlled objects using 3D printing includes two or
more liquid reactant reservoirs, and a mixing sub-system for mixing
the two or more liquid reactant compositions, which in turn
includes a flow control sub-system to control a mass ratio of the
mixed two or more liquid reactant compositions. The
computer-controlled system further includes a scanning sub-system
that, under control of the computer, causes relative motion of a
mixed liquid reactants nozzle over a substrate; thereby depositing
the mixed liquid reactant compositions onto the substrate. The
system still further includes an illuminations system, operated
under control of the computer, to polymerize the deposited mixed
liquid reactant compositions.
DESCRIPTION OF THE DRAWINGS
[0009] The detailed description refers to the following figures in
which like numerals refer to like objects, and in which:
[0010] FIG. 1 illustrates an example system for 3D printing of
composition-controlled copolymers; and;
[0011] FIGS. 2A and 2B illustrate example 3D products printed by
the system of FIG. 1.
DETAILED DESCRIPTION
[0012] Disclosed is a novel and nonobvious 3D printing system and
corresponding method or process that may be used to manipulate
chemical, physical and mechanical properties at each 3D location of
an object. In an embodiment, the 3D printing method includes the
steps of preparing a reactants mixture, extruding the mixture
through a scanning nozzle, and solidifying the mixture by
photo-polymerization. The mixture may be prepared by blending two
or more different reactant liquids supplied from separate
reservoirs. The relative composition of each reactant liquid in the
mixture may be controlled with a flow control unit installed
between its reservoir and a blending unit. The
composition-controlled reactant mixture may be extruded onto a
substrate through a scanning nozzle with or without a separate flow
controller. In an embodiment, as the mixture touches the substrate,
the mixture is solidified rapidly by photo-polymerization with
visible or UV light irradiation.
[0013] Using this 3D printing method, the chemical, physical,
mechanical, and biological properties of a printed product can be
controlled by various means including, but not limited to: (1) the
relative compositions of reactants in the mixture; (2) the flow
rate of the mixture liquid; (3) the intensity, irradiation time,
and wavelength of photo-polymerizing light; and (4) the scanning
nozzle velocity. Additional post-printing processes may be added to
improve the final product properties, e.g., photo- or
heat-annealing for leachable reactants removal.
[0014] The herein disclosed method for 3D printing of
composition-controlled copolymers makes it possible for a single
printing process to produce 3D products with complex geometries as
well as to continuously or discretely control the chemical,
physical and mechanical properties within the 3D product. The
method also allows addition of solid dispersion components into the
liquid mixture for specific applications, e.g., filler
nanoparticles for dental materials. The photo-polymerized 3D
products of the reactants may be durable and bio-compatible resin
networks and composites.
[0015] FIG. 1 illustrates an example of a composition-controlled 3D
printing system. In FIG. 1, composition-controlled 3D printing
system 100 includes a liquid composition sub-system, a liquid flow
control sub-system, a polymerizing sub-system, and a processor
sub-system. The above sub-systems cooperate to produce 3D,
composition-controlled product 200. More specifically, the system
100 includes computer 110 which may execute machine instructions to
control specific components of the system 100, specifically flow
control system 112, illumination system 114, and scanning stage
130. The flow control system 112 operates valves 122.sub.i to
control flow of reactant compositions from reservoirs 120.sub.i
into discharge component 124, and further operates mixing chamber
and mixing valve 126 to control the rate of deposition of the
blended reactant compositions through nozzle 128. The nozzle 128
deposits the blended reactant compositions onto scanning stage 130.
The computer 110 further controls three-dimensional motion of the
nozzle 128 as over a substrate placed on, or integral to, the
scanning stage 130. Alternately, the nozzle 128 may be fixed, and
the scanning stage 130 may be moved. The computer 110 still further
controls illumination system 114, which may provide light (e.g., a
laser) for curing the deposited, blended reactant compositions. The
light provided by illumination system 114 may pass through lens
component 114. The light may be applied in a step wise fashion as
the 3D product is printed.
[0016] FIGS. 2A and 2B illustrate, respectively, 3D-printed
products 210 and 220. Product 210 is an example 3D-printed tooth
having a varying composition including layers 212, 214, and 216, as
in an actual human tooth. Product 220 is an aberration-free single
lens with gradient-index (GRIN) optics printed according to the
herein disclosed concepts, and can be compared to
conventionally-formed lens 20. See Example 16 of this
disclosure.
[0017] Using the example system 100, the composition of liquid
reactant mixtures may be controlled during 3D printing.
Furthermore, the example system 100 allows the chemical,
mechanical, and biological properties at all locations in a 3D
product to be defined by changing relative compositions of
reactants in the mixture, and by other means, as described in the
example that follow. In addition, the chemical, physical,
mechanical, and morphological properties of the 3D products may be
optimized further by adding additional solid components into a
reactant, such as fillers for dental products. Still further, the
spatial resolution of the 3D products also may be adjusted by
varying compositions of reactants with different rheological
characteristics.
[0018] In an embodiment, the liquid reactant compositions in the
reservoirs 120.sub.i include reactant(s), initiators, porogenic
particles, reinforcing particles, solvent(s), and combinations
thereof. In an aspect, the reactants are may be monomers or monomer
mixtures that form composition-controlled copolymers at different
degrees of monomer to polymer conversion. In an aspect, the
initiators may be initiators for free-radical polymerization,
cationic polymerization or anionic polymerization. In an aspect,
the porogenic particles may be water soluble sugar or salt and
organic solvent soluble polymer particles. In an aspect, the
reinforcing particles may be metal oxide particles and
nanoparticles.
[0019] In an embodiment, the system 100 may be operated to vary the
mass fraction of liquid reactant compositions by controlling flow
rate from the reservoirs 120.sub.i and mixing in the nozzle 128. In
an embodiment, the degree of monomer to polymer conversion is
controlled using laser intensity and irradiation time of
illumination system 114.
[0020] Once the 3D product 200 is produced, additional
post-printing processes may be employed to improve the final
product in terms of chemical, mechanical, or biological
performance, e.g., by removal of leachable reactants in dentures
and other medical devices. In an embodiment, the printed 3D
products are submitted to post printing treatments. In an aspect,
the post printing treatments include of soaking in water or aqueous
solutions, soaking in organic solvents, and annealing.
[0021] In the examples that follow, the inventors used aspects of
the above-described methods to create composition-controlled 3D
products and to verify the properties of the 3D products. In the
past, Raman and infra-red (IR) spectroscopy methods have been used
to measure degree of vinyl conversion in photo-polymerization
reactions. However, conventional spectroscopic methods are not
sufficiently fast to monitor reactions on the millisecond (ms)
scale, which is critical scale for practical 3D printing. Moreover,
the "irreversible" nature of the photo-polymerization makes it
impossible to perform a repetitive synchronized reaction
monitoring.
[0022] To overcome the deficiencies of current Raman and IR
spectroscopy methods, sensitive CARS spectroscopy can be used to
monitor the photo-polymerization reaction. A visible light
illuminates a localized area with a CARS signal collection
objective lens. The illumination time and period are controlled by
an electronic shutter with a millisecond (ms) opening/closing time.
For example, CARS spectra can be collected every 10 ms to record
changes in Raman spectra during the photo-polymerization
reaction.
[0023] The inventors also devised a microscopy study by measuring
the spatial profile of degree of conversion near the illuminated
area. In this study, an 80 .mu.m line scan measured spatially can
resolve Raman spectra every second to monitor the spatial evolution
of polymerization from the illuminated area. These data will help
the inventors understand how best to control the spatial resolution
of the 3D product.
[0024] Examples 1-16 provide various examples directed to the
above-disclosed concepts envisaged by the inventors.
Example 1: Monomer Mixtures for Composition-Controlled
Photo-Polymerization
[0025] In Example 1, two monomers with free-radical polymerizable
vinyl groups were used as models. One monomer, triethylene
glycol-divinylbenzyl ether (TEG-DVBE), was lab-prepared. TEG-DVBE
is stable to hydrolysis and esterase degradation because of the
ether-based chemical structure. The other monomer, urethane
dimethacrylate (UDMA), is one of the key components in medical
devices such as dental restorative materials used to treat carious
teeth. The commercial monomer UDMA was supplied by Esstech
(Essington, Pa., USA) and was used as received. TEG-DVBE was
synthesized and fully characterized in house according to a
previously reported procedure. The monomer mixtures were activated
by 0.2 wt % of camphorquinone (CQ, Aldrich, St. Louis, Mo., USA)
and 0.8 wt % of ethyl 4-N,N-dimethylaminobenzoate (amine, Aldrich,
St' Louis, Mo.).
[0026] Photo-polymerization methods: The monomer mixtures (10
.mu.L) were sandwiched between two Mylar films, and photo-cured
using a handheld dental curing light (SmartLite max LED curing
light, model: 644050, Dentsply International, Milford, Del., USA).
The intensity of light irradiation was adjusted through the
distance of light to sample.
[0027] A unique feature of the monomer mixture of Example 1 is the
azeotropic composition at equimolar TEG-DVBE and UDMA when CQ/amine
are used as initiators. Azeotropic compositions in copolymers means
that the mole fractions of the feed monomers are retained in the
polymer and are constant throughout the polymerization process. The
viscosity of the monomers plays an inconsequential role during the
polymer chain propagation, considering that the viscosity of UDMA
(6.7 Pas) (Pascal second) is approximately 240 time higher than
that of TEG-DVBE (0.028 Pas).
Example 2. Monomer Mixtures for Composition Shift
Photo-Polymerization
[0028] In contrast to Example 1, copolymerization of UDMA and
triethylene glycol dimethacrylate (viscosity=0.012 Pas) showed
significant composition drift when degree of conversion was above
20%. More diluting monomers that diffused quickly in the resin
network converted into polymers at high degrees of vinyl
conversion. This composition drift is due to the diffusion
limitation when the mixture was vitrified upon polymerization. In
general, the low viscosity monomers diffused faster and thus react
to the active radicals more efficiently. Consequently, the low
viscosity monomers converted into the polymer network more rapidly
than did the high viscosity monomers.
Example 3. Monomer Mixtures with Solvents: Enhanced Ease of
Handling
[0029] UDMA or other high viscosity monomer or monomer mixtures
were dissolved in dichloromethane or other low boiling temperature
solvents at 50% by mass. The UDMA solution was stored in one
container, ready to be mixed with components from other containers,
or to be printed out by itself.
Example 4. Mixtures of Monomers and Water-Soluble Particles for
Generating Porous Structures
[0030] In one container, a monomer (for example, TEGDMA) was mixed
with various mass fractions of metal particles or metal oxide
particles (such as silica, alumina, and titania). The viscosity of
this mixture was adjusted to flow through the nozzle. The mixture
in this container was ready to be mixed with components from other
containers or to be printed out by itself.
Example 5. Mixtures of Monomers and Particles to Provide a Broad
Range of Mechanical Properties
[0031] In one container, a monomer (for example, TEGDMA) was mixed
with various mass fraction of water-soluble particles including
sugar and salt, or polymer particles (e.g., polystyrene particles)
that may be dissolved by organic solvents. The viscosity of this
mixture was adjusted to flow through the nozzle. The mixture in
this container was ready to be mixed with components from other
containers or to be printed out by itself.
Example 6. Composition of Monomer Mixtures Determines Mechanical
Properties (Same Pair of Monomers with Different Mole Ratios)
[0032] By varying the mole ratio of UDMA and TEGDVBE, the
mechanical properties of the 3D product, including elastic modulus
and hardness, were changed accordingly. Using mole ratios at 3/1
and 1/1 as examples, the elastic modulus of the 3/1 mixture
(1.78+/-0.04 GPa) was approximately 23% more than that of the 1/1
mixture (1.45+/-0.04 GPa) when their degree of vinyl conversion was
80%. Furthermore, the hardness of the 3/1 mixture (14.9+/-0.8) was
73% higher than that of the 1/1 mixture.
[0033] Flexural Modulus (E) and Flexural Strength (F) by 3-Point
Bending:
[0034] To determine Flexural modulus (E) and flexural strength (F)
six rectangular specimen bars were prepared by inserting a
composite into a stainless-steel mold (25 mm.times.2 mm.times.2 mm)
and covering the specimen surfaces with a Mylar film to prevent
air-inhibited layers. The specimen bars were cured (2 min/each open
side of the mold) using a Dentsply Triad 2000 visible light curing
unit (Dentsply, York, Pa., USA) with a tungsten halogen light bulb
(75 W and 120 V, 43 mW/cm.sup.2). After curing, the specimen bars
were stored at room temperature for 24 hours. The flexural modulus
of the specimen bars was determined using the Universal Testing
Machine (Instron 5500R, Instron Corp., Canton, Mass., USA) at a
cross-head speed of 1 mm/min. The specimen bars were placed on a
3-point bending test device with a 20 mm distance between supports
and an equally distributed load. The flexural modulus (E) and
flexural strength (F) values were calculated following ISO4049:
2009 protocols/equations.
[0035] Knoop Hardness (HK):
[0036] A microhardness machine (Wilson Tukon 2100; Instron Corp.,
Canton, Mass., USA) with indentation loads of (0.25-5) N was used
for HK measurements (ASTM standard E 384). The loading time for an
indentation was 15 seconds with a dwell at peak load of 15 seconds.
Indentation sizes were measured with a 10.times. or a 50.times.
objective. The HK values were calculated by dividing a test force
by the indentation projected surface area. The reported HK values
represent the average of five repetitive measurements. The standard
uncertainty associated with the HK measurements was 5%.
Example 7. Composition of Monomer Mixtures Determines Mechanical
Properties (Different Pairs of Monomers)
[0037] In this example, the mechanical properties in terms of E and
HK of equimolar mixtures of UDMA/TEGDVBE and UDMA/TEGDMA were
evaluated. The mixture containing TEGDMA had a flexural modulus (E)
pf (2.37+/-0.04 GPa) and HK of (13.6+/-1.0), which were 63% and 48%
higher, respectively, than those values for TEGDVBE.
Example 8. Composition of Monomer Mixtures Determines Mechanical
Properties (with Fillers)
[0038] The addition of fillers significantly enhanced the
mechanical properties. The flexural modulus (E) of composites with
75 wt % fillers was 5.6 and 4.1 times more rigid in comparison to
the TEGDVBE containing and TEGDMA containing resins in Example 7,
respectively.
Example 9. Control Composition of Monomer Mixtures by Changing the
Flow Rate of Liquids Through the Nozzles
[0039] In this example, the composition of monomer mixtures may be
varied by changing the flow rate of liquids from different
containers. The amount of liquids from the containers may be
controlled through the flow rate to the mixing unit where the
liquids are mixed.
Example 10. Degree of Vinyl Conversion (DC) Determines Mechanical
Properties
[0040] Using equimolar UDMA/TEGDVBE resin as an example, when the
DC of this resin increased from 80% to 99%, its flexural modulus
was increased to 70%. The flexural modulus of equimolus UDMA/TEGDMA
was increased to 41% for the same amount of DC increase.
[0041] Determine the degree of vinyl conversion (DC) using FTIR-ATR
and peak fitting methods. The degree of vinyl conversion (DC) was
evaluated immediately after curing using a Thermo Nicolet Nexus 670
FT-IR spectrometer (Thermo Scientific, Madison, Wis., USA) with a
KBr beamsplitter, an MCT/A detector and an attenuated total
reflectance (ATR) accessory. The areas of absorption peaks of the
vinyl group of TEG-DVBE at 1629 cm.sup.-1, and the methacrylate
groups of UDMA at 1638 cm.sup.-1 were integrated, and the degree of
conversion was calculated using the aromatic group of TEG-DVBE at
1582 cm.sup.-1 or the amide group of UDMA at 1537 cm.sup.-1 as an
internal standard. Peaks were resolved with the assistance of the
curve fitting program Fityk (version 0.9.8). To correct any
potential discrepancy, a standard curve was produced by plotting
varied resin composition ratio values analyzed by NMR spectroscopy
against the values obtained through FTIR peak fitting. The phenyl
absorbance at 1612 cm.sup.-1 was the internal standard for TEG-DVBE
homo-polymers. The degree of vinyl conversion (DC) was calculated
according to the following equation:
DC=(A1/A0-A1'/A0')/(A1/A0)100%, where A1/A0 and A1'/A0' stand for
the peak-area-ratio of the vinyl-of-interest and internal standard
before and after polymerization, respectively. The
vinyl-of-interest may be vinyl groups from TEG-DVBE, UDMA, or
both.
Example 11. Control the Degree of Vinyl Conversion (DC) Through
Light Intensity and Irradiation Time
[0042] Real-time Raman micro-spectroscopy further confirmed that
the equimolar composition of UDMA/TEGDVBE was constant over time
during photo-polymerization and was independent of the
polymerization rate, which was controlled through light intensity
and irradiation time. To achieve a step-wise polymerization,
specimens were exposed to light at 4 mW/cm.sup.2 for 5 seconds up
to a total of four exposures. The classical least squares (CLS)
method was used from pure monomer spectra to estimate unpolymerized
monomer composition in the samples using the C.dbd.C stretching
bands of TEG-DVBE and UDMA. CLS scores for each specimen were
normalized to 100 for the pre-polymerized monomer mixtures. As the
vinyl groups converted to polymers, the associated C.dbd.C band
intensity decreased, and the degree of vinyl conversion (DC)
increased accordingly. At each light irradiation, the intensity
dropped immediately, and then decreased at a much slower rate,
before the next irradiation. During the full-time range (10 min) of
this set of experiments, DC reached approximately 20%, and the
ratio of TEG-DVBE/UDMA was always 1/1. A faster
photo-polymerization took place when the sample was irradiated at
150 mW/cm.sup.2 for 20 seconds. The DC of this specimen reaches
approximately 55% immediately after light irradiation. At this DC,
the resin was cured. With light intensity at 1000 mW/cm.sup.2, the
DC reached 90% within seconds. During the course of this set of
experiments, the ratio of TEG-DVBE and UDMA was always 1/1.
Example 12. Chemical Composition of Copolymers Determines the
Refractive Index
[0043] The refractive index of UDMA/TEGDVBE mixtures was linearly
correlated with the mole fraction of the monomers: y=0.6x+1.510
(R2=0.996), where y is the refractive index of the mixture, and x
is the mole fraction of TEGDVBE. The refractive index of UDMA,
TEGDVBE, and an equimolar mixture of these two was 1.510, 1.571,
and 1.528, respectively.
[0044] Refractive Indexes (n):
[0045] The n of copolymers and their corresponding composites were
measured by matching with the refractive index liquids (interval of
n=0.004, Cargille Labs Inc., NJ, USA) at 22.degree. C. The value of
matched n was based upon OLYMPUS BX50 light microscope (OLYMPUS,
Tokyo, Japan) observations when the specimen and the n-liquid were
indistinguishable.
Example 13. 3D Object with Variant Chemical Compositions
[0046] The chemical composition is defined as composition of cured
copolymer, and the degree of vinyl conversion of the cured
copolymer. The chemical composition may be modified by varying the
flow rate of liquids from different containers, the irradiation
intensity and duration, and post light-curing process.
Example 14. Post Cure Treatment by Annealing
[0047] After light curing, the 3D product may be subjected to
annealing at varying temperatures based on the glass transition
temperature of the resin network. This annealing process generates
slight movement within the resin network, and thus fine tunes the
3D geometry and the mechanical properties as mentioned in the
examples above.
Example 15. 3D Product with Porous Structures--Dissolving Fillers
after Curing
[0048] The 3D product was prepared using activated TEGDMA (with
initiator CQ/amine) in one container and TEGDMA blended with sieved
NaCl crystals in a second container. The mass fraction of NaCl in
the porous region was set between 60 to 84% to achieve optimal
porosity and strength. After the product was printed out and cured,
the 3D product was soaked in deionized water for 5 days with
multiple changes of water to dissolve the salt porogen, and then
was air dried. The NaCl particles were successfully removed. The
pore size of the 3D product matched the size of the NaCl particles.
The porosity of the 3D product agreed well with the mass fraction
of the NaCl added.
Example 16. 3D Programmed Gradient-Index (GRIN) Optics
[0049] Gradient-index (GRIN) optics are a type of optics with a
gradual change of the refractive index of a material. Such
variation is used to produce lenses with flat surfaces or spherical
lenses without aberrations. A spherical lens is inexpensive to
fabricate compared to an aspherical lens. However, due to inherent
spherical aberration, a spherical lens cannot be used alone for a
high-performance optical instrument. An aspherical lens or a
complex lens (multiple lenses with different curvatures and
refractive indices) may be used as an alternative. However, the
production cost of these complex lenses is much higher than a
single spherical lens, and the complex lenses have other unwanted
optical limitations, such as limited numerical aperture, overall
optics thickness, and reduced transmission. A GRIN lens can reduce
spherical aberration of a single spherical lens or even a lens with
a flat geometry. It is very challenging to reproducibly control the
optical property of a conventional GRIN lens. A recent technology
based on two-photon polymerization can fabricate a 3D lithographic
controlled GRIN optics. However, its cross-linking based control of
the refractive index is limited in the range of refractive index
variation (e.g., .DELTA.n=0.01) and in the long-term product
stability due to slow conversion of unreacted monomers. GRIN optics
made by the using the herein disclosed concepts have a wider range
of refractive index variation (e.g., .DELTA.n=0.06, from Example
12) and a much longer performance stability by controlling the
ratios of fully converted compositions. In addition to refractive
index for GRIN optics, 3D programmed optics made by using the
herein disclosed concepts can have precisely controlled other
optical properties, including transmission, reflectance, color, and
glossiness. The spatial control can be radial, spherical, linear,
or axial, depending on the intended optical properties.
[0050] The herein disclosed methods can be implemented as
operations performed by a processor on data stored on one or more
computer-readable storage devices or received from other sources. A
computer program (also known as a program, module, engine,
software, software application, script, or code) can be written in
any form of programming language, including compiled or interpreted
languages, declarative or procedural languages, and it can be
deployed in any form, including as a stand-alone program or as a
module, component, subroutine, object, or other unit suitable for
use in a computing environment. A computer program may, but need
not, correspond to a file in a file system. A program can be stored
in a portion of a file that holds other programs or data (e.g., one
or more scripts stored in a markup language document), in a single
file dedicated to the program in question, or in multiple
coordinated files (e.g., files that store one or more modules,
sub-programs, or portions of code). A computer program can be
deployed to be executed on one computer or on multiple computers
that are located at one site or distributed across multiple sites
and interconnected by a communication network
* * * * *